中国海相超深层油气形成

The formation of marine ultra-deep petroleum in China

超深层是指现今或曾经埋藏深度超过6000 m的沉积地层。中国海相超深层时代老,热演化程度高,经历的构造运动多,独特的构造-沉积和生烃环境,决定了海相超深层油气藏形成与分布的复杂性,成烃-成储-成藏规律明显不同于中浅地层,勘探的难度也远远大于国外中新生代克拉通盆地。经过半个多世纪的探索,近年来中国海相超深层油气勘探在中西部盆地取得一系列重大突破,显著提升了超深层领域油气资源的战略地位。与此同时,中国海相超深层油气地质理论也取得重大进展,形成了以重大地质转折期构造活动控制超深层油气地质要素发育、深埋高温环境导致多途径天然气生成、沉积-构造作用控制超深层油气储集空间形成与保持、超深层温压系统控制油气藏相态演化和多期成藏、多层系分布等为核心的理论认识,极大地发展了国外学者基于中新生代海相地层提出的油气生成与成藏模式,拓展了海相油气资源形成和分布的时空界限。

Ultra-deep strata refer to stratigraphic formations that are presently or were once buried at depths over 6 km.The ultra-deep strata of marine formations in China are generally characterized by old age and high maturation,and had experienced numerous tectonic movements.Their unique tectonic,sedimentation and hydrocarbon generation settings determined the complexity of the formation and distribution of hydrocarbon reservoirs in ultra-deep marine strata.The mechanisms of hydrocarbon generation,reservoir formation and accumulation are quite distinct from that of relatively shallow strata,and the exploration is far more challenging than that of the Meso-Cenozoic craton basins abroad.After more than 50 years of exploration,a series of great breakthroughs have been made in ultra-deep oil and gas exploration in central and western China basins,which have significantly elevated the strategic significance of ultra-deep resources.Highlights of the great progress has also been made in our theoretical understandings on ultra-deep geology in China include:①tectonic activities during major geological transition period controlled the development of geological factors in ultra-deep reservoirs;②deep-burial at high temperatures led to multiple natural gas generation pathways;③sedimentary and tectonic processes determined the formation and preservation of ultra-deep reservoirs;④temperature and pressure in ultradeep petroleum system controlled the petroleum phase evolution,multi-stage accumulation and multi-layer distribution of hydrocarbon in reservoirs,etc.These insights have significantly improved the model of hydrocarbon generation and accumulation previously proposed by foreign scholars based on Meso-Cenozoic marine strata,and greatly expanded the temporal and spatial boundaries for the formation and distribution of hydrocarbon resources in deep marine strata.