Reservoir Connectivity Research Articles

Geological conditions and controls on accumulation of tight sandstone gas, deep part of the Shengbei sub-sag, Turpan-Hami basin, NW China

With the further exploration of the Jurassic strata in the Turpan-Hami Basin, the targets for hydrocarbon exploration have been gradually shifted from the tectonic belts around sags to the proximal lithological zones of deep sags. Based on the systematic coring of the first exploration well (well Qintan-1) in the center Shengbei sub-sag, this study conducted experiments of organic carbon, pyrolysis, gas chromatography (GC), nuclear magnetic resonance (NMR), and low-temperature nitrogen adsorption. Then, this study systematically analyzed the geological conditions and major controlling factors for the accumulation of tight sandstone gas in the deep part of the Shengbei sub-sag. The results show that: (1) Multiple sets of coal-measure source rocks have developed in the Jurassic strata in the center Shengbei sub-sag, providing plenty of gas sources for multilayered hydrocarbon accumulation; (2) Tight sandstones have poor physical properties and complex pore structures. However, high-permeability zones and anomalous zones of nano-scale pores have developed in the deep part, providing favorable spaces for the accumulation and preservation of tight oil and gas in the deep part; (3) Compaction and late carbonate cementation are key factors in reservoir densification. The microscopic storage space and connectivity of the tight sandstone reservoirs in the Shengbei sub-sag were improved due to the dissolution of fluids in coal measure strata. The occurrence of high-quality reservoirs in the Shengbei sub-sag is significantly controlled by source rocks, and both the former and the latter are characterized by adjacent sources and reservoirs and short-distance migration and accumulation. Furthermore, the special geological phenomena of chert cementation, abnormally high homogenization temperatures of fluid inclusions, and abnormal pyrolysis parameters confirm the presence of low-temperature hydrothermal activity in the deep part of the target strata. Therefore, the center Shengbei sub-sag has geological conditions for the large-scale accumulation of primary gas and, thus, is a key area for future hydrocarbon exploration.

Study on Connectivity Analysis and Injection–Production Optimization of Strong Heterogeneous Sandstone Reservoir Based on Connectivity Method

The D reservoir in the Bongor Basin, southern Chad, is highly heterogeneous. In the stage of waterflood development, the injected water is seriously channeled along the dominant channel, and the water drive effect becomes worse. At the same time, due to the strong edge and bottom water, the water flooding situation is aggravated, the water cut is increased, and the development efficiency is reduced. To accurately identify the inter-well connectivity relationship, we developed a reservoir inter-well connectivity model based on the principle of inter-well connectivity and dynamic production data and reservoir geological parameters. Thus, the plane water injection split coefficient and water injection efficiency of each reservoir layer were obtained. The results are in good agreement with the calculation results of inter-well connectivity through verification with field tracer interpretation. The practical application results show that the method can increase the annual output of oil by 1.3%, which has a good oil increase effect. In this study, a model of inter-well connectivity in multi-layer sandstone reservoirs was established for the first time. The production performance of the model injection–production well was optimized in real time by a historical fitting and production optimization algorithm and then applied to real reservoirs, so that it could effectively improve the oilfield development and optimize the injection–production structure.

Sensitivity of shear wave splitting to fracture connectivity

SUMMARY Shear wave splitting (SWS) is currently considered to be the most robust seismic attribute to characterize fractures in geological formations. Despite its importance, the influence of fluid pressure communication between connected fractures on SWS remains largely unexplored. Using a 3-D numerical upscaling procedure based on the theory of poroelasticity, we show that fracture connectivity has a significant impact on SWS magnitude and can produce a 90° rotation in the polarization of the fast quasi-shear wave. The simulations also indicate that SWS can become insensitive to the type of fluid located within connected fractures. These effects are due to changes of fracture compliance in response to wave-induced fluid pressure diffusion. Our results improve the understanding of SWS in fractured formations and have important implications for the detection and monitoring of fracture connectivity in hydrocarbon and geothermal reservoirs as well as for the use of SWS as a forecasting tool for earthquakes and volcanic eruptions.

