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深部煤储层水平井组缝网压裂数值模拟研究

Numerical simulation study on network fracturing in horizontal well groups of deep coal reservoirs

  • 摘要: 水平井组同步压裂是深部煤储层开发的主要核心技术,压裂方式及压裂参数的选择对裂缝扩展规律及其形态会产生显著的影响。因此,基于水力压裂数值模拟方法,系统探究了深部煤储层同步压裂正对布缝与交错布缝模式下裂缝扩展规律及其改造效果,重点分析了水平地应力差、排量等关键参数对裂缝形态与储层改造效率的影响机制,并结合两簇压裂模式,定量评价了不同布缝方式的适应性,为深部煤层气高效开发提供理论支撑与技术参考。研究表明:在压裂过程中,两井中间位置的地应力受两井裂缝共同作用,应力状态更为复杂。相向扩展的裂缝尖端接近时,应力阴影相互覆盖,且尖端产生的拉应力叠加,致使裂缝尖端前方的应力减小。裂缝尖端附近应力变化剧烈,存在应力集中现象,而随着与裂缝距离的增加,应力变化程度逐渐减弱。随着应力差的增加,水力裂缝逐渐沿X方向线性扩展,相较于正对布缝,在交错布缝方式下,岔开布局会逐渐削弱簇间应力干扰,裂缝扩展逐步过渡为以单簇内分散改造为主。整体而言,低应力差下天然裂缝的协同作用优化了局部复杂度,而高应力差下裂缝扩展效率受限于线性化趋势。对比2种布缝方式下的压裂效果,交错布缝相较于正对布缝,其裂缝面积最大增加了25.69%(应力差3 MPa、排量0.005 m3/s)。因此,对于双水平井同步压裂,交错布缝方式整体更优,可通过井间应力干扰形成复杂裂缝网络,显著提升深部煤储层双水平井压裂的水力裂缝改造效果。

     

    Abstract: Simultaneous fracturing of horizontal well groups is a core technology for deep coal reservoir development, where fracturing methods and parameter selection significantly influence fracture propagation patterns and morphology. Therefore, fracture propagation mechanisms and stimulation effects under aligned and staggered fracture layouts in deep coal reservoirs are systematically investigated via hydraulic fracturing numerical simulation. It specifically analyzes the impact mechanisms of key parameters such as horizontal stress difference and injection rate on fracture morphology and reservoir stimulation efficiency. Through quantitative evaluation of different layout adaptabilities combined with two-cluster fracturing patterns, the research provides theoretical support and technical references for efficient deep coalbed methane development. The findings reveal: During fracturing, the inter-well mid-region experiences complex stress states under combined fracture effects. When oppositely propagating fracture tips approach, their stress shadows overlap and superimposed tensile stresses at the tips reduce forward stress. Stress variations intensify near fracture tips with evident stress concentration, gradually diminishing with distance from fractures. Increasing stress difference promotes X-directional linear fracture extension. Compared with aligned layouts, staggered configurations gradually weaken inter-cluster stress interference through offset arrangement, transitioning fracture propagation toward dispersed stimulation within single clusters. Overall, low stress differences enhance local complexity optimization through natural fracture synergy, while high stress differences limit propagation efficiency through linearization tendencies. Comparative analysis shows staggered layouts increase fracture area by up to 25.69% versus aligned patterns (at 3 MPa stress difference and 0.005 m3/s injection rate). Thus, staggered layouts prove superior for dual horizontal well simultaneous fracturing, leveraging inter-well stress interference to create complex fracture networks and significantly enhance hydraulic fracturing effectiveness in deep coal reservoirs.

     

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