川西坳陷新场构造带须二段致密砂岩储层特征及综合评价

Characteristics and comprehensive evaluation of tight sandstone reservoirs in Xu 2 Member of Xinchang structural belt in western Sichuan Depression

川西坳陷新场构造带须二段发育厚层含气的致密砂岩储层,开展其储层特征、有利区综合评价和有利层段优选研究,对于深化该区须二段储层地质认识具有重要的指导意义。文中运用岩石薄片、X射线衍射、扫描电镜、成像测井等分析测试方法,明确了新场构造带储层基本特征和天然气成藏机制,并开展了有利区综合评价和有利层段的优选。研究结果表明:川西坳陷新场构造带须二段以岩屑砂岩为主,砂岩具有特低孔、超低渗的特征,局部裂缝较为发育,发育低孔高渗储层;川西坳陷新场构造带油气经历了多幕次的充注而聚集成藏,平面上新场构造带表现为整体含气,近烃源断层区域成藏富集的特征,须二上亚段和下亚段含气性较好;在充分考虑储层含气性的基础上,纵向上单井分析结果SiO_(2)含量高、脆性指数高、破裂压力小的层段为川西坳陷须二段测试有利层段。研究成果为川西坳陷须二段致密砂岩气的规模勘探和测试选层提供地质依据。

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 SiO_(2) 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.