油气地球化学勘探的理论与实践

本文提出将油气扩散原理与干酪根热降解生油理论结合起来研究,以解决油气地球化学勘探的理论问题。文中除了对Fick第一定律进行数学推导外,还指出这种方法的不足,还要考虑油气生成年龄和开始向地表运移至今的时间。这个时间等于或超过烃气从油气藏扩散到达地表所需要的时间,说明烃气扩散流已经到达地表,在该面积上进行化探可获得良好的结果。根据文中计算公式,对大庆和胜利等油田进行了计算,大庆油田的白垩系生油层的干酪根为Ⅰ型,生油层年龄约110百万年。采用D=10^-6cm/s计算,烃气扩散到达地表所需的时间为39.45百万年,生油层沉降到生油门限深度所需时间为6.65百万年,计算烃气开始扩散至今的时间为103.35百万年。说明大庆油田白垩系生油层的烃气已经扩散到达地表,在该区进行化探可获得较好结果。又如胜利油田,老第三系生油层的干酪根为Ⅱ型,计算结果说明胜利油田老第三系的烃气尚未扩散到达地表,只在断裂带处有扩散烃气。根据本文的原理予测克拉玛依和南阳等油田,进行化探可获得较好结果。此外还例举了我国东北和西北两个油田的化探成果实例。

THEORY AND PRACTICE OF GEOCHEMICAL PROSPECTING OF OIL AND GAS

On the basis of the author's practice for gas research, a comprehensive theory of gas diffusion and oil genesis had been offered to solve the problems about geochemical hydrocarbon prospecting. In addition to the derivation of Fick first law equation, it is pointed out that the using of the equation is not enough to solve the problems about the theory of geochemical petroleum exploration. The age of oil and gas generation and the time from the start of HC gas diffusion to the earth surface must be considered. If the time from the start of diffusion to present days is equal to or larger than the time needed from the start of HC gas diffusion to the surface, HC gas wight reach the sureface, and good result of geochemical exploration in this area can be expected. This paper has calculated the cases in several oil and gas fields, such as Daqing and Shengli oil fields. It is demonstrated that good results may be expected in Daqing Area, while poorer results may be exhibited in Shengli Area. On the basis of the theory in this paper, it is predicted prospecting in Kuramay and Nanyang oil fields may be good. Two practical examples are given, one is in northeast-China, the other in northwest.