查看更多>>摘要：Shale oil is a promising alternative unconventional energy to conventional fossil fuels. Its exploration and production are critical to improve the present energy consumption pattern and mitigate dependence on foreign energy. Particularly, the key factors determining shale oil occurrence are the most important issues for its production. In this review, we briefly summarize the dominant space of shale reservoirs for accommodating shale oil. We also provide a comprehensive overview of occurrence state of shale oil and analyze in detail the factors such as pore size, organic matter, inorganic minerals of oil-bearing shale and reservoir burial depth. Finally, we discuss the existing challenges and perspectives on how to explore and address occurrence of shale oil in practical shale reservoirs to promote the future shale oil production. An accurate description of shale oil occurrence through viable research methodology, advanced instrument characterization and theoretical simulation is crucial for estimating shale oil reserves, optimizing and enhancing shale oil production.
查看更多>>摘要：Accurate determination of coalbed methane (CBM) content can not only prevent and control coal and gas outburst disasters in mines, but also facilitate the prediction of coal seam methane resource reserves, which is significant for injecting carbon dioxide to enhance CBM recovery. The freezing core sampling technique proposed in recent years for accurate determination of the CBM content has faced temperature-pressure coupling effects on gas desorption in coalin a low-variable temperature environment. In this paper, we utilized a self-developed high-low temperature alternating adsorption-desorption experimental device to study the gas desorption process in coal under temperature-pressure coupling conditions in a low-variable temperature environment. The experimental results show that the main promotion and inhibition effects of temperature on the gas adsorption and desorption in coal in a low-temperature environment were consistent with those in an ambient temperature environment, i.e., the decrease of temperature promoted coal gas adsorption, while the increase of the temperature promoted coal gas desorption. It is found that throughout the temperature change process (TCP), there existed a 'pseudo-desorption' phenomenon, and the cumulative desorption amount showed a consecutive risingdeclining-rising trend and finally stabilized. The whole process can be regarded as consisting of a main desorption process and a retrograde desorption process. In the main desorption process with the same TCP, the cumulative desorption amount and initial desorption rate increased with the increase of initial equilibrium pressure. In the retrograde desorption process, there existed a peak retrograde desorption rate, and the staged retrograde desorption amount conformed to the linear decrease law. A comprehensive analysis of the temperature-pressure coupling effect on gas desorption throughout the TCP was conducted. Thus, we proposed some considerations and precautions for the configuration and supply monitoring of the cold source in the process of the measurement of CBM content using the freeze-coring method.
查看更多>>摘要：As the need for reaching fuel reserves at greater depths increases, scientists have been exploring and developing the technology required to efficiently drill rock at highly pressured environments over the past 30 years. However, there are still gaps in the understanding of the physical phenomena involved. One of the basic problems has to deal with is the rock-bit interaction during the rock breaking process. In order to evaluate the drilling efficiency and bit wear in ultra-deep formation, parameters of ultra-deep drilling simulator were calculated based on the similarity principle, followed by the design and manufacture of ultra-deep rock-bit interaction simulator. Considering the influence of formation differential stress change on bit footage, the effects of weight on bit (WOB) and rotary speed on torque, bit wear and rate of penetration (ROP) were studied firstly under the conditions of in-situ stress of 240 MPa and temperature of 200 degrees C. The results of similar simulation test show that under the conditions of in-situ stress of 240 MPa and temperature of 200 degrees C, WOB at 8.0-8.5 kN and rotary speed at 180-240 rad are the optimal drilling parameters. Correspondingly, the on-site WOB at 128-136 kN and rotary speed at 45-60 rad are the optimal mechanical parameters on the drilling site, which can lead to high cutting efficiency and low wear rate of the bit. The horizontal differential stress has a significant impact on the ROP. With the increase of the stress difference in the horizontal direction, the footage efficiency decreases obviously, and the decrease degree is about 87.5%. The test results will help optimize rock breaking tools and drilling parameters to improve rock breaking efficiency.
Hassan, Yarima MudassirGuan, Beh HoeChuan, Lee KeanHalilu, Ahmed...
