Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (6): 1324-1332.doi: 10.11743/ogg20190616

• Methods and Technologies • Previous Articles     Next Articles

A new method to calculate shale gas content based on gas reservoir characterization-A case study of Wells JY 1 and PY 1 in Sichuan Basin and its surrounding areas

Li Donghui1,2,3, Nie Haikuan1,2,3   

  1. 1. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 100083, China;
    2. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China;
    3. Key Laboratory of Shale Oil and Gas Exploration & Production, SINOPEC, Beijing 100083, China
  • Received:2018-08-14 Revised:2019-08-09 Online:2019-12-28 Published:2019-10-15

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Abstract: Lost gas content is an integral part of the total shale gas content,and also a significant parameter for determination of total shale gas volume and evaluation of shale gas in place and reserves.However,the USBM method,the existing calculation method of lost gas content based on core desorption test of coal-bed methane,along with its modified methods,cannot truly reflect the loss of gas content in shale gas reservoirs.Focusing on the instantaneous lost gas content and desorption rate during the core-drilling,we proposed a new method to calculate the lost gas content and the total shale gas content after performing a series of analyses,including characteristics of shale gas reservoirs,reservoir types,pore structure,pore throat size,gas reservoir pressure,coring time,desorbed gas content,and desorption time.The Well JY1 in the shale gas reservoir of overpressure and Well PY1 in the gas reservoir of normal pressure were taken as examples in the study.In applying the new method to Well JY1,we figured out the total gas content of the high-quality lower shale interval,varying from 6.87 m3/t to 9.02 m3/t with an average of 7.47 m3/t,and the total gas content of the upper shale interval,varying from 3.25 m3/t to 3.82 m3/t with an ave-rage of 3.64 m3/t; while in the Well PY1,the total gas content of the high-quality shale intervals ranges from 3.18 m3/t to 4.29 m3/t with an average of 3.83 m3/t,and the total gas content of the upper shale layers ranges from 1.67 m3/t to 2.28 m3/t with an average of 1.94 m3/t.Obviously,these values above are significantly higher than those calculated by using conventional methods.The new method proposed above has been verified by both the theoretical calculation method and performance-based calculation method with the shale gas production wells in Jiaoshiba area as examples.For shale gas reservoirs,especially the overpressured shale gas reservoirs,the new method highlighted in the study serves to provide not only a great theoretical support but also a practical way to calculate shale gas content and reserves,so as to evaluate the reservoir productivity.

Key words: lost gas, pore structure, gas reservoir pressure, gas content, shale gas, Jiaoshiba area, Sichuan Basin

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