Development and Application of the Environmentally Friendly HL-FFQH Water Base Drilling Fluid

A new environmentally friendly water base drilling fluid HL-FFQH has been developed to address the problems encountered in using conventional environmentally friendly drilling fluids, such as poor engineering performance and high cost. This new drilling fluid was formulated with previously developed five additives which are nontoxic, easy-to-degrade and have heavy metal contents that meet the standard. The formula of the drilling fluid is:4% bentonite +0.3%HLBE-2 (encapsulator) + 2% HLJ-1 (filter loss reducer) + 3% HLGB-3 (borehole wall strengthening agent) + 1% HLFD-1 (plugging agent) + 2% HLR-2 (lubricant) + barite. This drilling fluid showed good rheology in laboratory evaluation. Length of expansion of shale core in 8 h was only 2.5 mm, indicating that this fluid had good inhibitive capacity. After contaminated with drilled cuttings, the change of the filter loss of the drilling fluid was less than 0.4 mL, indicating that the drilling fluid was resistant to cuttings contamination. After aging at 150℃ for 16 h, the drilling fluid had friction coefficient and mud cake friction coefficient of 0.10 and 0.08, respectively, proving that this drilling fluid had good lubricity. Biotoxicity, biodegradability and content of heavy metals all met the relevant standards. The waste drilling fluid was light-colored, and the mud cake and filtrates of the drilling fluid did not affect the growth and life of animals and plants. No damage to the reservoir and downhole troubles have been found using this drilling fluid. Compared with offset wells, the ROP was increased by 85.5%. The HLFFQH drilling fluid conforms to the requirements of environmental protection from formulating to waste fluid treatment.