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Journal of Hydrodynamics 2015年第2期27卷 234-241页

作者：刘建军宋睿崔梦梦 State key laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum University School of Geoscience and Technology Southwest Petroleum University School of petroleum and natural gas Engineering Southwest Petroleum University

Due to the intricate structure of porous media, the macroscopic petrophysical transport properties such as the permeability and the saturation used for the reservoir prediction also show a very complex nature and are difficult to obtain. Thus, a better understanding of the influence of the rock structure on the petrophysical transport properties is important. In this paper, we present a universal finite volume element modeling approach to reconstruct the three dimensional pore models from the micro-CT images based on the commercial software Mimics and ICEM, prior to the pore network model based on some basic assumptions. Moreover, tetra finite volume elements are piled up to realize the geometry reconstruction and the meshing process. Compared with the former methods, this process avoids the tremendously large storage requirement for the reconstructed porous geometry and the failures of meshing these complex polygon geometries, and at the same time improves the predictions of petrophysical transport behaviors. The model is tested on two Berea sandstones, four sandstone samples, two carbonate samples, and one Synthetic Silica. Single- and two phase flow simulations are conducted based on the Navier-Stokes equations in the Fluent software. Good agreements are obtained on both the network structures and predicted single- and two- phase transport properties against benchmark experimental data.

关键词： porous media pore-scale finite volume element model micro-CT images single-and two-phase flow

Deciphering the upper ordovician Wufeng siliceous shale depositional environments(Wuxi,NE Chongqing)based on multi-proxy record

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petroleum 2021年第1期7卷 10-20页

作者： Longbo Xu Xingzhi Wang Mingyou Feng Xiaohong Liu School of Geoscience and Technology Southwest Petroleum UniversityChengdu610500China sichuan Provincial key laboratory of natural gas geology Southwest Petroleum UniversityChengdu610500China

Based on stratigraphic variations of petrology,geochemistry(major,trace elements),and pyrite framboids,we study the sedimentary environment of siliceous rocks of the Wufeng Formation in Wuxi,Northeastern Chongqing,*** Al2O3/(Al2O3þFe2O3),SiO2/Al2O3,with AleFeeMn values indicate that Wufeng Formation are deposited in a continental margin and influenced by detrital ***-MoEF and V/CreU/Th cross-plots suggest that the siliceous shale was formed in dysoxic to anoxic *** proxies imply that the lower,the middle to upper,and the top part of the Wufeng sediments were deposited in an anoxic,dysoxic and oxic environment,***,the average size of pyrite framboids are gradually increased from bottom to top,showing that increased oxidisability.A complete vibratory third-order cycle of sea level fluctuations during the Wufeng deposition can be *** Wufeng to Longmaxi transition,the sedimentary environment exhibits a short-scale oscillatory pattern and was probably transformed from an outer shelf to inner *** multi-proxies are considered more reliable proxies for deciphering redox conditions in fine-grained sediment.

关键词： Siliceous rocks Late ordovician Wufeng formation Multi-proxy record Pyrite framboid Sea-level fluctuations

Insights into in-situ imbibition behavior of fracturing fluid in propped shale fractures based on nuclear magnetic resonance:A case study from Longmaxi Formation shale,sichuan Basin,China

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petroleum Science 2024年第1期21卷 410-429页

作者： Jing-Jing Guo Kai-Xiang Di Lie-Hui Zhang Yu-Long Zhao Hui-Ying Tang Rui-Han Zhang Ye Tian National key laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum UniversityChengdu610500SichuanChina

Shale gas is an important component of unconventional oil and gas *** the imbibition behavior is helpful to optimize flowback parameters and enhance gas *** imbibition studies have focused on shale matrix,and the pressure conditions discussed were mostly *** initial imbibition behavior begins from propped fractures to matrix,but there are few studies working on explaining the imbibition behavior in propped fractures or the phenomenon of many shale wells exhibit higher productivity after a“soaking”***,propped fracture samples were designed for imbibition and migration *** order to accurately study the mechanism and main influencing factors of fracturing fluid imbibition and migration in propped and unpropped shale fractures under high temperature and high pressure,a series of experiments based on nuclear magnetic resonance(NMR)were carried *** showed that NMR T_(2) spectra of all samples exhibited a bimodal *** final imbibition volume of fracturing fluid was positively related to pressure and fracture *** imbibition effect of fracturing fluid was more evident in matrix pores under high *** the migration during soaking stage,the fracturing fluid gradually migrated from large pores to small pores and gradually displaced the shale gas from the matrix,thus allowing the water blocking in propped fractures to self-unlock to some *** permeability decreased in the imbibition stage,while it recovered in the migration stage to some extent.

