Because of Gas drilling’s distinguishing feature, drilling tool is wornouted seriously by high velocity liquid’s erosive action and drilling tool substitute thread is cracked easily by air hammaer upward’s shock wave, all of which impact drilling speed and increase drilling cost. Based on the theory of rock mechanics and gas/solid two⁃phase flow, drilling tool erosived by liquid in gas drilling is analysed, return velocity model of mixture in annular is established, return velocity in annular impacted by back pressure is calculated with illustration. In order to avert erosiving by high velocity, return velocity of mixture in annular has to be between minimal carrier velocity and interface erosive velocity. Increasing well head back pressure could decreased the drill tool’s erosiving. Based on mechanical theory，the deformation harmonization equation of drilling tool substitute thread under the influence of pretightening load is fetched. The stress of drilling tool thread is analysed by finite element. The screw thread load distribution regular pattern of drilling tool substitute thread is found out. The thread stress centralized area is obtained, which could provide measure to prevent drilling tool failure and to enhance thread strength.

Furfural extraction oil, ethylene tar and vacuum residue were studied in this paper, the three kinds of oil were blended under laboratory conditions, the viscosities were determined on a certain temperature, and the causes of viscosity change were analyzed by using petroleum disperse system theory. The results show that, when the volume ratio of furfural extraction oil, ethylene tar to vacuum residue are 3∶5∶1, 1∶3∶1, 2∶5∶1 and 1∶5∶1, the viscosity, flash-point and stability are all up to the standard of marine fuel.

The hydrodesulfurization and dearomatization process for C6 solvent oil were investigated in multisteps including hydrorefining, adsorptive desulfurization and hydrodearomatization. The results show when the catalyst for hydrorefining section is MC-1 and for adsorption desulfurization section is HTZM-1, and reaction conditions are listed below: temperature 260 ℃, space velocity 6 h-1, pressure 2.0 MPa and the volume ratio of hydrogen to oil 100, the sulfur content of product can be reduced to 0.5 μg/g; Hydrodearomatization was carried out with HTB-1H as the catalyst under the following reaction conditions: temperature 120 ℃, space velocity 0.5 h-1, pressure 0.6 MPa and the volume ratio of hydrogen and oil is 100, the aromatic content of product is reduced to less than 100 μg/g to meet the new standard of C6 solvent oil.