Study On High Temperature Diesel Base Oil - In - Water Drilling Fluid

With the advantage of high inhibition, good lubrication, anti-high temperature, anti-contamination and stable performance, oil-based drilling fluid is mainly used in the objective interval in shale gas well drilling, and is a hot drilling fliud which is much accounted in the domestic. But the development of oil-based drilling fluid is lagging in the domestic.There is few kinds of treating chemicals, which’s performance is deficient, and the drilling fluid system is single.Taking the cost factor into consideration, the study of diesel-based drilling fluid was carried out in this paper. First of all, from the study of emulsifier, three kinds of surfactants were used to prepare an anti-high temperature emulsifier which was named YJR-1. The mechanism of emulsifier was analyzed. Results showed that the HLB value of YJR-1 was 3.5, the best composition was 74 percent of oleic acid,13 percent of oleic acid diethanolamine alkanol amide and 13 percent of fatty alcohol polyoxyethylene ether carboxylic acid sodium. YJR-1 had good emulsifying performance because it could greatly reduce the interfacial tension between oil and water, and formed a tenacious interfacial film. In addition, YJR-1 could be stable at 220℃.Fluid loss additive which was the key treating agent in oil-based drilling fliud was mainly researched. Octadecylamine and humic acid were used to create a fluid loss additive which was named HJ-1. The optimum reaction conditions were optimized by single-factor analysis, the molecular structure of HJ-1 was proved by infrared spectrogram, the performance and the action mechanism were also analyzed. Results showed that HJ-1 had good performance of fluid loss, and could be stable at 180℃. Mechanism analysis showed that HJ-1 reduced the filtration volume of drilling fluid by improving the grain size distribution of particles and the compressibility of mud cake, and forming dense filter cake which had a low permeability.On the basis of the developed key treatment agents, a kind of diese-based drilling fluid which was anti-high temperature was obtained by optimizing other auxiliary treatment such as organophilic clay, wetting agent and richmond agent. The formula is diesel(0#)+solution of 20%(ω) CaCl2 (the ratio of oil and water was 8 to 2)+3% emulsifier YJR-1+3% fluid loss additive HJ-1+2%-3% organophilic clay FB-MOGEL+1%CaO+1.5% wetting agent MOWET-1+0.5%-2% richmond agent TQ+heavy stone. The amount of heavy stone could be adjusted according to the need. Evaluation experiment results showed that the formula was suitable for drilling fluid with various density. The drilling fluid with the highest density of 1.80 g/cm3 was stable at 150℃. The system showed good rheological property under high temperature and high pressure, good sedimentation stability, high inhibition and anti-contamination.