Study on Compatibility of Drilling Fluid Lubricants and Screw Rubbers

This paper discusses the experimental studies on the compatibility of drilling fluid lubricants with screw rubbers at high temperature and deep well conditions. At different temperatures and additive concentrations, eight kinds of rubbers were tested for rates of volume increment, rates of mass increment and changes in tensional strength when they were in contact with drilling fluid additives, and the test results were compared and evaluated. The experimental results show that the rubber sample has big changes in drilling fluids treated with the lubricants R-1 and R-3; in the drilling fluid treated with R-1, the rates of volume increment of the rubbers were distributed between 56% and 175%, while in the drilling fluid treated with R-3, the rates of volume increment were distributed between 49% and 148%. When the concentrations of the lubricants were increased, the rates of volume and mass increments of the two rubbers are all increased, and the rubbers swell at higher rates. These results indicate that the raw oil of a lubricant is the key factor affecting the swelling of rubber. Using GC-MS technology, the raw oils were analyzed, and it was found that a lubricant whose raw oil has high content of aromatics has relatively large influence on the swelling of the rubbers. Based on the application properties of the lubricants, some lubricants suitable for use in high temperature deep well drilling were selected. The selected lubricants were used to replace those lubricants with high contents of unsaturated hydrocarbons in the third interval and the reservoir section of the wells drilled in the Taipen block, and rubber disintegration from the screw was significantly reduced. Statistic data showed that times of rubber disintegration was reduced from 11 well times/month in the past to 0.5 well times/month, and this greatly reduced the number of times of tripping and improved the productive efficiency.