Home Phase change of the Ordovician hydrocarbon in the Tarim Basin: A case study from the Halahatang–Shunbei area
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Phase change of the Ordovician hydrocarbon in the Tarim Basin: A case study from the Halahatang–Shunbei area

  • Yifeng Wang , Weibing Shen EMAIL logo , Jian Li , Jixian Tian , Shengyuan Xu , Quzong Baima and Shuo Chen
Published/Copyright: May 11, 2024
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Open Geosciences
From the journal Open Geosciences Volume 16 Issue 1

Abstract

To clarify the genetic mechanism for phase change of the hydrocarbon in the ultra-deep reservoirs, a case study from the Ordovician hydrocarbon in the Halahatang–Shunbei area (HSA), Tarim Basin, NW China, was conducted. The results show that the Ordovician reservoirs in the HSA are characterized as multi-phase reservoirs with a lateral co-existence of condensates, volatile-oil reservoirs, normal oil reservoirs, and heavy oil reservoirs. From north to south, there are regular variations in the geochemical characteristics of the Ordovician hydrocarbon in different blocks of the HSA, showing an increasing trend in GOR, dryness coefficients, methane contents, methane carbon isotope values, and ethane carbon isotope values, while a decreasing trend in oil densities and wax contents. Because the same Cambrian–Lower Ordovician source for the Ordovician hydrocarbon is observed and the kerogen-cracking gas is dominated in the HSA, the regular variations of the hydrocarbon phases and geochemical characteristics can be interpreted as records of biodegradation and multistage oil–gas filling rather than controlled by the source rock organofacies, oil cracking, and gas invasion. The formation mechanism of the Ordovician multi-phase reservoirs in the HSA suggests that the deep strata of the Tarim Basin hold potential for the exploration of natural gas resources.

Keywords: hydrocarbon phase; carbon isotopes; geochemical analysis; Ordovician; Tarim Basin

1 Introduction

Diversity of the hydrocarbon phase is globally observed in the deep and super-deep strata of a basin [1,2,3], and the exploration and development of the multi-phase hydrocarbon attracted more and more attentions of the geologists [4,5,6,7]. Because the distribution characteristics of the hydrocarbon phase and its main controlling factors are important for evaluating deep petroleum resources and the exploration decision-making, numerous studies have been carried out in this regard.

The formation of multi-phase reservoirs in the subsurface is affected by temperature and pressure conditions, as well as the geochemical compositions of hydrocarbon fluids [8,9], which are greatly impacted by source rock organofacies, thermal maturation, and multiple secondary alterations. After the type and thermal evolution degree of hydrocarbon-generating materials [10,11,12,13,14,15,16,17], the formation of multi-phase reservoirs in a deep basin is strongly affected by secondary alterations, mainly including multi-stage hydrocarbon filling, thermal evolution in the reservoir, biodegradation, water washing, oxidation, gas invasion/gas washing, and fractionation [12,16,18,19]. The key to controlling the phase of oil and gas by multistage filling and accumulation is the addition of different hydrocarbon components in a later stage. This addition can change the phase of the oil and gas by changing the earlier hydrocarbon components [20,21]. The effect of thermal evolution on the phase is attributed to a change in the temperature, which is one of the main controlling factors of oil cracking [17,22]. When the reservoir temperature reaches the cracking threshold of the liquid oil, it begins to crack into gaseous hydrocarbons, changing the phase of the original reservoir [23,24,25,26]. The formation of heavy oil in deep reservoirs is often related to the geological processes such as biodegradation [27], oxidation, and water/gas washing [28]. The essence of biodegradation to change the phase state of oil and gas is to change the physical properties of crude oil and the composition of molecular compounds, resulting in an increase in the crude oil density and wax content [27]. Gas invasion and gas washing are often associated with fractionation, which refers to the process of migration through reservoirs or filling in reservoirs by relatively high mature natural gas while dissolving and removing some components of the crude oil [28,29,30]. The gas invasion, gas washing, and fractionation change the crude oil composition in the original reservoir, while the composition of intrusive natural gas also changes. These changes constitute an important controlling factor for the phase change of oil and gas. In summary, secondary alterations can lead to changes of hydrocarbon phases, through which oil reservoirs will sequentially transition into condensates and even gas reservoirs, which further results in the formation of multi-phase reservoirs. Different kinds of secondary alterations may occur simultaneously in one area [31].

In recent years, great breakthroughs have been made in the oil–gas exploration in deep carbonate formations (6,500–8,000 m) in the Halahatang–Shunbei area (HSA) of the Tarim Basin, NW China. Exploration results show that there exists great diversity in the Ordovician oil and gas properties and phases in the HAS [32,33,34]. Gas-condensate, volatile-oil, normal oil, heavy oil, and other phase reservoirs are constantly discovered [35,36,37,38,39]. There are no obvious boundaries for oil and gas reservoirs with different phases. Clearly, the formation of such oil and gas in different phases cannot be explained merely by the difference of genetic elements (source and maturity). How to understand the formation mechanism of multi-phase reservoirs with the scale of this reserve and effectively predict the phases and spatial distribution of oil and gas has become an important scientific issue in the study of petroleum geology in this area. For the up-mentioned reasons, in this article, based on the latest exploration achievements, comprehensive utilization of geological analysis and geochemical methods, following the analysis of distribution characteristics of hydrocarbon in different phases, systematically dissects the control factors of hydrocarbon phase. We try to analyze the formation mechanism of hydrocarbon in different phases and establish the accumulation mode of the hydrocarbon in different phases.

2 Geological setting

The HAS, including the northern Halahatang area and the southern Shunbei area, is located in the northwestern Tarim Basin (Figure 1). The Halahatang area is the secondary sag within the Tabei Uplift and is under the jurisdiction of the CNPC (Figure 1c) [36]. The Shunbei area is the southwestern extension of the Halahatang area and falls under the jurisdiction of the SINOPEC (Figure 1c) [37]. In the context of integrated exploration for deep oil and gas resources in the basin, these two areas are collectively referred to as the Halahatang-Shunbei hydrocarbon-bearing region, with the main hydrocarbon-bearing strata belonging to the Ordovician (Figure 1).

Figure 1 Map of geological location of HSA in the Tarim Basin, NW China, and its multi-phase reservoirs in the Ordovician reservoirs. (a) Location of the Tarim Basin; (b) structural elements of the Tarim Basin; (c) structural elements of the Tabei Uplift; and (d) structural map of the top of the Ordovician Yingshan Formation in the HAS.
Figure 1

Map of geological location of HSA in the Tarim Basin, NW China, and its multi-phase reservoirs in the Ordovician reservoirs. (a) Location of the Tarim Basin; (b) structural elements of the Tarim Basin; (c) structural elements of the Tabei Uplift; and (d) structural map of the top of the Ordovician Yingshan Formation in the HAS.

Based on the structural burial depth and the combination of overlying formations in the Ordovician reservoirs, the HSA can be divided into three zones and six blocks from north to south: the northern concealed mountainous zone, the central slope transition zone, and the southern deep burial zone [36], comprising the Ha-Xinken block, the Repu-Jinyue block, the Yueman-Fuyuan block, the Northern Shunbei block, the Middle Shunbei block, and the Southern Shunbei block (Figure 1d) [36,37,38]. The HSA is primarily characterized by four tectonic phases [36,40]: large-scale strike-slip faulting during the early to middle Caledonian, small-scale strike-slip faulting during the late Caledonian to early Hercynian, the late Hercynian volcanic faulting, and the Indosinian-Yanshanian faulting. The first three tectonic phases, especially the early to middle Caledonian large-scale strike-slip faulting, play a significant role in controlling the distribution of Ordovician oil and gas in the HSA (Figure 1) [34]. The Paleozoic-Mesozoic strata are well-developed in the HSA, and the Ordovician can be divided into the Lower Penglaiba Formation, the Middle-Lower Yijianfang/Yingshan formations, and the upper Sangtamu/Lianglitage/Tumuxike formations (Figure 2). The upper Ordovician has been eroded from south to north and is directly overlain by the Silurian Kepingtage Formation in the northern region. The Middle-Lower Ordovician Yijianfang Formation and Yingshan Formation have undergone multiple stages of karst alteration, forming large-scale karst fracture-cavity reservoirs, which are the main target layers (Figure 2). The widely distributed mudstone and limestone of the upper Ordovician Tumuxiuke/Santamu formations and the Middle-Lower Ordovician Yingshan/Yijianfang formations provide a stable and high-quality seal-reservoir combination (Figure 2) [41,42].

