南堡油田馆陶组玄武岩井壁失稳机理和技术对策研讨

Borehole Wall Sloughing of Basalt Rocks in Guantao Formation in Nanbao Oilfield:Mechanism and Technological Solution

在南堡油田勘探初期，钻进馆陶组大段玄武岩的过程中经常发生井塌事故，影响了钻井速度和油气层保护。对馆陶组玄武岩的地质和岩石学特征、矿物组分、理化性能、力学性能和坍塌压力进行了分析，讨论了玄武岩井壁失稳的力学、地质、钻井液和工程因素，提出了稳定井壁的技术对策。采用具有强抑制、强封堵特点和合适密度的成膜封堵低侵入钻井液，能够有效抑制凝灰岩、玄武质泥岩、蚀变玄武岩的水化膨胀、分散坍塌；能够有效封堵裂隙而阻止压力传递，防止近井壁地层岩石强度下降和引发地层坍塌压力升高，从而防止玄武岩地层井壁坍塌，并通过用南堡1—1井239g～2401m井段灰色玄武质泥岩岩样（带微裂缝）进行流量法渗透率测定实验和PT实验（测定渗透率）验证了上述钻井液的稳定井壁能力。

Borehole wall sloughing in the Guantao Formation(Basalt rocks) was encountered more often than not during the exploration period of the Block Nanbao.The permeability of the reservoir rocks was damaged because of the sloughing.This paper analyzed the geology,lithology and mechanical property of the basalt rocks and discussed the mechanism behind which the borehole sloughing was happening.It was concluded that the drilling fluid played a great role in the stabilization of the borehole wall in the basalt rock formation penetrated.A filming drilling fluid with strong inhibition,sealing and an appropriate mud density was able to inhibit the hydration,swelling and sloughing of the basalt formation.The filming generated by the drilling fluid on the surface of the rock had the ability to contain the transit of the pressure near the wellbore,and to protect the rocks from being weakened by the invasion of the liquid phase from the drilling fluid.Permeability rests were done on rock samples taken from well Nanbao 1-1 in depths between 2,399~2,404 m using the said drilling fluid to testify its capacity in reservoir protection.