查看更多>>摘要：The computational cost of simulation on fine-scale reservoir models can be prohibitively expensive. While upscaling typically helps in reducing cost, it also results in a reduction in accuracy. Two-scale approaches such as dual mesh methods (DMM) have been developed over time in an attempt to reduce simulation cost while maintaining near fine-scale levels of accuracy and resolution. While these two-scale methods can be very effective in improving accuracy, they can be quite expensive as well. This paper presents two multimesh methods, namely, the Triple Mesh Method (TMM) and the Extended Triple Mesh Method (ETMM). Both methods involve introducing a third grid at an intermediate scale between the coarse and fine scales. These involve two levels of upscaling of the grid properties and two levels of downscaling the solutions to the flow equation. TMM involves two successive local downscaling steps of the flow solution from the coarsest to the finest mesh. ETMM on the other hand involves two successive extended local downscaling steps of the flow solution from the coarsest to the finest mesh. Each downscaling step in ETMM involves the application of 'Directional Oversampling' first introduced in the extended dual mesh method EDMM. These two methods along with DMM and EDMM methods were tested on different waterflooding problems and results compared with the coarse-scale and fine-scale solutions. The results show both ETMM and TMM to be effective in error reduction and also more cost effective than their respective dual mesh alternatives.
查看更多>>摘要：Tidal sand ridges are the most typical and extensive products of tidal processes and the large-scale layered structures that occur in the coastal area. Although there are abundant sand-riched reservoirs developed in tidal sand ridges, surprising that few people can intuitively identify the distribution in ancient strata. By comparing the seismic microfacies and seismic Root Mean Square Amplitude attribute of high-precision 3-D seismic data, we summarized a new method to identify and describe their superposition and plane distribution. Application examples of the Pingbei Slope Belt in the East China Sea Shelf Basin show the detailed analysis process and the results show that 6 sets of tidal sand ridges have been identified in three intervals of LST, TST, and HST, 5 sets of sand ridges with the same extension direction (342-358 degrees) in LST and HST intervals are obviously affected by tides. This method and application example provides a new meticulous process for tidal sand ridges identification according to the superimposition relationship of seismic microfacies and the plane extension direction of the Root Mean Square Amplitude attribute. The seismic microfacies of it is very easy to be distinguished compared to that of other similar sediments and can accomplish the spatial morphology and parameters characterization of tidal sand ridges in ancient sedimentary strata which buried several kilometers depth in a large-scale area. This method is suitable for most sedimentary basins with tidal background, just need the aid of high-precision 3-D seismic data, and provides practical guidance for the petroleum exploration related to sandstone.
查看更多>>摘要：As an economic and efficient method, asphaltene dispersants are widely used to inhibit the precipitation of asphaltenes in the crude oil tank. In this study, a series of multi-alkylated aromatic amides (MAA) amphiphiles containing benzene rings and a different number of alkyl side chains were synthesized and evaluated as asphaltene dispersants for the Saudi crude oil. After adding 500 ppm MAA-3, the initial flocculation point of the oil sample is significantly increased from 42.48% to 70.94%, the size of asphaltene aggregates is reduced from 3.99 +/- 0.2 mu m to 1.45 +/- 0.2 mu m, and the viscosity of the oil sample has increased by 21.77%. The influence of the number of alkyl side chains on the performance of asphaltene dispersants was also studied. The result shows that increasing the number of the alkyl side chain is beneficial to improve the performance of dispersant, and the MAA has the best performance of dispersing asphaltenes at the number of alkyl side chains of 3 (MAA-3). The molecular simulation (MS) further verified the experimental results from the perspective of interaction energy.
查看更多>>摘要：Horizontal and multilateral wells increase continuously and are considered as a mechanical stimulation method for enhancing reservoir performance. However, drilling these wells is challenging with the conventional circulation technology because of the existence of significant pressure loss. Hence, Friction Reducers (FR) may offer a solution to this problem. The objectives of this paper are: (1) to present the possibility of using polyacrylamide based FRs in water base drilling fluids to replace oil based drilling fluids used to drill long lateral sections; (2) to show the optimal pH values of the newly developed FR water base drilling fluids; and (3) to present the effect of FR on both drilling fluid rheological performance and shale inhibition at optimal pH values. Two commercial groups of FR were used in this study, anionic FR (AFR) and cationic FR (CFR). Lab experiments were conducted initially to obtain the effect of pH on the FRs with water and with bentonite by using a low pressure and high temperature rheometer and a Zeta potential analyzer. The rheological properties of formulated Water Based Fluid (WBF) with and without anionic FRs were measured at temperatures ranging from 120 degrees F to 180 degrees F. The zeta potential was also measured to investigate the capability of using anionic FRs as shale inhibition in WBF. The experimental results reveal that the isoelectric point of CFR is at pH value of 8.5 and this CFR charges negatively above pH 8.5. With increasing pH, the viscosity of CFR decreases and there is rise in shear stress of bentonite with CFR. There are obvious effects of pH on anionic FRs with bentonite due to the attraction of negative carboxylate group on AFR surface to positive edge of bentonite. This attraction is a good indicator that anionic FRs can be used as shale inhibition. The optimal pH of using AFR with WBF is from 8.5 to 9.5 for better WBF system stability. The results also reveal that AFR supports thermal stability of the formulated KCl polymer WBF. Furthermore, the formulated WBF with AFR minimize formation damage due to having lower API and high pressure and high temperature filter loss. Zeta potential measurements indicates the initial concentration of AFR used in WBF without KCl for shale stabilization is 18 pptg (0.72 lbm/bbl). This study introduces a promising alternative WBF which could be used to replace oil based drilling fluids when drilling long lateral sections. This proposed approach is important for the oil and gas industry not only for cost effectiveness but also to avail environmental concerns.