Figure 2 Stratum and petroleum geological settings in the HSA, Tarim Basin. O1y: Lower Ordovician Yingshan Formation; O2yj: Middle Ordovician Yijianfang Formation; O3tm: Upper Ordovician Tumuxiuke Formation; O3l: Upper Ordovician Lianglitage Formation; O3s: Upper Ordovician Sangtamu Formation; S1k: Lower Silurian Kepingtage Formation; S1t: Lower Silurian Tataai’etage Formation.
Figure 2

Stratum and petroleum geological settings in the HSA, Tarim Basin. O1y: Lower Ordovician Yingshan Formation; O2yj: Middle Ordovician Yijianfang Formation; O3tm: Upper Ordovician Tumuxiuke Formation; O3l: Upper Ordovician Lianglitage Formation; O3s: Upper Ordovician Sangtamu Formation; S1k: Lower Silurian Kepingtage Formation; S1t: Lower Silurian Tataai’etage Formation.

3 Sample and methods

The Ordovician oil samples were taken directly from oil and gas drill wells, and the method for oil property analysis is from previous studies [43,44]. Natural gas samples were taken directly from oil and gas drill wells, and 0.5–1.0 L stainless steel bottles with aluminum alloy double-valve were used. The sampling pipeline and steel bottle were first flushed 10–15 times to exclude air contamination in the bottle. The pressure of the natural gas collected in the bottle was generally higher than 0.5 MPa. The gas components and isotopic composition were analyzed at the State Key Laboratory of Oil and Gas Resources and Exploration, China University of Petroleum (Beijing). By using a MAT-271 mass spectrometer, the ion source was EI, the electrical energy was 86 eV, the mass was 1–350 u, the resolution was 3,000, the accelerating voltage was 8 kV, the fleeting intensity was 0.200 mA, and the vacuum (pressure less than 1. 0 × 10−7 Pa).

4 Results

4.1 Gas/oil ratios

The Ordovician hydrocarbon phases in the HSA are varied and dominated by oil reservoirs with condensates (Figure 1). The GOR in the Halahatang area is 0–600 m3/m3, with an average of 159 m3/m3 and a peak at 0–100 m3/m3. From north to south, the GOR in the Halahatang area increases significantly, including an average of 93 m3/m3 in the Ha-Xinken block, an average of 232 m3/m3 in the Repu-Jinyue block, and an average of 234 m3/m3 in the Yueman-Fuyuan block, respectively (Figure 3). In comparison, the GOR in the Shunbei area is relatively large, ranging from 46 to 678 m3/m3, with an average of 232 m3/m3 and peaks at 0–100 and 300–400 m3/m3. Similar to the Halahatang area, the GOR in the Shunbei area gradually increases from north to south, including an average of 123 m3/m3 in the northern Shunbei block, an average of 302 m3/m3 in the middle Shunbei block, and an average of 678 m3/m3 in the southern Shunbei block, respectively (Figure 3).

Figure 3 GOR distribution of the Ordovician reservoirs in the HSA, Tarim Basin. (a) Comparison chart of the GOR in the Halahatang area and Shunbei area; (b) Comparison chart of the GOR in different blocks of the HSA. Data source of the Shunbei area is from Ma et al. and Wang et al. [37,38,41].
Figure 3

GOR distribution of the Ordovician reservoirs in the HSA, Tarim Basin. (a) Comparison chart of the GOR in the Halahatang area and Shunbei area; (b) Comparison chart of the GOR in different blocks of the HSA. Data source of the Shunbei area is from Ma et al. and Wang et al. [37,38,41].

4.2 Crude oil properties

Oil properties are similar to GOR, with a regular change from north to south. Generally, the oil density in the Shunbei area is less than that in the Halahatang area (Figure 4). Specifically, the oil density decreases from north to south, including 0.87 g/cm3 in the Ha-Xinken block, 0.82 g/cm3 in the Repu-Jinyue block, 0.80 g/cm3 in the Yueman-Fuyuan block, 0.83 g/cm3 in the northern Shunbei block, 0.80 g/cm3 in the middle Shunbei block, and 0.79 g/cm3 in the southern Shunbei block (Figure 4). It is worth emphasizing that the oil densities present anomalously high values in the northern Halahatang area, such as 0.96, 0.94, and 0.93 g/cm3 for the Ha7001, Ha702, and Ha901-2, respectively. According to a statistical analysis of the wax contents of the Ordovician reservoirs in different blocks of the HSA, they are regularly distributed from north to south. The wax contents of the Ha-Xinken block, the Repu-Jinyue block, the Yueman-Fuyuan block, the northern Shunbei block, the middle Shunbei block, and the southern Shunbei block are 6.0, 6.7, 5.8, 3.6, 3.2, and 2.2%, respectively, showing an overall trend of decreasing (Figure 4).

Figure 4 Distribution of oil densities and wax contents of the Ordovician reservoirs in the HSA, Tarim Basin. (a) Comparison chart of the oil density in the Halahatang area and Shunbei area; (b) Comparison chart of the oil density in different blocks of the HSA; (c) Comparison chart of the wax content in the Halahatang area and Shunbei area; (d) Comparison chart of the wax content in different blocks of the HSA. Data source of the Shunbei area is from Ma et al., Wang et al., and Qi and Ding [38,41,42,63].
Figure 4

Distribution of oil densities and wax contents of the Ordovician reservoirs in the HSA, Tarim Basin. (a) Comparison chart of the oil density in the Halahatang area and Shunbei area; (b) Comparison chart of the oil density in different blocks of the HSA; (c) Comparison chart of the wax content in the Halahatang area and Shunbei area; (d) Comparison chart of the wax content in different blocks of the HSA. Data source of the Shunbei area is from Ma et al., Wang et al., and Qi and Ding [38,41,42,63].

4.3 Hydrocarbon gas compositions

The difference in hydrocarbon compositions of the Ordovician natural gas between the Halahatang area and Shunbei area is relatively small, but overall, the natural gas in the Shunbei area is more mature than that in the Halahatang area (Figure 5). The methane contents of the natural gas in the Halahatang area range from 31.3 to 88.9%, with an average of 67.2% and a peak of 60–70%. Ethane contents range from 3.0 to 20.2%, with an average of 11.3%. Contents of the heavy hydrocarbon gases range from 4.3 to 47.9%, with an average of 22.3% and a peak at 20–30%. Dryness coefficients range from 0.50 to 0.95, with an average of 0.75 and a peak of 0.70–0.80. Methane contents of the natural gas in the Shunbei area range from 46.9 to 84.2%, with an average of 72.5% and a peak of 80–90%. Ethane contents range from 2.4 to 20.9%, with an average of 10.6%. Contents of the heavy hydrocarbon gases range from 14.7 to 45.0%, with an average of 20.9% and a peak of 10–20%. Dryness coefficients range from 0.52 to 0.97, with an average of 0.80 and a peak of 0.80–0.90 (Figure 5). According to a statistical analysis of the hydrocarbon compositions of the Ordovician natural gas in different blocks of the HSA, they are regularly distributed from north to south. The methane contents of the Ha-Xinken block, the Repu-Jinyue block, the Yueman-Fuyuan block, the northern Shunbei block, the middle Shunbei block, and the southern Shunbei block are 62.6, 73.1, 77.6, 61.4, 78.6, and 77.3%, respectively, showing an overall trend of increasing. Similarly, the dryness coefficients are 62.6, 73.1, 77.6, 61.4, 78.6, and 77.3, respectively, also exhibiting a distribution pattern of high values in the south and low values in the north (Figure 5). On the contrary, the contents of heavy hydrocarbon gases in these blocks are 24.9, 18.8, 21.4, 26.0, 14.3, and 14.3%, respectively, gradually increasing from south to north (Figure 5).

