水力压裂多裂缝起裂射孔参数优化研究

THE PERFORATION PARAMETER OPTIMIZATION FOR MULTI FRACTURE INITIATION IN HYDRAULIC FRACTURING

  • 摘要: 针对复杂地质近井筒多裂缝起裂的难题, 结合岩体力学与损伤力学相关理论, 建立了近井筒地层流固——损伤力学模型, 采用数值求解获得了射孔壁面的应力及损伤状态, 计算表明:初始地应力最小值越小, 地层的起裂压力越低;射孔方位角越小, 起裂压力越低. 随着射孔方位角增大, 近井筒微裂缝为45° 夹角的拐折裂缝, 起裂压力增大, 基于此, 对于正断层及顺滑断层地应力类型, 取射孔方位角小于30°, 螺旋射孔夹角30°或45°, 对于逆断层地应力类型, 螺旋射孔夹角取45°, 可有效地实现多裂缝起裂.

     

    Abstract: A model of damage mechanics of fluid and solid near the wellbore is established, for the multi-fracture initiation near wellbore under complicated geological conditions, and the distribution of stress and damage of perforated wall is obtained by numerical analysis. Calculation shows that the smaller the crustal stress value is, the smaller the well perforation azimuth angle is, the lower the crack pressure will be. The crack stress increases with the increase of the perforation azimuth angle. When the near wellbore has inflexion cracks and an angle of 45° micro crack, the crack pressure increases. Based on this conclusion, the perforation azimuth angle is less than 30° for normal fault and smooth fault, when the spiral perforation angle is 30° or 45° and the thrust fault is 45°, multi-fracture initiation will be implemented effectively.

     

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