油气聚集链:内涵、特征与勘探实践:以渤海湾盆地冀中、黄骅坳陷为例

成熟盆地仍然蕴藏着可观的油气资源,目前的油气成藏理论面临越来越难、复杂、隐蔽油气藏勘探的挑战。受“链”事物属性的启发,通过调研、类比国内外油气成藏过程与分布规律,在继承和发展已有油气成藏理论基础上,结合勘探实践,学界提出了“油气聚集链”的概念和认识。油气聚集链指在成因上有密切联系、空间上多呈串珠状链式排列在一起的一系列油气藏组合,是油气成藏与分布本质规律的客观体现。油气聚集链在形式上多表现为油气藏多呈串珠状的链式空间分布特征,实质上表现为油气生成、运移、聚集的沿优势运移通道的链式反应和成藏事件;现今复杂的油气分布是地史上多条油气聚集链叠合的反映;一条完整的油气聚集链由内链、中链和外链组成,它们在成藏背景、成藏条件、成藏机理、富集规律和分布模式上既各有特征,又有连续性,更是紧密有机的油气生运聚成藏整体。“同源多链、一链多藏、多链成域、主链富集”是“油气聚集链”的四大特征。与目前油气成藏理论相比,油气聚集链认识的突出优势在于:发现和论证了油气聚集的链式成藏特点和多呈串珠状链式分布规律,提出沿“油气聚集链”寻找油气藏,比沿“油气聚集带”寻找油气藏的效率更高;将勘探目标的预测精度从油气聚集区带范围提高到某个具体圈闭或甜点。油气聚集链认识具有目前其他油气成藏理论所不具有的独特优势——链式思维,精准定位。依据油气聚集链的认识,提出了“找准链源,梳理链节,确定链环,重视主链”和“全链思维、整体研究,顺链找油、精准勘探”的思路,对指导成熟盆地继续挖掘勘探潜力、新区新领域获得勘探突破,都具有重要现实意义。以油气聚集链的认识为指导,转变勘探思维,在冀中、黄骅坳陷油气勘探中获得重大突破。

“Hydrocarbon accumulation chain”—concept,characteristics and application

Mature basins still contain considerable oil and gas resources, but the current theory of oil and gas accumulation is increasingly inapplicable to the structurally complex, concealed reservoirs in mature basins. Inspired by the attributes of “chain”, this paper put forth the concept of “hydrocarbon accumulation chain” developed on the basis of existing theories, through a global-scale researching and comparison of hydrocarbon accumulation processes and distribution laws. A “hydrocarbon accumulation chain” refers to a series of oil and gas reservoir combinations that are closely related by formation mechanism and arranged in a specific way in space. “Hydrocarbon accumulation chain” accurately describes the pattern/process of hydrocarbon distribution/accumulation: It shows the beaded, chain-like distribution pattern of oil and gas reservoirs, and describes the process of oil/gas generation, migration, accumulation along dominant migration pathways. And, superposition of many such ‘hydrocarbon accumulation chains’ through the geological history gives rise to today's complex pattern of hydrocarbon accumulation. A complete ‘hydrocarbon accumulation chain’ contains the inner, middle and outer sections that have not only their own characteristics of but also continuity in the hydrocarbon accumulation background, condition, mechanism, enrichment law and distribution mode—and most of all, it is a compact, complete hydrocarbon generation-migration-accumulation system. The four main characteristics of “hydrocarbon accumulation chain” are source sharing by multiple chains; multiple reservoirs per chain; multi-chain network; and reservoir enrichment along dominant chains. The “hydrocarbon accumulation chain” concept has some unique practical advantages over other theories as it proposes “whole-chain thinking, entirety research, prospecting along the chain, and precision exploration”, which is of great significance for guiding exploration breakthroughs in new areas as well as maximizing the exploration potential of mature basins. This concept has been applied to the oil and gas exploration in the Jizhong-Huanghua depressions with great success.