A Study On The Structural Evolution And The Control On The Oil And Gas Accumulation In The Central Tarimâ…¡ Fault Zone

Theâ…¡structural zone is the key area for further prospecting in the central uplift of Tarim Basin. But constrained mainly by the insufficient research on the structure development and evolution and its controls on reservoir and hydrocarbon accumulation, the exploration result of the central and westernâ…¡structural zone in Central Tarim is not good, with discovered industrial oil and gas flow only in Ordovician system of TZ 4 oil field. Through accurately analyzing the geometric features of theâ…¡structural zone, recovering palaeostructure, and simulating stress, synthetically study the relation between structure and hydrocarbon accumulation, and put forward the hydrocarbon-exploring favorable zone ofâ…¡structural zone in central Tarim.In the light of the accurate seismic structure interpretation of theâ…¡structural zone, quantitatively analyze the horizontal and the section geometric elements of the faults, and determine the main structure styles of theâ…¡structural zone, then find out the trap types of theâ…¡structural zone in central Tarim; meanwhile, connect the geometric elements'distribution characteristics of theâ…¡structural zone such as vertical fault throw with the donghetang formation sandstone who is the key reservoir of the research area, then reveal the controls of fault geometric elements on hydrocarbon accumulation.Synthetically analyze regional tectonic evolution data, and recover the structure patterns of the five key interfaces-the top of the Middle Cambrian series, the base of the Upper Ordovician series, the base of the Silurian series, the base of Upper Devonian Donghetang formation and the base of the Permian series-by the balanced cross section, then divide theâ…¡structure zone into five evolution stages, and through calculating the relative shorting amounts of the cross-sections above these five interfaces, put forward the tectonic evolution patterns of theâ…¡structure zone in central Tarim; the result of researching on the shorting amount variety combined with the major time of volcanic rocks developing, shows that the Permian stratum with minimum shorting amount is in the state of extension, which created the conditions for volcanic-intruding.Through analyzing the characteristics of the regional stress field and the present stress field, set up geological model base on recovered paleo-tectonics, and numerically simulate its tectonic stress by using finite element method to gain the stress distribution characteristics of theâ…¡structure zone in central Tarim in different geological age, then reveal the fault closure and its opening extent in each age and the predominant direction of hydrocarbon migration, which supplies the important reference and guidance for hydrocarbon reservoir'exploration.Combined with the previous findings about the Central Tarim uplift, synthetically analyzing the sedimentary evolution, the source rocks, the strata denudation, the hydrocarbon accumulation stages and the reservoir cap rock combination, divide the unconformity interface of theâ…¡structure zone in central Tarim into three levels, and identify restricted carbonate platform and open carbonate platform, and Study the characteristics of the three sets of source rocks and the two types of reservoirs-clastic sandstone and carbonate rocks, which indicates polygenetic - multiphase -multi-source-reservoir-cap rocks assemblage hydrocarbon reservoir characteristics in theâ…¡structure zone of central Tarim.Discussing the controls of the faults and the uniformity on hydrocarbon accumulation and correlating the hydrocarbon accumulation conditions of the eastern and the westernâ…¡structure zone in central Tarim, point out the"massive container and little oil sources"(called the model of big bowl and little pot)disadvantage conditions of western hydrocarbon accumulation; reveal the coincidence relation between the distribution law of karst reservoir rocks and the distribution law of tectonic stress; use the stress simulation result to find out the stress zone which is advantage for hydrocarbon accumulation, and compare these stress zone to the advantage structural traps to outline the advantage traps of each age, then predict the favorable target for further prospecting in theâ…¡structure zone of central Tarim.