Optimization Research On Anti-collapse Drilling Fluid For Deep-water Drilling

There are many special difficulties in deep-water drilling fluid such as hole stability in complex formation,rheology control,hydrate inhibition and tight environmental regulations.Therefore,it is necessary to research and develop an excellent-performance water-based drilling fluid applicable to deepwater.Thus,in this paper,in order to meet the performance requirements of deepwater drilling,a new encapsulator named SDUcap which would apply to deep-water drilling fluid was developed,in which both encapsulating ability and influence to drilling fluid rheology were considered.Based on the newly developed encapsulator,a deepwater highperformance water-based drilling fluid was optimized and established.Single-factor analysis and orthogonal experiments were conduct,and the best synthesis conditions were optimized as followed: the monomer ratio is 6:1:3;the monomer concentration is 15%;the initiator concentration is 0.1%;the reaction time is 2h;the reaction temperature is 60?;the initiator ratio is 1:1;pH is 8.Structural analysis,inhibition experiments and lowtemperature rheological experiments show the new encapsulator has good inhibition and lowtemperature rheology,which can perfectly meet the technique requirements for deep-water drilling fluid.Based on the single-additives optimization and drilling fluid system assessment experiments,a high-performance water-based drilling fluid system used in deepwater was optimized as followed: 2%bentonite+0.35%XC+0.2%SDUcap+3%SDJA+0.5%PAC-LV+ 5%SD-101+1%HLUB+4%KCl+10%~25%NaCl+Barite.The system has outstanding inhibitive ability,good low-temperature rheology,strong lubrication and gas hydrate inhibition performance.