Characteristics Of Regional Unconformities And Their Relationship To Oil And Gas In The Kongquehe Slope,Tarim Basin

There are3tectonic units in the Kongquehe Area, which are Caohu Depression,Kuerle Uplift and Kongquehe Slope, which experiences Caledonian, Hercynian,Indosinian, Yanshanian and Himalayan period, and developed6regionalunconformities corresponding to these tectonic periods. In this paper, we reveal thetemporal and spatial evolution characteristics and its effect to produce hydrocarbon inthe second time of the source rock and the control of oil and gas reservoirs of regionalunconformities through research the characteristics of them.We identify the regional unconformities based on the drilling and seismic data, inaccordance with previous data we can analysis their geological significances, then wecan discuss their temporal and spatial evolution characteristics; we can also simulatethe basin burial history of a single well and thermal evolution history of the sourcerock to analysis the effect to the produce hydrocarbon in the second time of the sourcerock of regional unconformities; we discuss the control of oil and gas reservoirs ofregional unconformities through research the structural characteristics of the mainunconformities and hydrocarbon accumulation event.Through the research, we believe the time interval between the Cretaceous andJurassic is20~60Ma, the time interval between the Jurassic and the Triassic is25~65Ma, which erosion amount of the Carboniferous and Devonian is0~950m and0~868m. In the Kongquehe Slope, the time interval between Jurassic and Silurian is220~230Ma, which between Jurassic and Ordovician is250~270Ma, the erosion ofthe Silurian is amount to0~2200m, which amount to0~3600m at the top of theOrdovician. The time interval between the Silurian and Ordovician is about15Ma.Through the simulation of the basin burial history and the thermal evolutionhistory we believe the burial features for the Caohu Depression is continuous buriedtype, the source rocks of the layer Paleozoic can be maturing rapidly in the earlyPaleozoic, and be able to produce hydrocarbon in the second time in the Mesozoic;there is something different for buried type between the west and east sides of theKongquehe Slope, In the west side is the paleo-uplift area, the buried type is uplift earlier and shallow buried later, In the east which is the slope area’s deeply buriedearlier and rolling buried later. The source rocks of the layer Paleozoic can bematuring rapidly in the early Paleozoic too, but can not be able to producehydrocarbon in the second time in the later.Through the research of the structural characteristics of the main unconformitieswe can believe in the Kongquehe Area, the unconformities at the bottoms of theCarboniferous and Jurassic both have Three-tier structure, which from upper to layerare basal conglomerate zones, weathering clay zones and weathered leaching zones,the weathering clay zones are excellent seals, and the basal conglomerate zones andweathered leaching zones could be the migration route of the oil and gas which couldalso be good reservoirs. So, above the unconformity below Carboniferous there maybe Overlying reservoirs, below the unconformities at the bottoms of the Carboniferousand Jurassic there may be occlusion Oil and gas reservoirs.