标题：EXPERIMENTAL STUDY OF A NOVEL WHITE OIL BASED WATER-IN-OIL DRILLING FLUID USED FOR HORIZONTAL WELLS IN SHALE GAS RESERVOIR OF YANCHANG OILFIELD, CHINA
摘要：Open hole wellbore instability is very common during the drilling of horizontal shale gas horizontal wells in Ordos Basin of Yanchang oilfield. To solve these problems, this paper innovatively proposed a water-in-oil emulsified drilling fluid formula. Laboratory experiments are conducted to optimize the drilling fluid additives, and two water- in-oil emulsified drilling fluid formula are chosen. The evaluation experiments show that the two drilling fluids have good rheological properties, antifiltration loss, and good ability to inhibit mudstone expansion. After aging for 48h at 100°C, the high- temperature/high-pressure filtration loss is almost zero, and the rheological properties maintained good performance after aging. After hot rolling for 16h in 100 °C, the shale rolling recovery rate is respectively determined to be 92.08%, 86.45% for 1# and 2# drilling fluid formula. After that, a concentration of 0%, 5%, 10%, and 15% of water, CaSO4 and brine were added in the 1# formula. The rheological properties did not change too much, indicating that the system has a strong antipollution ability. Therefore, the 1# white oil drilling fluid system has better comprehensive performance and can meet the requirements of shale gas horizontal well drilling process.
