基于致密砂岩气藏初始含水饱和度的水锁伤害评价

针对现有的水锁伤害评价方法不适用于致密气藏岩心的现状，建立了基于初始含水饱和度情况下的抽真空饱和水锁伤害评价方法，完成一种塔里木油田聚磺钻井液滤液对岩心的水锁伤害实验，并通过使用气测渗透率的方法，测定污染前后岩心的渗透率变化，计算钻井液滤液对岩心的水锁伤害程度的方法。该实验方法可以对比初始含水饱和度条件下岩心的气体渗透率和束缚水饱和度条件下的气体渗透率变化情况，相对于常规方法更加符合气藏的实际状况。实验过程中，设计了致密砂岩气藏较低初始含水饱和度的建立方法。另外，开展实验评价了抽真空饱和时间、气驱返排时间、气驱流速等对抽真空饱和法的影响。用建立的实验方法测定了塔里木油田聚磺钻井液滤液对致密岩心的水锁伤害程度为54.83%~72.73%。 

Permeability Impairment by Water Block in Tight Sandstone Gas Reservoirs with Initial Water Saturation

A vacuum saturation method has been worked out to evaluate permeability impairment by water block of cores (with initial water saturation).This method is established to replace traditional methods which are not suitable for the evaluation of permeability impairment by water block of cores taken from tight gas reservoirs. Laboratorystudies of a polymer sulfonate drilling fluid have been done on cores taken from Tarim Basin with the method developed. Permeability impairment of cores by water block before and after mud contamination was measured with gas flowing through the cores. The new method, giving a result that better tallies with the reality of a gas reservoir, can be used to make a comparison between the gas permeability of a core with initial water saturation and the gas permeability of the same core with bound water saturation.A procedure of setting lower initial water saturation of tight gas reservoir was established for the method. Further experiments have been done to study the effects of time for vacuum saturation, time for backflow after gas flooding and flowrate of gas flooding etc. on the vacuum saturation method. Permeability impairment of tight cores by polymer sulfonate drilling fluids used in Tarim Basin tested with the method developed is between 54.83% and 72.73%.