Oil & Gas Geology ›› 2020, Vol. 41 ›› Issue (3): 484-491,557.doi: 10.11743/ogg20200305

• Petroleum Geology • Previous Articles     Next Articles

Fracture characteristics and their influence on natural gas production: A case study of the tight conglomerate reservoir in the Upper Triassic Xujiahe Formation in Jian'ge area,Sichuan Basin

Lyu Wenya1,2, Miao Fengbin2,3, Zhang Benjian4, Zeng Qi4, Xu Xiang2, Ji Min5   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China;
    2. College of Geosciences, China University of Petroleum(Beijing), Beijing 102249, China;
    3. Wuhan Center of China Geological Survey, Wuhan, Hubei 430205, China;
    4. Branch of Chuanxibei Gas Field, PetroChina Southwest Oil and Gas Field Company, Jiangyou, Sichuan 621709, China;
    5. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
  • Received:2019-05-25 Revised:2020-03-26 Published:2020-06-16

Abstract: Natural fractures are important storage space and main seepage channels in tight conglomerate reservoirs,which function to influence the accumulation,enrichment and single-well productivity of tight gas.An integration of analogous outcrop,core,thin section,well log and production data,is applied to the study on the types and characteristics of natural fractures in the tight conglomerate reservoir of the Upper Triassic Xujiahe Formation in Jian'ge area,Sichuan Basin,and then the influence analysis of natural fractures on tight gas productivity.Trans-gravel,intra-gravel and gravel-edge fractures are developed in the tight conglomerate reservoirs.In terms of geological origin,trans-gravel fractures are tectonic fractures; intra-gravel fractures include tectonic,tectonic-diagenetic and parent-rock fractures; and gravel-edge fractures are tectonic-diagenetic fractures.Among others,trans-gravel fractures are the largest in areal density,porosity and permeability,followed by intra-gravel fractures and gravel-edge ones.Thus,the trans-gravel fractures are more contributive to the formation of the tight conglomerate reservoirs,and the most conducive to natural gas enrichment with high yield.The degree of fracture development is positively correlated with gas production:the greater the fracture density is,the greater the tight gas productivity could be.Under the present-day in-situ stress trending towards the nearly east-west (EW) to NWW-SEE direction,the contributions made by fractures of diverse directions are differential on the tight gas productivity.The nearly EW-trending fractures feature bigger apertures and good connectivity,being the most favorable area for tight gas production,followed by nearly NS- and NW-SE-trending fractures,and then the NE-SW-trending ones.

Key words: productivity, natural fracture, tight conglomerate reservoir, Xujiahe Formation, Jian'ge area, Sichuan Basin

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