Figure 5 Distribution of CH4 contents, heavy hydrocarbon gas, and dryness coefficient of the Ordovician natural gases in the HSA, Tarim Basin. (a) Comparison chart of the CH4 contents in the Halahatang area and Shunbei area; (b) Comparison chart of the heavy hydrocarbon gas in the Halahatang area and Shunbei area; (c) Comparison chart of the dry coefficient in the Halahatang area and Shunbei area; (d) Comparison chart of the CH4 contents of different blocks of the HSA; (e) Comparison chart of the heavy hydrocarbon gas in different blocks of the HSA; (f) Comparison chart of the dry coefficient in different blocks of the HSA. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].
Figure 5

Distribution of CH4 contents, heavy hydrocarbon gas, and dryness coefficient of the Ordovician natural gases in the HSA, Tarim Basin. (a) Comparison chart of the CH4 contents in the Halahatang area and Shunbei area; (b) Comparison chart of the heavy hydrocarbon gas in the Halahatang area and Shunbei area; (c) Comparison chart of the dry coefficient in the Halahatang area and Shunbei area; (d) Comparison chart of the CH4 contents of different blocks of the HSA; (e) Comparison chart of the heavy hydrocarbon gas in different blocks of the HSA; (f) Comparison chart of the dry coefficient in different blocks of the HSA. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].

4.4 Gas carbon isotopes

Methane carbon isotopes of the Ordovician natural gas in the Halahatang area range from −57.3 to −45.4‰, with an average of −48.9‰ and a peak at −49.0 to −48.0‰. Ethane carbon isotopes range from −42.9 to −34.3‰, with an average of −48.9‰ and a peak of −40.0 to −38.0‰. Propane carbon isotopes range from −37.8 to −25.9‰, with an average of −33.8‰. N-butane carbon isotopes range from −38.1 to −30.2‰, with an average of −33.0‰. Isobutane carbon isotopes range from −36.8 to −29.9‰, with an average of −32.3‰ (Figure 6). Methane carbon isotopes of the Ordovician natural gas in the Shunbei area range from −49.6 to −44.7‰, with an average of −47.5‰ and a peak of −47.0 to −46.0‰. Ethane carbon isotopes range from −39.3 to −32.5‰, with an average of −35.0‰ and a peak of −34.0 to −32.0‰. Propane carbon isotopes range from −35.6 to −30.6‰, with an average of −32.2‰. N-butane carbon isotopes range from −35.2 to −30.8‰, with an average of −32.7‰. Isobutane carbon isotopes range from −33.4 to −29.0‰, with an average of −31.0‰ (Figure 6). According to a statistical analysis of the carbon isotopes of the Ordovician alkane gas in different blocks of the HSA, the carbon isotope values are regularly distributed from north to south: (1) methane carbon isotopes of the Ha-Xinken block, the Repu-Jinyue block, the Yueman-Fuyuan block, the northern Shunbei block, the middle Shunbei block, and the southern Shunbei block are −50.1, −47.4, −47.1, −48.0, −47.1, and −47.5‰, respectively, (2) ethane carbon isotopes are −38.7, −36.4, −36.9, −37.3, −34.0, and −33.0‰, respectively, showing an overall trend of increasing in these blocks (Figure 6). Similarly, the carbon isotope values of propane and butane also show a distribution pattern of high values in the south and low values in the north.

Figure 6 Distribution of methane and ethane carbon isotopes of the Ordovician natural gases in the HSA, Tarim Basin. (a) Comparison chart of the methane carbon isotope in the Halahatang area and Shunbei area; (b) Comparison chart of the ethane carbon isotope in the Halahatang area and Shunbei area; (c) Comparison chart of the methane carbon isotope in different blocks of the HSA; (d) Comparison chart of the ethane carbon isotope in different blocks of the HSA. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].
Figure 6

Distribution of methane and ethane carbon isotopes of the Ordovician natural gases in the HSA, Tarim Basin. (a) Comparison chart of the methane carbon isotope in the Halahatang area and Shunbei area; (b) Comparison chart of the ethane carbon isotope in the Halahatang area and Shunbei area; (c) Comparison chart of the methane carbon isotope in different blocks of the HSA; (d) Comparison chart of the ethane carbon isotope in different blocks of the HSA. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].

5 Discussion

5.1 Hydrocarbon phase

Original GOR and oil density of reservoirs indicate the hydrocarbon phase because this ratio increases and the density decreases while the oil reservoirs transition into volatile-oil reservoirs and then condensates [31]. In general, the GOR and oil density of oil reservoirs are less than 500 m3/m3 and larger than 0.80 g/cm3, that of volatile-oil reservoirs are between 300 and 500 m3/m3 and between 0.80 and 0.83 g/cm3, and in the condensates the GOR and oil density come to over 500 m3/m3 and below 0.80 g/cm3, respectively. In particular, the oil densities of heavy oil reservoirs are larger than 0.87 g/cm3 [31].

Based on these identification standards, the Ordovician reservoirs in the HSA are characterized as multi-phase reservoirs with a lateral co-existence of condensates, volatile-oil reservoirs, normal oil reservoirs, and heavy oil reservoirs (Figures 1, 3 and 4). Well SB53X in the southern Shunbei block, with a GOR of 678 m3/m3 and an oil density of 0.79 g/cm3, is representative of condensates in the study area. Volatile-oil reservoirs and normal oil reservoirs mainly distribute in the middle HSA, including the middle Shunbei block, the northern Shunbei block, the Repu-Jinyue block, and the Yuema-Fuyuan block, while the Ha-Xinken block to the west typically reflected oil reservoirs with heavy oils. In particular, heavy oil reservoirs with extremely high oil density (over 0.87 g/cm3) regularly transition westwards into normal oil reservoirs with moderate oil density (0.83–0.87 g/cm3) and then to volatile-oil reservoirs with low oil density (below 0.83 g/cm3).

5.2 Gas type

The carbon isotope composition of the Ordovician alkane gas in the HSA follows the pattern of positive sequence (δ 13C1 < δ 13C2 < δ 13C3 < δ 13C4), which shows the characteristics of organic-genetic gas. The scatter plots of the moisture-methane and carbon isotope for gas also show that the Ordovician natural gas in the region is mainly thermogenic organic gas (Figure 7).

Figure 7 Scatter plots for the identification of the Ordovician natural gases genesis by δ 13C1 and C1/(C2 + C3) in the HSA, Tarim Basin (modified after Bernard et al. [62]). Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].
Figure 7

Scatter plots for the identification of the Ordovician natural gases genesis by δ 13C1 and C1/(C2 + C3) in the HSA, Tarim Basin (modified after Bernard et al. [62]). Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].

Numerous studies have shown that δ 13C2 values in natural gases are efficient indicators to distinguish coal-type gases from oil-type gases: natural gases with δ 13C2 values greater than −29.0‰ are coal-type gases, and natural gases with δ 13C2 values less than −29.0‰ are oil-type gases [16,45]. The δ 13C2 values of the Ordovician natural gases in the HSA are generally less than −32.5‰, which are typical oil-type gases. A small portion of the gases have lighter δ 13C1 isotope and lower maturity, with biogas characteristics (Figure 8a) [46]. Combined with the carbon isotope characteristics of hydrocarbon gases, it is determined that the Ordovician natural gas is dominated by oil-associated gas with a low degree of thermal evolution (Figure 8b). On the scatter plots of methane carbon isotope and ethane carbon isotope [16], the Ordovician natural gas in the HSA is closer to the Type II kerogen-derived gas in the Delware/Val Verde Basin (Figure 8c).

