沁南东区块煤储层特征及煤层气开发井网间距优化
Analysis of coal reservoir characteristics in the Qinnan-East block and its spacing optimization of CBM development well networks
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摘要: 煤层气井网优化与部署是煤层气开发方案的重要组成部分,合理的井网布置可大幅度提高煤层气井产量,降低开发成本。针对这一问题,以沁水盆地沁南东区块为依托,系统分析了研究区煤层条件、煤层含气量和渗透性分布特征;通过数值模拟计算不同井网方案下的生产动态,提出了综合考虑累积现金流和采收率等经济评价参数确定合理井网井距的优化方法。研究结果表明,研究区山西组3号煤层厚度4～6 m,平均5. 61 m,煤层埋藏深度在417. 93～1 527. 49 m。煤层含气量2. 87～24. 63 m3/t,平均为13. 78 m3/t,且随着煤层埋藏深度的增加,煤层含气量按对数函数规律增高。煤层渗透率较低,试井渗透率为0. 01×10-15～0. 2×10-15m2,平均为0. 06×10-15m2,且随着埋藏深度的增加煤储层渗透性呈指数函数降低。根据研究区煤储层条件,对不同埋藏深度煤层气井的井网间距进行了产能模拟计算,并综合考虑累积现金流和采收率等经济评价参数,确定了不同煤层埋藏深度煤层气井合理井网间距,500 m以浅的区域为350 m×300 m,在500～1 000 m的区域为300 m×250 m,在1 000 m以深的区域为250 m×250 m,实际井网部署实施时应根据实际地质条件适当调整,这些认识为本区煤层气开发制定合理的井网间距提供了参考。Abstract: Well pattern optimization and deployment of coalbed methane (CBM) are the important part to the develop- ment scheme of CBM. A reasonable well pattern can dramatically increase the CBM production as well as reduce the development costs. For this problem,based on the Qinnan-East block in the Qinshui basin,this paper systematically analyzed coal seam conditions and distribution characteristics of gas contents and permeability in study area. By calcu- lating the production dynamics of different well pattern schemes on the basis of numerical simulation,an optimization method for determining reasonable well spacing is put forward by synthetically considering the economic evaluation pa- rameters including cumulative cash flow and recovery rate. It is shown that the thickness of No. 3 coal seam in Shanxi formation varies from 4 to 6 m with average of 5. 61 m,and burial depth varies between 417. 93 and 1 527. 49 m. Gascontents of No. 3 coal seam vary from 2. 87 to 24. 63 m3 / t with average of 13. 78 m3 / t and increase with burial depth by the law of logarithmic function. Well test permeability of target coal seam is lower,which vary from 0. 01×10-15 to 0. 2×10-15 m2 with average of 0. 06×10-15 m2 and decrease with burial depth by exponential function law. According to the coal reservoir conditions in study area,CBM production with well spacing of different burial depths well pattern was calculated on the basis of numerical simulation as well as determined the reasonable well spacing of different burial depths by synthetically considering cumulative cash flow and recovery rate. It is analyzed that well spacing in study ar- ea is 350 m×300 m for the burial depth shallower than 500 m,350 m×250 m for the burial depth between 500 m and 100 0 m and 250 m×200 m for the burial depth deeper than 1 000 m. But the actual well pattern deployment should be adjusted according to the actual geological conditions. These understandings provide a theoretical basis for the reasona- ble formulation of well pattern in the CBM development in this area.
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