延川南区块深部煤层气U型分段压裂水平井地质适用性研究

深部煤层渗透性普遍较差，直井压裂开发单井产量低效果不甚理想，而U型水平井分段压裂开发煤层气技术已取得很好的效果。该项技术试验前必须进行适合该井型的地质评价。以鄂尔多斯盆地东缘延川南区块为例，首先分析影响水平井压裂产能的地质因素，主要为单井控制资源量、储层渗透性和煤层气解吸难易程度，其中单井控制资源量受含气量和煤层厚度影响，渗透性与煤层埋深、构造及煤体结构等有关，碎裂煤发育区渗透性相对好。而后假定吸附性能不变的前提下，利用数值模拟方法分别模拟了不同渗透率、含气量和煤层厚度条件下水平井压裂的产气情况，模拟结果表明水平井压裂后累计产气量与渗透率、含气量、煤层厚度正相关。最后在经济效益评价的基础上，查明适合水平井压裂的地质条件：渗透率>0.25×10^–3μm²，含气量>12.3m³/t，煤层厚度>2.9m。该地质适用性评价标准在现场得到广泛应用，并收到了良好的开发效益。

Geological adaptability of deep CBM U-shaped staged fracturing horizontal well in the south block of Yanchuan

The permeability of deep coal seam is generally poor, while the low production efficiency of fractured straight well is not ideal, therefore, the fractured U-shaped horizontal well development has been carried out and achieved good results. Geological evaluation must be carried out before the test to optimize the area suitable for U-shaped horizontal well. The main geological influence factors of the productivity of the fractured horizontal well are resources controlled by a single well, permeability and desorption difficulty, in which the resources controlled by single well are affected by the gas content and the thickness of the coal seam, and the permeability is related to the burial depth of coal seams and the characteristics of structural development and the degree of coal structure development. The permeability of broken coal is relatively good. Then, on the assumption that the adsorption performance is constant, the numerical simulation method was used respectively. The gas production of fractured horizontal wells with different permeability, gas content and thickness of coal seam was simulated. The simulation results show that the gas production of fractured horizontal well is positively related to permeability, gas content and thickness of coal seam. Finally, based on the evaluation of economic benefits, the geological conditions for the development of fractured horizontal well were identified as permeability > 0.25×10-3μm2, the gas content > 12.3 m3/t, the thickness of coal seam > 2.9 m. The geological suitability evaluation standard has been widely applied in the field, and has received good development benefits.