吐哈盆地台北凹陷吉7 H井侏罗系致密砂岩油气藏勘探发现与启示

Exploration discovery and implications of the Jurassic tight sandstone oil and gas reservoir in Well Ji7H in Taibei Sag,Turpan-Hami Basin

吐哈盆地致密砂岩气资源丰富,前期勘探仅在台北凹陷周缘正向构造带发现巴喀、温吉桑和米登等小型油气藏。在对烃源岩、沉积体系、储层条件及源储盖组合特征综合分析基础上,构建了台北凹陷源内致密砂岩油气成藏模式。研究认为,台北凹陷水西沟群纵向发育八道湾组煤岩、三工河组泥岩及西山窑组二段煤岩3套两类优质烃源岩,有机质丰度高、类型好,均达到成熟演化阶段,在凹陷区广泛发育;水西沟群发育西山窑组二段、西山窑组一段、三工河组和八道湾组一段多套储盖组合,西北部、北部和南部3个方向五大辫状河三角洲物源供给充足、满凹富砂,烃源岩层既生油气也可作为区域盖层,形成多层“三明治”式源储盖组合;凹陷区负向构造稳定、保存条件好、地层压力高、烃源岩成熟度高,具备形成源内大面积致密砂岩油气藏有利地质条件。按照“进源、进凹、水平井”思路钻探的吉7H水平井压裂后7mm油嘴放喷获得日产气51283m^(3)、日产油40.37m^(3)高产工业油气流,油藏类型为源内致密砂岩凝析气藏,开辟了吐哈盆地下凹勘探新领域,揭开了吐哈盆地二次勘探序幕。

Turpan-Hami Basin has abundant tight sandstone gas resources.In the early exploration,only small-scale oil and gas reservoirs such as Baka,Wenjisang and Mideng were discovered in positive structural belts in the peripheral Taibei Sag.Based on the comprehensive analysis of source rocks,sedimentary systems,reservoir conditions and source rock–reservoir–cap rock assemblages,the accumulation pattern of tight sandstone oil and gas reservoir is established interior of source rocks in Taibei Sag.The study result shows that two types of high-quality source rocks are developed in Shuixigou Group in Taibei Sag,namely the coal measure source rock of Badaowan Formation,mudstone of Sangonghe Formation and coal measure source rock of the second member of Xishanyao Formation,with high TOC,good organic matter type,mature stage of thermal evolution,and widely developed in the sag;Multiple reservoir–cap rock assemblages are formed in the second and first members of Xishanyao Formation,as well as Sangonghe and Badaowan Formations.The sandstone deposits are widespread in the sag supplied by sufficient sediment sources from five braided river deltas in the west,north and south directions.The source rocks generate large-volume hydrocarbon and serve as the regional cap rocks to form multi-layer“sandwiched”type source rock–reservoir–cap rock assemblage;The sag has the favorable geological conditions for forming large-area tight sandstone gas reservoirs interior of source rocks,such as stable negative structures,good preservation conditions,high formation pressure and high maturity of source rocks.A horizontal well Ji7H was drilled based on the idea of“interior of source rock,marching towards deep sag and drilling horizontal well”,and high yield oil and gas flows of 40.37 m^(3)/d and 51283 m^(3)/d were obtained after fracturing by open flow with 7 mm choke.The tight sandstone condensate gas reservoir interior of source rocks supports to discover a new field of exploration and open up the prelude to the second exploration in Turpan-Hami Basin.