直井水力喷砂射孔排量波动对井壁开孔形状的影响

Influence of pumping flowrate fluctuation on penetration shape during hydra-jet perforation

地面高压泵组排量波动不可避免,水力喷砂射孔管柱会随着排量波动而轴向运动,这使得射孔井壁开孔形状并非圆形,而是以井轴方向为长轴的椭圆形。基于线弹性变形和磨料射流切割理论,建立了水力射孔井壁椭圆孔形状评价模型。该模型通过确定各时刻喷射点坐标和射流切割深度来判断射流是否穿透套管形成有效孔眼。假设排量在波动范围内取值服从均匀概率分布,可得排量波动范围对椭圆长短轴的影响规律。结果表明,直井水力射孔排量波动范围与椭圆长轴呈线性递增关系;当排量波动范围低于±0.04 m3/min时,椭圆孔长短轴之比小于2.0,能够保证定点射孔要求。

Flow-rate fluctuation cannot be avoided for high pressure pump group on surface during fracturing pumping. The hydra- jet perforation string moves along wellbore axis with the flow-rate fluctuation, which causes the penetration shape is not a circle, but an ellipse with major axis in wellbore direction. In the paper, an evaluation model for hydra-jet perforation shape was built based on the linear elasticity deformation and abrasive jet cutting theory. In order to judge whether the casing is penetrated, we proposed the compute scheme of the jet coordinates at each time and cutting depth. Assuming the pumping flowrate is of uniform statistical distribution within fluctuation region, the results show that the major axis of ellipse hole is proportional to the range of pumping fluctuation in vertical wells. If pumping flow-rate fluctuation is below ＋0.04 mVmin, the ratio of major axis to minor axis of the ellipse hole would be less than 2.0, which can satisfy the pin-point perforation. Therefore, the paper recommends the flow-rate fluctuation needs to be controlled in the range of ±0.04 m^3/min.