环保型PRD钻开液的性能研究

针对大位移井和水平井储层段存在携带钻屑及起下钻困难等问题，研制了一种井眼清洁能力强的环保型PRD钻开液。该钻开液主要处理剂是极易生物降解的天然高分子聚合物。PRD钻开液的BOD₅/COD_Cr为0.42；溶解氧(DO)衰减法评价结果表明，PF-VIS及PF-FLO两种天然高分子聚合物易生物降解；PRD钻开液生物毒性检验结果符合一级海区生物毒性允许值要求；LSRV(低剪切速率黏度)高达60 000 mPa·s，携带及悬浮钻屑能力很强，不会形成岩屑床，岩心渗透率恢复值在90%以上，对储层伤害很小。该钻开液用在我国渤海、东海、南海西部、南海东部及新疆等油田，油气产量有较大提高。

Study on Performance of Environment-friendly PRD Drilling-in Fluid

A kind of environmental-friendly water base drilling fluid, PRD drilling-in fluid, was developed to deal with tripping difficulty and carrying cuttings in extended reach wells and horizontal wells. PRD drilling-in fluid composes of several highly biodegradable natural high polymer additives. The BOD5/CODCr ratio of PRD system is 0.42. The dissolved oxygen decay evaluation showed that the two natural polymers, PF-VIS and PF-FLO were readily biodegradable, and PRD drilling-in fluid’s biological toxicity test met the biological toxicity limit requirement for the first level seas. Low shear rate viscosity (LSRV) was up to 60 000 mPa?s so that the system could carry and suspend cuttings with no cuttings bed and the core return permeability was more than 90%, which caused tiny damage to reservoir. The PRD drilling-in fluid was successfully applied in Bohai Bay, East Sea, South Sea and Xinjiang Oilfield, with greater oil and gas production than other drilling fluids systems.