Figure 8 Scatter plots for the identification of the Ordovician natural gases genesis by (a) δ 13C1, δ 13C2 and δ 13C3; (b) and (c) by δ 13C1 vs δ 13C2. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].
Figure 8

Scatter plots for the identification of the Ordovician natural gases genesis by (a) δ 13C1, δ 13C2 and δ 13C3; (b) and (c) by δ 13C1 vs δ 13C2. Data source of the Shunbei area is from Gu et al. and Ma et al. [32,37,38].

Based on the Ln(C1/C2)-Ln(C2/C3) diagram proposed by Behar et al. and the δ 13C2-δ 13C3-Ln(C2/C3) diagram proposed by Prinzhofer and Huc [15,47], both kerogen-cracked gases and oil-cracked gases in the marine strata of the Tarim Basin are determined [48]. As shown in Figure 9a, except for some individual samples distributed in the oil-cracked gas area, most of the samples in the HSA are distributed in the kerogen-cracked area. Meanwhile, their distribution is relatively concentrated with strong homogeneity, indicating that the Ordovician natural gas in the study area is mainly kerogen-cracked gas, mixed with a small amount of oil-cracking gas. Li et al. had established a new Ln(C1/C2)-Ln(C2/C3) diagram for distinguishing the oil-cracking gas from the kerogen-cracking gas [49]. Based on the Ln(C1/C2)-Ln(C2/C3) diagram of the Ordovician natural gas in the HSA, the Ln(C1/C2) values range from 0.72 to 3.55, and the Ln(C2/C3) values range from 0.05 to 1.96. They mainly fall on the curve of kerogen-cracking gases, with a maturity value mostly below 1.0%, and some of the gases are located in the transitional zone between the oil-cracking gases and kerogen-cracking gases, indicating little contribution of oil-cracking gases in the kerogen-cracking gases (Figure 9b).

Figure 9 Scatter plots for the identification of the Ordovician natural gases genesis by (a) δ 13C1–δ 13C2 and C2/C3; (b) by Ln(C1/C2) and Ln(C2/C3). Data source of the Shunbei area is from Ma et al. and Wang et al. [37,38,41].
Figure 9

Scatter plots for the identification of the Ordovician natural gases genesis by (a) δ 13C1–δ 13C2 and C2/C3; (b) by Ln(C1/C2) and Ln(C2/C3). Data source of the Shunbei area is from Ma et al. and Wang et al. [37,38,41].

5.3 Hydrocarbon origin

The origin of Ordovician hydrocarbons in the Tarim Basin, whether they come from Cambrian–Lower Ordovician source rocks or Middle-Upper Ordovician source rocks, has been controversial [6,25,26,50,51,52,53,54].

The Cambrian–Lower Ordovician source rock and the related crude oil have higher levels of dinosteranes, and triaromaticdi nosteranes, together with low levels of diasteranes and regular steranes with a slanted-line or reverse-L distribution (C27 < C28 < C29). In contrast, the Middle-Upper Ordovician source rock and its related crude oil generally show that the presence of regular steranes has a V-shaped distribution (C27 > C28 < C29) [50]. Although these are traditionally used to determine Ordovician oil origin in the Tarim Basin, a recent discovery of large-scale liquid petroleum in the Lower Cambrian subsalt dolomite reservoirs in the Tazhong area Li et al. provided a direct reference for oil-source comparison [51,52]. Wang et al., Cai et al., and Zhu et al. have proposed that these light oils in the Lower Cambrian subsalt traps were identified from the Lower Cambrian source rock [53,55,56]. The characteristics of geochemical parameter of the Ordovician crude oil in the HSA were analyzed and compared with the Cambrian crude oil in the well Zhongshen 1. The results show that oils from the well Zhongshen 1 are very similar to the Ordovician crude oil in the HAS, indicating that these crude oil in the study area are mainly derived from Cambrian–Lower Ordovician source rocks (Figure 10). This view is consistent with previous studies [37,38,57]. In particular, Li et al. established new indicators for oil-source comparison based on an analysis of the aryl isoprenoid, the sulfur isotope, and the individual n-alkane isotope, revealing that the main source for the Lower Paleozoic hydrocarbons in the basin is the Cambrian and that the hydrocarbons discovered in the Ordovician mainly migrated through the fault system [58].

Figure 10 Chromatograms of terpanes and steranes in the Ordovician crude oils from the HAS and its surrounding areas. Data source of the ZS1 is from Huo et al. [57]. Є: Cambrian; O: Ordovician.
Figure 10

Chromatograms of terpanes and steranes in the Ordovician crude oils from the HAS and its surrounding areas. Data source of the ZS1 is from Huo et al. [57]. Є: Cambrian; O: Ordovician.

Traditionally, the source identification of Ordovician natural gas in the Tarim Basin is mainly based on maturity parameters, including drying coefficients and methane carbon isotopes, and the oil and gas with high maturity mostly came from the Cambrian source rocks [56,59]. The maturity of the Ordovician natural gases in the HSA is similar to that of crude oils, and natural gases are oil-associated gases, indicating that natural gases have the same source as crude oils in the area. The Ordovician crude oil in the HSA has been confirmed to be of Cambrian–Lower Ordovician origin, and thus, the gas source in the Shunbei area also may be the Cambrian–Lower Ordovician. The natural gas obtained from the Cambrian Wusongtage Formation in the CNPC’s Luntan 1 well is wet gases with a dryness coefficient of 0.88, and the methane carbon isotope value is small, further supporting that the wet gas can be originated from the Cambrian sources in the Tarim Basin [60]. Meanwhile, the Luntan 1 well is located in a tectonically gentle position, and the wet gas cannot be migrated through the fracture to communicate with the Middle-Upper Ordovician source in the adjacent depression [60]. For the Halahatang area, the gas compositions are similar to those of the Shunbei area, showing the similar methane contents and dryness coefficients. Although the carbon isotope value and the maturity of natural gas in the Halahatang area are relatively low, they are not very different from those in the Shunbei area, indicating the same genetic type and probably the same Cambrian source as the natural gas in the Shunbei area. In summary, the Ordovician hydrocarbon in the has is mainly from the Cambrian–Lower Ordovician source rock.

5.4 Formation mechanism of the multi-phase reservoirs

As discussed above, condensates transited westwards into volatile-oil reservoirs and then to normal oil reservoirs and heavy oil reservoirs in the HSA. Laterally, the GOR, methane contents, and dryness coefficients of the reservoirs gradually decrease from south to north. Similarly, the carbon isotope values of the Ordovician hydrocarbon gas also show a distribution pattern of high values in the south and low values in the north. Oil properties, including oil densities and wax contents, are similar to natural gas components and carbon isotope compositions, with a regular change from north to south. The formation of the Ordovician multi-phase reservoirs and variations of the hydrocarbon geochemistry in the HSA are affected by biodegradation and multistage oil–gas filling rather than controlled by source rock organofacies, oil cracking, and gas invasion. Multi-phase reservoirs observed in the HAS cannot be attributed to the source rock organofacies because of the same Cambrian–Lower Ordovician source for the hydrocarbon in the HSA. Nor could multi-phase reservoirs be attributed to oil cracking and gas invasion because the kerogen-cracking gases are dominated for the Ordovician reservoirs; yet, the oil-cracking gas is little in the HSA. These observations are supported by the gas carbon isotopes and agree with previous studies [37,38]. In combination, multi-phase reservoirs in the HAS can only be interpreted as records of biodegradation and multistage oil-gas filling (see the details below). The HSA has developed three stages of hydrocarbon inclusions, indicating three stages of oil and gas filling, namely the Late Caledonian, Late Hercynian, and Himalayan periods [57]: (1) the first period is characterized by a large amount of black-brown-asphalt and brown hydrocarbon inclusions; (2) in the Late Hercynian period, oil and gas inclusions can be seen throughout the entire region, indicating a large-scale oil and gas migration and filling during this period and an important reservoir formation period in the study area; and (3) the third phase involves the injection of light oil and natural gas, which should be widely present.

