大牛地气田致密砂岩气藏水锁伤害特征分析

大牛地气田致密砂岩气藏具有非均性强、开发难度大的特点,储集层沉积环境变化快,沉积微相类型多,岩石胶结成分种类多、含量差异大、致密化成岩作用强;孔隙小、喉道窄,储集层渗透率低;气、水两相流动的通道小,渗流阻力大,水、气界面的表面张力大,水锁效应明显。特别是水平井压裂液规模大,一般是3 000~5 000 m~3。大量的压裂液在较高的工作压力下进入地层中,进一步加大了水锁伤害程度。通过对致密砂岩储层的伤害实验、理论计算及实际压后特征的统计分析,明确了致密砂岩气藏的孔隙度、渗透率及压裂液侵入时间对压裂水平井水锁伤害的影响,分析了3种不同的水锁伤害类型特征,并提出了降低水锁伤害的建议。

Analysis of the damage characteristics of the tight sandstone gas reservoir water lock in Daniudi gas field

Tight sandstone gas reservoirs in Daniudi gas field are characterized by strong heterogeneity, high difficulty in development, rapid changes in reservoir sedimentary environment, many sedimentary microfacies types, many kinds of rock cementation components and great difference in content. Strong compaction, small porosity, narrow throat and low permeability of reservoir; The gas and water two-phase flow has small passage, large seepage resistance, large surface tension between water and gas, and obvious water locking effect. Especially, the scale of horizontal well fracturing fluid is large, which is generally 3,000m ~ 5, 000 cubic meters. A large amount of fracturing fluid enters the formation under high working pressure, which further increases the degree of water lock damage. Through the damage experiment of tight sandstone reservoir, theoretical calculation and statistical analysis of the characteristics after actual pressure. The effects of porosity, permeability and fracturing fluid invasion time on water lock damage in fractured horizontal wells are clarified. The characteristics of three different types of water lock damage are analyzed, and suggestions for reducing water lock damage are put forward.