关键词： Forced imbibition Migration Soaking NMR T_(2)spectra Propped fracture Permeability recovery

The tectonic fracture modeling of an ultra-low permeability sandstone reservoir based on an outcrop analogy: A case study in the Wangyao Oilfield of Ordos Basin, China

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petroleum Science 2014年第3期11卷 363-375页

作者： Zhao Xiaoming Liu Li Hu Jialiang Zhou Xiaojun Li Min key laboratory of natural gas geology of sichuan Province Southwest Petroleum University School of Geoscience and Technology Southwest Petroleum University Abu Dhabi National Oil Company Abu Dhabi 898 United Arab Emirates State key laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum University

Due to inherent limits of data acquisition and geophysical data resolution, there are large uncertainties in the characterization of subsurface fractures. However, outcrop analogies can provide qualitative and quantitative information on a large number of fractures, based on which the accuracy of subsurface fracture characterization can be improved. Here we take the tectonic fracture modeling of an ultra-low permeability sandstone reservoir based on an outcrop analogy, a case study of the Chang6t~ Formation of the Upper Triassic Yanchang Group of the Wangyao Oilfield in the Ordos Basin of China. An outcrop at the edge of the basin is a suitable analog for the reservoir, but the prerequisite is that they must have equivalent previous stress fields, similar final structural characteristics, relative timing and an identical depositional environment and diagenesis. The relationship among fracture density, rock type and bed thickness based on the outcrop is one of the most important fracture distribution models, and can be used to interpret fracture density in individual wells quantitatively. Fracture orientation, dip, geometry and scale, also should be described and measured in the outcrop, and can be used together with structure restoration and single well fracture density interpretation to guide fracture intensity prediction on bed surfaces and to constrain the construction of the 3D fracture geometry model of the subsurface reservoir. The application of the above principles shows the outcrop-based tectonic fracture models of the target ultra-low permeability sandstone reservoir are consistent with fractures inferred from microseismic interpretation and tracer tests. This illustrated that the fracture modeling based on the outcrop analogy is reliable and can reduce the uncertainty in stochastic fracture modeling.

关键词： Ultra-low permeability sandstone tectonic fracture modeling outcrop analog subsurface reservoir 3D modeling

Molecular dynamics simulation of decomposition and thermal conductivity of methane hydrate in porous media

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Chinese Physics B 2017年第7期26卷 49-54页

作者：郭平潘意坤李龙龙唐斌 State key laboratory of Oil and gas Reservoir geology and Exploitation southwest petroleum university School of Sciences southwest petroleum university

The hydrate has characteristics of low thermal conductivity and temperature sensitivity. To further analysis the mechanism of thermal conductivity and provide method for the exploitation, transportation and utilization of hydrate, the effect of decomposition and thermal conductivity of methane hydrate in porous media has been studied by using the molecular dynamics simulation. In this study, the simulation is carried out under the condition of temperature 253.15 K-273.15 K and pressure 1 MPa. The results show that the thermal conductivity of methane hydrate increases with the increase of temperature and has a faster growth near freezing. With the addition of porous media, the thermal conductivity of the methane hydrate improves significantly. The methane hydrate-porous media system also has the characteristics of vitreous *** the decrease of the pore size of the porous media, thermal conductivity of the system increases gradually at the same temperature. It can be ascertained that the porous media of different pore sizes have strengthened the role of the thermal conductivity of hydrates.

关键词： methane hydrate thermal conductivity molecular dynamics simulations porous media

Construction of complex digital rock physics based on full convolution network

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petroleum Science 2022年第2期19卷 651-662页

作者： Jia Kang Nian-Yin Li Li-Qiang Zhao Gang Xiong Dao-Cheng Wang Ying Xiong Zhi-Feng Luo State key laboratory of Oil and gas Reservoir geology and Exploitation Engineering Southwest Petroleum UniversityChengdu610500SichuanChina Research Institute of natural gas Technology Southwest Oil and Gas Field CompanyPetroChinaChengdu610213SichuanChina

Digital rock physics(DRP)is a paramount technology to improve the economic benefits of oil and gas fields,devise more scientific oil and gas field development plans,and create digital oil and gas ***,a significant gap is present between DRP theory and practical *** digital-core construction focuses only on simple cores,and the recognition and segmentation effect of fractures and pores of complex cores is *** identification of rock minerals is inaccurate,which leads to the difference between the digital and actual *** promote the application of DRP in developing oil and gas fields,based on the high-precision X-ray computed tomography scanning technology,the U-Net deep learning model of the full convolution neural network is used to segment the pores,fractures,and matrix from the complex rock core with natural fractures ***,the distribution of rock minerals is divided,and the distribution of rock conditions is corrected by X-ray diffraction.A pore—fracture network model is established based on the equivalent radius,which lays the foundation for fluid seepage ***,the accuracy of the established a digital core is verified by the porosity measured via nuclear magnetic resonance technology,which is of great significance to the development and application of DRP in oil and gas fields.