During the late Caledonian hydrocarbon accumulation period, with the deposition of the Upper Ordovician in the HSA, the Cambrian source rocks quickly matured and rapidly generated a large amount of liquid oil and gas. These oil and gas migrate upwards and accumulate in the Ordovician reservoir (Figure 11a). However, due to the relatively weak cap rock conditions at this time, the massive crude oil generally suffered serious biodegradation [46,51,52]. A large amount of biodegraded bitumen can be found in the Ha 6 region, especially in the dissolution pores and cavities of the Ordovician reservoir in the northern buried hill zone and in the fractures not filled with calcite. A high abundance of 25-norhopane was detected in crude oil samples from the Ha 6 region and most of the wells in the northern part of the Ha-Xinken block [46,51,52].

Figure 11 Accumulation model of oil and gas in the Ordovician multi-phase reservoirs from the HSA, Tarim Basin. (a) Hydrocarbon accumulation in the late Caledonian period；(b) Hydrocarbon accumulation in the late Hercynian period；(c) Hydrocarbon accumulation in the Himalayan period. The section A–A′ can be seen in the Figure 1d. Є: Cambrian; O1p: Lower Ordovician Penglaiba Formation; O1y: Lower Ordovician Yingshan Formation; O2yj: Middle Ordovician Yijianfang Formation; O3tm: Upper Ordovician Tumuxiuke Formation; O3l: Upper Ordovician Lianglitage Formation; O3s: Upper Ordovician Sangtamu Formation; S: Silurian; D1+2: Lower and Middle Devonian; D3: Upper Devonian; C: Carboniferous; P: Permian; T: Triassic; J: Jurassic; K: Cretaceous; E: Tertiary.
Figure 11

Accumulation model of oil and gas in the Ordovician multi-phase reservoirs from the HSA, Tarim Basin. (a) Hydrocarbon accumulation in the late Caledonian period；(b) Hydrocarbon accumulation in the late Hercynian period；(c) Hydrocarbon accumulation in the Himalayan period. The section A–A′ can be seen in the Figure 1d. Є: Cambrian; O1p: Lower Ordovician Penglaiba Formation; O1y: Lower Ordovician Yingshan Formation; O2yj: Middle Ordovician Yijianfang Formation; O3tm: Upper Ordovician Tumuxiuke Formation; O3l: Upper Ordovician Lianglitage Formation; O3s: Upper Ordovician Sangtamu Formation; S: Silurian; D1+2: Lower and Middle Devonian; D3: Upper Devonian; C: Carboniferous; P: Permian; T: Triassic; J: Jurassic; K: Cretaceous; E: Tertiary.

In the late Hercynian period, the Cambrian source rocks continued to be deeply buried and a large amount of hydrocarbons were expelled, forming another important oil and gas accumulation period for HSA. Compared with the Caledonian period, the oil and gas generated during this stage have a higher maturity but are still liquid crude oil or volatile oil. These hydrocarbons are transported vertically through faults into the Ordovician reservoir, forming some primary oil and gas reservoirs, while others are transformed into oil and gas reservoirs that were biodegraded and damaged during the Caledonian period. Subsequently, only a small portion of the oil and gas reservoirs that were previously renovated are currently observed (Figure 11b).

The Himalayan period is the last oil and gas accumulation period experienced by HSA. During this period, the burial depth of Cambrian source rocks continued to increase, reaching mature and over mature stages, generating a large amount of light oil or natural gas. During this period, oil and gas migrated along the vertical transport system, from the Lower Cambrian to the Ordovician, and accumulated into reservoirs (Figure 11c). It can be inferred that the Shunbei reservoirs, compared with the Halahatang reservoirs, have trapped much more this-stage fluids with relatively high maturity.

Due to the same or similar origin and filling process of the hydrocarbon, the changes in the Ordovician hydrocarbon properties and phases in the HSA indicate that the hydrocarbon filling mode is completely consistent with that proposed by England [61]. That is, the maturity of crude oil generated during the early stage is relatively low and relatively far from the source stove, with a relatively long migration distance. While the maturity of crude oil generated in the late stage is relatively high, and it is relatively close to the source stove, with a relatively short migration distance. Thus, it can be inferred that the Shunbei reservoirs, compared with the Halahatang reservoirs, have trapped much more late-stage fluids with relatively high maturity, leading to the distribution of the condensates and volatile-oil reservoirs. Based on the above change rules in oil and gas phase and physical properties, it can also be deducted that oil and gas in the HSA mainly migrated along the northwest-southeast direction and the multi-phase reservoirs were formed (Figure 11). The geochemical characteristics and accumulation model of the Ordovician hydrocarbon in the HSA indicate that the deep strata in the Tarim Basin are potential targets for natural gas exploration breakthrough.

6 Conclusion

  1. Both the Halahatang and Shunbei areas are dominated by oil reservoirs with wet gas: (1) the GOR are 159 and 232 m3/m3, respectively; (2) the oil densities are 0.85 and 0.82 g/cm3, respectively; (3) the dryness coefficients are 0.75 and 0.80, with methane contents of 67.2 and 72.5%, respectively; and (4) the carbon isotope values for methane are −48.9 and −47.5‰, respectively, and carbon isotope values for ethane are −37.7 and −35.0‰, respectively.

  2. The Ordovician reservoirs in the HSA are characterized as multi-phase reservoirs with a lateral co-existence of condensates, volatile-oil reservoirs, normal oil reservoirs, and heavy oil reservoirs. From north to south, there are regular variations in the geochemical characteristics of the Ordovician hydrocarbon in different blocks of the HSA, showing an increasing trend in GOR, dryness coefficients, methane contents, methane carbon isotope values, and ethane carbon isotope values, while a decreasing trend in oil densities and wax contents.

  3. The same Cambrian–Lower Ordovician source for the hydrocarbon is observed and the kerogen-cracking gas is dominated in the Ordovician reservoirs. Apart from some regions in the Ha-Xinken block where the geochemical characteristics of hydrocarbon were anomalously influenced by biodegradation, the regular variations of the phases and geochemical characteristics of the Ordovician hydrocarbon in the HSA were mainly influenced by the multistage oil–gas filling rather than controlled by source rock organofacies, oil cracking, and gas invasion.

  4. The geochemical characteristics and accumulation process of the Ordovician multi-phase reservoirs in the HSA suggest that the deep strata of the Tarim Basin hold potential for the exploration and development of natural gas resources.

Acknowledgements

This study was funded by the PetroChina Science and Technology Projects (2021DJ0603), and the Basic scientific research from the Chinese Academy of Geological Sciences (JB2322).

  1. Author contributions: Methodology, Quzong Baima, Shengyuan Xu and Shuo Chen; software, Quzong Baima, Shengyuan Xu and Shuo Chen; investigation, Jian Li and Jixian Tian; writing—original draft preparation, Yifeng Wang and Weibing Shen; visualization, Jian Li and Jixian Tian; supervision, Weibing Shen; project administration, Yifeng Wang and Weibing Shen; funding acquisition, Yifeng Wang and Weibing Shen.

