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我国煤层气储层渗透率普遍偏低,为达到合理产能需进行压裂改造。煤层气储层裂隙发育导致压裂液滤失严重,强吸附能力使流体得不到有效返排,造成储层损害降低了渗流能力,大大削弱了增产改造的效果。开展了煤岩水相自吸实验,系统研究了煤岩水相自吸特性及应力状态的影响。结果表明,煤样渗透率越高自吸速率越大,自吸曲线可以分为自吸和扩散吸附2段,考虑应力作用自吸速率降低近一个数量级,揭示了煤岩物性和应力条件是煤岩水相自吸的影响因素。通过煤吸附水机理和煤岩孔隙结构分析指出,煤表面与水的相互作用和毛细管压力决定了水的自吸特性。研究获得的认识对煤岩气藏水相圈闭评价、压裂方式优选和压裂液设计具有借鉴意义。
China’s coalbed methane reservoir permeability is generally low, in order to achieve reasonable capacity required fracturing. The development of fractures in coalbed methane reservoirs led to serious loss of fluid filtration and strong adsorption capacity, which resulted in that fluid could not be effectively returned to the reservoir, causing reservoir damage to reduce seepage capacity and greatly weakened the effect of stimulation. A self-priming experiment was carried out on the water phase of coal and rock, and the effect of self-suction on the water phase and the state of stress were systematically studied. The results show that the higher the self-suction rate is, the more the self-sucking rate is. The self-sucking curve can be divided into two stages of self-absorption and diffusion adsorption, and the self-suction rate decreases about one order of magnitude considering stress. The physical and stress conditions of coal are coal Influencing factors of water phase self - suction in rock. Through coal adsorption water mechanism and pore structure analysis of coal and rock, it is pointed out that the interaction between coal surface and water and capillary pressure determine the water self-absorption characteristics. The understanding gained from the research is of great value to the assessment of water traps, the optimization of fracturing methods and the design of fracturing fluid in coal and gas reservoirs.