期刊
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
卷 142, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijrmms.2021.104740
关键词
Glutenite reservoir; Cyclic injection; 3D fracture surface; Fracture surface roughness; Penetration ratio
资金
- National Science Fund for Distinguished Young Scholars [51925405]
- National Natural Science Foundation of China [51774299]
- China National Petroleum Corporation (CNPC) [ZLZX2020-01]
- China University of Petroleum-Beijing [ZLZX2020-01]
The study demonstrates that cyclic injection can effectively reduce the roughness of fracture surfaces in glutenite reservoirs, increasing penetration ratio of gravel and improving understanding and adjustment of fracturing design.
In glutenite reservoirs, hydraulic fracture surfaces are always rough due to the presence of gravels. The fracture surface roughness significantly affects the proppant transport, settlement, and supporting effectiveness during and after hydraulic fracturing. To reduce the fracture surface roughness in fracturing glutenite reservoirs, the cyclic injection was proposed and verified with hydraulic fracturing experiments on glutenite samples. After fracturing in experiments, a laser scanning system was used to scan and extract the fracture surface 3D data, of which the fracture surfaces were characterized with 5 parameters. Experimental results showed that the cyclic injection reduced the fracture asperity height by 30-70%, the standard deviation of the normal fracture asperity height reduced by over 52%. Meanwhile, the cyclic injection increased the penetration ratio (the number of those penetrated by hydraulic fractures divided by the total number of gravels along the fracture path) by 20% for gravel size of 2 - 6 mm and 30% for gravel size of 6 - 25 mm. The mechanism of the cyclic injection reducing fracture surface roughness was summarized: (i) the gravels damage enhanced by cyclic loads makes them prone to fracture penetrating; (ii) cyclic compression weakens gravels and the cements holding them near the fracture, then the fracture surface deformation (shearing/slipping) is responsible to gravel detachment. In the end, the fracturing fluid friction affected by the fracture surface roughness was evaluated. This study is helpful for understanding and tailoring the fracturing design when the fracture surface roughness plays a critical role in the glutenite reservoir stimulation.
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