  2. Conflict of interest: Authors state no conflict of interest.

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Received: 2023-10-19
Revised: 2023-12-25
Accepted: 2023-12-29
Published Online: 2024-05-11

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  38. A new look at the geodynamic development of the Ediacaran–early Cambrian forearc basalts of the Tannuola-Khamsara Island Arc (Central Asia, Russia): Conclusions from geological, geochemical, and Nd-isotope data
  39. Spatio-temporal analysis of the driving factors of urban land use expansion in China: A study of the Yangtze River Delta region
  40. Selection of Euler deconvolution solutions using the enhanced horizontal gradient and stable vertical differentiation
  41. Phase change of the Ordovician hydrocarbon in the Tarim Basin: A case study from the Halahatang–Shunbei area
  42. Using interpretative structure model and analytical network process for optimum site selection of airport locations in Delta Egypt
  43. Geochemistry of magnetite from Fe-skarn deposits along the central Loei Fold Belt, Thailand
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  45. Hunger Games Search for the elucidation of gravity anomalies with application to geothermal energy investigations and volcanic activity studies
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  49. New database for the estimation of dynamic coefficient of friction of snow
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  51. Comparative models of support-vector machine, multilayer perceptron, and decision tree ‎predication approaches for landslide ‎susceptibility analysis
  52. Experimental study on the influence of clay content on the shear strength of silty soil and mechanism analysis
  53. Geosite assessment as a contribution to the sustainable development of Babušnica, Serbia
  54. Using fuzzy analytical hierarchy process for road transportation services management based on remote sensing and GIS technology
  55. Accumulation mechanism of multi-type unconventional oil and gas reservoirs in Northern China: Taking Hari Sag of the Yin’e Basin as an example
  56. TOC prediction of source rocks based on the convolutional neural network and logging curves – A case study of Pinghu Formation in Xihu Sag
  57. A method for fast detection of wind farms from remote sensing images using deep learning and geospatial analysis
  58. Spatial distribution and driving factors of karst rocky desertification in Southwest China based on GIS and geodetector
  59. Physicochemical and mineralogical composition studies of clays from Share and Tshonga areas, Northern Bida Basin, Nigeria: Implications for Geophagia
  60. Geochemical sedimentary records of eutrophication and environmental change in Chaohu Lake, East China
  61. Research progress of freeze–thaw rock using bibliometric analysis
  62. Mixed irrigation affects the composition and diversity of the soil bacterial community
  63. Examining the swelling potential of cohesive soils with high plasticity according to their index properties using GIS
  64. Geological genesis and identification of high-porosity and low-permeability sandstones in the Cretaceous Bashkirchik Formation, northern Tarim Basin
  65. Usability of PPGIS tools exemplified by geodiscussion – a tool for public participation in shaping public space
  66. Efficient development technology of Upper Paleozoic Lower Shihezi tight sandstone gas reservoir in northeastern Ordos Basin
  67. Assessment of soil resources of agricultural landscapes in Turkestan region of the Republic of Kazakhstan based on agrochemical indexes
  68. Evaluating the impact of DEM interpolation algorithms on relief index for soil resource management
  69. Petrogenetic relationship between plutonic and subvolcanic rocks in the Jurassic Shuikoushan complex, South China
  70. A novel workflow for shale lithology identification – A case study in the Gulong Depression, Songliao Basin, China
  71. Characteristics and main controlling factors of dolomite reservoirs in Fei-3 Member of Feixianguan Formation of Lower Triassic, Puguang area
  72. Impact of high-speed railway network on county-level accessibility and economic linkage in Jiangxi Province, China: A spatio-temporal data analysis
  73. Estimation model of wild fractional vegetation cover based on RGB vegetation index and its application
  74. Lithofacies, petrography, and geochemistry of the Lamphun oceanic plate stratigraphy: As a record of the subduction history of Paleo-Tethys in Chiang Mai-Chiang Rai Suture Zone of Thailand
  75. Structural features and tectonic activity of the Weihe Fault, central China
  76. Application of the wavelet transform and Hilbert–Huang transform in stratigraphic sequence division of Jurassic Shaximiao Formation in Southwest Sichuan Basin
  77. Structural detachment influences the shale gas preservation in the Wufeng-Longmaxi Formation, Northern Guizhou Province
  78. Distribution law of Chang 7 Member tight oil in the western Ordos Basin based on geological, logging and numerical simulation techniques
  79. Evaluation of alteration in the geothermal province west of Cappadocia, Türkiye: Mineralogical, petrographical, geochemical, and remote sensing data
  80. Numerical modeling of site response at large strains with simplified nonlinear models: Application to Lotung seismic array
  81. Quantitative characterization of granite failure intensity under dynamic disturbance from energy standpoint
  82. Characteristics of debris flow dynamics and prediction of the hazardous area in Bangou Village, Yanqing District, Beijing, China
  83. Rockfall mapping and susceptibility evaluation based on UAV high-resolution imagery and support vector machine method
  84. Statistical comparison analysis of different real-time kinematic methods for the development of photogrammetric products: CORS-RTK, CORS-RTK + PPK, RTK-DRTK2, and RTK + DRTK2 + GCP
  85. Hydrogeological mapping of fracture networks using earth observation data to improve rainfall–runoff modeling in arid mountains, Saudi Arabia
  86. Petrography and geochemistry of pegmatite and leucogranite of Ntega-Marangara area, Burundi, in relation to rare metal mineralisation
  87. Prediction of formation fracture pressure based on reinforcement learning and XGBoost
  88. Hazard zonation for potential earthquake-induced landslide in the eastern East Kunlun fault zone
  89. Monitoring water infiltration in multiple layers of sandstone coal mining model with cracks using ERT
  90. Study of the patterns of ice lake variation and the factors influencing these changes in the western Nyingchi area
  91. Productive conservation at the landslide prone area under the threat of rapid land cover changes
  92. Sedimentary processes and patterns in deposits corresponding to freshwater lake-facies of hyperpycnal flow – An experimental study based on flume depositional simulations
  93. Study on time-dependent injectability evaluation of mudstone considering the self-healing effect
  94. Detection of objects with diverse geometric shapes in GPR images using deep-learning methods
  95. Behavior of trace metals in sedimentary cores from marine and lacustrine environments in Algeria
  96. Spatiotemporal variation pattern and spatial coupling relationship between NDVI and LST in Mu Us Sandy Land
