Research On Equipment Matching Of Air-lift Reverse Circulation Drilling For Oil And Gas Wells

With the development of the national economy and burgeoning large economic aggregate, the demand for oil and gas exceeds the supply. So far, the exploration and extraction for oil and gas in our country point to two directions include deep resources and unconventional resources. The key problem in these resources exploration is how to improve drilling speed and reduce drilling cost. However, the air-lift reverse circulation drilling technology has been widely applied in water wells and geothermal wells because of its advantages. Instead, it has not been applied in oil and gas wells ever. To improve the drilling speed, reduce the drilling cost and solve the problem of drilling with formation leakage in oil and gas drilling, the air-lift reverse circulation drilling technology has been studied and improved.The different between oil wells and geothermal wells has been analyzed, and the requirement to the air-lift reverse circulation drilling technology for oil and gas wells has been proposed. According to these requirements, the method of air-lift reverse circulation drilling equipment matching has been discussed. In order to provide scientific evidence for drilling equipment selection and improve its applicability, the theory of air-lift reverses circulation drilling technology has been studied. The relationship between cutting carrying capacity and the diameter of drill pipe, gas pressure, gas flow rate, drilling fluid density, particle size and other factors has been acquired. Based on the relationship, the criterion which is the maximum drilling speed allowed has been proposed, and the drilling equipment selection method has been studied relied on the criterion. The recommended equipment model of air-lift reverse circulation drilling for several well sizes is given which is based on the calculation of dual-wall Kelly, dual-wall drilling pipe, drilling pipe and air compressor in glaring examples.According to the requirements of oil and gas wells, drilling fluid circulation system has been redesigned which can turn to normal circulation quickly. What is more, to ensure the safety in drilling engineering, the blowout preventer for drilling string has been complement and the air-lift reverse circulation drilling well control system has been improved.To test the applicability of air-lift reverse circulation drilling technology in oil and gas wells, experiment in Changning H9-6 wells had been completed and succeed. It shows that the air-lift reverse circulation drilling technology is feasible in oil and gas wells. Furthermore, it means that the drilling equipment selection method is right, and it has accumulated the experience for the promotion and application of the air-lift reverse circulation drilling in oil and gas wells.