支撑裂缝长期导流能力模拟研究

Modeling of Long-term Flow Conductivity in Propped Fractures

目前主要采用裂缝导流能力仪、生产历史拟合及压力恢复试井法评价支撑缝长期导流能力,已有的方法或难以全面考虑各种伤害因素对导流能力的影响,或测试时间长、难度大、成本高。用颗粒物质力学、对流扩散理论和压力溶蚀理论,考虑支撑剂颗粒成岩作用的3个过程(接触面溶蚀过程、边缘扩散作用控制的传质过程和颗粒自由表面沉淀过程)共同作用的压力溶蚀成岩作用、支撑剂颗粒弹性压缩变形、颗粒排列方式及由弹性和蠕变变形引起的支撑剂颗粒嵌入等因素对导流能力的影响,导出了新的支撑裂缝长期导流能力模型。该模型计算结果与温庆志等的实验数据更相符,证明了该模型的正确性。该模型能准确方便地预测复杂条件下支撑缝导流能力变化规律,为正确评价和选择支撑剂提供可靠的依据参考,有效地指导压裂油气井的合理开发。

The long-term flow conductivity in propped fractures was evaluated by fracture conductivity test instrument,production history matching and pressure build-up test.These methods could not take all of the damage mechanisms into consideration,some of them were time-consuming,difficult and high cost for testing.Based on the particle material mechanics,convection diffusion theory and pressure dissolution theory,a novel long-term propped fracture conductivity simulation model was presented.This novel model considered the effect of diagenesis incorporated pressure dissolution process at grain-to-grain contact interfaces,dissolved mass transfer process controlled by diffusion on the edge of particle and precipitation process at free surface of proppant grains,elastic compressed deformation of proppant grains attachment,grains arrangement,and proppant embedment caused by elastic deformation and creep deformation on the flow conductivity of fractures.The simulation results are matched with the experimental data and can explain the experimental phenomena very well.Therefore,the novel model could conveniently and accurately predict the variation relationship of long-term propped fracture conductivity under complicated condition.Not only could this novel model provide a reliable guidance for evaluating and selecting proppant properly,but also provide a rational guide for the exploitation and development of oil and gas reservoirs.