  97. Formation mechanism and oil-bearing properties of gravity flow sand body of Chang 63 sub-member of Yanchang Formation in Huaqing area, Ordos Basin
  98. Diagenesis of marine-continental transitional shale from the Upper Permian Longtan Formation in southern Sichuan Basin, China
  99. Vertical high-velocity structures and seismic activity in western Shandong Rise, China: Case study inspired by double-difference seismic tomography
  100. Spatial coupling relationship between metamorphic core complex and gold deposits: Constraints from geophysical electromagnetics
  101. Disparities in the geospatial allocation of public facilities from the perspective of living circles
  102. Research on spatial correlation structure of war heritage based on field theory. A case study of Jinzhai County, China
  103. Formation mechanisms of Qiaoba-Zhongdu Danxia landforms in southwestern Sichuan Province, China
  104. Magnetic data interpretation: Implication for structure and hydrocarbon potentiality at Delta Wadi Diit, Southeastern Egypt
  105. Deeply buried clastic rock diagenesis evolution mechanism of Dongdaohaizi sag in the center of Junggar fault basin, Northwest China
  106. Application of LS-RAPID to simulate the motion of two contrasting landslides triggered by earthquakes
  107. The new insight of tectonic setting in Sunda–Banda transition zone using tomography seismic. Case study: 7.1 M deep earthquake 29 August 2023
  108. The critical role of c and φ in ensuring stability: A study on rockfill dams
  109. Evidence of late quaternary activity of the Weining-Shuicheng Fault in Guizhou, China
  110. Extreme hydroclimatic events and response of vegetation in the eastern QTP since 10 ka
  111. Spatial–temporal effect of sea–land gradient on landscape pattern and ecological risk in the coastal zone: A case study of Dalian City
  112. Study on the influence mechanism of land use on carbon storage under multiple scenarios: A case study of Wenzhou
  113. A new method for identifying reservoir fluid properties based on well logging data: A case study from PL block of Bohai Bay Basin, North China
  114. Comparison between thermal models across the Middle Magdalena Valley, Eastern Cordillera, and Eastern Llanos basins in Colombia
  115. Mineralogical and elemental analysis of Kazakh coals from three mines: Preliminary insights from mode of occurrence to environmental impacts
  116. Chlorite-induced porosity evolution in multi-source tight sandstone reservoirs: A case study of the Shaximiao Formation in western Sichuan Basin
  117. Predicting stability factors for rotational failures in earth slopes and embankments using artificial intelligence techniques
  118. Origin of Late Cretaceous A-type granitoids in South China: Response to the rollback and retreat of the Paleo-Pacific plate
  119. Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China
  120. Geological characteristics of the Daduhe gold belt, western Sichuan, China: Implications for exploration
  121. Rock physics model for deep coal-bed methane reservoir based on equivalent medium theory: A case study of Carboniferous-Permian in Eastern Ordos Basin
  122. Enhancing the total-field magnetic anomaly using the normalized source strength
  123. Shear wave velocity profiling of Riyadh City, Saudi Arabia, utilizing the multi-channel analysis of surface waves method
  124. Effect of coal facies on pore structure heterogeneity of coal measures: Quantitative characterization and comparative study
  125. Inversion method of organic matter content of different types of soils in black soil area based on hyperspectral indices
  126. Detection of seepage zones in artificial levees: A case study at the Körös River, Hungary
  127. Tight sandstone fluid detection technology based on multi-wave seismic data
  128. Characteristics and control techniques of soft rock tunnel lining cracks in high geo-stress environments: Case study of Wushaoling tunnel group
  129. Influence of pore structure characteristics on the Permian Shan-1 reservoir in Longdong, Southwest Ordos Basin, China
  130. Study on sedimentary model of Shanxi Formation – Lower Shihezi Formation in Da 17 well area of Daniudi gas field, Ordos Basin
  131. Multi-scenario territorial spatial simulation and dynamic changes: A case study of Jilin Province in China from 1985 to 2030
  132. Review Articles
  133. Major ascidian species with negative impacts on bivalve aquaculture: Current knowledge and future research aims
  134. Prediction and assessment of meteorological drought in southwest China using long short-term memory model
  135. Communication
  136. Essential questions in earth and geosciences according to large language models
  137. Erratum
  138. Erratum to “Random forest and artificial neural network-based tsunami forests classification using data fusion of Sentinel-2 and Airbus Vision-1 satellites: A case study of Garhi Chandan, Pakistan”
  139. Special Issue: Natural Resources and Environmental Risks: Towards a Sustainable Future - Part I
  140. Spatial-temporal and trend analysis of traffic accidents in AP Vojvodina (North Serbia)
  141. Exploring environmental awareness, knowledge, and safety: A comparative study among students in Montenegro and North Macedonia
  142. Determinants influencing tourists’ willingness to visit Türkiye – Impact of earthquake hazards on Serbian visitors’ preferences
  143. Application of remote sensing in monitoring land degradation: A case study of Stanari municipality (Bosnia and Herzegovina)
  144. Optimizing agricultural land use: A GIS-based assessment of suitability in the Sana River Basin, Bosnia and Herzegovina
  145. Assessing risk-prone areas in the Kratovska Reka catchment (North Macedonia) by integrating advanced geospatial analytics and flash flood potential index
  146. Analysis of the intensity of erosive processes and state of vegetation cover in the zone of influence of the Kolubara Mining Basin
  147. GIS-based spatial modeling of landslide susceptibility using BWM-LSI: A case study – city of Smederevo (Serbia)
  148. Geospatial modeling of wildfire susceptibility on a national scale in Montenegro: A comparative evaluation of F-AHP and FR methodologies
  149. Geosite assessment as the first step for the development of canyoning activities in North Montenegro
  150. Urban geoheritage and degradation risk assessment of the Sokograd fortress (Sokobanja, Eastern Serbia)
  151. Multi-hazard modeling of erosion and landslide susceptibility at the national scale in the example of North Macedonia
  152. Understanding seismic hazard resilience in Montenegro: A qualitative analysis of community preparedness and response capabilities
  153. Forest soil CO2 emission in Quercus robur level II monitoring site
  154. Characterization of glomalin proteins in soil: A potential indicator of erosion intensity
  155. Power of Terroir: Case study of Grašac at the Fruška Gora wine region (North Serbia)
  156. Special Issue: Geospatial and Environmental Dynamics - Part I
  157. Qualitative insights into cultural heritage protection in Serbia: Addressing legal and institutional gaps for disaster risk resilience
https://doi.org/10.1515/geo-2022-0629
Keywords for this article
hydrocarbon phase; carbon isotopes; geochemical analysis; Ordovician; Tarim Basin
Creative Commons
BY 4.0

