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煤层气开发井网样式和井距优化研究以鄂尔多斯盆地大宁区块为例

Study on optimization of well pattern and well spacing for CBM development:Taking Daning Block as an example

  • 摘要: 煤层气井网优化设计与部署是煤层气开发方案编制的关键部分,合理的井网部署不仅可以优化煤层气产量,还可降低煤层气开发成本,提高经济效益。针对这一问题,以鄂尔多斯盆地大宁区块为研究对象,系统分析了研究区煤层条件及煤储层特征,确定了煤层气开发适用的井型和井网方位。结果显示:大宁区块山西组5号煤层具有厚度大,结构简单,含气量高,渗透率低等特点,煤层顶底板封隔性好,资源潜力巨大。煤层气开发井型应以定向井为主,水平井为辅,配合相应的井网进行规模开发,井网方位为NE66°;利用煤层气产能数值模拟软件COMET3,对大宁区块当前采用的井网样式和井排距进行产能预测,模拟评价了不同井网样式和不同井排距开放方案下的产能。数值模拟结果表明:当前大宁区块煤层气开发所采用的井网样式和井排距,在排采3 086 d后,煤层气采收率仅为19.03%,煤层气资源动用程度低。在井排距为300 m×80 m和400 m×100 m(即井排距比为4∶1)时五点式井网的单井累计产气量最大,在井排距为300 m×100 m和360 m×120 m(即井排距比为3∶1)时矩形井网单井累计产气量最大,据此认为大宁区块在设置4∶1的井排距比时应选用五点式井网,设置3∶1的井排距比时应选用矩形井网,井网样式和井排距经过优选后,煤层气采收率分别达44.18%和36.85%,煤层气资源动用程度大幅度提高。

     

    Abstract: CBM well pattern optimization design and deployment is a key part of CBM development plan formulation. Reasonable well pattern deployment can not only optimize CBM production, but also reduce CBM development costs and improve economic benefits. In response to this problem, taking Daning block in the Ordos Basin as the research object, the coal seam conditions and coal reservoir characteristics in the study area were systematically analyzed, and the suitable well type and well pattern orientation for CBM development were determined. The results show that the No.5 coal seam of Shanxi Formation in the Daning block has the characteristics of large thickness, simple structure, high gas content and low permeability. The well type of CBM development should be mainly directional wells, supplemented by horizontal wells, with the corresponding well pattern for large-scale development, and the well pattern orientation is NE66°; using the CBM productivity numerical simulation software COMET3, the current use of the Daning block is analyzed. The productivity was predicted based on the well pattern and well spacing, and the productivity under the open scheme of different well pattern and well spacing was simulated and evaluated. Numerical simulation results show that the CBM recovery rate is only 19.03% after3086d of well pattern and well spacing used in the current CBM development in the Daning block, indicating a low degree of CBM resource production. When the well spacing is 300 m×80 m and 400 m×100 m (that is, the well spacing ratio is 4∶1), the cumulative gas production of a single well in the five-spot well pattern is the largest. That is, when the well row spacing ratio is 3∶1), the cumulative gas production of a single well in the rectangular well pattern is the largest. Therefore, it is considered that the five-point well pattern should be selected when setting the well row spacing ratio of 4∶1 in the Daning block, and the 3∶1 Rectangular well pattern should be selected for the well spacing ratio of 1. After the well pattern and well spacing are optimized, the CBM recovery rate reaches 44.18% and 36.85% respectively, and the CBM resource production degree is greatly improved.

     

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