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本文运用D.McKenzie提出的拉张盆地延伸沉降模式,结合南海北部的钻井和地震剖面资料,经过数学处理,解除沉积压实作用,考虑了古水深及海平面变化等因素影响,得出盆地的沉降演变过程,并估计了盆地的拉张程度。根据不同的拉张程度,研究了盆地的古地温及热演变过程,作出在沉降过程的时间-温度-深度曲线。根据这些曲线计算了地层中油气的热成熟度指数,得出富含有机质的生油岩约在2000—2500米深度上开始生油,在近3000米深度上大量生油,约近5000米生油基本结束。
In this paper, we use the extensional subsidence mode proposed by D. McKenzie and the data of drilling and seismic profiles in the northern part of the South China Sea. After mathematical treatment, the sedimentation and compaction are removed. Taking into account the paleoclimate and sea level changes and other factors, Subsidence evolution process, and estimated the degree of tension in the basin. According to different extensional extents, the paleogeothermal and thermal evolution of the basin were studied, and the time-temperature-depth curve during the sedimentation process was made. Based on these curves, the thermal maturity index of oil and gas in the strata is calculated, and it is concluded that the oil-rich rocks rich in organic matter begin to generate oil at a depth of about 2000-2500 m and a large amount of oil is generated at a depth of nearly 3000 m, The oil is basically over.