煤岩压裂裂缝形态-压力响应实验研究及应用

Experimental Research on Fracture Morphology-pressure Response of Coal Rock Fracturing and Application

大量施工数据表明,煤岩压裂施工压力值常高于预测值,且大部分井无明显破裂压力。从物模实验着手,通过实验数据与现场施工数据对比方法,解释上述施工现象。煤层气施工压力是煤岩裂缝扩展在地面的响应结果,与裂缝形态关系密切。调研裂缝形态影响因素并应用物模实验方法,人工起裂多种形态裂缝。起裂实验结果显示:实验裂缝形态主要分为单裂缝、平行多裂缝、相交多裂缝,不同裂缝形态对应的压力曲线形态明显不同。单裂缝起裂时破裂压力明显,且延伸压力接近最小水平主应力;平行多裂缝施工压力曲线平滑,无明显破裂压力;相交多裂缝存在多个破裂压力;多裂缝延伸压力高于单裂缝。根据现场施工压力并结合实验结论,分析柿庄南2口井裂缝形态,并采取措施,取得较好效果。

A large number of construction data show that construction pressure is often higher than the predicted pressure in coal rock fracturing, and most wells have no obvious fracture pressure. Proceeding from physical model experiments and comparison between experimental data and construction data, we explain the phenomenon. Construction pressure is result of fracture propagation in ground, which is close to fracture morphology. In this paper, the influence factors of fracture morphology were investigated and the experimental method was applied to fracture various types of cracks artificially. Results of crack initiation show that： fracture morphologies mainly include single fractures, parallel multi-fracture, intersecting multi-fracture, and the pressure curves of different fracture morphologies were different. Single fracture has obvious fracturing pressure, and the extension pressure is close to the minimum horizontal principal stress. The pressure curve of parallel multi-fracture is smooth, without obvious fracture pressure. Intersecting multi-fracture has multi-fracturing pressure. Propagation pressure of multi-fracture is higher than that of single fracture. According to the field construction pressure and the experimental conclusion, the fracture morphology of the two wells in south Shizhuangnan Mine is analyzed and the measures are taken to achieve better results.