查看更多>>摘要：Fractured-vuggy reservoirs have extremely complex reservoir characteristics, leading to a large amount of remaining oil not being recovered after water flooding. In order to solve the problem of the low recovery in fractured-vuggy reservoirs, we utilized 3D printing technology to fabricate two-dimensional and three-dimensional experimental models based on the typical reservoir structure. A series of experiments with different models on improving water flooding is conducted to study the production improvement effect. The difference in oil-water distribution or oil saturation distribution before and after improved water flooding is also compared, and the mechanism is analyzed. The results show that the oil-water gravity differentiation is the most critical factor affecting the remaining oil distribution, and changing the injected pressure or its propagation direction is the root of improving water injection. Reversing injection-production wells, increasing injection strength, water plugging, and cyclic water injection can effectively increase the sweeping scope or displacement efficiency. The attic oil, residual oil in filling medium, bypass remaining oil, and water cone remaining oil can be produced by one or more improving water flooding methods. This paper provides effective measures and mechanisms for the efficient and rapid development of fractured-vuggy reservoirs.
查看更多>>摘要：In this study, the potential of geostatistical(GS) methods in estimating petrophysical logs (Vp sonic logs here), independently and in combination with empirical petrophysical relations (PRs) was evaluated. Moreover, the efficiencies of these two methods were compared with each other and with that of a simple PR which was Gardner's Relation (GR) here. The GS-GR method combines GS with GR to acquire a higher accuracy beyond a simple geostatistical prediction which is already expected to have a higher accuracy than that of GR. For this purpose, two different data-sets from Iranian hydrocarbon reservoirs were used. In the first case, three adjacent wells from a reservoir consisting dominantly of carbonate rocks with a rather high hydrocarbon saturation were used. To evaluate the generalizability of the propsed techniques, they were assessed on another data-set from a well in a different hydrocarbon reservoir, mainly consisting of the sandstone-carbonate lithology (with a lower hydrocarbon saturation). To estimate the sonic logs of compressional wave velocities (Vp), Gardner's Relation (GR) was implemented here using the existing density logs in the wells. Then, several univariate and bivariate geostatistical methods (the latter combined with GR) were used to assess the capabilities of the GS and the combined GS-GR methods. To evaluate the efficiencies of the GS and GS-GR methods, Cross-Validation (CV) and Jackknife (JK) techniques were employed here. Based on the CV and JK assessments, for the both reservoirs, the GS and methods especially those combined with GR (i.e. GS-GR), generally provided considerably higher accuracies than those of the GR method. GS-GR framework facilitated the integration of the secondary variable of density (p) here to further increase the accuracy of Vp estimations. Hence, geostatistics (GS), especially combined with the petrophysical relations (GS-PR) could be suggested as an accurate and functional tool in estimating the missing logs, having some logs from the same or the other neighboring wells.
查看更多>>摘要：Over the past few decades, foam flooding has emerged as a decent option for diverting flow from high permeable layers toward dense layers. Here, a visualization study of the conventional foam and polymer enhanced foam (PEF) behavior in the heterogeneous porous media is presented and the PEF performance in horizontal and vertical injection modes is evaluated. A heterogeneous porous medium made of transparent plexiglass packed with two different layers of glass beads to attain a heterogeneity ratio of 4:1 was used in various flooding experiments. The results of dynamic tests in the absence of oil showed that the presence of polymer in the foaming solution increases the flow resistance of foam in the porous medium and prevents foam fingering in the low-permeable layers. Horizontal oil displacement experiments showed that PEF flooding has an excellent plugging capacity and oil recovery increased by 72.5% of water flooded residual oil (S*_(or)), which was 19.1% more than that of conventional foam injection. Comparison between vertical and horizontal PEF flooding proved that due to the positive gravity effect, the performance of PEF in vertical mode was better than that in horizontal mode, and the recovery factor increased to 78.3% water-flooded residual oil.
