夹层型陆相页岩油储层压裂裂缝扩展实验研究

doi:10.13809/j.cnki.cn32-1825/te.2025.01.016

摘要/Abstract

摘要：

鄂尔多斯盆地延长组沉积了一套泥页岩及细粒砂质岩，具有丰富的页岩油资源，勘探开发评估资源量合计达十几亿吨。但页岩油储层可动性差、地层埋深浅，水平段层理、断缝、断层发育，裂缝扩展形态未知，体积压裂改造难度大。针对长7段井下储层获取的全直径致密砂泥岩岩心和页岩岩心，利用水泥包裹岩心方法开展真三轴室内压裂物模实验，获取水力裂缝形态，揭示弱应力场下页岩油储层水力裂缝扩展机理。实验发现，页岩油储层层状结构较密集，岩石颗粒之间胶结性较弱，压裂液容易沿着层理渗滤，在垂向应力与最小水平主应力之差小于2 MPa时，水力裂缝形态多为水平缝，压裂液主要沿层理或水平的天然裂缝渗滤；垂向应力与最小水平主应力之差增加到7 MPa时，会出现垂向穿层缝，形成局部台阶，最后被弱胶结层理面捕获后，沿层理渗滤延展。因此，压裂施工时，优选垂向应力与最小水平主应力差值较大的区域进行施工（井口位于山顶），有利于水力裂缝垂向延展，增加储层的体积压裂效果，提高页岩油产量和增大经济效益。

关键词: 夹层型页岩油储层, 水力压裂实验, 最大水平主应力, 水力裂缝形态, 天然裂缝, 数值模拟

Abstract:

The Yanchang Formation in the Ordos Basin has deposited a set of mudshales and fine-grained sandy rocks, rich in shale oil resources, with an estimated resource potential exceeding billions of tons. However, shale oil reservoirs exhibit poor mobility, shallow burial depths, the development of bedding, fractures, and faults in horizontal sections, and unknown fracture propagation patterns, making volumetric fracturing challenging. To address this, cement-encased cores of full-diameter tight sandstone-mudstone and shale from the sublayer in the seventh member of the Yanchang Formation (Chang 7) were used in actual triaxial hydraulic fracturing physical model experiments. These experiments revealed hydraulic fracture morphologies and the fracture propagation mechanism under weak stress fields in shale oil reservoirs. The experiments found that shale oil reservoirs had tight layered structures and weak bonding between rock grains, causing fracturing fluid to easily infiltrate along bedding planes. When the difference between vertical stress and minimum horizontal principal stress was less than 2 MPa, hydraulic fractures predominantly formed horizontal fractures, with the fluid primarily infiltrating along bedding planes or horizontal natural fractures. When this stress difference increased to 7 MPa, vertical cross-layer fractures appeared, forming localized steps that eventually became captured by weakly bonded bedding planes, propagating horizontally along the layers. For fracturing operations, regions with a larger difference between vertical stress and minimum horizontal principal stress, such as wellheads at hilltops, are preferred. This facilitates vertical fracture propagation, improves volumetric fracturing effectiveness in reservoirs, enhances shale oil production, and increases economic benefits.

Key words: interbedded shale oil reservoir, hydraulic fracturing experiment, maximum horizontal principal stress, hydraulic fracture morphology, natural fractures, numerical simulation

中图分类号:

TE357

柴妮娜,李嘉瑞,张力文等. 夹层型陆相页岩油储层压裂裂缝扩展实验研究[J]. 油气藏评价与开发, 2025, 15(1): 124-130.

CHAI Nina,LI Jiarui,ZHANG Liwen, et al. Experimental study on hydraulic fracture propagation in interbedded continental shale oil reservoirs[J]. Petroleum Reservoir Evaluation and Development, 2025, 15(1): 124-130.

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方向	垂向应力/ MPa	水平最大地应力/MPa	水平最小主应力/MPa
最大地应力位于垂向	17	15	9、11、13、15
最大地应力位于水平	17	18	9、11、13、15

方向	垂向应力/ MPa	水平最大主应力/MPa	水平最小主应力/MPa
最大地应力位于垂向	18	11、13、15、17	9
最大地应力位于水平	10、12、14、16	18	9