9页
查看更多>>摘要：Metal oxide nanoparticles (NPs) are useful in modifying two critical mechanisms for enhanced oil recovery (EOR): interfacial tension (IFT) and rock surface wettability. Regrettably, due to the harsh reservoir conditions, perpetual agglomeration of the NPs is prevalent in the reservoir. Consequently, performance of NPs is hindered particularly as they are trapped in the rock pores. To upgrade this issue, injecting NPs in form of nanofluids under the influence of an electromagnetic (EM) field was discovered recently. The EM driven approach of tuning the EOR technique is significant to improve the NPs mobility in the reservoir. In this present work, a new ZnOFe2O3/SiO2 nano hybrid was synthesized and characterized for the preparation of ZnOFe2O3/SiO2-basednanofluid. The single-phase ZnOFe2O3/SiO2 nanofluid incorporated both magnetic attribute with similar to 19.371 emu/g magnetization and dielectric properties with up to 0.523 mu F capacitance. These properties were found to energize electrification of the ZnOFe2O3/SiO2 nanofluid during EM driven field exposure for enhance IFT and wettability analysis. In essence, the electrical conductivity of the ZnOFe2O3/SiO2 nanofluid initiated some disruption along the oil/nanofluid interface under EM field inducement. Particularly, this influenced crude oil deformation and cause the IFT to reduce from 17.39 up to 1.27 mN/m. Considering the change in wettability, the free charges of the NPs were found to be attracted by the electric field at the boundary of oil/nanofluids/sandstone which produced internal agitation that enhanced the spread of the ZnOFe2O3/SiO2 nanofluid on the sandstone. In verification, the contact angle decreased to the level of 72 degrees from 141 degrees. Hence, for the first time, ZnOFe2O3/SiO2 nanofluid have shown a positive impact on IFT and wettability. These results are significant by providing information for enhancing oil recovery and oil displacement using electromagnetic field inducement.
查看更多>>摘要：Directional electromagnetic (EM) logging while drilling (LWD) tools have been widely used in well navigation for its azimuthal sensitivity and deep depth of detection (DOD). In this paper, an efficient 2.5D finite difference method (FDM) associated with non-uniform meshes and parallel computing is applied to evaluate the formation structure effects on the EM tools. The algorithm is validated by comparing the numerical results with analytical/ 3D FEM solutions in 1D and 2D heterogeneous formations. The effects of complex formation structures, e.g., faults, curved boundaries and unconformities are further analyzed by using the FDM code. Two new curves GPF and GAF are defined by subtracting the geosignals in a 1D layered model from that of a 2D fault model to quantitatively evaluate the fault detection capability. Numerical results show that the EM tools are sensitive to faults, especially the low dip angle ones. The depth of detection to fault reduces from 10.6 m to 4.0 m as the dip angle increases from 15 degrees to 45 degrees. Numerical cases also indicate that the EM tool responses can be affected by the sharp slope curved boundaries, while the effects of the gentle slope (<0.2) boundaries can be neglected. Furthermore, examples in unconformity and oil/water contact formation demonstrate that a 2D structure can affect the signal amplitude significantly.
查看更多>>摘要：We provide novel evidence of two different types of volatility-patterns of oil spot prices that are generated depending on which is the predominant trigger: a) spikes of volatility (which are highly erratic) are produced during periods of supply/demand crises of oil disruptions (such as the 1990/91 First-Gulf-War, 2001 US-terrorist attack, the oil conflict of Saudi-Arabia with the US in 2014/16 and with Russia in 2020-together with the Covid-19 impact-); while b) periods where economic/financial/stock market crises are the predominant trigger (such as the 1997/98 Asian and 2008/09 Global-Financial Crises and the 2017/19 oil conflicts including the 2018 stock market crisis) are associated to higher volatility persistence. Our results are very relevant since oil markets in the coming months/years are very likely to have a very high degree of uncertainty, and knowledge of the type of volatility that is generated under each of the different triggers and how it affects oil markets is very relevant for investors, speculators and policy makers.
查看更多>>摘要：Physicochemical structure characteristics and its effects on the heat of gas adsorption are the foundation for coalbed methane (CBM) development. Herein, this paper selected different rank coals before and after acid treatments to analyze the relationship among nanopore structure, chemical functional groups and the heat of gas adsorption through low-temperature N-2 adsorption, Fourier transform infrared spectroscopy (FTIR) and calorimetric tests. This enabled us to explore the effect of acid solvents on nanopore structure and functional groups, and finally reveal a coupling mechanism between physicochemical structure and gas adsorption. Results showed that the specific surface area of Brunauer-Emmett-Teller model (BET-SSA) and pore volume of Barret-JoynerHalenda model (BJH-PV) decrease first and subsequently increase with increasing coal evolution before and after acid treatments. However, both pore structure parameters and fractal dimension show a decrease or an increase at different degrees under pore expansion and increase effects. On the other hand, after acid treatments, aliphatic structures evidently decrease and aromatic structures relatively increase. For oxygen-containing functional groups affected by ester hydrolysis and Fourier reaction, more carboxyl and hydroxyl groups appear but ether groups reduce. This suggests that acid treatment is actually accompanied by more physicochemical changes. Then, according to its physicochemical response, less aliphatic structures and more aromatic structures significantly contribute to appear more micropores. However, a non-significant effect of aliphatic structure on gas adsorption is observed, while micropores, aromatic structure and oxygen-containing groups give a positive effect on gas adsorption.
