Study On The Formula Of Anti-sloughing Drilling Fluid

Sidewall instability is one of the main technical problems of the drilling engineering and the drilling fluid is one of the key factors. Therefore, researching and developing a anti-sloughing drilling fluid system with excellent properties, solving the problem of sidewall collapse in the drilling process as well as keeping sidewall stably is the important technology for assurance the oil well quality and improve the drilling speed. It also has a great significance on protect the reservoir.This paper aims to research an anti-sloughing drilling fluid formula with excellent properties. Firstly, the single treating agents with good inhibitory property were screened out from evaluating the inhibitory property of common used single treating agents in drilling fluid. Secondly, drilling fluid system with excellent properties at normal temperature was obtained by complex formulation study of the single treating agents. Thirdly, the anti-sloughing drilling fluid system formula which has excellent rheology, salt resistance, temperature tolerance and good inhibition was obtained carried on the salt resistance, temperature tolerance and inhibition optimizing experimental study. The components of the formula system are as follows:3%bentonite,1.5%CMS,0.6%LV-CMC,0.15%XC,0.2%FA367(or0.2%KPAM),0.2%JT888,1%NH4-HPAN,1%FT-1,3%NH4C1(or3%KC1). At last, comprehensive performance evaluation of this anti-sloughing drilling fluid formula were experimented.Based on the comprehensive evaluation, This formula has good water loss rheology property at normal temperature and at120℃by heat rolling16h and its sand bed filtration loss is zero. This formula system that their shale linear expansion ratio is about8%, dropped about32%contrast with distilled water. Cutting recovery could catch above95%below100℃and about90%at120℃. Especially, its secondary recovery could keep about90%, the recovery raised about80%contrast with distilled water. In addition, the filtrate of this formula system has well inhibition that the rate of anti-swelling is about95%, shale linear expansion ratio is about12%. Core damage permeability recovery value of this formula system is about80%.