Physical simulation experiment of gas and water distribution during the accumulation of a tight sandstone gas reservoir
China is rich in tight sandstone gas resources and has broad exploration and development potential.However,the existing developmental practices regarding the development of tight sandstone gas reservoirs still faces great challenges,such as detailed understanding of the gas-water distribution is one of the main challenges at present.In order to further reveal the gas-water distribution of tight sandstone reservoirs under different accumulation environments,this paper takes the Upper Paleozoic gas reservoir members 1 and 2+3 of the Hezi Formation as examples,and establishes a macroscopic physical simulation experiment on the basis of similarity criteria.The gas-water distribution of a horizontal well under different injection modes,different injection forces and different core types was studied.The results showed that,compared with continuous injection,the gas saturation in the reservoir under power injection was 7.95％higher on average than that under continuous injection.The phased injection mode enabled the injected gas to redistribute the saturation field during the stopping period and increased the swept volume.The distribution type of gas and water was mainly in the same layer of gas and water or the gas-bearing water layer,with no boundary bottom water.It was found that under the condition of continuous injection,the strong injection force aggravated the uneven injection degree,reduced the sweep efficiency of the inject gas,and led to the sealing of a large amount of formation water in the middle and upper parts of the tight reservoir.Under the power-injection condition,a strong injection power improved the degree of uneven injection,improved the displacement efficiency of the swept area,and increased the gas saturation of the reservoir.A core type test showed that the gas injected in a low physical property area could be diverted or incompletely charged due to the stronger heterogeneity of the outcrop sample.The fault zone communicated or was far away from the injection location,and the injected gas did not spread,but instead formed water bodies of different scales.The results of the physical simulation experiment were consistent with the well logging interpretation results in the study area,and the research results have reference significance for understanding the gas-water distribution characteristics in different accumulation processes in this area.
tight sandstone gas reservoirreservoir forming environmentsimilarity criterionphysical simulation experimentgas-water distribution characteristics
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