Investigation of pore structure alteration and permeability enhancement of shale matrix by supercritical water treatment after hydraulic fracturing

IF 4.2 Q2 ENERGY & FUELS

Petroleum Pub Date : 2024-06-01 DOI:10.1016/j.petlm.2022.05.002

Yili Kang , Peisong Li , Wangkun Cao , Mingjun Chen , Lijun You , Jiang Liu , Zhehan Lai

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引用次数: 0

Abstract

Shale gas reservoirs are unconventional tight gas reservoirs, in which horizontal wells and hydraulic fracturing are required to achieve commercial development. The fracture networks created by hydraulic fracturing can increase the drainage area extensively to enhance shale gas recovery. However, large volumes of fracturing fluid that is difficult to flow back to the surface and remained in the shale formation, will inevitably lead to damages of the shale formations and limit the effectiveness of stimulation. Supercritical water (SCW) treatment after hydraulic fracturing is a new method to enhance shale gas recovery by using appropriate heat treatment methods to the specific formation to convert the retained fracturing fluid into a supercritical state (at temperatures in excess of 373.946°C and pressures in excess of 22.064 MPa). An experiment was conducted to simulate the reaction between shale and SCW, and the capacity of SCW treatment to enhance the permeability of the shale was evaluated by measuring the response of the shale porosity and permeability on SCW treatment. The experimental results show that the shale porosity and permeability increase by 213.43% and 2198.37%, respectively. The pore structure alteration and permeability enhancement of the shale matrix were determined by analyzing the changes in pore structure and mineral composition after SCW treatment. The mechanisms that affect pore structure and mineral composition include oxidative catalysis decomposition of organic matters and reducing minerals, acid-catalyzed decomposition of carbonate minerals and feldspar minerals, hydrothermal catalysis induced fracture extension and cementation weakening induced fracture extension. SCW treatment converts harm into a benefit by reducing the intrusion of harmful substances into the shale formation, which will broaden the scope and scale of shale formation stimulation.

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水力压裂后超临界水处理对页岩基质孔隙结构改变和渗透性增强的研究

页岩气藏属于非常规致密气藏，需要通过水平井和水力压裂技术实现商业开发。水力压裂所形成的裂缝网络可以大量增加排水面积，从而提高页岩气的采收率。然而，大量压裂液难以流回地表，滞留在页岩层中，势必会对页岩层造成破坏，限制增产效果。水力压裂后的超临界水（SCW）处理是一种提高页岩气采收率的新方法，它针对特定地层采用适当的热处理方法，将保留的压裂液转化为超临界状态（温度超过 373.946°C，压力超过 22.064 兆帕）。实验模拟了页岩与超临界水的反应，并通过测量页岩孔隙度和渗透率对超临界水处理的响应，评估了超临界水处理提高页岩渗透率的能力。实验结果表明，页岩的孔隙率和渗透率分别增加了 213.43% 和 2198.37%。通过分析超临界水处理后孔隙结构和矿物成分的变化，确定了页岩基质孔隙结构的改变和渗透率的提高。影响孔隙结构和矿物组成的机制包括有机物和还原性矿物的氧化催化分解、碳酸盐矿物和长石矿物的酸催化分解、热液催化诱导裂缝扩展以及胶结弱化诱导裂缝扩展。超临界水处理通过减少有害物质对页岩地层的侵入，化害为利，这将扩大页岩地层激励的范围和规模。

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来源期刊

Petroleum Earth and Planetary Sciences-Geology

CiteScore

9.20

自引率

0.00%

发文量

审稿时长

124 days

期刊介绍： Examples of appropriate topical areas that will be considered include the following: 1.comprehensive research on oil and gas reservoir (reservoir geology): -geological basis of oil and gas reservoirs -reservoir geochemistry -reservoir formation mechanism -reservoir identification methods and techniques 2.kinetics of oil and gas basins and analyses of potential oil and gas resources: -fine description factors of hydrocarbon accumulation -mechanism analysis on recovery and dynamic accumulation process -relationship between accumulation factors and the accumulation process -analysis of oil and gas potential resource 3.theories and methods for complex reservoir geophysical prospecting: -geophysical basis of deep geologic structures and background of hydrocarbon occurrence -geophysical prediction of deep and complex reservoirs -physical test analyses and numerical simulations of reservoir rocks -anisotropic medium seismic imaging theory and new technology for multiwave seismic exploration -o theories and methods for reservoir fluid geophysical identification and prediction 4.theories, methods, technology, and design for complex reservoir development: -reservoir percolation theory and application technology -field development theories and methods -theory and technology for enhancing recovery efficiency 5.working liquid for oil and gas wells and reservoir protection technology: -working chemicals and mechanics for oil and gas wells -reservoir protection technology 6.new techniques and technologies for oil and gas drilling and production: -under-balanced drilling/gas drilling -special-track well drilling -cementing and completion of oil and gas wells -engineering safety applications for oil and gas wells -new technology of fracture acidizing