射孔间距-倾角对深煤层水力裂缝扩展影响的离散元分析

Discrete Meta-analysis on Effect of Shot Hole Spacing-inclination on Hydraulic Fracture Extension in Deep Coal Seams

研究煤岩储层裂缝扩展的影响因素,对提高煤层气采收率十分重要。为探究不同射孔间距-倾角对深层煤岩裂缝扩展规律的影响,利用离散元分析方法,考虑井周煤岩应力变化特征、最大周向应力准则、原始储层等条件,研究射孔间距-倾角对压裂缝网扩展形态及延伸范围的影响规律。模拟结果表明:随射孔间距从40 mm变化至100 mm,当间距为60 mm时裂缝条数数量最多;当射孔倾角从15°到60°变化时,当射孔角度为45°时,缝网形态最为复杂;即射孔间距为60 mm且射孔倾角为θ=45°时,水力裂缝的缝网形态复杂度显著增大,缝网扩展范围最大。通过神府北木瓜区Y-1井验证,预测结果与实测数据具有一致性,证明所建煤岩数值模型的正确性。

It is important to study the influencing factors of fracture extension in coal rock reservoirs to improve the recovery rate of coal bed methane.In order to investigate the influence of different shot hole spacing and inclination angle on the fracture extension law of deep-seated coal rock,discrete element analysis method was used to study the influence of shot hole spacing and inclination angle on the fracture network extension pattern and extension range,taking into account of the stress change characteristics of the coal rock around the wells,the maximum circumferential stress criterion,and the original reservoir and other conditions.The simulation results show that:the number of cracks is the highest when the shot hole spacing is 60 mm,and the morphology of the fracture network is the most complex when the shot hole inclination angle is 45°,i.e.,the complexity of the fracture network of hydraulic fracture increases significantly and the extension range of the fracture network is the largest when the shot hole spacing is 60 mm and the shot hole inclination angle isθ=45°.Through the validation of Y-1 well in Shenfu North Mugua Zone,the prediction results are consistent with the measured data,proving the correctness of the constructed numerical model of coal rock.