Parameter Sensitivity Analysis in Geology-Engineering Integration Optimization for Shale Gas in Nanchuan Block
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摘要: 地质工程一体化综合施策是页岩气降本增效、提高开发效益的重要途径,综合、定量是一体化优化决策研究的重要发展方向.但目前的定量优化更多针对单井进行,常以优化得到的单井最优的裂缝半长/水平井长作为井网部署的依据.在利用运筹学技术构建的单井和区块效益目标函数的基础上,以中国南方海相页岩气为例,对比分析了单井和区块优化结果对主要地质条件和工程参数变化的敏感性.结果表明,尽管随着压裂规模(裂缝半长)的增大,单井和区块的效益都呈现先增后减的趋势,但最优的裂缝半长明显不同.同时,随孔隙度、含气饱和度、压力系数、天然气价格、压裂成本、钻井成本的升高,优化所得的单井和区块的最优裂缝半长变化规律不同.这表明,单井优化的结果不能作为井网部署的依据,区块和单井得到的最优值并不一致,应该以区块地质工程整体一体化优化的结果来布井.这一认识对页岩气及其他非常规油气井网优化部署和效益开发有现实的指导意义.Abstract: Geology-engineering integration policy is an important way to reduce cost and increase efficiency of shale gas. Integrated and quantitative approach is an important development direction of integrated optimization decision research. However, the current quantitative optimization is more often performed for single well, and the optimal fracture half-length/horizontal well length obtained from the optimization of a single well is often used as the basis for well pattern deployment. In this paper, it compares the sensitivity of single-well and block optimization results to major geological conditions and engineering parameters based on the objective functions of single-well and block benefits constructed using operational research techniques. The results show that although the benefits of both single-well and block show a trend of increasing and then decreasing with increasing fracture size (fracture half-length), the optimal fracture half-lengths are significantly different. Meanwhile, with the increase of porosity, gas saturation, pressure coefficient, natural gas price, fracturing cost and drilling cost, the optimal fracture half length of single well and block varies. It indicates that the optimal values obtained for blocks and single well are not consistent, and wells should be laid out with the results of the overall geology-engineering integration optimization of the blocks. This finding has realistic implications for the optimal deployment and efficient development of shale gas and other unconventional oil and gas well networks.
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图 1 南川地区五峰组底界构造及目标层段地质柱状图
Fig. 1. Geological histogram of bottom boundary structure and target interval of the Wufeng Formation in the Nanchuan area
表 1 页岩气数值模型基本参数(据Wang et al., 2019)
Table 1. Basic parameters of shale gas numerical model(from Wang et al., 2019)
参数 值 吸附气含量(m3/t) 3 兰氏压力(MPa) 4 兰氏体积(cm3/g) 2 初始地层压力(MPa) 32 基质渗透率(mD) 0.000 03 含气饱和度(%) 65 基质孔隙度(%) 4 水力压裂裂缝半长(m) 120 主裂缝导流能力(mD·m) 7 水力压裂裂缝开度(m) 0.001 簇间距(m) 20 水力压裂裂缝高度(m) 30 压裂段数 26 天然裂缝间距(m) 1 生产时间(a) 15 可采储量(108 m3) 19.32 表 2 影响因素的范围
Table 2. Variation range of influencing factors
水平 孔隙度
(%)含气饱和度
(%)压力系数 裂缝半长
(m)簇间距
(m)裂缝导流能力
(mD·m)水平段长度
(m)水平1 1 10 1.0 50 10 1 1 000 水平2 2 40 1.2 100 15 10 3 000 水平3 3 60 1.4 150 20 20 5 000 水平4 4 90 1.6 200 25 30 8 000 表 3 工程参数对区块的效益和成本的影响
Table 3. Influence of engineering parameters on benefit and cost of the whole block
参数值(m) 井数 单井产量
(108m3)单井收入
(亿元)单井成本
(亿元)区块总成本
(亿元)区块总收入
(亿元)区块总效益
(亿元)裂缝半长 50 1 711 0.466 0.485 0.433 741 830 88.7 100 841 0.784 0.971 0.509 428 816 388 130 667 0.957 1.240 0.585 390 824 434 150 551 1.070 1.410 0.684 377 775 399 200 406 1.350 1.830 1.250 508 745 237 水平段长度 1 000 1 711 0.391 0.371 0.358 612 635 23 3 000 551 1.175 1.570 0.669 369 864 495 5 000 319 1.955 2.760 1.010 324 880 556 7 000 232 2.732 3.940 1.400 324 915 591 注:工区大小如图 3所示. -
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