查看更多>>摘要：Two new, non-intrusive reduced order frameworks for the faster modelling of gas reservoirs with time-varying production are presented and compared. The first method is an extension of a method using proper orthogonal decomposition (POD) in conjunction with radial basis functions (RBFs) that has previously been applied to predicting the performance of oil reservoirs undergoing a constant rate waterflood. The second method uses an autoencoder rather than RBFs to estimate the flow dynamics (pressure distributions) in hyperspace for unseen cases. Both frameworks are 'trained' using sample outputs from off-line, commercial reservoir simulations of a realistic heterogeneous gas reservoir with time-varying production controls typical of gas field operation. These controls include time-varying rate and switching between bottom hole pressure and rate control as well as cases where wells get shut-in. Both POD-based models produce reasonable forecasts of the reservoir performance for new unseen/prediction cases and are between 0.22 and 300 times faster than conventional simulation, including the time spent performing training simulations with conventional simulation solutions. The POD-RBF models are more accurate and consistent with reference commercial simulation outputs than the POD-AE models. In addition, the POD-AE models required more trial and error to set up as the number of hidden layers needed, depends on the particular scenario being modelled. There is no ab initio way of predicting the best number of layers for a given type of scenario. This makes them less suitable for practical application by reservoir engineers. Overall the POD-RBF framework is the most robust and accurate of the two methods.
查看更多>>摘要：Nuclear magnetic resonance (NMR) relaxometry and high-pressure mercury intrusion (HPMI) are substantially utilized techniques to characterize the inherent heterogeneity of reservoirs. Bioturbation is one such type of microscale heterogeneity that provides challenges to optimal recovery planning and volumetric estimation of hydrocarbon reserves. A comprehensive approach is determined by acknowledging the applicability and limitation of each method. Due to the wide variation in petrophysical properties resulting from the effect of bioturbation, the sample size ranges from mm to cm; hence, a proper methodology needs to be formulated. The present study extends the available method of generating pseudo Pc curves from NMR studies to analyze the effect of multiscale bioturbation heterogeneity. The samples were chosen from two different classes on a bioturbation scale referred to as the bioturbation index (BI) ranging from 0 to 6, 0 being 0% bioturbation and 6 meaning 100% bioturbation. The results indicate that lower BI samples had unimodal behavior, while the higher BI sample had bimodal characteristics in pore network distribution. Increased anisotropy was evident in the higher BI samples, and the HPMI study revealed a contrasting nature of pore throat connectivity with a lower threshold and displacement pressure and an increased median throat diameter in the bioturbated part compared with the nonbioturbated. The bioturbated volume essentially had better and less tortuous pore throat connectivity. The effects of bioturbation were identifiable in a core-scale study using NMR. The bimodal characteristic behavior with two distinct pore throat classes with the larger throat class as dominant claims the bioturbation-assisted pore throat connectivity established in them. The purpose of the paper is to investigate pore throat distribution in bioturbated or heterogeneous reservoirs by integrating NMR and HPMI methods. This study proposes a method that can correlate NMR responses from logging into pore throat distribution in bioturbated zones of the reservoir.
查看更多>>摘要：This paper expounds on the process of deformation and seepage field change of single coarse fracture under normal stress and puts forward a numerical simulation framework based on fluid-structure coupling method to reasonably link contact deformation of fracture surface with seepage field change. The geometric model of a three-dimensional rough single fracture surface with controllable JRC is established based on the random surface generation method. The numerical test model of radiation flow of single fracture in rough rock is constructed, which is consistent with the laboratory test. Through carrying out numerical simulation tests of different JRC and normal stress conditions, this paper discusses the phenomenon and intrinsic nature of the influence of JRC on fracture seepage characteristics. The increase in eddy current intensity and eddy current area ratio is the inherent characteristics of the seepage field characteristics after JRC increases. With the rise of energy loss, the macroscopic seepage flow decreases. In addition, with the advantage of the fluid-structure interaction method, the fracture deformation characteristics under different normal stresses are reflected by the ratio of the contact area. The correlation among fracture surface deformation, velocity vector, and seepage pressure are analyzed. Finally, the cubic polynomial correlation between gap width ratio and contact area ratio is established and verified. It is of positive significance to quantify the influence of coarse single fracture contact ratio on deformation-seepage coupling characteristics under normal stress.
NSTL
Elsevier