摘要
顺北地区多口井在钻进奥陶系桑塔木组辉绿岩侵入体时掉块严重,导致井下频繁蹩钻、阻卡,上提钻井液密度后多次引发井漏,多次堵漏但效果不明显。基于辉绿岩的微观结构特性分析,通过开展辉绿岩理化性能测试和岩石力学实验,结果表明:辉绿岩基岩矿物主要以斜长石为主,缝间填充物矿物主要包括石英、斜长石和黏土矿物,水化不易分散、稳定性好、水化膨胀应变非常小,不易造成井壁坍塌失稳;辉绿岩具岩石硬脆性、强度高而弹塑性差的力学特征,微裂缝发育的弱理面效应导致辉绿岩岩体整体强度降低易造成井壁坍塌失稳。根据裂缝对辉绿岩强度的影响规律,建立了辉绿岩地应力与坍塌压力剖面,从而得出了辉绿岩合理钻井液密度窗口,并在顺北1-3、顺北1-6H等后续钻井中取得成功应用,具有推广应用价值。
The borehole collapse was serious when drilling the diabase of Ordovician Sangtamu Formation in Shunbei area, which resulted in frequent tripping and sticking problems. Lost circulation happened many times upon increasing the mud density and the control measures did not work well. Integrated study was carried out ？ involving investigation of micro-structure of diabase formation, the physical-chemical properties test, and the rock mechanics experiments. The results indicate that the diabase mainly consists of plagioclase, and some quartz and clay minerals in its fractures. The formation has a low hydration/swelling tendency, and is stable in water based muds, which suggests that hydration is not the main cause to induce borehole instability. The dia-base is hard and brittle, with high strength and poor elastoplasticity; the weak plane effect with developed mi-cro-fractures could make the diabase strength lower, leading to borehole collapse. The profiles of geostress and collapse pressure in diabase formation were figured out based on the influence of fractures on diabase strength. The safety drilling fluid window for diabase formation were also established and applied successfully in wells SB 1-3,SB 2-6H and other wells in Shunbei Block, exhibiting promising potential.
出处
《中国海上油气》
CAS
CSCD
北大核心
2017年第5期119-125,共7页
China Offshore Oil and Gas
基金
"十二五"国家科技重大专项"顺北1井区钻完井评价与优化研究(编号:2011ZX05049-002-002)"部分研究成果
关键词
辉绿岩
井壁稳定性
岩石力学
坍塌压力
钻井液密度窗口
diabase
borehole stability
rock mechanics
collapse pressure
drilling fluid density safety window