查看更多>>摘要：Carbonate reservoir properties and their heterogeneities are of the main issues in reservoir qualitative and quantitative studies. In this paper, the role of facies and diagenesis processes on reservoir quality in the Cenomanian-Early Turonian Sarvak formation of SW of Iran was studied using 1504 samples from the core and a set of full suite logs from three wells. The depositional setting ranges from grain-rich reefal to lagoonal facies with grain-dominated and mud-dominated textures. Several diagenetic realms such as meteoric vadose, phreatic (vadose and marine) and mixing were identified based on petrographic observations. Compared to the muddominated facies of the Sarvak formation, the grain-dominated facies were intensely subjected to diagenetic processes. Furthermore, dissolution and neomorphism resulting from the subaerial exposure during meteoric diagenesis enhanced the reservoir quality, while further cementation, compaction and micritization have a negative impact on reservoir characteristics. The quantitative approaches show the eustatic sea-level rise in the Cenomanian-Turonian and the regional Turonian unconformity provide a textural and diagenetic pathway towards enhancing/reducing the reservoir quality. Reservoir properties are highly dependent on the sedimentary processes of the Rudist biostromes where secondary diagenetic agents are probably contributed through the selective leaching of aragonitic grains and matrix under the meteoric water environment.
查看更多>>摘要：The upper and lower limits and grading evaluation scheme of tight gas reservoirs (TGRs) at a microscopic pore structure level were explored by conducting high-pressure mercury intrusion porosimetry (HMIP), rate-controlled mercury intrusion porosimetry, nuclear magnetic resonance (NMR), and wettability experiments on tight rock samples from the Lower Cretaceous Shahezi (SHZ) Formation in the Xujiaweizi Rift, northern Songliao Basin. The results showed that the upper throat radius limit of the SHZ TGRs corresponds to 1.86 mu m, derived from the microscopic equilibrium state of buoyance and capillary forces. The above value is closely related to several geological factors, including a pore-to-throat radius ratio, the density difference between formation water and gas, formation dip angle, gas-water interfacial tension, and wettability. The SHZ Formation enters a tight reservoir stage when the burial depth is deeper than 3460 m. A new method integrating HMIP and NMR experiments was proposed to estimate the thickness of the adsorbed water film with a value of similar to 21.56 nm. The theoretical lower throat radius limit of the SHZ TGRs was determined as similar to 22 nm, considering the individual methane dimension. Natural gas can be scarcely injected into tight reservoirs below the theoretical lower limit, serving as theoretically invalid tight reservoirs in the study area. From the configuration relationship between pores and throats, two TGR types were identified in the SHZ Formation (types I and II). Type-I TGRs are char-acterized by relatively excellent seepage capacity, with the maximum connected throat radius and permeability of 0.4 mu m(-1).86 mu m and (0.015-0.27) x 10(-3) mu m(2), respectively, and their storage space mainly comprises abundant dissolution and residual intergranular pores. Furthermore, an adequate storage space (3.6% to more than 12%) and an appropriate burial depth (<5000 m) promote type-I TGRs to be the most favorable targets for current SHZ tight gas accumulation development in the Xujiaweizi Rift.
Lashari, NajeebullahGanat, TarekElraies, Khaled AbdallaAyoub, Mohammed Abdalla...
19页
查看更多>>摘要：Nanoparticles are extensively used at lab scale to improve physicochemical characteristics like interfacial tension, wettability, rheological behavior in different hydrocarbon recovery processes. Nevertheless, stability in the base fluid is the main limitation in chemical enhanced oil recovery for field implementation. The instability of nanofluids contributes to deteriorating characteristics of injectant fluid efficiency over time. This review deals with various facets of nanofluid stabilization, from the preparation stage until practical application. Specific stability aspects are investigated in terms of aggregation state, composition, shape, size, and surface chemistry. Following that, techniques for enhancing nanoparticle stability are outlined and linked to these same nanoparticle attributes. Methods for evaluating and modeling nanoparticles stability in terms of physiochemical characteristics are described. The aggregation state influences the stability of solution-phase nanoparticles. Thus, nanofluid stability as a feature of system parameters in a range of nano-hybrid applications and the relationship between nanoparticle stability and the physical/chemical properties of nanoparticles is discussed. Finally, the problems and possibilities in comprehending what nanoparticle stability entails are discussed to aid future research with this novel class of materials.
Safari, MehdiJye, James Wong JiunRahimi, AliGholami, Raoof...
