Development and Performance Evaluation of a Deep Water Synthetic Based Drilling Fluid System

With the enhancement of environmental protection awareness, the requirements on drilling fluid are increasingly strict, and the use of ordinary oil-based drilling fluid has been strictly restricted. In order to solve the environmental protection and oil-gas reservoir protection problems of offshore oil drilling, a new synthetic basic drilling fluid system is developed. The basic formula is as follows: a basic fluid (80% Linear a-olefin + 20% Simulated seawater) + 2.5% nano organobentonite + 3.5% emulsifier RHJ-5# + 2.5% fluid loss agent SDJ-1 + 1.5% CaO + the right amount of oil wetting barite to adjust the density, and a multifunctional oil and gas formation protective agent YRZ has been developed. The performance was evaluated using a high-low-high-temperature rheometer, a high-temperature and high-pressure demulsification voltage tester, and a high-temperature and high-pressure dynamic fluid loss meter. The results show that the developed synthetic based drilling fluid has good rheological property, demulsification voltage ≥ 500 V, temperature resistance up to 160°C, high temperature and high pressure filtration loss < 3.5 mL. After adding 2% - 5% YRZ into the basic formula of synthetic based drilling fluid, the permeability recovery value exceeds 90% and the reservoir protection effect is excellent. The new synthetic deepwater drilling fluid is expected to have a good application prospect in offshore deepwater drilling.

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 ℃, temperature tolerance of 160 ℃, seawater salinity tolerance of 5%, shale cuttings tolerance of 10%, and is environmentally friendly.