Musa O. AwoyemiSesan C. FaladeAugustine B. Arogundade
12页
查看更多>>摘要：This study analysed high-resolution aeromagnetic data over part of Chad Basin, Nigeria to determine the implications of geological structures and heat flow on the geothermal and hydrocarbon potential of the basin. Curie Point Depth (CPD) analysis, Curvature analysis and Source Parameter Imaging (SPI) were applied in this study. The estimated CPD and heat flow range from 11 to 19 km and from 75 to 125 mW/m2 respectively. The geological structures in the area predominantly trend in the E-W direction, followed by the ENE-WSW direction. Other prominent structural trends include NE-SW and WNW-ESE. The depths to the magnetic sources range from about 0.1 km to over 5 km. A large number of shallow-seated magnetic structures, believed to be intra-sedimentary intrusive bodies, were mapped in the southern and northwestern parts of the study area. The estimated heat flow in Chungul Buturi and Gumsa areas was found to be sufficient for the economic exploitation of geothermal energy. The results of this study showed that the basin is thermally matured for hydrocarbon generation. However, high magnitudes of heat flow and the presence of a large number of intrusive bodies in parts of the basin might have been the reason behind the unsuccessful attempts to find hydrocarbon in commercial quantities in the basin. The results also showed that the basin has a higher potential for gas accumulation than oil. Future exploration for commercial hydrocarbon accumulation in the basin may be successful if the exploration sites are narrowed down to the regions where moderate heat flow, high sedimentary thicknesses with few shallow seated magnetic sources (intrusives), and elongated geological structures were mapped in this study.
查看更多>>摘要：Initializations of the petrophysical parameters significantly affect the results of reactive transport simulations on unstable dissolution fronts. As the phenomenon arises from the inherent heterogeneity of the rocks, heterogenous initialization of the petrophysical fields is needed to model such a phenomenon. While modeling of unstable dissolution fronts has been extensively studied in the past, the geostatistical information required to initialize the heterogeneous petrophysical fields is usually assumed and still missing. The objective of this paper is to acquire such information for Indiana limestones on a core-scale. This is done by combining high resolution tomography with pore scale calculations to determine: i) the rock minimum representative volume (REV), ii) the frequency distributions of the petrophysical parameters, namely; porosity, permeability, and reactive surface area, iii) the relationships between the petrophysical parameters, and iv) the rock spatial correlation model and lengths. The results obtained should help reduce the uncertainties associated with petrophysical initialization of core-scale reactive transport simulations of carbonate rocks in general, and Indiana limestones in particular.
Intisar K. Al-BusaidiRashid S. Al-MaamariDawoud Al Mahrouqi
13页
查看更多>>摘要：In recent years, there has been a growing interest in the petroleum industry to improve the ultimate oil recovery method by using low-salinity polymer flooding (LSPF) with the synergistic effect by combining polymer and low-salinity water injection. Although numerous research studies have focused on the technical and economic benefits of low salinity polymer (LSP), to the best of our knowledge, crude oil/brine/rock (COBR) interactions in LSP did not receive enough attention due to the complexity of the interactions between brine, polymer, crude oil, and the rock surface. Therefore, this study aimed to investigate the impact of polymer on COBR interactions with different brine chemistry and improve the understanding of active mechanisms of LSPF. Partially hydrolyzed polyacrylamide (HPAM) polymer, Boise rock, a crude oil sample from an Omani oil field, and several brine solutions were used in the study. Zeta potential and pH measurements were performed to examine the role of polymer on electrical properties of brine/rock and oil/brine interfaces. In addition, rheological properties of the polymer were investigated at different salinity and brine compositions. Changes in Boise rock surface charge through zeta potential measurements were investigated in the absence and presence of polymer. pH and rheology measurements for equilibrated brines with and without polymer and zeta potential of crude oil/equilibrated brine were performed. The results revealed that the addition of polymer to the brine not only increased the viscosity, but also affected the electrical charge at crude oil/brine/rock (COBR) interfaces and triggered pH increase of the brine. The impact of polymer on COBR interactions is mainly controlled by the water chemistry. In the absence of ions, polymer molecules did not affect the charge of COBR interfaces, while in the presence of ions, at different compositions and concentrations, the charge of COBR interfaces changed to become more negative. Thus, the presence of polymer in brine increases the electrostatic repulsion between crude oil/brine and brine/rock interfaces, increases electrical double layer (EDL) thickness, and makes the water film more stable. A direct relationship between the viscosity and zeta potential of the polymer solutions was observed at different brine chemistry. Moreover, the presence of polymer at different brine chemistry resulted in an increase in pH of the aqueous phase. This could in turn reduce the adsorption of polar organic acids from crude oil. Therefore, in addition to the reduction of the water-oil mobility ratio, polymer molecules could contribute to an increase in the repulsion forces between COBR interfaces and an increase in the pH of the aqueous solution.
