高精度重力资料剩余密度反演与孔隙裂缝发育带分析

RESIDUAL DENSITY INVERSION FOR HIGH ACCURACY GRAVITY DATA AND ANALYSIS ON ROCK LITHOLOGY AND FRACTURE ZONE

地矿部石油物探研究所,南京210014

Research Institute of Geophysical Prospecting for Petroleum, MG M R, 210014 Nanjing

利用高精度重力资料及已具备的地质地震资料,去掉由于密度界面产生的重力场及区域重力场的影响,消除浅部干扰,求得剩余重力异常。用钻井资料作控制,反演求得剩余密度分布,以了解储层岩石孔隙裂缝发育带,从而达到直接或间接寻找油气藏的目的。理论模型试算证明方法是可行的;通过四川大足弥陀场地区实际资料的处理,推断了本区的岩性裂隙圈闭;并与已知的钻井地质资料及其它地球物理资料对比验证,说明了反演结果是可靠的。为在海相碳酸盐岩地区寻找岩性缝油气藏提供了一种方法手段。

This paper srggests removing the effects of regional gravitational fields, and the gravitational fields arising from density interfaces and shallow interference by making use of high accuracy gravity data together with known geological and seismic information so as to yield the residiual gravity anomalies. Constrained by drilling data, inversion for residual density distribution is then performed to find out where fractures densely flock (i. e. the zone in which oil/gas potentialy accumulates) in reservoir rocks. While confirmed to be effective via some theoretical model examples, the method was also applied to the real data from DaZuo area of Sichuan Province in delineating the lithology and fracture traps of this area. The results from the inversion are further verified via the comparison with known well-log, geological and other geophysical data. It is concluded that the method proposed in the paper is promising to be an useful tool in locating fracture type reservoirs in marine carbonate areas.