Optimal capacity configuration of the hydro-wind-photovoltaic complementary system considering cascade reservoir connection

To address the critical issues on environmental pollution and energy consumption, humans began vigorously developing and employing renewable energy sources (RESs). Hydro-wind-photovoltaic(PV) complementary system plays an indispensable part in the sphere of renewable energy research, while the optimal capacity proportion serves as a foundation and premise for building hybrid energy systems. Taking the lower portion of the Jinsha River in Sichuan Province as an example, this research presents a novel capacity configuration model of hydro-wind-PV complementary systems. Based on the consideration of cascade hydropower station connection, the model aims to minimize discarded energy and maximize delivery channel utilization. A new DE based on chaotic local search is then employed to solve the model. The result shows that the optimal proportions for the complementary system with 35 GW, 40 GW and 45 GW of delivery channel capacity are (0.93,0.93), (1.18,1.18) and (1.35,0.35), respectively. Meanwhile, as the affordability of complementary systems increases, the total installed capacity of wind power and photovoltaic power that may be accessible will also rise. Consequently, this paper not only offers a novel strategy for tackling similar issues on optimal capacity configuration, but also makes a contribution to maximizing the accessed installed capacity of RESs.

“Geology-geophysics-data mining” integration to enhance the identification of deep fault-controlled paleokarst reservoirs in the Tarim Basin

Large-scale strike-slip faults play a dual role as conduits for fluid flow, channeling both atmospheric freshwater and deep hydrothermal fluids, thereby creating porous carbonate reservoirs at significant depths. Moreover, these faults serve as vertical conduits, connecting deep source rocks to oil and gas reservoirs capable of generating substantial hydrocarbon fields. In recent years, the Tarim Basin has yielded numerous high-yield reservoirs along large-scale strike-slip faults, exhibiting exceptional hydrocarbon potential. Nevertheless, the intricate heterogeneity of deep-seated traps engendered by these faults presents a formidable challenge in accurately determining reservoir geometry, consequently complicating the drilling of high-yield wells. Currently, enhancing the precision of reservoir identification stands as a paramount issue within the Tarim Basin.This paper introduces an innovative solution termed the “Geology-Geophysics-Data Mining” workflow, designed to enhance the resolution of multiscale geophysics data through the lens of geological insights. Drawing inspiration from the geological model of “fault-controlled paleokarst,” and utilizing a fusion of well logs and seismic data, we elect seismic impedance as a discerning parameter to differentiate between porous reservoirs and impermeable host rocks. The proposed methodology unfolds through several steps.Primarily, noise reduction and frequency domain extension of the original seismic data are achieved through spectral shaping and diffusion filtering algorithms. Subsequently, the impedance curve of the logging wave is computed, establishing a non-linear correlation with seismic waveforms using a waveform indication inversion algorithm, ultimately yielding inverse impedance data. In the subsequent phase, the impedance originating from stable sedimentary features is quantified and subsequently extracted from the inversely derived seismic data. This step accentuates the high-quality reservoirs formed via fault-controlled karstification. Ultimately, we validate the identification of reservoir geometry using interpretations from well log data and drilling outcomes.Furthermore, this paper employs the seismic impedance obtained from wellbore logging data as “hard data” and deploys machine learning algorithms to map this information to three-dimensional high-precision seismic data. Following the removal of sedimentary features' influence, we extract the longitudinal connectivity and transverse mutation characteristics inherent in fault-controlled paleokarst reservoirs. This extraction enables the capture of geometric structural information related to fault-controlled paleokarst reservoirs, further substantiating the geological distribution of effective reservoirs controlled by strike-slip faults. These findings establish a dependable foundation for directional drilling and studies focused on hydrocarbon accumulation. Notably, the “Geology-Geophysics-Data Mining” approach is extendable to analogous strongly heterogeneous reservoirs.

A double-cycle echo state network topology for time series prediction.

Echo state network (ESN) has gained wide acceptance in the field of time series prediction, relying on sufficiently complex reservoir connections to remember the historical features of the data and using these features to obtain the outputs by a simple linear readout. However, the randomness of its input and reservoir connections pose negative impacts on the prediction performance and performance stability of the models, the complexity of reservoir connections brings high time consumption during network computing, and the presence of randomness and complexity makes the hardware implementation of the ESN difficult. In response, we propose a double-cycle ESN (DCESN) based on the Li-ESN model, which has fixed weights to improve prediction performance and performance stability and simpler reservoir connections compared to the classical ESN to reduce the time consumption. The existence of both greatly reduces the difficulty of hardware implementation of the ESN and provides many conveniences for the future application of the ESN. Experimental results on many widely used time series datasets show that the DCESN has comparable or even better prediction performance than the ESN and good robustness against noise and parameter fluctuations.

