The biodiesel-based flat-rheology drilling fluid system

As the base oil of the current flat-rheology synthetic drilling fluid is high in cost and not renewable, the biodiesel-based flat-rheology drilling fluid with low-cost, environmental protection and renewable advantage was studied. Based on the optimization of raw materials, a cheap, environment-friendly biodiesel of soybean oil ethyl ester with good fluidity at low temperature was selected as the base oil. By selecting high oil-water ratio and introducing cationic surfactant into the auxiliary emulsifier, the thickening of biodiesel-based emulsion caused by hydrolysis and saponification after high-temperature aging was effectively eliminated. The organoclay prepared with cationic modifier of hexadecyl trimethyl ammonium chloride was used to improve the rheologic properties, stability and fluid loss of the drilling fluid while preventing low-temperature thickening. A flat-rheology modifier was synthesized with dimer fatty acid and cocoanut fatty acid diethanolamide, which could form strong network structure in the biodiesel-based drilling fluid to adjust effectively rheological properties of the drilling fluid. A biodiesel-based flat-rheology drilling fluid system with the density of 1.2 g/cm(3) has been formulated which has constant rheology in the temperature range of 2-90 degrees C, temperature tolerance of 160 degrees C, seawater salinity tolerance of 5%, shale cuttings tolerance of 10%, and is environmentally friendly.

Automated summary

This study focuses on the high cost and non-renewability issue of the base oil used in current synthetic drilling fluids, and investigates a low-cost, environmentally friendly, and renewable biodiesel-based flat-rheology drilling fluid. By optimizing the raw materials, soybean oil ethyl ester biodiesel with good flowability at low temperatures is selected as the base oil. Various techniques, such as selecting a high oil-water ratio and introducing a cationic surfactant, are employed to improve the rheological properties and stability of the drilling fluid. The formulated biodiesel-based flat-rheology drilling fluid system maintains constant rheology within a temperature range and exhibits good environmental adaptability.