Development and Application of a Novel Filming Plugging Agent CMF

A new flming plugging agent, CMF, has been developed to deal with the problems encountered in drilling the brittle fractured shale formations in an oilfeld in the Liaodong Gulf area. CMF is formulated with nesquehonite whisker, hydrated basic magnesium carbonate wafer and a commonly used flming agent LPF-H. The nesquehonite whisker and the hydrated basic magnesium carbonate wafer, having length/diameter ratios of 20-30, were developed under controlled reaction conditions. The ratio of LPF-H, the whisker and the wafer is 7:1.6:0.4. Laboratory experimental results showed that CMF has good compatibility with the drilling fluid treated with it, and the rheology of the drilling fluid is able to satisfy the needs of cuttings carrying. Experiment on sand specimens of different porosity showed that CMF is superior to LPF-H in plugging the sand specimens. The synergism of the whisker, the wafer and LPF-H results in a dense and tough flm on the borehole wall, effectively plugging the formation fractures and stabilizing the borehole wall, and therefore reducing the consumption of drilling fluid additives. Application of CMF on the well X-1 in an oilfeld in Liaodong Gulf showed that the properties of the drilling fluid treated with CMF satisfed the needs of drilling operations. The fltration rate of the drilling fluid was lower than that of the drilling fluid (treated with LPF-H) used on the adjacent well X-2, indicating that CMF is able to protect the reservoir from being damaged, and is therefore worth spreading.