Due to great variety additives and disposal difficulty, chemical method, biochemical method and solidification are adopted to treat fracturing wastewater in oil field. These processes easily bring about shortcomings, including high cost and secondary pollution. Studied on the treatment of fracturing wastewater of 4# well in Sichuan Oilfield by modified bentonite loading TiO2-Ag2O composite catalyst, COD removal rate is determined for different condition of pH value of solution, adding content of TiO2, inflating volume and light application time. The optimal condition is obtained as follows: pH value of solution is 3, adding content of TiO2 is 0.4-0.5%, inflating volume is 15L/min and light application time is 3h. Under this condition, COD removal rate of fracturing wastewater is 58.1%. The composite catalyst performance is stable and without secondary pollution. It is reusable by high temperature activation, so it can reduce wastewater treatment cost, and should be widely applied.

A polymer drilling fluid containing high content of hydrogen sulfide was used as the corrosive medium to investigate the effects of temperature, flow velocity, pH value and partial pressure ratio of CO2/ H2S on the corrosion behavior of high strength drill pipe steel S135 and G105. The morphology and composition of the corrosion products were analyzed as well. It was found that the average corrosion rate of the two types of steel increased with increasing temperature of the corrosive medium, with the corrosion rate to decrease slightly within 60°C-80°C and keep almost unchanged above 120°C. At the same time, the corrosion rate of the drill pipe steels had little to do with the flow rate but increased with decreasing pH value of the corrosive medium. Moreover, the partial pressure ratio of CO2/ H2S had a slight effect on the corrosion behavior of the drill pipe steel. However, the two types of drill pipe steel showed a larger corrosion rate in gas phase than in liquid phase corrosive medium, which was contrary to what were observed in gas and liquid phases corrosion tests of conventional acidic drilling fluids. In addition, it was confirmed by sulfide stress corrosion test that the drill pipe steel of a higher strength had smaller critical stress, and the resistance of the drill pipe to stress attack was ranked as G105(C)＞G105(D)＞S135(B)＞S135(A). It was anticipated that the present research results could be used to guide the selection of materials for drilling pipe steels used in natural gas field of high acidity.

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