新型聚合物钾盐抑制泥页岩水化的性能与机理

泥页岩水化膨胀是井壁失稳的重要原因。本文通过膨润土压片浸泡与线性膨胀实验、页岩钻屑滚动回收实验以及流变性、滤失性测试，评价了一种新型聚合物钾盐抑制剂聚阴离子纤维素钾（K-PAC）的抑制性能及其对水基钻井液流变性和滤失性的影响。评价结果表明，0.5% K-PAC的抑制泥页岩水化膨胀的性能明显优于5% KCl、2%聚醚胺-D230（PEA-D230），与0.5%聚丙烯酰胺钾盐（K-PAM）相近；0.5% K-PAC的增黏提切、降滤失性能要优于0.5% K-PAM。通过扫描电镜和X射线衍射分析了K-PAC的抑制机理，结果表明，K-PAC的阳离子部分（K⁺）能够进入膨润土晶层中并置换出水化钠离子，从而起到抑制黏土晶层膨胀的作用；K-PAC的阴离子部分吸附在黏土颗粒上起到护胶、降滤失的作用，二者协同增效，从而起到强抑制作用。由于K-PAC由聚阴离子纤维素和K⁺构成，对环境友好、成本低廉。因此，K-PAC具有成为低成本、环保型、强抑制性的水基钻井液抑制剂的巨大潜力。

Performances of a novel potassium polymer on inhibiting shale hydration and the mechanisms

The hydration and swelling of shale is an important cause of wellbore instability. In this work, the inhibitive performance of a novel potassium polymer K-PAC and its influences on the rheological and filtration properties of a water-based drilling fluid were evaluated by the immersion test, linear swelling experiment, shale recovery test and rheological and filtration tests. Evaluation results showed that 0.5% K-PAC had a better inhibition property than 5% KCl and 2% poly(propylene glycol)bis(2-aminopropyl ether) (PEA-D230). Although the inhibitive performance of 0.5% K-PAC is similar with 0.5% potassium polyacrylamide (K-PAM), but its influences on the rheological and filtration properties of water-based drilling fluid are better than K-PAM. The inhibition mechanisms were studied by using Scanning Electron Microscopy and X-ray diffraction. K⁺ from K-PAC could intercalate into the clay interlayers, followed by expelling water and minimizing the clay swelling. Polyanionic from K-PAC could adsorb on the clay surface, protecting the colloidal properties of drilling fluid and control the filtration loss. The synergistic effect between K⁺ and Polyanionic in K-PAC could lead to a better inhibitive performance. K-PAC is composed of polyanionic cellulose and K⁺, environmentally friendly and low cost. Therefore, K-PAC has a great application potential in water-based drilling fluids which are a low-cost, environmental friendly and have excellent inhibitive performance.