两性离子聚合物/多元醇复合井壁强化剂的研制与作用机理

针对水基钻井液钻探页岩油气频繁遭遇的井壁失稳难题，同时考虑阳离子基团与多重醇羟基在井壁上的吸附作用，通过酯化反应将两性离子聚合物丙烯酰胺（AM）-丙烯酸（AA）-二甲基二烯丙基氯化铵（DMDAAC）与聚乙烯醇接枝，研制了一种复合井壁强化剂（WSC-1）。性能评价结果表明，WSC-1对人造岩心点载荷强度的提高率达26.90%，页岩岩心浸泡后可保持71.3%的内聚力；3%加量下可控制页岩线性膨胀量为63.22%，页岩屑150 ℃的滚动回收率达87.2%，优于聚醚胺、聚合醇等常用井壁稳定剂，且兼具一定的降滤失性能。通过红外光谱分析、扫描电镜观察，并结合聚DMDAAC和聚乙烯醇的稳定井壁机理讨论了WSC-1的作用机理:WSC-1通过离子键与氢键强吸附在井壁岩石表面，抑制了黏土矿物水化、分散，且在聚乙烯醇的“多点吸附”作用下形成吸附膜，封堵裂缝并减少自由水向地层中的渗滤，有效强化了井壁。 

The Development and Function Mechanisms of an Zwitterionic Polymer/Polyol Borehole Wall Strengthening Additive

A compound borehole wall strengthening agent WSC-1 was developed to deal with the borehole wall instability frequently encountered in shale oil development with water based drilling fluids. The WSC-1 additive was synthesized through esterification reaction with a zwitterionic polymer AM-AA-DMDAAC (acrylamide-acrylic acid-dimethyl diallyl ammonium chloride) and polyvinyl alcohol. WSC-1 possesses cationic groups and poly hydroxy groups which make it easy for the WSC-1 to be adsorbed onto the surfaces of the borehole walls. In laboratory evaluation, the point load strength of an artificial core was increased by 26.90% with the help of WSC-1, and the cohesion of the core after soaking was maintained at 71.3%. The linear expansion of shale cores can be reduced by 63.22% tested with a 3% WSC-1 solution. In hot rolling test, the percent recovery of shale cuttings after hot rolling at 150 ℃ was 87.2%, a recovery higher than the results tested with commonly used borehole wall stabilizers such as polyetheramine and polyglycol. WSC-1 also showed some filtration control capacity in the test. Using IR and SEM analyses, it was found that WSC-1 can be adsorbed on the surfaces of the rocks through ionic bonding and hydrogen bonding, thereby inhibiting the hydration and dispersion of clay minerals. WSC-1 can also form an adsorption film through the “multi-point adsorption” of the polyvinyl alcohol, the film can seal off the fractures in the formation rocks, thus minimizing the filtration of free water into the formation and strengthening the borehole walls.