Study On Borehole Stability Technology In Jiuxi Area Of Yumen Oilfield

Along with our country implementation for complex geological conditions,deep drilling for oil and gas resources development strategy,how to maintain wellbore stability,drilling,puts forward a more comprehensive requirements;especially in the deep well of complex strata,which can seriously affect the drilling efficiency and development cost,a great obstacle to the safe,high quality,fast and efficient drilling,and even related to drilling,which has attracted great attention both at home and abroad.The current drilling technology is in a new historical period in which the bottleneck is taken as an important symbol to solve the problem of wellbore stability.Studies the block of Yumen oilfield is jiouxi area in this paper,with complex lithology,has obvious fragmentation and high dip angle,stress anisotropy,abnormal high temperature and high pressure,the occurrence of hole leakage and well collapse occurred in drilling engineering,so wellbore instability is a very realistic and urgent problem.Based on the formation conditions in Jiuxi area and the actual situation in the field,the mechanism of wellbore instability and the drilling fluid technology for stable formation are analyzed.This paper first describes the background of Yumen Oilfield jiouxi area,and wellbore instability research status at home and abroad;analysis of geological characteristics of the west area drilling engineering difficulties;from the collapse layer of mineral composition and microstructure analysis,analysis of physical and chemical properties,strength layer and three pressure profile study on the mechanism of wellbore instability,and then through the physical and chemical effects;analysis of mechanical properties,formation and drilling fluid occurred for borehole collapse cycle,cationic drilling fluid system and Optimization for field application.The study found that the relationship between water content and collapse cycle and wellbore radius,time of the formation of complex jiouxi area,recognizing the complexity change of rock water absorption,rock mechanics parameters and rock strength parameters;and the dosage of cationic drilling fluid formulation optimization,plugging agent selection and anti pollution ability the evaluation results,the final formula:4%base mud +0.4%NW-1+ 0.5%CHM+2%HS-1+1%HS-2+0.5%CaO+20%Si02 soil slurry,finally add API to density to 1.40g/cm3.After the optimization of cationic polymer drilling fluid rheology and filtration properties is good,has certain inhibition of water and salt resistant ability of dispersing calcium and cutting pollution ability;in order to further stabilize the borehole,adding nanometer silica to enhance their ability to block micro pores;the research method of plugging effect evaluation of nano plugging material.