水对致密气藏气相渗流能力作用机理研究

Action Mechanism of Water on the Gas Seepage Capacity in Tight Gas Reservoir

为研究边底水和压裂液等流体的侵入对超低含水饱和度气藏气相渗流能力的影响,选取渗透率约为0. 100 mD的致密砂岩岩心,对岩心水驱过程中渗透率变化、气水两相渗流规律进行了实验研究。结果表明:地层水和去离子水引起的岩样渗透率变化模式相似,地层水引起的渗透率下降幅度小于去离子水引起的渗透率下降幅度;束缚水饱和度时,随含水饱和度增加气相渗透率下降明显,渗透率大的岩心下降规律是“先慢后快”,渗透率小的岩心下降规律是“先快后慢”;水的侵入对气相渗流能力影响严重,且随含水饱和度降低,气相渗透恢复率低于10%,渗透率损失高达90%以上。其中,由于气水两相相互作用导致的渗透率损失约为50%;由于微观结构变化导致的渗透率下降约为15%~40%。压裂液的性质对于储层开发具有重要影响,储层开发前,应配备合适的压裂液。

In order to reveal the effects of edge-bottom aquifer, fracturing fluid and other fluid intrusion on the gas seepage capacity of gas reservoir with ultra-low water saturation, the laboratory core waterflooding experiment was carried out to study the permeability changing and the gas - water two - phase seepage patterns based on the tight sandstone core samples with permeability around 0.100 mD. Research indicates that the formation water and deion ized water cause a similar declining pattern for the core sample permeability. The permeability decrease caused by the formation water is less than that of deionized water. It shows a significant gas permeability decrease with the in crease of water saturation under the condition of bound water saturation. The gas permeability respectively decreases slowly in the initial stage and rapidly in the late stage for the core samples with relatively high permeability. The gas permeability respectively decreases rapidly in the initial stage and slowly in the late stage for the core samples with relatively owl permeability. The gas seepage capacity is greatly influenced by water intrusion. With the decrease of water saturation, the gas permeability recovery rate is less than 10% and the gas permeability loss is as high as 90% or more. The permeability losses result from gas-water interaction and microscopic structure change are about 50% and 15%- 40% respectively. The reservoir development performance is closely dependent on the fracturing fluid properties and suitable fracturing fluid should be prepared before development.