渤中A3井井壁稳定技术研究

Research on Borehole Stabilization Technology of Well A3 in Bozhong Block

该文对BZ-A3井的钻井问题和井壁稳定性进行了分析和研究。BZ-A3井在钻进过程中遇到了大量的问题,并导致了两次侧钻及相应的经济损失。该文通过分析已有测井数据,建立井壁稳定岩石力学模型,进行井壁稳定性分析,发现由于使用了过低密度的钻井液,BZ-A3井及两次侧钻的井壁破坏范围大,而且井壁崩落弧长大于90°,这样就导致了较大的页岩块从井壁脱落甚至井壁垮塌,从而引起严重的卡钻问题;采用Eaton法进行了地层孔隙压力的计算,分析结果表明东营组及沙河街组存在明显超压,主要超压机制为欠压实及生烃,最大孔隙压力为1.4~1.5g/cm^(3);基于孔隙弹性模型开展了水平地应力的计算,确定水平最大地应力方向为N65°E,这与该区块的地质构造和世界地应力图是一致的。该文找到BZ-A3井井壁失稳与卡钻的机理,对钻井泥浆密度提出建议,以帮助避免此类事故在今后本区块调整井钻井作业时重复发生。

In this paper,the drilling problems and the borehole stability of Well BZ-A3 are analyzed and studied.There are a lot of problems during the drilling process of Well BZ-A3,which resulted in two sidetracking and corresponding economic losses.In this paper,through reviewing the existing logging data,establishing the rock mechanics model of the borehole stability and analyzing the borehole stability,it is found that due to the use of low-density drilling fluid,the damage range of Well BZ-A3 and two sidetracking is large,and the length of borehole collapse arc is greater than 90°,which leads to large shale blocks falling off from the borehole or even borehole collapse,which leads to serious sticking problems.The Eaton method is used to calculate the formation pore pressure.The analysis results show that there is obvious overpressure in Dongying Formation and Shahejie Formation.The main overpressure mechanism is undercompaction and hydrocarbon generation.The maximum pore pressure is 1.4~1.5 g/cm^(3).Based on the pore elastic model,the horizontal low stress is calculated,and the maximum horizontal principal stress direction is N65°E,which is consistent with the geological structure of the block and the world diagram of the crustal stress.This paper finds out the mechanism of borehole instability and sticking in Well BZ-A3,and puts forward suggestions for drilling mud density,so as to help avoid such accidents from happening repeatedly drilling operations of adjustment wells in this block in the future.