Pore-scale study on methane hydrate formation and dissociation in a heterogeneous micromodel

During the development of carbonate reservoirs, the risk of bottom water invasion is a frequent concern. Pore-scale simulation methods are commonly acknowledged as effective tools for investigating the dynamics involved in water invasion mechanisms. Despite extensive research on gas-water two-phase flow, few studies have investigated reservoirs with interlayers, which can remarkably affect assessments of water invasion. Three models were designed to study the effects of different interlayer distributions on flow behavior. A mathematical model based on the volume of fluid (VOF) method was employed to describe variations in water saturation. The four primary influencing factors (interlayer distribution, gravity, pressure difference, and wettability) were studied based on simulations. The accuracy of the model was validated through comparisons with microfluidic visualization experiments. Compared to the model without interlayers, the models with semi-permeable and semi-sealed interlayers reduced the risk of water invasion, resulting in slower upward water saturation rates and delayed water breakthrough times. Neglecting gravity would introduce errors of up to 5.6% in water saturation and 24.2% in water breakthrough time for the models with interlayers. Controlling the pressure difference within 1.5 MPa/100 m would effectively reduce the produced water-gas ratio and delay the water breakthrough time. The water invasion behavior in the models with interlayers was highly sensitive to contact angles in the range of 50°–60°, while its effect on the model without interlayers was relatively small. Field-scale water invasion dynamics with examples from the Yuanba (YB) gas field in the Sichuan Basin, China, were consistent with the pore-scale simulation results. This work provides fundamental support for and valuable insights into the development of similar gas reservoirs, offering a strong foundation for future endeavors in this field. 

Pore-scale investigation of bottom water invasion dynamics in carbonate gas reservoirs with different interlayer distributions

CT-based 3D pore-fracture network analysis of volcanic reservoirs of Lower Cretaceous Yingcheng formation in southern Songliao Basin, China: Impact on natural gas migration

The complex resistivity spectra of 16 artificial sandstone samples with different physical property at different water and solution saturations were measured and fitted with the Cole–Cole model in the frequency band of 40 Hz to 110 MHz. The frequency exponent in the model indicates the ideal degree of the sample's capacitive property. The experimental result shows that the frequency exponents of the samples are concentrated mainly between 0.82 and 0.88 and present a segmented law that decreases first and then increases with decreasing the water saturation. The minimum frequency exponent has a linear relationship with porosity and cementation index and an exponential relationship with formation factors. The frequency exponent is expected to be used in the study of the oil–water distribution in the reservoir. The frequency exponents of the samples decrease with an increase in clay content. Frequency exponents are independent of the ion type in the solution. Numerical simulation results support that the capacitive property generated by the connected pore‐throat spaces is near ideal, but the capacitive property contributed by the closed pore‐throat spaces is non‐ideal. This could be the possible reason why the frequency exponents of the samples are less than one. The pore‐throats with higher capillary pressure can be blocked and become secondary closed pore‐throat space during the flooding process and result in a decrease in frequency exponent. This can explain the influence of reservoir parameters on frequency exponent and can further clarify the physical significance of the Cole–Cole frequency exponent on the rock's complex resistivity.

The Frequency Exponent of Artificial Sandstone's Complex Resistivity Spectrum

Effects of Microscopic Pore Structures on the Spontaneous Imbibition of Longmaxi Shale

Feng Wu*, Yanping Xi, Qicheng Fan, Cong Yao, Linlin Cong, Fengsheng Zhang, and Yan Kuang State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan, China Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral, Shandong University of Science and Technology, Qingdao 266590, Shandong, China School of geoscience and technology, Southwest Petroleum University, Chengdu 610500, China Hua xinsheng oil and gas operations management limited company, Chengdu 6105051, China Yanchang Oilfield Co., Ltd, Shaanxi Yanchang Petroleum(Group) Co., Ltd, Yan’an, Shanxi 717208, China Oil and Gas Evaluation Centre, China Petroleum Logging Corporation, China National Petroleum Corporation, Xi’an 710021, China

