Volume 5, Issue 2

Objective: This study reconsiders the problem of wellbore storage and skin distortion for the transient flow of non-Newtonian power law fluids through porous media injection tests. A better method of pressure analysis data from such tests is derived which corrects some mathematical inconsistencies present in the literature. Methodology: Because the problem being considered results in non-linear boundary conditions, Laplace transform and other solution devices cannot be used to obtain analytical solutions. Hence the finite element method was chosen to solve the problem numerically. This study uses the finite element method to generate type curves for the partial differential equation resulting from the flow of non-Newtonian power law fluids through porous media and the associated nonlinear boundary condition that accounts for the wellbore storage distortion and skin effects. Results and conclusions: The mathematical reasons for the inaccuracies in the previously presented solutions are described. A corrected step by step analysis procedure for obtaining the formation properties, skin factor and the associated wellbore storage constant is described using type curves. The application is augmented by one real field test data, and three simulated test data examples.

The maltene component of Nigerian crude oils was analyzed with a view to ascertaining its characteristics and assess the environmental health implications of its uses. Crude oils collected from 3 different oil fields (Belema, Imo and Eket) were deasphaltened using n-pentane, analyzed using Inductively Coupled Plasma Optical Emission Spectrometer (model Varian 71 O-ES ICP) for the elemental content, a Perkin Elmer Model spectrum 100 Fourier Transform Infrared Spectrometer (FTIR) to identify the organics, while Gamma counting equipment consisting of a calibrated Canberra vertical high-purity germanium (HPGe) coaxial detector was used for radionuclide content measurement. Chromium, Cu, Fe, Mn, Ni, S, V and Zn levels were determined and were lower in the maltene than the crude oil. This was confirmed by their T-test values. Strong and positive correlations (R 2 = 0.50) existed between the maltene and crude oil. Elemental clustering result indicated two major groups – (Cu, Mn, Cr, V, Zn, Fe and Ni) and (S) and was corroborated by Principal component analysis result. The FT-IR analysis results peaks indicated the presence of mixtures of alkanes, aromatic rings, ketones, organic sulphoxides, amines and heteroaromatic compounds. The radionuclides identified belonged to the decay series headed by 238 U and 232 Th as well as the non-series 40 K. The maltene component was found to contain permissible levels of the radionuclides with mean activity values of 18.13±2.01, 2.31±0.66 and 4.35±2.71 Bq/kg respectively. The absorbed dose rate due to the radionuclides in the samples gave an average value of 4.02 nGy/h which was lower than the UNSCEAR standard (60 nGy/h). The levels of radiological hazard to the environment and threat to human health from gamma radiation by the maltene are low, as the hazard indices are below the recommended standards. However, long exposure to the harmful smoke generated from burning of maltene may pose an intrinsic health hazard.

Recent drilling and hydraulic fracturing activities in the Utica-Point Pleasant shale play have recorded true vertical depth of over 13,500 feet. Drilling wells at this depth is very costly and challenging. With the current commodity pricing, drilling in such conditions becomes unaffordable. One immediate solution to the current low energy prices is optimizing well spacing to enhance hydrocarbon recovery and, thus, the commercial feasibility of the project. Horizontal well spacing constitutes a fundamental parameter for the success of a shale-drilling venture. Determining the optimum horizontal well spacing in shale reservoirs represents a challenging task because of the complexity of controlling factors. These factors can be categorized into three groups: geological, engineering, and economic. Geological modeling and reservoir simulation are the standard tools utilized in the industry to integrate these controlling factors. In this study, we employed these tools to perform sensitivity analysis of reservoir characteristics and future production optimization for a deep drilling case study in the Utica-Point Pleasant formations. We sought to find the optimum horizontal well spacing scenario as well as hydraulic fracturing design, in order to attain the highest net present value for 50 years of gas production. Our reservoir model represented a portion of Utica-Point Pleasant formations at the depth of 13,000 feet and the dry gas window. A commercial reservoir simulator was coupled with an optimization algorithm to reach the best solution with a minimum simulation cost. Although the outcome of our study is subjective to the chosen asset, the workflow provides a good example of horizontal well spacing and hydraulic fracturing design optimization.

Various crude oil classifications have been proposed by geochemists and petroleum refiners. Geologists and geochemists are more interested in identifying and characterizing the crude oils, to relate them to source rocks and to measure their grade of evolution using advanced geochemical technologies. Carbonate source rocks studied are organically very rich, containing oil-prone kerogen capable of generating significant quantities of hydrocarbons. Tertiary and Cretaceous oils studied are of carbonate origin and classified as aromatic-intermediate class. Most of the Tertiary oils studied are severely biodegraded while those from Cretaceous reservoirs are non-degraded. Almost all the oils investigated show the following biomarker parameters, characteristic of oils derived from carbonate source rocks deposited in a marine environment under reducing conditions: • Predominance of phytane over pristane, (pristane/phytane ratio below 1), • Predominance of C 29 - norhopane over C 30 -hopane,(C 29 /C 30 hopanes above 1), • High C 35 -homohopane index, • Low sterane/αβ-hopanes ratio, and • High dibenzothiophene/phenanthrene ratio (mostly above 1).