高陡复杂构造带页岩气水平井方位优选——以永川页岩气区块五峰—龙马溪组为例

Orientation optimization of shale gas horizontal wells in high steep complex structural belt

中石化永川页岩气区块钻井解释地应力方位井间差异较大,水平井轨迹无统一方位,测试产量差异较大。通过对研究区地应力方位与断裂产状的分布规律、已钻井水平井轨迹方位、产能影响的主要因素等方面的分析,得出以下结论①永川区块中部背斜区大断层附近地应力方向偏转较大,沿断层走向逐渐偏转,最大水平主应力方向与断层走向趋于一致;南部及北部向斜区中小规模断层附近地应力方向偏转幅度较小,与区域地应力方向基本一致,整体呈近东西向,地应力方位50°~95°;②在断裂发育区,I类储层钻遇率及钻遇长度对单井产能的贡献明显强于地应力方位的影响;③复杂断裂区水平井方位设计应以顺断裂走向为主,同时兼顾轨迹方位与最大水平主应力方向保持大于60°的夹角,气井日产量可以提高到20×10^(4)m^(3)以上。该研究对同类盆地页岩气开发部署及钻井跟踪具有重要的指导意义。

There is a big difference between wells in geostress orientation interpretation of Sinopec Yongchuan shale gas block,and there is no uniform orientation for horizontal well trajectory,so the test production is quite different.Based on the analysis of the distribution of in-situ stress orientation and fault occurrence,the trajectory orientation of drilled horizontal wells,and the main factors affecting productivity,it is concluded that:①The direction of geostress near the major fault in the central anticline area of Yongchuan block deflects greatly,and gradually deflects along the fault strike,and the direction of the maximum horizontal principal stress tends to be consistent with the fault trend;in the southern and northern syncline areas,the direction of the maximum horizontal principal stress tends to be consistent with that of the fault.The in-situ stress direction deflection amplitude near the large-scale fault is small,which is basically consistent with the regional geostress direction,and the overall direction is nearly east-west,and the geostress azimuth is 50°~95°;②In the fault development area,the contribution of the drilling encounter rate and drilling length to the single well productivity is obviously stronger than the influence of the geostress orientation;③The azimuth design of horizontal wells in complex fault areas should be mainly along the fault strike,and at the same time,the angle between the trajectory orientation and the maximum horizontal principal stress direction should be kept more than 60°,the daily production of gas wells can be increased to more than 20×10^(4)m^(3).The above research and understanding has important guiding significance for shale gas development deployment and drilling tracking in similar basins.