红星区块多粒径致密封堵油基钻井液技术

An Oil-Based Drilling Fluid with Varied Particle Size Plugging Agents for Use in the Borehole Collapse and Mud Loss Coexisting Wells in Hongxing Block

红星区块是江汉油田部署在建南构造上主力产气区,中石化页岩气勘探开发的重点区块。该区块飞仙关组、长兴组经多年开采,地层骨架应力低;吴家坪组微纳米裂缝发育。油基钻井液在钻进过程中,井漏、井塌矛盾突出,处理难度大,为此研究形成一套“强封堵、低活度、低黏度高切力”多粒径致密封堵油基钻井液体系,该体系采用4%微纳米复合刚性颗粒、0.5%石墨烯片状材料、1.5%球状凝胶MPA、1%超细矿物纤维等多粒径微纳米材料,协同封堵致密封堵地层微纳米级裂缝,且在井壁上形成致密泥饼,控制钻井液高温高压滤失量低于3 mL;采用高浓度CaCl2水溶液(≥36%)为水相,活度低于该区块页岩岩心活度,提高钻井液的抑制性;采用提切型乳化剂提高钻井液切力,实现高效携带岩屑、掉块,净化井眼的目的。现场应用表明,多粒径致密封堵油基钻井液体系能有效地减缓井漏、井塌复杂,复杂时间降低了90.34%,应用效果显著。

The Hongxing block,a main gas production area of the Jianghan oilfield in the Jiannan structure,is an important shale gas development area of Sinopec.After many years of development,the matrix stresses of the Feixianguan formation and the Changxing formation become very low,and the Wujiaping formation is highly developed with nanometer-sized fractures and fissures.When drilling with oil-based drilling fluids,mud losses and borehole wall collapse take place frequently and are difficult to deal with.To solve these problems,an oil-based drilling fluid with particles of varied sizes to form dense plugging is developed.This oil-based drilling fluid is characterized with strong plugging capacity,low activity,low viscosity and high gel strengths.It is formulated with 4%nanometer-and micrometer-sized rigid particles,0.5%graphene flake material,1.5%spherical gelled MPA,1%ultra-fine mineral fibers.These materials work together to plug and seal the micrometer-sized and nanometer-sized fractures in the formations and coat the borehole wall with dense mud cakes,thereby controlling the high temperature high pressure filter loss of the drilling fluid below 3 mL.High concentration CaCl2 solution(≥36%)as the water phase of the oil-based drilling fluid lowers the activity of the drilling fluid to below that of the formation waters and thus improves the inhibitive capacity of the drilling fluid.The emulsifier used has the ability to increase the gel strengths of the drilling fluid to the required level,hence effectively carrying the drilled cuttings and the sloughing out of hole.In field operation,this drilling fluid effectively mitigates the severity of mud losses and borehole wall collapse.An obvious application result is that the time spent in dealing with downhole troubles is reduced by 90.34%.