/pdf/influence-of-spatial-distribution-of-pores-on-nmr-transverse-kr6ibij96l.pdf

Influence of Spatial Distribution of Pores on NMR Transverse Relaxation Time in Pebbly Sandstone

Abstract The characteristics of pore-scale two-phase flow are of significance to the effective development of oil and gas resources, and visualization has gradually become one of the hot spots in the research of pore-scale two-phase flow. Based on the pore structure of rock, this research proposed a microscopic glass etching displacement experiment and a Navier–Stokes equation based finite element simulation to study the pore-scale gas–water two-phase flow. Then, this research conducted the proposed methods on the type I, type II and type III tight sandstone reservoirs in the Penglaizhen Formation of western Sichuan Basin, China. Results show that the outcomes of both the microscopic glass etching displacement experiment and the finite element simulation are by and large consistent. The water distributed in the large pores is displaced, and the trapped water mainly exists in the area induced by flow around high-permeability pores, perpendicular pores and disconnected ends of pores. The microscopic glass etching displacement experiment is conducive to better observing the phenomenon of a viscous finger-like breakthrough and air jumps in migration flows in narrow throats, while the finite element simulation has the advantages of cost effectiveness, easy operation and strong experimental reproducibility.

/pdf/pore-scale-gas-water-flow-in-rock-visualization-experiment-1skz9pq7p8.pdf

Pore-scale gas–water flow in rock: Visualization experiment and simulation

The invention discloses a fractured formation permeability curve calculation method based on an acoustic and electric imaging logging map. The method comprises the following steps of S1, converting acolor acoustic and electric imaging logging map into a grey-scale map; S2, segmenting a crack and a hole in the grey-scale map to obtain a binary map; S3, through selecting an appropriate window length and a step size, cutting the binary map into several small binary maps; S4, taking one small binary map to construct a three-dimensional physical model of the crack and the hole of the small binarymap; S5, calculating permeability based on the three-dimensional physical model; S6, repeatedly executing the steps S4 to S5 to obtain the permeability of all the small binary maps; and S7, using thepermeability of all the small binary maps to draw a fractured formation permeability curve. In the invention, based on the color acoustic and electric imaging logging map, the fractured formation permeability curve can be accurately calculated so that an evaluation of a fractured oil and gas reservoir is accurate and exploration and development of the fractured oil and gas reservoir can be well guided.

Fractured formation permeability curve calculation method based on acoustic and electric imaging logging map

The invention provides a core centrifugal rotor device, and belongs to the field of bridges. The core centrifugal rotor device comprises a disc body and a centrifugal unit. The centrifugal unit comprises a centrifugal tank and a transparent cover sheet. The centrifugal tank comprises a casing in contact fit with an assembly hole. One side of the casing is provided with an observation hole. When the centrifugal tank is installed in the assembly hole, the edge of the observation hole is flush with the edge of the assembly hole. The edge of the assembly hole is also provided with a first mountingfixing hole, and the transparent cover sheet is provided with a second mounting fixing hole matched with the first mounting fixing hole. A core liquid discharging assembly comprises a core fixing tube, a gas distribution chamber and a balance weight chamber. The centrifugation in the centrifugal tank can be observed through the observation hole after shutdown, without the need to specifically open the centrifugal unit. The additional gas distribution chamber can provide an inert atmosphere in the core fixing tube. In addition, the turbulent flow of the gas can further enhance the flow of theliquid to prevent the liquid from being blocked in capillaries of the core.

Core centrifugal rotor device

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Papers

Influence of Spatial Distribution of Pores on NMR Transverse Relaxation Time in Pebbly Sandstone

Pore-scale gas–water flow in rock: Visualization experiment and simulation

Fractured formation permeability curve calculation method based on acoustic and electric imaging logging map

Core centrifugal rotor device