Geochemical Characteristics And Oil Source Identification Of Multiphase Oil And Gas In Tazhong Uplift Area

The Tazhong uplift area oil and gas were characterized by rich,complex properties,diverse phases,and multi-stage accumulations.In the early stage of this area,the Ordovician was the main target layer for oil and gas exploration,and a series of oil and gas discoveries were obtained,but the exploration of the Cambrian as the target layer failed to make a big breakthrough.In recent,with the advancement of deep-ultra-deep drilling and the improvement of research understanding,such as ZS1,ZS1 C,and ZS5 wells have obtained high-yield oil and gas flow in the Cambrian,showed that the Cambrian-Ordovivian in the Tazhong uplift area has good prospects for exploration,but the complexity of the oil and gas phase becomed more prominent,increased the difficulty of oil and gas exploration.many problems still exists to be solved are mainly:(1)The genesis and sources of oil and gas are still controversial;(2)The distribution characteristics and controlling factors of oil and gas multi-phase state need to be further studied;(3)The formation and control of multi-phase oil and gas are different from secondary effects,and the reasons need to be analyzed and compared.Based on these,this thesis is guided by the theory of oil and gas geochemistry,used comprehensive full two-dimensional gas chromatography technology,combined with geologicalgeochemical data,etc.to carry out a large number of geochemical tests and analysis in the Tazhong area,and conduct a fine analysis and dissection of oil and gas reservoirs transformation and accumulation,simultaneously,through special molecular compounds(diamondoids,thiadiamondoids,ethanodiamondoids)to quantitatively evaluate the degree of oil cracking and gas invasion conducted in-depth research.(1)Through the analysis of oil and gas properties,the oil in the study area can be divided into three types: condensate,volatile oil and normal oil,showing the characteristics of "oil rich in the west and gas rich in the east" on the plane;and the natural gas in Tazhong area is in the mature high mature stage,the maturity in the east is higher than that in the west.Meanwhile,the geochemical characteristics show that the Cambrian is the main source rock of oil and gas in Tazhong area.(2)The comprehensive geology and geochemistry analysis showed that TSR and cracking have occurred in the deep oil in the area,and the cracking degree of Cambrian oil was relatively large.In the eastern Tazhong region,the mixture of over mature gas and oil cracking gas intrudes laterally through unconformity,while in the western part,the oil cracking gas after TSR transformation intrudes vertically along the fault,resulted in a higher degree of gas invasion in the east than in the west.(3)The study area has experienced three stages of tectonic movement,and largescale gas invasion occurred in the late Himalayan period,deep natural gas strongly transformed the paleo-oil reservoirs formed in the late Hercynian period,resulting in significant changes in oil and gas properties and phase behavior.The fault system in this area was well-developed,connecting the deep Cambrian source rocks,forming a favorable oil and gas transportation network between source and reservoir.Therefore,the deep layers of the Tazhong area of the Tarim Basin have huge potential for liquid petroleum exploration.