高密度水基钻井液降黏剂的研制及应用

Development of Viscosity Reducer for High Density Water-Based Drilling Fluid and Its Application

高密度水基钻井液流变性失控的主要原因之一是劣质固相含量的增加。劣质固相在高密度水基钻井液中分散,增强体系网架结构,导致钻井液黏度和切力上涨。基于竞争吸附降黏原理,以2-丙烯酰胺-2-甲基丙磺酸、苯乙烯、马来酸酐、N,N-二甲基丙烯酰胺四种单体按摩尔比1∶2∶1∶1合成了低分子量聚合物降黏剂WNTHIN。降黏剂评价实验表明,WNTHIN能够有效降低密度为2.40 g/cm3的高密度钾聚磺水基钻井液的黏度和切力,塑性黏度降低率达42.85%,静切力降低率达51.35%,WNTHIN推荐加量为1.5%。在蓬莱气区某井现场应用中,WNTHIN的使用改善了高密度钾聚磺水基钻井液流变性,塑性黏度由58 mPa·s下降至30 mPa·s,动切力由29 Pa下降至14 Pa,10 min静切力由28 Pa下降至16 Pa,高密度水基钻井液性能得到有效改善,满足了深井钻井安全钻进的技术需求。

One of the main reasons for rheology out-of-control of high density water-based drilling fluid is the increase of inferior solid phase content.Inferior solid phase is dispersed in high density water-based drilling fluid,which enhances the system architecture,resulting in increased drilling fluid viscosity and higher shearing force.Based on the principle of viscosity reduction by competitive adsorption,WNTHIN,a low molecular weight polymer viscosity reducer was synthesized with 2-acrylamide-2-methylpropanesulfonic acid,styrene,maleic anhydride,N and N-dimethylacrylamide in a molar ratio of 1∶2∶1∶1.Test results of the viscosity reducer show that WNTHIN can significantly reduce the viscosity and shearing force of high density potassium polysulfonate water-based drilling fluid with a density of 2.40 g/cm3,with plastic viscosity reduced by 42.85%,static shearing force reduced by 51.35%,and the recommended WNTHIN dosage addition is 1.5%.The field application of WNTHIN in a well in Penglai Gas Field showed improved rheology of high density potassium polysulfonate water-based drilling fluid.The plastic viscosity dropped from 58 mPa·s to 30 mPa·s,the yield point dropped from 29 Pa to 14 Pa,and the 10 min static shearing force dropped from 28 Pa to 16 Pa.The performance of the high density water-based drilling fluid has been improved to meet the technical requirements for safe drilling in deep wells.