Drilling String Design Of High Hydrogen Sulphide, High Pressure And High Production Gas Field

During drilling operation of high hydrogen sulphide; high pressure and high production gas field, it was common drilling accident that acidic environment and complicated stress condition lead to fracture. At the moment, the research on the strength of drilling string during drilling operation of high hydrogen sulphide and complicated stress condition was lack, and the research on designing of hole assembly was lack.In this paper, a summary of the calculation method of drilling string limitation with different well style and drilling mud of domestic and abroad on the basis of comparison was given to build calculating model of compound stress under complicated load. In view of fatigue failure and fracture during operation of air drilling, design method of hole assembly of air drilling was proposed on the basis of variable cross-section modulus, and this method was the guideline of lessening accumulation of stress of hole assembly. In view of uncertainty problems of different operational modes of directional well and horizontal well, integrated design method which was begun with well head, kick off point and bottom of a well of drilling string limitation was proposed as the basis of drilling string design of directional well and horizontal well.On the basis of drilling string force analysis and drilling string limitation analysis, drilling string design methods of different well style and drilling mud were summed up. On the basis of theoretical analysis of hole assembly and example of field application, data base of hole assembly design with different well style and drilling mud, and API drilling string data base was also built, and then programmed the software of drilling string design of high hydrogen sulphide; high pressure and high production gas field was developped. On the basis of theory, prepared the computer programs to calculate the strength of drilling string, the example completed by the program showed that, the bigger variable cross-section modulus of hole assembly of field application showed that serious accumulation of stress. The failure was lessened greatly by optimizing hole assembly, and the safety was improved greatly. The weight of drilling string was reduced by optimizing hole assembly, and lower grade drill pipe was selected on the condition of safe coefficient not precipitous decline, and the tendency of sulfide stress cracking was precipitous decline.