塔里木盆地沙井子构造带志留系油气勘探突破及启示

Silurian hydrocarbon exploration breakthrough and its implications in the Shajingzi structural belt of Tarim Basin,NW China

塔里木盆地西北部志留系油气勘探曾经久攻未克,2018年钻探的新苏地1井首次在塔西北沙井子构造带获得工业气流,其油气成藏模式与资源规模亟待明确。通过对钻井、试油、地球化学及沉积与成藏史研究,结合野外剖面实测、实验分析、构造精细解释及演化恢复,认为:①塔西北志留系发育大型潮控三角洲沉积,可形成良好储盖组合;②沙井子断裂及其伴生断裂有效沟通阿瓦提凹陷深部寒武系—奥陶系烃源岩,控制志留系构造圈闭的形成,圈闭沿断裂构造带有序分布、叠合连片;③沙井子构造带志留系油气类型以气为主,成藏期以圈闭定型后的喜马拉雅期为主;④沙井子构造带志留系圈闭资源量达2.018×10^(11)m^(3),塔西北志留系圈闭资源量达2.03×10^(12)m^(3),勘探潜力巨大,志留系有望成为盆地碎屑岩层系油气“增储上产”的重要领域;⑤沙井子断裂规模大,持续活动时间长,沟通深部烃源岩,沙井子构造带下古生界多个层系均有望获得油气勘探突破。

The Silurian hydrocarbon exploration in the northwest Tarim Basin had long been fruitless,till Well XSD1 drilled in 2018 in the Shajingzi structural belt,northwest Tarim Basin tapped industrial gas flow from the Silurian for the first time.The reservoir-forming model and resource extent need to be made clear urgently.Based on the comprehensive research of drilling,formation testing,geochemical data,and sedimentary and accumulation history,in combination with field surveys,experiments,structure interpretation and reconstruction of structure evolution,it is found that:(1)The northwest Tarim Basin had widespread tidal deltaic deposits in the Silurian period,which contain good reservoir-cap combinations;(2)the Shajingzi fault and associated faults connected the Cambrian-Ordovician source rocks in the Awati sag,and controlled the formation of Silurian structural traps,hence,the traps turned up along the structural belt in an orderly pattern and came together into contiguous tracts;(3)the Silurian petroleum in Shajingzi structural belt was dominated by gas,and the major accumulation period was the Himalayan period when the traps fixed in shape;(4)the Silurian gas resources in the Shajingzi belt were estimated at around 2.018×10^(11)m^(3),and Silurian gas resources of the northwest Tarim Basin were estimated at 2.03×10^(12)m^(3),implying huge exploration potential,so this area will become a major area for reserve and production increase from clastic strata in the basin;(5)with the Shajingzi fault of large scale and long active time connecting deep source rock layers,multiple formations in Lower Paleozoic of Shajingzi structural belt may have breakthroughs in hydrocarbon exploration.