基于不稳定渗流压裂水平气井产能研究

A STUDY OF DELIVERABILITY OF FRACTURED HORIZONTAL GAS WELL BASED ON UNSTEADY-STATE FLOW

对于低渗、特低渗气藏,用水平井开采不一定能取得满意的效果,水平井水力压裂技术已成为开采低渗透气藏的重要手段,水平井压裂后的产能预测又是水平井压裂技术的一大难题。文章以生产过程中裂缝内流体的非稳态流动为基础,应用复位势理论、叠加原理和数值分析求解方法,并考虑压裂水平井地层渗流和水平井筒管流耦合,建立了压裂水平井多条裂缝相互干扰的产能预测新模型,使计算结果更加合理。计算结果表明:该模型计算产量与实际生产数据符合率高;水平井筒内的压力损失对压裂水平井的生产动态有一定的影响;水平井内每条压裂缝的产量并不相等,端部裂缝的产量高于中部裂缝的产量;水平井筒内的压力呈不均匀分布,从指端到根端压力逐渐降低;裂缝不对称会使压裂水平井产量降低。研究成果对低渗透气藏的压裂水平井的设计具有一定的指导意义。

For gas reservoir with low or ultra-low permeability, fracturing operation has become an important way of stimulation in horizontal wells. However, it is a big challenge for the deliverability prediction after fracturing operation. Based on unsteady-state flow in fractures during production, a new model for predicting deliverability of fractured horizontal wells with multiple interactive fractures is built by using potential function theory, superimposition principle and numerical analysis method and taking into consideration of the coupling between percolation in formation and conduit flow in borehole of fractured horizontal well, to obtain more rational calculation results. The theoretical output calculated by using this model coincides well with the measured production data. The pressure loss in horizontal borehole may have certain influences on production performance of fractured horizontal wells. The deliverability of each hydraulic fracture in horizontal well is not identical, with deliverability of the end fractures being larger than the middle fractures. Pressure in horizontal borehole is in non-uniform distribution with pressure declining from tip to end. Asymmetrical distribution of fractures can lower deliverability of fractured horizontal wells. This model can be used to guide fracturing operation design of horizontal wells in gas reservoir with low permeability.