Disposal countermeasures of drilling fluid in loess zone

A large quantity of waste drilling fluid and drainage are yielded during the exploration procedure of oil. These wastes may pollute soil, groundwater and surface water because of the surface leakage and overflow. The north of Shaanxi province, which is the oil production area of the Changqing Oilfield, was chosen as study area. Analysis of waste drilling fluid was carried out in five different wells sited in the study area. The results indicated that it was hard to achieve solid-liquid separation with physical method. The study put forward the solidification-after-gelout disposal technique for waste drilling fluid. In the technique, iron salts were chosen as gel breaker, fly ash and lime were chosen as curing agents and loess was chosen as supplementary material. The optimum conditions were investigated and the results of experiment showed that when the content of FeCl₃ was 0.6 percent of waste drilling fluid, the content of fly-ash was 25 percent, the content of lime was 6 percent and the content of loess was 40 percent. The results showed that it was effective to use the technique for treating the waste drilling fluid.