Well perforating—More than reservoir connection

Well perforating—More than reservoir connection

Unconventional Use of Tracer Technology Provides Flow Insights for EOR, IOR

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207431, “Advanced Research and Development in Unconventional Use of Tracer Technology for EOR and IOR: What Lies Beyond?” by Monalisa Chatterjee and Sean Toh, Tracerco, and Ahmed Alshmakhy, SPE, ADNOC, et al. The paper has not been peer reviewed. _ In recent decades, tracers have provided crucial insight into fluid-flow behavior in assessing reservoir connectivity. While advancements in versatility of tracer molecules have been published before in the literature, to the best of the authors’ knowledge, no work has been published to date that discusses the latest advances in unconventional uses of tracer molecules aiding enhanced oil recovery (EOR) and improved oil recovery (IOR) processes. This work is meant to address that gap by exploring four unconventional uses of tracers that hold significant potential. Microencapsulation of Solid Tracers: Enhancing Intelligent Tracers Previous research specified that factors affecting the current technology of solid tracers include physical space restrictions, temperature, tracer-loading capacity, initial surge, release of the tracer into fluid, and target-tracer concentrations. While the first two factors often are dictated by project conditions, advances in the other factors have been largely attributed to the tracer-polymer composition. For the tracers to be released in a controlled manner across a designated period, polymer structure plays a pivotal role in achieving longevity. The complete paper discusses a technique that is an application revolving around microencapsulation of chemical tracers in a solid shell before the addition of polymer material. Encapsulation vs. Microencapsulation. The encapsulation technique is a complex process involving selection of compatible molecular carriers, understanding their effects, and building the appropriate encapsulation (usually molecular encapsulation) to ensure that the capsules meet the desired outcome of each study. In this paper, an advanced subset of encapsulation—microencapsulation—is presented and its applications in inflow chemical tracing are discussed. Microencapsulation involves a particle, usually of micrometer dimensions, comprising a core material surrounded by a wall material significantly different from that of the core. The difference between them mainly arises from the morphology and the internal structure. The process allows the active ingredient to be protected from adverse external environmental conditions by the encapsulating coating agent. By applying the microencapsulation technique, the release profiles of tracers can be further controlled by changing the thickness, material, and morphology of the encapsulating agent. When applied onto tracers, this changes the tracer-release mechanism to a two-step, instead of the typical one-step, process. Oil tracers that generally are oleophilic will be released when in contact with oil; similarly, water tracers that are hydrophilic will be released when in contact with water. The tracers will remain dormant until the phase of interest encounters the polymer bars, and the two-step process allows the encapsulating agent to further improve the longevity of the tracers.

Diagenetic differentiation of tuffaceous interstitial materials in sandy conglomerate and their effect on reservoir properties

