四川盆地须家河组致密砂岩天然气富集规律

摘要

The paper discusses the tight sandstone gas reservoir accumulation mode, the main controlling factors and the gas accumulation pattern in the Upper Triassic Xujiahe Formation (T3x)of Sichuan basin,aiming to predict the natural gas gathering areas and pointing out the next step prospecting direction.Tight gas reservoirs are characterized by deep burial depth,poor reservoir property and low production rate,but have large exploration potentials.The natural gas explored and discovered from the Xujiahe Formation in Sichuan Basin mainly concentrates in Member 2,4 and 6 of Xujiahe Formation.The gas reservoirs are characterized by low degree of fullness,high water saturation in lower positions,low level of produced reserves,and limited gas-bearing range of the reservoirs.The comparison of the Xujiahe Formation source rocks and the natural gas light hydrocarbon and the research of the natural gas accumulation combination indicate that the hydrocarbon accumulation pattern is characterized by multiple hydrocarbon supplies,accumulation near the source,lithology reservoirs,oil-gas conversion and later adjustment.The main controlling factors of the natural gas enrichment in Xujiahe Formation are that the Triassic hydrocarbon sources distribution controls the source and the adequacy of natural gas,the structural strength controls the development and distribution area of the traps, and the favorable sedimentary facies belt and diagenetic facies belt control the gathering place and scale of natural gas. Natural gas mainly assembles in the tectonic uplift lower area,the moderate faulting area and the developmental reservoir area.%重点探讨了四川盆地上三叠统须家河组致密砂岩气藏的成藏模式、成藏主控因素及天然气富集规律，旨在预测天然气聚集有利区域。致密砂岩气藏具有埋藏深、物性差、产量低的特点，但勘探潜力巨大。四川盆地须家河组勘探和发现的天然气主要集中于川中、川西、川北的须二、须四、须六段，气藏总体表现出充满度不高、低部位含水饱和度偏高、储量动用比例偏低、储集层含气范围有限的特点。通过须家河组烃源岩和轻烃的对比，以及对须家河组成藏组合的研究，表明须家河组天然气藏具有多元供烃、近源聚集、岩性控藏、油气转化、晚期调整的成藏模式。须家河组天然气藏的富集主控因素，一是三叠系烃源灶分布控制了天然气来源及充注程度；二是构造作用强度控制圈闭的发育与分布区域；三是有利沉积相带和成岩相带控制天然气聚集的场所与规模。天然气主要富集在构造隆升低缓区、断裂活动适中区、储层相对发育区。