裂缝性油藏中压力损耗引起的储层伤害机理研究

Research of Mechanism of Reservoir Damage caused by Pressure Depletion in Fractured Reservoirs

世界上最丰富的储层中多数是天然裂缝性碳酸盐岩和碎屑岩系统。由于其复杂特征为优化这类储层带来很大困难。为了研究其复杂特性,需要分别描述储层基质和裂缝子系统,并且在整个生产阶段不断优化特性描述以适应压力损耗对产能的影响。室内试验采用Clashach岩心模拟单一裂缝,研究裂缝性油藏中压力损耗和有效应力增加引起的储层伤害机理。实验结果表明,在生产过程中,过度的压力消耗会导致裂缝性储层系统中有效应力增加。有效应力达到临界值后,砂粒在接触面上被压碎,碎屑颗粒会随流体进入储层,导致孔喉和裂缝被堵塞,增加了裂缝性油藏的压力损耗。

A great number of the world’s most prolific reservoirs are naturally fractured carbonate and clastic rock systems.Optimisation of production from this kind of reservoirs is a great challenge owing to complexities inherent in their characterization.These complexities arise,from the need to characterize the matrix and the fracture sub-systems separately and to continually optimize the characterization process throughout the production phase to accommodate pressure depletion effects on production.Laboratory experiments were performed on a Clashach core sample with a simulated single fracture to investigate the mechanisms for formation damage induced by pressure depletion and subsequent increase in effective stress in fractured reservoir systems.The experimental results show that excessive pressure depletion during production resulted in increased effective stress loading on the simulated fractured formation system.The effective stress reached a critical value at which the fracture plates were brought into contact,leading to the crushing of sand grains at these contacts.The grain crushing resulted in grain accumulation in the flow streams which,in turn,led to pore throat and fracture space blockage and increased pressure drop across the fractured core system.