Tuffaceous material of the Lower Triassic Baikouquan Fm., NE Junggar Basin is closely associated with detrital particles and particularly with crenulated quartz grains and kaolinite. The amount tuff is reduced closed to the source area. The main component of the tuffaceous interstitial material is SiO2, followed by K2O, FeO, and MgO. The tuffaceous interstitial material can be further divided into three types: medium (basic) potassium-rich tuffaceous material, ultrabasic iron-magnesium tuffaceous material, and ultrabasic iron-magnesium rich tuffaceous material. Medium (basic) potassium-rich is dominated by fusiform shrinkage pores, often associated with kaolinite, while ultrabasic iron-magnesium rich tuff pores are not developed, and ultrabasic iron-magnesium tuffaceous material is dominated by dissolution pores. The solution pores have large diameters and large volume of pores and throats, but low pores and throats coordination number. The pore size and the pores and throats volume of shrinkage fractures are small, but the pores and throats coordination number are large. Dissolution pores are mainly distributed in Mbr 1, whereas shrinkage pores mainly occur in Mbr 2. However, the interlayer productivity data from a single well show that the Mbr 1 has a higher productivity than Mbr 2. However, the interlayer productivity data from a single well show that Mbr 1 has a higher productivity than Mbr 2. In addition, tuff is not responsible for wind action, but the cause of intermittent water flow transport in volcanic rocks. Distributary channels at the fan delta front comprise the dominant facies for development of tuffaceous interstitial materials. The composition of tuffaceous interstitial material clearly determines reservoir quality. Medium basic potassium-rich tuff has a high SiO2 content and is prone to devitrification, so it is dominated by shrinkage pores, whereas ultrabasic iron-magnesium tuff contains FeO and MgO and is vulnerable to acid corrosion and the formation of corrosion pores. However, acid minerals such as kaolinite reduce reservoir connectivity. Compared with solution pores, shrinkage pores have a small pore volume, but high pores and throats coordination number, indicating that they have a high seepage capacity. Shrinkage pores are an important factor in causing production differences between single layers and should be given more attentions.

Experimental study on the effect of the gas reservoir on the performance of a nitrogen-charged cryogenic grooved heat pipe

Nitrogen-charged cryogenic grooved heat pipes require gas reservoirs to reduce their initial charging pressure. However, the effect of gas reservoir on the performance of the heat pipe has rarely been investigated. In this paper, experimental studies were conducted to analyze the effects of different gas reservoir connection positions (the evaporation section and the condensation section) and different gas reservoir volumes on the startup and steady-state operation performance of heat pipes. The results indicate that the connection position of the gas reservoir affects the pressure drop of vapor flow in the heat pipe. When the gas reservoir connected to the evaporator of the heat pipe, the vapor flow pressure drop is lower, which is more favorable for the steady-state performance of the heat pipe. Additionally, a smaller gas reservoir volume allows the heat pipe to startup at higher temperatures and pressures, which can accelerate the startup rate of the heat pipe. The selection criteria for the application of gas reservoir in cryogenic heat pipes were provided. These results can be useful for optimization design of cryogenic grooved heat pipe.

Anatomy of fractures: Quantifying fracture geometry utilizing X-ray computed tomography in a chalk-marl reservoir; the Lower Cretaceous Valdemar Field (Danish Central Graben)

Naturally fractured reservoirs tend to show heterogeneous permeability with open fractures enhancing the inherent diagenetic and depositional matrix fabric. Natural open fractures may function as pathways for fluid flow in tight (low matrix permeability) carbonate reservoirs and have a significant impact on the directions, magnitudes and heterogeneities of fluid flow and reservoir rock strength. Open fractures may however also facilitate the invasion of formation water while fractures that are partially or completely cemented can act as barriers to fluid flow. As a result, natural fractures significantly impact reservoir flow rates, anisotropy, storage, connectivity, recovery, and production. X-ray Computed Tomography (CT) offers a non-destructive technique to evaluate petrophysical parameters, such as porosity and permeability, and to assess the geometry, connectivity, and density of natural fractures, which are important constituents of chalk reservoirs. The purpose of this study is to investigate different types of naturally occurring fractures within the Lower Cretaceous succession of the Valdemar Field in the Danish North Sea. Six samples of core displaying at least one natural fracture on the surface are imagined; two samples of open fractures with plumose structure and hackle marks, three samples of shear fractures and finally one sample with deformation bands. The samples are imaged by CT and internal fractures are manually mapped. Image analysis provides detailed information on the fracture geometry in addition it indicates the presence of numerous microfractures hitherto not recorded in the Lower Cretaceous of the Danish North Sea. Core data show that fracture intensity can be significantly greater than calculated by conventional core interpretation techniques based on core surface observations. Further, apertures of both major and minor fractures are measured in CT images of all samples to determine if specific fracture types display characteristic that can distinguish them from other fracture types. As open fracture intensity increases, so too does permeability, likely enhancing reservoir connectivity on the field scale.

