Hydrocarbon accumulation conditions and exploration prospects of ultra-deep oil and gas reservoirs in the Paleogene Linhe Formation in the northern Linhe Depression,Hetao Basin
In recent years,the geological understanding of late hydrocarbon accumulation in deep to ultra-deep clastic rocks has been deepened,and a major oil and gas discovery has been achieved in ultra-deep clastic rocks in Linhe Depression in Hetao Basin.Based on the thermal simulation of the Paleogene source rock,well drilling,logging and testing data,and analysis of reservoir formation and hydrocarbon accumulation evolution,the new geological understanding has been formed in three aspects:(1)The high-quality source rocks rich in resinite(terrestrial)and algae(aquatic)were developed in the Paleogene in the northern Linhe Depression,which generated and expulsed a large amount of hydrocarbon in the low thermal evolution stage,and showed characteristics of high intensity and wide window of hydrocarbon generation.The source rock in ultra-deep Naoxi trough has a high thermal evolution degree and great potential of oil and gas resources.(2)The large-scale braided river delta deposits were developed in the far-source shallow and gentle slope,with sand body widely distributed.Affected by weak diagenetic factors such as low formation temperature,late deep burial,high quartz content,weak compaction and weak cementation,a new reservoir formation mechanism is formed,which is dominated by weak diagenesis for pore maintenance,and superimposed by epigenetic ultra-high pressure transformation and fracture expansion.The reservoir has good physical properties,greatly expanding the space for petroleum exploration in ultra-deep formations.(3)A new understanding of hydrocarbon accumulation is put forward,which includes the initial oversaturated and ultra-high pressure oil and gas reservoirs in hydrocarbon generation period formed by the early hydrocarbon charging,continuous subsidence,deep burying and thermal evolution,accelerated hydrocarbon generation,expulsion,and continuous charging,and ultimately the late hydrocarbon accumulation of conventional oil and gas reservoirs once the fracture pressure of reservoir-source rock interaction body is broken through by ultra-high pressure,with characteristics of fracture-pore connection,accumulation in both source rock and reservoir,and continuous and large-area distribution,greatly improving the exploration potential.The hydrocarbon accumulation conditions in the ultra-deep Palcogene Linhe Formation in the northern Linhe Depression are superior,and the favorable exploration area is large,showing promising exploration prospects.Meanwhile,the new theoretical understanding of late hydrocarbon accumulation in the ultra-deep clastic rocks has important guiding significance for the exploration in similar basins,especially for the inside-source exploration in ultra-deep formations with a burial depth of 10000 meters.
Linhe DepressionPaleogeneultra-deep formationultra-high pressureoil well with a flow rate of thousand tons
万方数据
维普