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  3. The research of common drought indexes for the application to the drought monitoring in the region of Jin Sha river
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  7. Zircon U–Pb ages of the Paleozoic volcaniclastic strata in the Junggar Basin, NW China
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  15. Differences in urban daytime and night block vitality based on mobile phone signaling data: A case study of Kunming’s urban district
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  17. Integrated geophysical approach for detection and size-geometry characterization of a multiscale karst system in carbonate units, semiarid Brazil
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  30. Classification and logging identification of reservoir space near the upper Ordovician pinch-out line in Tahe Oilfield
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  37. Vibration prediction with a method based on the absorption property of blast-induced seismic waves: A case study
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  39. Spatio-temporal analysis of the driving factors of urban land use expansion in China: A study of the Yangtze River Delta region
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  42. Using interpretative structure model and analytical network process for optimum site selection of airport locations in Delta Egypt
  43. Geochemistry of magnetite from Fe-skarn deposits along the central Loei Fold Belt, Thailand
  44. Functional typology of settlements in the Srem region, Serbia
  45. Hunger Games Search for the elucidation of gravity anomalies with application to geothermal energy investigations and volcanic activity studies
  46. Addressing incomplete tile phenomena in image tiling: Introducing the grid six-intersection model
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  54. Using fuzzy analytical hierarchy process for road transportation services management based on remote sensing and GIS technology
  55. Accumulation mechanism of multi-type unconventional oil and gas reservoirs in Northern China: Taking Hari Sag of the Yin’e Basin as an example
  56. TOC prediction of source rocks based on the convolutional neural network and logging curves – A case study of Pinghu Formation in Xihu Sag
  57. A method for fast detection of wind farms from remote sensing images using deep learning and geospatial analysis
  58. Spatial distribution and driving factors of karst rocky desertification in Southwest China based on GIS and geodetector
  59. Physicochemical and mineralogical composition studies of clays from Share and Tshonga areas, Northern Bida Basin, Nigeria: Implications for Geophagia
  60. Geochemical sedimentary records of eutrophication and environmental change in Chaohu Lake, East China
  61. Research progress of freeze–thaw rock using bibliometric analysis
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  64. Geological genesis and identification of high-porosity and low-permeability sandstones in the Cretaceous Bashkirchik Formation, northern Tarim Basin
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  67. Assessment of soil resources of agricultural landscapes in Turkestan region of the Republic of Kazakhstan based on agrochemical indexes
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  69. Petrogenetic relationship between plutonic and subvolcanic rocks in the Jurassic Shuikoushan complex, South China
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  75. Structural features and tectonic activity of the Weihe Fault, central China
  76. Application of the wavelet transform and Hilbert–Huang transform in stratigraphic sequence division of Jurassic Shaximiao Formation in Southwest Sichuan Basin
  77. Structural detachment influences the shale gas preservation in the Wufeng-Longmaxi Formation, Northern Guizhou Province
  78. Distribution law of Chang 7 Member tight oil in the western Ordos Basin based on geological, logging and numerical simulation techniques
  79. Evaluation of alteration in the geothermal province west of Cappadocia, Türkiye: Mineralogical, petrographical, geochemical, and remote sensing data
  80. Numerical modeling of site response at large strains with simplified nonlinear models: Application to Lotung seismic array
  81. Quantitative characterization of granite failure intensity under dynamic disturbance from energy standpoint
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  83. Rockfall mapping and susceptibility evaluation based on UAV high-resolution imagery and support vector machine method
  84. Statistical comparison analysis of different real-time kinematic methods for the development of photogrammetric products: CORS-RTK, CORS-RTK + PPK, RTK-DRTK2, and RTK + DRTK2 + GCP
  85. Hydrogeological mapping of fracture networks using earth observation data to improve rainfall–runoff modeling in arid mountains, Saudi Arabia
  86. Petrography and geochemistry of pegmatite and leucogranite of Ntega-Marangara area, Burundi, in relation to rare metal mineralisation
  87. Prediction of formation fracture pressure based on reinforcement learning and XGBoost
  88. Hazard zonation for potential earthquake-induced landslide in the eastern East Kunlun fault zone
  89. Monitoring water infiltration in multiple layers of sandstone coal mining model with cracks using ERT
  90. Study of the patterns of ice lake variation and the factors influencing these changes in the western Nyingchi area
  91. Productive conservation at the landslide prone area under the threat of rapid land cover changes
  92. Sedimentary processes and patterns in deposits corresponding to freshwater lake-facies of hyperpycnal flow – An experimental study based on flume depositional simulations
  93. Study on time-dependent injectability evaluation of mudstone considering the self-healing effect
  94. Detection of objects with diverse geometric shapes in GPR images using deep-learning methods
  95. Behavior of trace metals in sedimentary cores from marine and lacustrine environments in Algeria
  96. Spatiotemporal variation pattern and spatial coupling relationship between NDVI and LST in Mu Us Sandy Land
  97. Formation mechanism and oil-bearing properties of gravity flow sand body of Chang 63 sub-member of Yanchang Formation in Huaqing area, Ordos Basin
  98. Diagenesis of marine-continental transitional shale from the Upper Permian Longtan Formation in southern Sichuan Basin, China
  99. Vertical high-velocity structures and seismic activity in western Shandong Rise, China: Case study inspired by double-difference seismic tomography
  100. Spatial coupling relationship between metamorphic core complex and gold deposits: Constraints from geophysical electromagnetics
  101. Disparities in the geospatial allocation of public facilities from the perspective of living circles
  102. Research on spatial correlation structure of war heritage based on field theory. A case study of Jinzhai County, China
  103. Formation mechanisms of Qiaoba-Zhongdu Danxia landforms in southwestern Sichuan Province, China
  104. Magnetic data interpretation: Implication for structure and hydrocarbon potentiality at Delta Wadi Diit, Southeastern Egypt
  105. Deeply buried clastic rock diagenesis evolution mechanism of Dongdaohaizi sag in the center of Junggar fault basin, Northwest China
  106. Application of LS-RAPID to simulate the motion of two contrasting landslides triggered by earthquakes
  107. The new insight of tectonic setting in Sunda–Banda transition zone using tomography seismic. Case study: 7.1 M deep earthquake 29 August 2023
  108. The critical role of c and φ in ensuring stability: A study on rockfill dams
  109. Evidence of late quaternary activity of the Weining-Shuicheng Fault in Guizhou, China
  110. Extreme hydroclimatic events and response of vegetation in the eastern QTP since 10 ka
  111. Spatial–temporal effect of sea–land gradient on landscape pattern and ecological risk in the coastal zone: A case study of Dalian City
  112. Study on the influence mechanism of land use on carbon storage under multiple scenarios: A case study of Wenzhou
  113. A new method for identifying reservoir fluid properties based on well logging data: A case study from PL block of Bohai Bay Basin, North China
  114. Comparison between thermal models across the Middle Magdalena Valley, Eastern Cordillera, and Eastern Llanos basins in Colombia
  115. Mineralogical and elemental analysis of Kazakh coals from three mines: Preliminary insights from mode of occurrence to environmental impacts
  116. Chlorite-induced porosity evolution in multi-source tight sandstone reservoirs: A case study of the Shaximiao Formation in western Sichuan Basin
  117. Predicting stability factors for rotational failures in earth slopes and embankments using artificial intelligence techniques
  118. Origin of Late Cretaceous A-type granitoids in South China: Response to the rollback and retreat of the Paleo-Pacific plate
  119. Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China
  120. Geological characteristics of the Daduhe gold belt, western Sichuan, China: Implications for exploration
  121. Rock physics model for deep coal-bed methane reservoir based on equivalent medium theory: A case study of Carboniferous-Permian in Eastern Ordos Basin
  122. Enhancing the total-field magnetic anomaly using the normalized source strength
  123. Shear wave velocity profiling of Riyadh City, Saudi Arabia, utilizing the multi-channel analysis of surface waves method
  124. Effect of coal facies on pore structure heterogeneity of coal measures: Quantitative characterization and comparative study
  125. Inversion method of organic matter content of different types of soils in black soil area based on hyperspectral indices
  126. Detection of seepage zones in artificial levees: A case study at the Körös River, Hungary
  127. Tight sandstone fluid detection technology based on multi-wave seismic data
  128. Characteristics and control techniques of soft rock tunnel lining cracks in high geo-stress environments: Case study of Wushaoling tunnel group
  129. Influence of pore structure characteristics on the Permian Shan-1 reservoir in Longdong, Southwest Ordos Basin, China
  130. Study on sedimentary model of Shanxi Formation – Lower Shihezi Formation in Da 17 well area of Daniudi gas field, Ordos Basin
  131. Multi-scenario territorial spatial simulation and dynamic changes: A case study of Jilin Province in China from 1985 to 2030
  132. Review Articles
  133. Major ascidian species with negative impacts on bivalve aquaculture: Current knowledge and future research aims
  134. Prediction and assessment of meteorological drought in southwest China using long short-term memory model
  135. Communication
  136. Essential questions in earth and geosciences according to large language models
  137. Erratum
  138. Erratum to “Random forest and artificial neural network-based tsunami forests classification using data fusion of Sentinel-2 and Airbus Vision-1 satellites: A case study of Garhi Chandan, Pakistan”
  139. Special Issue: Natural Resources and Environmental Risks: Towards a Sustainable Future - Part I
  140. Spatial-temporal and trend analysis of traffic accidents in AP Vojvodina (North Serbia)
  141. Exploring environmental awareness, knowledge, and safety: A comparative study among students in Montenegro and North Macedonia
  142. Determinants influencing tourists’ willingness to visit Türkiye – Impact of earthquake hazards on Serbian visitors’ preferences
  143. Application of remote sensing in monitoring land degradation: A case study of Stanari municipality (Bosnia and Herzegovina)
  144. Optimizing agricultural land use: A GIS-based assessment of suitability in the Sana River Basin, Bosnia and Herzegovina
  145. Assessing risk-prone areas in the Kratovska Reka catchment (North Macedonia) by integrating advanced geospatial analytics and flash flood potential index
  146. Analysis of the intensity of erosive processes and state of vegetation cover in the zone of influence of the Kolubara Mining Basin
  147. GIS-based spatial modeling of landslide susceptibility using BWM-LSI: A case study – city of Smederevo (Serbia)
  148. Geospatial modeling of wildfire susceptibility on a national scale in Montenegro: A comparative evaluation of F-AHP and FR methodologies
  149. Geosite assessment as the first step for the development of canyoning activities in North Montenegro
  150. Urban geoheritage and degradation risk assessment of the Sokograd fortress (Sokobanja, Eastern Serbia)
  151. Multi-hazard modeling of erosion and landslide susceptibility at the national scale in the example of North Macedonia
  152. Understanding seismic hazard resilience in Montenegro: A qualitative analysis of community preparedness and response capabilities
  153. Forest soil CO2 emission in Quercus robur level II monitoring site
  154. Characterization of glomalin proteins in soil: A potential indicator of erosion intensity
  155. Power of Terroir: Case study of Grašac at the Fruška Gora wine region (North Serbia)
  156. Special Issue: Geospatial and Environmental Dynamics - Part I
  157. Qualitative insights into cultural heritage protection in Serbia: Addressing legal and institutional gaps for disaster risk resilience
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