Characteristics and comprehensive evaluation of tight sandstone reservoirs in Xu 2 Member of Xinchang structural belt in western Sichuan Depression
The Xu 2 Member of Xinchang structural belt in western Sichuan depression develops thick-layer gas-bearing tight sandstone reservoirs,and conducting research on reservoir characteristics,comprehensive evaluation of favorable areas,and optimization of favorable intervals is of great guiding significance for the geological understanding of Xu 2 Member reservoirs in this area.Rock thin sections,X-ray diffraction,scanning electron microscopy,and imaging logging analysis are used to clarify basic characteristics of reservoirs and the natural gas accumulation mechanism in Xinchang structural belt.The comprehensive evaluation of favorable areas and optimization of favorable intervals are also carried out.The research shows that Xu 2 Member of Xinchang structural belt in western Sichuan Depression is mainly composed of lithic sandstone with characteristics of ultra-low porosity and ultra-low permeability.Local fractures are relatively developed,and low porosity and high permeability reservoirs are developed.The oil and gas in Xinchang structural belt of western Sichuan Depression have undergone multiple episodes of filling and accumulation to form reservoirs.On the plane,Xinchang structural belt exhibits characteristics of overall gas bearing and accumulation in the near-source fault area.The gas-bearing properties of the upper and lower sub segments of Xu 2 Member are relatively good.On the basis of fully considering the gas-bearing properties of the reservoir,the vertical single well analysis result shows that intervals with high SiO2 content,high brittleness index,and low fracture pressure are favorable for the testing of Xu 2 Member in western Sichuan Depression.The research results provide geological basis for the large-scale exploration and interval selection test of tight sandstone gas in Xu 2 Member of western Sichuan Depression.
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