东营凹陷古近系沙河街组深层油气相态及成藏模式.

In recent years, a large number of light oil and gas reservoirs have been discovered in the paleogene sand sub-section of the northern belt of the Dongying Sag, and their oil and gas phase characteristics and reservoir formation patterns still lack in-depth understanding. Through the study of oil and gas geochemistry, fluid inclusion, and burial history-thermal evolution history, combined with crude oil cracking experimental products and oil and gas PPT simulation in the deep reservoir of the four lower sub-sections of sand, the deep oil and gas genesis, phase evolution and reservoir formation mode in this area are discussed. The results show that with the increase of the degree of cracking of crude oil, the critical condensation temperature gradually decreases. At higher pressures (20 MPa), the cleavage of the heavy hydrocarbon gas group was inhibited, the molar fraction of methane in the fluid composition decreased, and the critical condensation pressure of the fluid envelope decreased with nonlinear fluctuations. The characteristics of natural gas composition and carbon isotope show that the mirror plastoid reflectivity (R) of natural gas maturity parameter is between 0.9% and 1.5%, and the natural gas samples detected are the mixed causes of crude oil cracking gas and kerogen degradation gas. The absolute content of amantane and steroid detected in crude oil indicates that the deep crude oil samples detected are in a highly mature state, but are still in the early stages of cracking, and the crude oil cracking gas is moved upwards by the off-site crude oil cracking of the deep depression. The simulation of burial history, thermal evolution history and the uniform temperature of fluid inclusions in the reservoir show that there are mainly two stages of oil and gas injection in the sub-reservoir of the FS2 wellsha four sub-sections, namely crude oil (including kerogen degradation gas) charge at the end of the sand three-stage sedimentation stage and crude oil cracking gas injection from the deep reservoir in the early sedimentation of the Minghua Formation. Late high-maturity crude oil crack gas filling caused evaporative fractionation and gas washing, which was an important reason for the formation of deep light reservoirs in the region, and eventually secondary unsaturated condensate gas reservoirs and volatile reservoirs were formed [ABSTRACT FROM AUTHOR]