Bridging Computational Stratigraphy and Reservoir Simulation for Geologically Realistic High-Resolution Reservoir Modeling

Summary Computational stratigraphy (CompStrat) is a state-of-the-art Earth-modeling method that captures the key heterogeneities in subsurface reservoirs through modeling of the detailed flow and sediment transportation processes in various depositional environments. The method is fully based on physics and generates high-resolution 3D Earth models that are much more geologically realistic than those generated by traditional Earth-modeling methods. It can accurately predict and preserve those spatially continuous but vertically thin and volumetrically insignificant layers, such as shale layers, thus enabling a much more accurate representation of natural reservoir connectivity. In the past few years, CompStrat has been studied mainly within the Earth science community and has not been broadly applied yet in reservoir simulation research and practices. Our objective is to bridge this gap and allow this frontier technology to offer geologically realistic Earth models for reservoir simulation to better understand how various geological features contribute and control subsurface flow patterns and performance, subsequently leading to better integration among Earth modeling, flow simulation, and more reliable reservoir performance predictions. CompStrat models often have large numbers of cells (hundreds of millions or more). A large proportion of them are related to thin shale layers. These thin cells can often cause convergence difficulties in reservoir simulations. We developed a grid coarsening method to dramatically reduce the cell number and the simulation time with minimal alteration of the overall model connectivity characteristics. The method reduces the cell number by 85% (to 93%) and the simulation time by 94% (to 99%) with limited loss of accuracy for representative examples. Without this method, the simulation may take impractically long time to run for large models with complex multiphase flow dynamics. The successful removal of the computational bottleneck enables the application of this frontier Earth-modeling method in high-fidelity reservoir simulation. It also facilitates a detailed understanding of the connection between geology and flow to offer valuable insight for reservoir modeling, production forecast uncertainty analysis, and history matching. We developed a method to label, evaluate, and rank geological features based on their influence on flow performance, with shale layers being the specific focus. The labeling is performed semiautomatically, and the evaluation and ranking are done efficiently with a reduced-physics solver. The result is statistically consistent across multiple realizations. The fluvial-deltaic CompStrat sector model on which our grid coarsening and shale analysis methods were tested is shared in the Supplementary Materials.

Study on Residual Oil Distribution Law during the Depletion Production and Water Flooding Stages in the Fault-Karst Carbonate Reservoirs

The fault-karst carbonate reservoir is a new type of deep carbonate oil and gas resource and a target for exploration and development. The distribution of remaining oil in this kind of oilfield is very complicated because of its unique reservoir characteristics of vertical migration and accumulation, segmented accumulation, and differential accumulation. Therefore, the S91 reservoir block, a typical fracture-vuggy carbonate reservoir in the Tahe oilfield, was taken as the object of this research. According to the development characteristics as well as the porosity and permeability characteristics of the fracture-vuggy, the reservoirs were divided into three types: cave, pore, and fracture. A numerical simulation model of the fracture-vuggy reservoir of the S91 unit was established, and the historical fitting accuracy with dynamic production data was more than 90%. Then, the distribution characteristics of the remaining oil in the depletion stage of the fault-karst carbonate reservoir were further studied and based on the analysis of the reservoir water-flood flow line, the remaining oil distribution characteristics in the depletion stage of the fault solution reservoir were revealed. The results show that the remaining oil distribution patterns during the depletion production stage can be divided into three types: attic type, bottom water coning type, bottom water running type. Due to the serious problem of the bottom aquifer lifting caused by the reservoir development, the residual oil between wells was relatively abundant during the depletion production stage. According to the simulation results, the remaining oil distribution modes in the water drive development stage were identified as three types: sweeping the middle between wells, bottom water connection and circulation, and oil separation through high-permeability channels. In addition, the reservoir connectivity was the main controlling factor for the remaining oil distribution in the fault-karst carbonate reservoir.

