Laboratory Study on Optimization of Drilling Fluid Used in Southwest Tarim Basin with Nanoemulsion

The southwest Tarim Basin has plenty of oil and gas resources, rendering this area excellent exploration and development potential. However, the complex geological condition in this area seriously restricts the exploration and development potential. Mud losses, pipe sticking, reaming, borehole wall collapse, resistance to the tripping of drilling tools and well kick have often been encountered during drilling. Among these, mud losses happened for more than 30 times and pipe sticking more than 10 times. The longest drilling time of a well was as long as 719 d. To deal with these problems, the main factors affecting the stability of the borehole wall was analyzed, and based on the analysis, a core nanoemulsion developed by the China University of Petroleum (Beijing) was selected as borehole wall stabilizer. The core nanoemulsion is a nanoemulsion with nano SiO₂ as the core, and the D₅₀ of the cores is about 100 nm. The oil phase of the nanoemulsion can be used to inhibit the swelling of clays, and form "soft + hard" plugging system in pores and fractures. Laboratory experiment showed that a drilling fluid optimized with 5% core nanoemulsion had HTHP filtration rate of only 3.8 mL. Pressure transmission test showed that time for the balance of pressure transmission was reduced by 125 min after optimization, and the pressure was reduced by 0.337 MPa. In hot rolling test, the percent recovery of shale cuttings was 85% when tested with the optimized drilling fluid. All these facts prove that the core nanoemulsion can be used as a water base mud additive for optimizing the mud performance.