11页
查看更多>>摘要：Nanoparticles (NPs) have been recognized as the agents that can improve the oil recovery given their positive impact on the surface wettability of rocks. However, their impacts on the interfacial tension (IFT) of the twophase fluid in a reservoir have not been widely reported. Given the significant impact of IFT on the oil recovery, it is important to develop an NPs based approach that not only alter the surface wettability but also reduce the IFT. This may be accomplished by combining nanofluids with low salinity water (LSW). In the present study, LSW and NPs are combined to study their impacts on the IFT of a two-phase flow system with water and oil. IFTs of different solutions with nano glass flakes (NGFs) and nano silica (Ns) were measured in the presence of monovalent and divalent salt ions. The results obtained were analysed using two different models as a function of time. It was found that NGFs and Ns have similar efficiency in reducing the IFT and can reveal an optimum performance once their concentration reaches 24.8% in the solution. It was observed that, unlike Ns, IFT can be further reduced by LWS in the presence of NGFs. In fact, reduction of salinity up to 3500 ppm can decrease the IFT in the NGFs solution by the salting-in effect or migration of oil components. Changing the pH of the system can also reduce the IFT, but fluctuations was observed once pH goes beyond 9. It appeared that the tension in the interface between water and oil reduces over time and the effect of adsorption time is significantly higher on the solutions with nanoparticles. It was concluded that combining NGFs with LSW not only reduces the concentration of NPs needed and can make the project economically feasible, but also favourably change the IFT during the flooding process. The findings of this study may help to understand how LSW, and nanofluids can be employed together for a better oil recovery.
查看更多>>摘要：Vertical fracture patterns are mapped in the outcrops to analyze the impact of mechanical stratigraphy on vertical fractures in the relatively undeformed Upper Triassic tight oil sandstones of the Yanchang Formation along Yanhe River in the east Ordos Basin, China. The relationship between natural fractures and different bounding interfaces are analyzed based on rock relative strength measurement by N-type Schmidt Hammer, fracture and facies description in the outcrops. According to the probability of the bounding interface terminating natural fractures being more than 20%, seven types of mechanical interfaces terminating fracture longitudinal propagation are identified, namely 1) the interface of laminae-set or laminae co-sets, 2) bedding surface interface, 3) accretionary interface, 4) mudstone interbed, 5) mudstone barrier, 6) calcareous barrier and 7) depositional scour interface. According to fracture sizes and the mechanical interfaces which constrain fracture propagation, the vertical fractures are divided into micro-scale, small-scale, meso-scale and macro-scale ones. Three possible vertical fracture patterns in various sedimentary microfacies of the shallow water delta deposits are discussed based on field outcrop observation, the restriction capacities of different mechanical interfaces and the temporally changing tectonic stress. Finally, the application of vertical fracture patterns for subsurface fracture prediction is carried out in the Ansai Oilfield in the eastern Ordos Basin, China. The predicted fractures in wells are consistent with the fractures obtained from cores and conventional logs. This study links sedimentary stratigraphy, mechanical stratigraphy and natural fractures in the tight oil sandstones within a relatively undeformed setting, meanwhile unravels the vertical fracture patterns in different sedimentary microfacies of the shallow water delta deposits in the study area. The results will thus guide subsurface fracture prediction between wells in the tight oil sandstones of the eastern Ordos Basin.
查看更多>>摘要：To understand the fracture behavior for variable density in-plane perforations on a horizontal well, true triaxial hydraulic fracturing experiments were performed with acoustic emission monitoring. The experimental results indicate that the variable density in-plane perforations can not only create transverse fractures but also arrest fracture propagation toward undesirable zones. The in situ stress and treatment parameters play significant roles in the fracture morphology and breakdown pressure. Under a large horizontal principal stress difference, there is a high possibility for simple transverse fracture creation, which results in a lower breakdown pressure. Moreover, the decrease in fracturing fluid viscosity can increase the fracture complexity and increase in pump rate can increase breakdown pressure and induce the complex fracture geomtetry. The acoustic emission (AE) characteristics and cutting fracture morphology demonstrate that not all perforations can be successfully initiated during the fracturing process. Because of the stress interaction from side perforations, fracture initiation and propagation from the middle perforation are strongly suppressed. Although the middle fracture is not fully initiated and propagated, it is still beneficial for the side hydraulic fracture connection and propagation in one plane. Secondary and axial fractures can still be observed, primarily due to the stress interaction between neighboring perforations and misalignment of the perforation tunnel orientation with the principal stress direction. In addition, the creation of complex fractures tends to occur using a high pump rate, which relates to tense fluid distribution competition from each perforation tunnel. Fracture initiation may follow an order but mostly tends to initiate from side perforations. Because of the stress interaction, hydraulic fractures from the side perforation can sometimes deviate from the perforation tunnel direction, twist and kink, and finally, generate nonplanar fractures. A large horizontal principal stress difference is recommended and beneficial for simple, straight and planar fracture creation during hydraulic fracturing stimulation with variable density in-plane completion for the horizontal well.
NSTL
Elsevier