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Abstract: Study on the Effect of Pressure on Oil Generation

CHEN XIAODONG, Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou, Gansu, Peoples Republic of China

Abnormal fluid pressures are probably universal in deep basin sediments with high sedimentation rates. However, the effect of fluid pressure on organic-matter metamorphism is still not clearly understood, and conflicting opinions exist concerning its influence. Properly performed pyrolysis may closely simulate hydrocarbon generation and maturation in nature, and thus offer a suitable way to study the effect of pressure. Although there are different results from pyrolysis experiments, some geological case studies show that high pressure retards organic matter maturation, such as Yinggehai basin, south China sea. Despite of different pyrolysis method, confined or open, with or without water, and different pressure medium used, it appears that the pressure effect is not continuously progressive, but may be more "quantum-like" in behavior, where certain threshold pressure must be reached before pressure effect becomes significant. In this investigation we will take confined thermopressure pyrolysis to eludicate the effect of pressure. Samples gathered from Yinggehai basin and Tarim basin where over pressure retards organic matter maturation will be used. The samples should include different type and maturity. We will design a wide pressure range and dense the pressure point in different temperatures to testify the existence of pressure threshold and whether the threshold pressure varies with different type, maturity and different temperature. The extent of the pressure influence will also be investigated. The results will help to predict the distribution of oil, condensate and gas in depth, and will be of great significance of oil exploration.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid