煤岩定向井水力裂缝起裂及非平面扩展实验

发布时间：2018-08-27 07:37

【摘要】：基于真三轴压裂装置对天然煤岩开展室内压裂模拟实验,对比了直井和定向井两种井型压裂水力裂缝的起裂特征及扩展形态,主要研究了不同相对方位角条件下,地应力、煤岩割理对定向井压裂水力裂缝非平面扩展规律的影响。实验结果表明,水力裂缝的整体扩展方式由相对方位角、割理和地应力状态共同决定:随着相对方位角的增加,水力裂缝形态复杂程度、泵注压力以及裂缝延伸压力增加;当水力裂缝沿着与井筒斜交方向起裂时,受割理影响在扩展过程中裂缝转向并发生扭曲,引起近井筒区域裂缝形态复杂化,起裂点附近出现多裂缝。相比直井形成的"工"或"十"型裂缝形态,近井筒主裂缝扭曲扩展并伴随着多次级裂缝的复杂裂缝形态,是造成煤层定向井压裂水力裂缝延伸困难的主要因素。
[Abstract]:Based on the laboratory fracturing simulation experiment of natural coal and rock with true triaxial fracturing device, the fracture initiation characteristics and propagation patterns of fracturing hydraulic fractures in vertical well and directional well are compared, and the in-situ stress under different relative azimuth angles is studied. Influence of coal and rock cleats on non-plane fracture propagation in directional well fracturing. The experimental results show that the whole propagation mode of hydraulic fracture is determined by relative azimuth angle, cleat and in-situ stress state: with the increase of relative azimuth angle, the complexity of hydraulic fracture morphology, pump injection pressure and fracture extension pressure increase; When the hydraulic fracture starts along the direction of inclined intersection with the wellbore, the fracture turns and distorts during the propagation process under the influence of the cleat, which leads to the complication of the fracture form near the wellbore and the appearance of multiple fractures near the initiation point. Compared with the "workmanship" or "ten" fracture form formed in the vertical well, the complex fracture form, which is the twisting and spreading of the main fracture near the wellbore and accompanied by the multiple grade fractures, is the main factor that causes the difficulty of hydraulic fracture extension in the directional well fracturing in the coal seam.
【作者单位】：中国石油大学(北京)油气资源与工程国家重点实验室;中国石油钻井工程技术研究院;中联煤层气有限责任公司;
【基金】：“十三五”国家科技重大专项基金(2016ZX05066) 国家杰出青年科学基金(51325402) 中国石油大学(北京)优秀青年教师基金(2462015YQ0203)
【分类号】：TE377

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