China Petroleum Exploration ›› 2017, Vol. 22 ›› Issue (6): 69-77.DOI: 10.3969/j.issn.1672-7703.2017.06.008

• PETROLEUM GEOLOGY • Previous Articles     Next Articles

Rock mechanics and brittleness of shale reservoirs in the lower Sha 3 Member in Luojia area, Zhanhua sag

Lu Yixiang1,2, Pan Renfang2, Tang Lianyu3, Li Xiaotian2, Wu Wenjing2, Shen Luyin2   

  1. 1 Guangxi Oil Production Plant of Southwest Oil and Gas Company, Sinopec;
    2 Key Laboratory of Oil and Gas Resources and Exploration Technology, Ministry of Education(Yangtze University);
    3 Downhole Service Company of PetroChina Jidong Oilfield Company
  • Received:2016-08-10 Revised:2017-09-28 Online:2017-11-15 Published:2017-11-11

Abstract: Shale, as one type of unconventional reservoir, is characterized by low porosity and low permeability. To improve its deliverability, large-scale hydraulic fracturing is required. Brittleness of the rock must be taken into consideration during the reservoir fracturing. The shale of the lower third Member of Shahejie Formation (lower Sha 3 Member or lower Es3) in the Luojia area of the Zhanhua sag is abundant with oil and gas resources. Its brittleness was investigated in respect of mineral composition, geophysical logging and triaxial stress test. The results show that, in respect of mineral composition, the brittleness index of the lower Es3 shale is 56.3%, suggesting that complex fracture system may easily form after fracturing; in respect of geophysical logging, the lower Es3 shale exhibits high Young's modulus and low Poisson's ratio, and its brittleness index is over 40%, which also prove that the shale is very brittle; in respect of triaxial stress test, the triaxial compressive stress-strain curves of the core samples present all brittle failure, which once again shows high brittleness of the shale. Accordingly, it can be concluded that the brittleness of the lower Es 3 shale in the Luojia area is good, revealing certain fracturability.

Key words: Zhanhua sag, shale brittleness, Young's modulus, Poisson ratio, triaxial stress test

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