河套盆地临河坳陷石油地质新认识与重大发现

New understandings of petroleum geology and great discovery in the Linhe depression, Hetao Basin

河套盆地为中—新生代坳断叠合型盆地,地震测网稀,构造演化及控烃控藏作用不清,油气成藏规律不明,长期制约油气勘探突破。近年来,积极转变勘探思路,以野外地质露头踏勘、加密二维地震部署为基础,通过井震结合精细构造解释和区带综合评价,提出临河坳陷经历了早白垩世反转成盆期、古近纪差异伸展期、新近纪强烈伸展断陷期、第四纪走滑(或反转)改造期的4期构造演化新机制,明确吉兰泰构造带和中央断裂带为油气勘探有利构造区带;厘定临河坳陷发育固二段、固一段和临河组3套烃源岩,定量表征了不同时期烃源岩的分布,揭示了"盆地演化—沉积环境—埋藏史"三元联合控烃,明确临河坳陷中北部为优势资源富集区。通过成藏条件综合分析,构建了源内、源外多种油气成藏新模式,在临河坳陷中南部吉兰泰构造带发现了变质岩潜山油藏和碎屑岩断鼻构造油藏,实现了源外太古宇潜山和白垩系油气勘探重大突破;在临河坳陷北部部署风险探井临华1X井,在源内古近系获日产305.76m3高产工业油流,实现了临河坳陷多区带多层系油气勘探快速突破。

Hetao Basin is a Meso-Cenozoic depression-fault superimposed basin. Due to the lack of seismic survey lines and unclear understandings on tectonic evolution, source and hydrocarbon accumulation controlling factors and the accumulation laws, the breakthrough of oil and gas exploration were limited for a long time. In recent years, exploration ideas have been actively changed. Based on the field outcrop survey and 2 D infill seismic line, through fine structural interpretation by well-seismic combination and comprehensive favorable play evaluation, new understandings on tectonic evolution mechanism have been proposed. The Linhe depression has experienced four stages of tectonic evolution: Early Cretaceous inversion and basin-forming period, Paleogene differential extension stage, Neogene strong extension fault stage and Quaternary strike slip(or inversion) reconstruction period. Also, it is determined that the Jilantai structural belt and the central fault zone are favorable structural zones for oil and gas exploration. There are three sets of source rocks in the Linhe depression, namely the 2 nd member of Guyang Formation(the Gu-2 member), the 1 st member of Guyang Formation(the Gu-1 member) and the Linhe Formation. The quantitative characterization of source rocks distribution in different sedimentary periods indicates that the source controlling laws of three combined elements of "basin evolution-sedimentary environment-burial history" and the central-northern area of the Linhe depression is the dominant resource enrichment area. Through the comprehensive analysis of hydrocarbon accumulation conditions, several new hydrocarbon accumulation models of inside and outside the source rocks are established. Based on this, metamorphic buried hill oil reservoirs and clastic fault-nose structural oil reservoirs have been discovered in the Jilantai structural belt in the central-southern Linhe depression, which has achieved great breakthrough of oil and gas exploration in the Archean buried hill and Cretaceous system outside the source rocks. Moreover, in the northern Linhe depression, risk exploration well, Well Linhua 1 X was deployed and obtained high-production oil flow of 305.76 m3 per day in Paleogene inside the source rocks, both which have achieved a rapid exploration breakthrough in multi-zone and multi-layer in the Linhe depression.