塔里木古生界克拉通盆地海相油气富集规律与古隆起控油气论

Marine hydrocarbon enrichment rules and palaeouplift-controlling hydrocarbon theory for the Paleozoic Tarim craton basin

塔里木古生界克拉通盆地海相油气分布十分复杂,大油气田形成及分布主要受古隆起、有效烃源岩分布以及后期构造变动三大因素控制。其中最重要的是古隆起及其斜坡,原因是古隆起及其斜坡是克拉通盆地各种成藏条件的最佳耦合区。塔里木克拉通古隆起可划分为继承型、残余型、叠加型、衰亡型4种类型。长期发育的大型继承性古隆起与残余古隆起及其斜坡是油气最富集的地区。古隆起控油、斜坡富集,隆起高部位油气易发生调整破坏、斜坡部位有利于富集保存,这是塔里木克拉通区油气藏形成和分布的重要规律。多期成藏、多期调整是塔里木克拉通区油气藏形成的重要特点。晚加里东—早海西期是克拉通区原生油藏最主要的成藏时期;晚海西期既是原生油气藏形成的主要时期,又是早期油气藏发生调整形成次生油气藏的重要时期;燕山期,特别是喜马拉雅期则是早期油气藏发生调整改造、定型定位及破坏的主要时期。据此认为,"晚期成藏论"并不适用于塔里木多旋回古老海相克拉通盆地。因此,古隆起及其斜坡,特别是大型继承性古隆起与残余古隆起及其斜坡是寻找大、中型油气田的最有利地区。据此提出了"古隆起控油气论"。

The distribution of marine hydrocarbon reservoirs in the Paleozoic Tarim craton basin is very complex. The formation and distribution of large oil and gas fields are controlled by several factors including paleouplifts, effective source rock distribution and later tectonization. Among these factors, the palaeouplifts and their slopes are the most important because they have the most favorable combination of hydrocarbon accumulation conditions in the craton basin. The palaeouplifts in the Tarim craton basin can be divided into four types：inherited, residual, superimposed, and failed. The first two types,which are larger in scale and have long history of development, as well as their slopes, are the best for oil and gas enrichment. That oil and gas accumulation is controlled by palaeouplifs, hydrocarbon is enriched in the slopes, reservoiris in the high of uplifts are easy to be adjusted and destroyed and the slope areas are favorable to hydrocarbon enrichment and preservation, are the rules of the hydrocarbon accumulation and distribution in the Tarim craton basin. The multiphase of accumulation and multistage tectonic adjustment are the important characteristics of the marine hydrocarbon accumulation in the Tarim craton basin. The Late Caledonian and the Early Hercynian were the main periods for the formation of primary oil reservoirs in craton areas. The Late Hercynian was both the main period for the formation of primary gas reservoirs and the important period for the adjustment of earlier-formed reservoirs to secondary hydrocarbon pools. The Yanshan and the Himalayan periods were the main periods of adjustment, finalization and destruction of early-formed hydrocarbon reservoirs. It was therefore concluded that the theory of late stage hydrocarbon accumulation was not applicable to the muhicyclic marine Tarim craton basin. Consequently, the inherited and residual palae-ouplifts and their slopes were considered to be the most favorable regions for the discovery of giant oil and gas fields in the Paleozoic craton basin. Base on these understandings, a palaeouplifts-controlling hydrocarbon theory was put forward and discussed.