Application of the software "ZHULDYZ". Adaptation and work with models

Background: One of the conditions for the effective development of oil and gas fields is reliable forecasting of its exploitation, including using the capabilities of modern software. As a result of many years of work, the first and only Kazakhstani import-substituting software product "Zhuldyz" was developed which helps to control the implementation of process solutions at the field.
 Aim: Implement a single software platform covering the complete cycle of exploration and development of the fields.
 Materials and methods: This paper presents the experience of using the Zhuldyz software at the Karatobe Yuzhnoye field, as well as software modules for optimizing modeling processes.
 Results: Using software accounting a set of geological and physical results and the production history of the Karatobe Yuzhnoye deposit, data were obtained for constructing development maps, assessing reservoir connectivity and distribution of injected water, analyzing field performance for wells, selecting candidate wells for well interventions, as well as software modules for optimizing modeling processes. Additional opportunities for assessing and comparing field development indicators have also been identified.
 Conclusion: Based on the results of the analysis carried out in the Zhuldyz software, solutions were developed to improve the reservoir pressure maintenance system at the Karatobe Yuzhnoye deposit. The selection of wells for well interventions and the calculation of efficiency were carried out, which will reduce the number of unsuccessful well interventions by increasing the quality of selected candidate wells through a new appraisal approach from a geological and technological point of view.

Control of faults and fractures on shale oil enrichment

The Qingshankou Formation is the primary shale oil exploration and development target in the Songliao Basin, but controlling factors of shale oil enrichment, especially the role of faults and fractures, are still poorly understood. We identify fault geometry in the Qingshankou Formation based on seismic interpretation. We characterize natural fractures with outcrop and core observations, and thin-sections petrography. By integrating faults and fracture observations at various scales, tectonic history of the basin, and burial history of the studied reservoir formation, we explain the control of faults and fractures on shale oil enrichment. Results show that high-density fault systems, namely “T11″ and “T2″ fault systems, were developed at the top and bottom of Qingshankou Formation in the north of Songliao Basin. Both fault systems is characterized as a group of high-density, closely spaced small faults forming a fault belt, with evident multi-stage activities. Nature fracture categories identified including folding and faulting related fractures, bed-parallel fractures and overpressure fractures, while the former two are better developed. Tectonic movements have caused the structural uplift and subsidence to take place at different times in different parts of the basin. The structural uplift happened late in the study area, consequently the source rocks have gone through a long burial history and are well matured, which favors shale oil enrichment. Tectonic uplifts generated large numbers of fractures locally, effectively increase oil production by improving the migration pathways and storage space of shale oil. Fault systems of different scale also provided two-way channels for oil migration in Qingshankou Formation. Large-scale faults that cut through the full shale column allow the shale oil to migrate to the conventional reservoirs above and below the Qingshankou Formation. The smaller faults in the high-density fault belt within the Qingshankou Formation (Qing-1 Member) enhanced seepage capacity and connectivity of the shale reservoir. As a result, shale oil and conventional oil development in the study area can collaborate with one another. High-density, well connected natural fractures also played an important role by providing storage space and fluid flow conduit which is essential in shale oil reservoirs. However, these fractures along faults may migrate oil from shale reservoirs to neighboring conventional reservoirs.

Semi-supervised echo state network with partial correlation pruning for time-series variables prediction in industrial processes

For an ordinary echo state network (ESN), redundant information in the huge reservoir will lead to degradation of the prediction performance of the network, especially when the labels of the samples are limited. To solve this problem, a semi-supervised ESN with partial correlation pruning (PCP-S2ESN) is proposed in this paper to scientifically capture the essential association between two reservoir variables while controlling for the influence of other factors. In this way, redundant neurons and their connection weights in the reservoir are eliminated, so that the prediction accuracy is significantly enhanced by optimizing the network structure. Moreover, an unsupervised pre-training procedure is introduced to modify the input weight matrix and reservoir connection weight matrix of the ESN, which successfully achieves precise prediction of time-series variables with limited labels. The superiority of the PCP-S2ESN model is demonstrated through two benchmark prediction tasks and the fed-batch penicillin cultivation process.

Inferring the interwell connectivity of multilayer waterflooded reservoirs accounting for incomplete injection/production profiles

The capacitance–resistance model (CRM) has been widely used to identify the interwell connectivity in waterflooding reservoirs. Although this technique has been extended to deal with the blocks having multiple layers, almost all these models require that the injection profiles of all the injectors or the production profiles of all the producers should be available. This demanding requirement limits its applications. We propose a multilayer capacitance–resistance model (ML-CRM) to identify the interwell connectivity within each layer using incomplete injection/production profiles. All the known injection/production profiles are input into the model directly, whereas the unknown profiles of the other wells are estimated by matching the historical production data. Based on the long short-term memory (LSTM) network, we also propose a method to identify the connectivity accounting for well shut-in. Our model is solved by coupling the biogeography algorithm (BBO) and the least-squares regression. We examine the performance of ML-CRM using both the data generated from numerical simulations of different synthetic fields and actual production data from the Shengli oilfield, China. We also discuss the noise effect on the model performance. Our results suggest that even though limited injection/production profiles are available, our proposed model fully utilizes the known information and can still provide reliable results. A comparison with the interwell tracer test in the real field indicates that this model well captures the different connectivities within the two layers, which is beyond the capability of traditional CRM.

