针对页岩气井钻井液的新型滤失造壁性能评价方法

鉴于目前页岩油气开采中使用致密低渗测试介质来测试滤失造壁性能的需要，从紧密堆积理论出发，以毫微重晶石和商用重晶石作为固体颗粒材料，采用实验室常见的高速搅拌器和高温高压滤失仪作为实验设备，制作模拟页岩地层低渗泥饼。通过改善毫微重晶石的分散稳定性和调整2者质量比等方法，逐步降低泥饼渗透率，最终确定配方为:1 000mL水+100 g毫微重晶石+10 g聚丙烯酰胺+50 g聚丙烯酸钠+200 g商用重晶石+7 g提切剂，按此配方得到的标准泥饼平均厚度为2.24 mm，平均渗透率为1.42×10-7 D，稳定性良好，重现性较高。以此法测试了常见页岩气井水基钻井液体系，进一步验证了该方法适用于模拟微孔、缝发育的页岩地层，可有效评价钻井液在该类地层中的滤失造壁性能。 

New Method for Evaluating Filtration and Mud Cake Building Performance of Drilling Fluid for Shale Drilling

To satisfy the need for filtration control performance test with dense low permeability media, a test required for shale gas drilling, a simulated low permeability mud cake formed in shale formation has recently been prepared using barite of millimicron in particle size and commercial barite as solid particle materials, and laboratory high-speed mixer and HTHP filter press as experiment equipment. The permeability of the mud cake was gradually reduced by improving the dispersing stability of the millimicron barite and adjusting the mass ratio of the two barites. The final formulation for making the mud cake was as follows:1,000 mL water + 100 g millimicron barite + 10 g polyacrylamide + 50 g sodium polyacrylate + 200 g commercial barite + 7 g plugging agent. The mud cake made with this formulation had average thickness of 2.24 mm, and average permeability of 1.42×10-7 D. The process of making the mud cake had good stability and repeatability. Using the prepared mud cake, several commonly used water base drilling fluids were tested for their filtration performance, further proving that the mud cake prepared with this method was suitable for use in simulating shale formations with developed micro pores and micro fractures, and in effectively evaluating the filtration and wall building performance of drilling fluids across the shale hole sections.