查看更多>>摘要：The choice of particle calculation time step in CFD-DEM (Computational Fluid Dynamics and Discrete Element Method) coupling calculation affects the accuracy and efficiency of particle collision calculation. In this paper, interpolation algorithm is introduced to weighted average the velocities of particles before and after collision. According to elastic theory, particle collision force is calculated and dynamic equation is solved. The initial value of the velocity was corrected by the velocity convergence criterion and the number of iterations was automatically adjusted. A high-efficiency and high-precision reinforced hard-ball model was proposed that is not affected by the calculation time step and does not require a detailed description of the collision process. In the case of collision of two particles with uniform and variable speed, the calculation error was less than 4%, and the calculation efficiency was increased by 36.3% and 36.8%. Pressure loss experiment showed that the model can accurately calculate the pressure loss. Analysis of the flow characteristics of the T-tube showed that increase in the flow rate and sand ratio, increased the density of the collision force distribution, increased the diameter ratio, significantly decreased the local collision and accumulation phenomenon, and resulted in more uniform collision force distribution.
查看更多>>摘要：Water jet drilling is considered a possible method used during the development of underground unconventional natural gas. Meanwhile, the fracture mechanisms of rock subjected to various in-situ stresses may differ significantly. Thus, laboratory experiments are conducted in this paper using the new jet testing system for the deep reservoir to simulate the drilling process of a water jet in the deep reservoir. The breakage mechanisms of rock are examined using the three-dimensional (3D) reconstruction visualization models of damage distributions, surface morphology. and micro-structural analysis on the influenced zone. The results revealed the dependence of two typical breakage characteristics on the stress state of the tested rock. When the samples were subjected to stress in the triaxial cell, the range of the hole was considerably reduced. Besides, as the horizontal stress difference was increased by 6 MPa, the diameter and depth of the erosion holes increase by 60% and 38.6% respectively. Moreover, the results of the scanning electron microscopy (SEM) showed that the fracturing of the hole wall was mostly caused by tensile failure generated by a water wedge that was easily controlled by high in-situ stress. The in-situ stress state of the reservoir significantly affected the pore size distribution and porosity. The increase of stress inhibited the increase of porosity around the hole. The porosity reaches 6.1% when the stress difference is 6 MPa, which increases by 135%. These results were anticipated to be used as a guide for the utilization of unconventional natural gas in deep reservoirs with complex stress.
查看更多>>摘要：Waste glass powder (WGP), as a kind of silicon-rich material, is used to replace 40 wt% oil well cement to inhibit the strength retrogression of hardened cement pastes (HCPs) at high temperature and high pressure (HTHP). The mechanical properties and microstructure of HCPs containing waste glass powder (WGP) of different particle sizes were studied. The results showed that HCPs modified by WGP exhibited greater compressive strength than those modified by silica flour (SF) at 80 °C × 0.1 MPa, due to the high activity of amorphous SiO2 in WGP. Compared with neat pastes, the incorporation of 325-mesh WGP or 1000-mesh WGP could effectively improve the compressive strength of HCPs at 260 °C × 21 MPa. Microscopic results indicated that the crystalline phases were tobermorite and xonotlite, providing great mechanical properties at HTHP, and xonotlite existed steadily after long-term curing. Mercury intrusion porosimetry results showed that, compared with neat pastes, incorporation of WGP improved the pore structure by stabilizing the total porosity of the cement. Magnesium participated in the transformation of xonotlite phase and change its microstructure. This paper provides a new way to recycle WGP and reduce the carbon dioxide generated in the production of cement.
查看更多>>摘要：Well construction operation is a crucial process that relies on the success of cementing job. Cementing failure could lead to catastrophic aftermaths and huge capital loss to the exploration and production (E&P) companies. In recent years, nanotechnology application in the petroleum industry has increased due to favorable results and compatibility with different E&P activities. Particularly for well-cementing operations, nanomaterials have been evaluated to understand the mechanism, performance, and economic viability. In this review, a brief introduction of nanotechnology, including the preparation and properties of nanomaterials is illustrated. Applications of nanoparticles in the oil and gas industry are also depicted to highlight the potential uses of nanomaterials in cementing. The effects of nanomaterials on different cement properties like density, viscosity, fluid loss, thickening time, and mechanical properties are discussed. The mechanisms of alteration of cement properties upon the addition of nanomaterials are depicted. Nanomaterials such as SiO2, MgO, TiO2, Fe2O3, Al2O3, and graphene-oxide have been used as potential cement additives for the improvement of cement properties. This review also sheds light on critical facts like optimal concentration and size of nanomaterials; inclusion of binary and ternary system-nanomaterials in cementing. Furthermore, it discusses the recent advancements, prospects, challenges, and economic viability of nanomaterials in well cementing. However, a lack of scientific rigour in the application of these nanomaterials has been observed. It is expected that the current review will help the newxomers in this research field to gain a quick idea about the development of the field and its way forward.
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