普光气田地层水启动压力梯度实验研究

针对现有的地层水启动压力梯度计算模型计算结果差异大的问题,选取四川盆地普光气田早三叠纪飞仙关组超深层碳酸盐岩储层标准岩心,开展了储层温度条件下的地层水启动压力梯度实验测试,根据实验测试结果建立了地层水启动压力梯度计算模型,对比分析了不同地层水启动压力梯度计算模型的计算结果,分析了影响地层水启动压力梯度的主要因素,以普光气田为例进行了实例计算和分析。结果表明:地层水启动压力梯度随渗透率的降低而增大,在渗透率相对较低时,地层水启动压力梯度随着渗透率的降低急剧增大;地层温度影响地层水黏度,从而改变地层水在细小孔道中流动时的非牛顿特征,进而影响地层水启动压力梯度的大小;储层渗透率和地层水黏度是影响地层水启动压力梯度大小的主要因素;普光气田Ⅱ、Ⅲ类储层地层水启动压力梯度较大,要准确描述气藏水侵规律,需考虑储层的地层水启动压力梯度。

Experimental study of Threshold Pressure Gradient for Formation Water in the Puguang Gas Field

Existing models of threshold pressure gradient for formation water induce non-negligible variations in calculation results. In order to solve this problem, cores from an ultra-deep carbonate reservoir in the Puguang gas field at the Feixianguan formation in the Sichuan basin are selected to test the formation water threshold pressure gradient under reservoir conditions. A model of threshold pressure gradient for formation water is established based on experimental results. Results from different models of threshold pressure gradient are compared. Main factors affecting threshold pressure gradient for formation water are analyzed. A case from the Puguang gas field is investigated. Results demonstrate that the threshold pressure gradient for formation water increases with the decrease of permeability. The threshold pressure gradient rises rapidly if permeability is extremely low. Temperature can affect viscosity of formation water. The non-Newtonian characteristics of formation water in small pores can be influenced. As a result, threshold pressure gradient for formation water is affected. Permeability and viscosity of formation water are the main influencing factors for the threshold pressure gradient for formation water. The threshold pressure gradient for formation water in the Puguang gas field is significant. Therefore, it should be considered in the studies of the water intrusion mechanism.