Improvement of WEAP model considering regional and industrial water distribution priority and its application

Study regionGuangdong-Hong Kong-Macao Greater Bay Area urban agglomeration (GBA). Study focusExisting Water Evaluation and Planning System (WEAP) lacks consideration of regional and industrial water distribution priority. This study proposes an improved WEAP model by integrating regional and industrial water distribution priority determined by water supply safety. The logistic curve model was introduced for water supply safety evaluation. The improved WEAP model was applied to the water resources allocation of GBA in the year of 2019 and 2030, and the effects of water allocation schemes with different regional and industrial water distribution priorities were compared. New hydrological insights of the regionThe results indicate that the water supply safety of each city in the GBA varies with region and industry, Guangzhou, Shenzhen and Dongguan have lower degree of domestic and industrial water supply safety. River and reservoir connections are essential to the water supply safety of GBA. The water demands of Shenzhen and Dongguan cannot be satisfied during dry period in 2019, while perfectly satisfied during the dry period in 2030 due to the operation of water transfer projects. The improved WEAP model obtained more reasonable water allocation results, improving the water satisfaction rates of regions with low water supply safety. The research demonstrates the advantage of the improved WEAP model considering regional and industries priority, enhancing the applicability of the WEAP model.

Control Mechanism of Microbial Degradation on the Physical Properties of a Coal Reservoir

This study addressed the effect of microbial methane production on the physical properties of a coal reservoir. Two kinds of coal samples before and after anaerobic degradation were tested by a low-temperature liquid nitrogen adsorption test and an isothermal adsorption and diffusion coefficient test. The influence of the characteristics of microbial gas production on the coal physical properties was analyzed. Due to the differences in the physical properties of the coal samples, the effect of microbial production is different. Coal is a macromolecular organic compound, mainly aromatic and lignin derivatives, containing carbon and nitrogen sources that can be used by microorganisms. Microorganisms secrete extracellular enzymes to decompose covalent bonds and functional groups of macromolecules in coal and eventually produce methane, which will change the physical properties of coal. It was found that microbial anaerobic degradation could increase the content of coalbed methane, change the pore structure of coal, reduce the fractal dimension of the coal surface and smooth the coal surface. At the same time, microbial degradation has changed the physical properties of coal reservoirs to some extent, increased the diffusion of coal reservoirs and improved the pore connectivity of coal reservoirs, which provides more of a scientific basis for the development of coalbed methane.

Effects of Shale Pore Size and Connectivity on scCO2 Enhanced Oil Recovery: A Molecular Dynamics Simulation Investigation.

The differences in pore width distributions and connectivity of shale reservoirs have significant influences on supercritical carbon dioxide (scCO2)-enhanced oil recovery (CO2 EOR) in shale. Herein, the molecular dynamics simulation was adopted to investigate the microscopic mechanism of CO2 EOR in the shale nanopores with different pore size width distributions and pore connectivity. The results show that the pore connectivity has significant effects on the oil displacement, and the recovery efficiency is ordered as: connected pore > double pore > single pore for the 3 nm pore, which are 91.32, 74.43, and 65.93%, respectively. Therefore, the increase in pore connectivity can significantly improve the recovery efficiency of the small pore of the connected pore system. For the shale reservoirs with different pore width distributions, the oil recovery rate of large pores is generally higher than that of small pores. In addition, the displacement of oil in the small pore of the double pore system is accelerated due to the pushing effect of the discharge fluid from the large pore. The results furnish a certain theoretical support for the research of the microscopic mechanism of CO2 EOR in the shale pore with different pore width distributions and connectivity and the exploit of shale oil.