| Gas drilling carries debris and cools bit through gas which is circulated medium. The gas may be air, nitrogen gas, natural gas, combustion gas etc... Gas drilling which owns its remarkable characteristics is a special underbalanced drilling technology. And the application about it is limited certainly.Gas drilling originated in the USA. It is based on the gas or gas-liquid mixed fluid as a circulating medium instead of drilling fluid. In China, Gas drilling started rather late. Sichuan had a try in the1950s and1970s. Since2005gas drilling has developed rapidly in Sichuan basin. But at present, it is generally in phase trials and promotion at home. Gas drilling has developed the rotating blowout preventer, no killing device and other equipments, tested air hammer, air screw and other downhole tools, and researched on theory and technology of air drilling. Gas drilling technology can greatly reduce the reservoir damage, improve the benefit of exploration and development, eliminate the leakage effect on the drilling operation.And it can optimize drilling speed, reduce the total cost of drilling operation and can improve the service life of a drill, working conditions and the environment. However, it require higher hole stability. If the formation is unstable, it will cause bit freezing, hole sloughing and mud loss. We should transfer drilling mode when the layer emerges water or oil. What’ more, well control will be more risky.Since America drilled the first shale gas wells in the world, gas drilling about shale has developed rapidly. It can well overcome the liquid of drilling fluid reservoir damage and difficulties in the process of drilling, such as bit freezing, borehole collapse. It is dangerous to employ gas drilling for The formation involving hydrogen sulfide. The conflagrations and corruptions of tools can happen. In recent years, the development about shale has become a hot spot. Currently Sinopec has launched the "Shale gas (oil) project demonstration zone in Daanzhai" project construction.This paper, based on a large number of the research results on gas drilling at home and abroad, summarizes the advantages and disadvantages of gas drilling, introduces the current situation of the development of gas drilling home and abroad. The paper has analyzed gas drilling equipments and tools and gas calculation theory, put forward the main basis to select the air compressor and the related calculation model. And this paper has analyzed the gas calculation theory and put forward the related model to calculate gas volume under the standard state in order to provide a theoretical reference for gas drilling. According to the formation and the actual drilling data in Fuling, this paper has analyzed the reasons that the actual construction period delayed about the upper well. Then the paper proposed the gas drilling speed optimization scheme. It recommended that the initial flow can use wash boring with PDC bit and try to drill through the Feixianguan formation. Changxing formation with fractured gas pay should use the foam drilling. The second flow ought to adopt the foam drilling with PDC for increasing drilling speed. At the same time, we should also strengthen the leak plugging, well control management. From moving installation, we have been to aging, then avoid stopping drilling for any problems, for example equipment, personnel, materials and so on. Thereby we can shorten the production and construction period. This paper provides a reference for the site construction, and then explores a feasible way for the efficient development of the upper formation in Fuling. Furthermore it has the extremely vital significance to realize the sustainable development of oil field. |
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