STUDY ON THE RESERVOIR-FORMING SYSTEMS OF THE TARIM BASIN

The reservoir-forming system (or named the hydrocarbon migration-accumulation system) is defined as a relatively independent system of hydrocarbon migration and accumulation within a petroleum system. The reservoir-forming system is also a natural unit of petroleum exploration and assessment, and its place in a petroliferous basin is just between a petroleum system and a play. The Tarim is a basin with multiple reservoir-forming systems within a petroleum system. In the Manjiaer petroleum system of the craton area, there exists at least three large reservoir-forming systems, i.e., the North Tarim, Central Tarim and West Manjiaer systems. And the North Tarim can be further divided into Lunnan and some other reservoir-forming systems. The Lunnan reservoir-forming system is actually composed of three subsystems, namely, the Ordovicion primary and se condary reservoir-forming subsystem, the Carboniferous overpressure semi closed reservoir-forming subsystem and the Triassic Jurassic secondary reservoir-forming subsystem where most oilfields are the results of oil re migration from the Ordovician and Carboniferous reservoirs along the newly formed normal faults nearby driven by gas intrusion. The Central Tarim includes two reservoir-forming systems named the Central Faulted Belt primary and secondary reservoir-forming system and the North Slope primary reservoir-forming system, and the latter can be subdivided into the Ordovicion and Carboniferous hydrocarbon migration-accumulation subsystems, in each of which vertical and lateral migration and accumulation is predominated respectively. In the Kuche foreland petroleum system, three reservoir-forming systems are distinguished, i.e., the North Kuche Slope normal pressure open system, the Central Thrust Belt normal and over pressure open closed system, and the Luntai normal pressure open reservoir-forming system. And the Central Thrust Belt system can be subdivided into the above Tertiary seal and the under Tertiary seal two subsystems. In the above Tertiary seal subsystem, se condary oil reservoirs are mainly formed; whereas, the under Tertiary seal subsystem is the character of over pressure gas accumulation.