| With the increasing demand for energy and the rapid development of drilling technology in the world,the depth of drilling is increasing,the strata drilled are becoming more and more complex,and the problem of borehole wall instability is particularly prominent.At the same time,in order to reduce environmental pollution,in the process of drilling,the anti-collapse and environmental protection of drilling fluid are the important factors to be considered.In view of the geological characteristics of the block,through sampling core and cuttings,scanning electron microscopy,whole rock analysis and physical and chemical properties testing of collapse-prone strata,the specific composition and structural characteristics of the rock are analyzed microscopically,the mechanism and causes of the block’s instability are revealed,and plugging is the main method,while taking into account its inhibition and environmental protection,in order to solve the problem of borehole wall loss.Stability and environmental protection of drilling fluid additives.We have a clear understanding of environmental protection drilling fluids and plugging drilling fluids at home and abroad.This paper combines them to study.With people’s increasing attention to environmental protection,In order to optimize drilling fluid additives,a lot of investigations and experiments have been carried out in this paper..Firstly,the evaluation indexes and standards of environmental protection of drilling fluids in China are investigated;then the evaluation methods are introduced in detail;finally,the biodegradability and biotoxicity of the selected main treatment agents such as filtrate reducers,plugging materials and lubricants are evaluated by environmental protection evaluation methods.Wellbore instability is the most common and frequent accident in drilling process.Beginning with the method of plugging evaluation,this paper introduces the most common and effective test methods,such as high temperature and high pressure filtration test.Addition experiments and plugging effect evaluation experiments of rigid particle plugging agent,variable plugging agent(asphalt,paraffin,polyol)and selected environmental protection plugging agent are carried out.The plugging mechanism of plugging agents commonly used in oilfields is summarized.The micro-structure of the environmental protection plugging agent was analyzed,and the micro-performance of the plugging agent was analyzed.According to the requirement of technology performance and environmental protection of drilling fluid system in block,by comparing the effect of filtrate reducer,plugging agent and lubricant equal to conventional treatment agent,a set of treatment agent with good performance was selected and formed as a drilling fluid system,4%base slurry + 3%E-1 + 2%TR-1 + 2%temporary plugging agent + 7%KCl + 3%ZF-1 + 0.2%SP-80 + barite.The system has good rheological property,good filtration loss reduction,obvious plugging effect,excellent lubricity and environmental protection. |