关键词： Digital rock physics Depth learning U-Net Complex core Complex fracture

An optimal fracture geometry design method of fractured horizontal wells in heterogeneous tight gas reservoirs

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Science China(Technological Sciences) 2016年第2期59卷 241-251页

作者： ZENG FanHui KE YuBiao GUO JianChun State key laboratory of Oil & gas Reservoir geology and Exploitation Southwest Petroleum University

In this work, the unified fracture design （UFD） is extended for the first time to the fractured horizontal wells in heterogeneous closed box-shaped tight gas reservoirs. Utilizing the direct boundary element method and influence function, the dimensionless fracture productivity index is obtained and expressed in the function of proppant volume and fracture geometry at the pseu- do-steady state. With the iterative method, the effectively propped permeability, kfe, is corrected using the i^-situ Reynolds number, NRe. The goal of this paper is to present a new UFD extension to design the proppant volume and the optimal fracture geometry. The results show that there exists an optimal proppant volume for a certain reservoir. The small aspect ratio （yJXe） and high permeability reservoirs need short and wide fractures to diminish the non-Darcy effect. On the contrary, long and narrow fractures are required for the large aspect ratio and low permeability reservoirs. A small proppant volame is prone to creating long fractures, while a relatively large proppant volume creates wide fractures. The new extension can be used to evaluate the previous fracture parameters and design the following fracture parameters of the fractured horizontal well in heterogeneous tight gas reservoirs, with the non-Darcy effect taken into account.

关键词： tight gas reservoir heterogeneity non-Darcy effect fractured horizontal well fracture geometry design

The gas recovery of water-drive gas reservoirs

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Journal of Hydrodynamics 2015年第4期27卷 530-541页

作者：李闽李滔蒋琼杨海刘世常 State key laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum University

This paper proposes a method for determining the gas recovery of water-drive gas reservoirs. First, the water influx coefficient B in the theoretical formula Pr =（1-Rg）/（1-RgB） is used to determine the influence of the aquifer behavior. According to the theoretical formula, the relationship between the norrnalized pressure Pr and the degree of the reserve recovery Rg can be obtained with different values of B, which can be used to determine the activity level of the aquifer behavior. Second, according to Pra = （1-Rga）/（1-aEva）（where a = 1-Sgr/Sgi ）, the relationship between the normalized abandonment pressure Pra and the ultimate gas recovery Rga can be obtained, as the Agarwal end-point line. The intersection of the above two lines represents the value of the estimated ultimate gas recovery and the normalized abandonment pressure pra. Finally, an evaluation table and a set of demarcation charts are established, with different values of Sgr/Sgi and Eva as well as the water influx coefficient B, which can be used to determine the gas recovery of water-drive gas reservoirs with different activity levels of the aquifer behavior.

关键词： water-drive gas reservoirs degree of reserve recovery water influx coefficient evaluation table demarcation charts

Transient flow model and pressure dynamic features of tree-shaped fractal reservoirs

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Journal of Hydrodynamics 2014年第4期26卷 654-663页

作者：谭晓华李晓平 State key laboratory of Oil and gas Reservoir geology and Exploitation southwest petroleum university

A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the trce-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch number N, the length ratio α, and the branch angle θ. The diameter ratio β has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch level M of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.

关键词： tree-shaped fractal transient flow pressure dynamic characteristic naturally fractured reservoir type curve

Experimental Investigation of Vibration Response of A Free-Hanging Flexible Riser Induced by Internal gas-Liquid Slug Flow

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China Ocean Engineering 2018年第6期32卷 633-645页

作者： ZHU Hong-jun ZHAO Hong-lei GAO Yue State key laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum University

The vibration response of a free-hanging flexible riser induced by internal gas-liquid slug flow was studied experimentally in a small-diameter tube model based on Froude number criterion. The flow regime in a curved riser model and the response displacements of the riser were simultaneously recorded by high speed cameras. The gas superficial velocity ranges from 0.1 m/s to 0.6 m/s while the liquid superficial velocity from 0.06 m/s to 0.3 m/*** slugging type 3, unstable oscillation flow and relatively stable slug flow were observed in the considered flow rates. Severe slugging type 3 characterized by premature gas penetration occurs at relatively low flow rates. Both the cycle time and slug length become shorter as the gas flow rate increases. The pressure at the riser base undergoes a longer period and larger amplitude of fluctuation as compared with the other two flow regimes. Additionally, severe slugging leads to the most vigorous in-plane vibration. However, the responses in the vertical and horizontal directions are not synchronized. The vertical vibration is dominated by the second mode while the horizontal vibration is dominated by the first mode. Similar to the vortex-induced vibration, three branches are identified as initial branch, build-up branch and descending branch for the response versus the mixture velocity of gas-liquid flow.

关键词： gas-liquid two-phase flow severe slugging liquid slug flexible riser flow-induced vibration