基于有效应力法的碳酸盐岩地层孔隙压力测井计算

LOGGING CALCULATION FOR PORE PRESSURE ON CARBONATE ROCK FORMATION BASED ON EFFECTIVENESS STRESS METHOD

利用测井资料预测地层压力是一条比较有效的途径。目前,砂泥岩剖面地层压力的预测技术比较成熟,而碳酸盐岩剖面的地层压力预测仍存在一定问题。针对碳酸盐岩地层孔隙压力预测相对较难这一问题,基于碳酸盐岩地层沉积压实机理,提出了利用有效应力法预测地层压力的方法,并重点讨论了模型中的横波时差和岩石泊松比的测井求取方法。利用该法对川东地区LJZ构造LJ5井等井的碳酸盐岩井段的测井资料进行了地层压力预测处理,获得了比较满意的效果。应用表明,该法从测井信息中提取的碳酸盐岩地层压力是可靠的,精度高、实用性强,且避免了在碳酸盐岩剖面中采用等效深度法预测地层压力时需要寻找纯泥岩层来构建正常压实趋势方程的难题。其结果可以用于碳酸盐岩井段三个地层压力剖面的建立和钻井液密度的设计。

Predicting formation pressure using well logging data is a comparatively effective method. Presently, the technique of predicting formation pressure in mud - sand profile is relatively perfect However, there are some problems to estimate accurately pore pressure of carbonate formation profile. Aimed at the problem that estimating formation pore pressure is relatively difficult in carbonate profile, based on analysing and studying the compaction mechanism of carbonate forma tion, the effectiveness stress method is presented to predict the formation pore pressure of the carbonate, and the method of transverse wave time difference and rock Poisson ratio, which are necessary to calculate effectiveness stress, can be emphasis researched. Based on the effectiveness stress method of logging data, formation pressure of Lj5 well etc. which belongs to LJZ structure on cast of Sichuan is predicted. The satisfactory ef feet is obtained. Result showed that the calculating formation pressure in the carbonate formation is reliable according to the method of logging data. Predicting precision is high, and practicability is better. Furthermore, the difficult problems that adopting the equivalent depth method construct normal com paction tendency equation are averted. The calculated result can be acted as the guide of establishing three formation pres sure and can be designed the mud density of carbonate forma tion.