Study Of Preventing And Plugging Lost Circulation Technology In Ludong-wucaiwan Area Of Junggar Basin

Circulation loss is the phenomenon that various kinds of driving fluid including drilling fluid/cement slurry/completion fluid and other operating fluid etc leak to the layer by the action of pressure difference while in the downhole operation process such as drilling/cementing/testing or workover. Circulation loss is a most serious hazard greatly affect the drilling operation safety. Circulation loss is not only cause the drilling inconvenient and loss (such as drilling-time waste, loss of drilling fluid and plugging materials, and can cause the complications of sticking/blowout/slough etc, even can the wellbore abandoned, also damage the producing pay, lead to significant economics losses) but also take the tremendous difficulties for the oil and gas exploration and development.In the development of Ludong-Wucaiwan area, circulation loss frequently, it drastically limited the drilling safety and construction program. there is circulation loss at the cretaceous(k) upside and carboniferous downside according to the layer. This article analyze the formation characteristics according to the log information and log data. It shows that the characteristics of cretaceous and Jurassic is that poor cementation, lofty porosity, big permeability, permeability leakage, low layer loading capacity. While the Permian period(p) and carboniferous is fracture development, lofty leakage,fracture leakage, high pore pressure and easily lead to leakage when drilling the upper layer.The leak-proof technology research of this area is mainly from the aspect of bore frame optimization/loading capacity improvement/specialized technology and cementing leak-proof technology. The optimization of casing program is based on the recognition of formation pressure system. Considering the leakage pressure based on the pore pressure make the casing program more reasonable. Improving the ability of formation pressure is mainly for the upper low pressure drain formation, the plugging effect is obvious while pre-drilling, it should also do the pressure test after the success of plugging to improve the bearing capacity. The implementation of controlled pressure drilling control the circulation loss should have a better effect in this block as combined the characteristic of fracture development in the carboniferous with the result analysis of implementation of liquid phase unbalanced drilling technology. It mainly take preventive measure for the leakage while cementing including regulating the drilling fluid, optimizing slurry and pad fluid performance.The primary problem of plugging construction in the Ludong-Wucaiwan area gas is that it can not inform the leakage position timely and accurately. In this paper, the changes of the stand pipe pressure before and after the leakage is used to analyze the leakage position, it reflects the changes of annular pressure lost above the leakage position, combined with the drilling parameter of this block,the method of locating the leakage position was formed, the result shows that the methods more applicable to the construction site. As certain the location of leakage layer, based on different type of leakage, the reason of leakage, the appropriate measure to plug, which is an important part of plugging success or not. This paper states various methods of dealing with circulation lost for different layers specific based on the summary and analysis of the experience and lesson of plugging in the drilled well, which makes the plugging technology more reasonable and suitable to the construction site.The plugging material is the hardware basis of plugging construction, the inappropriate choice of plugging material can result in the circulation loss for long time to solve or repeated loss. In this paper, it analyzes several plugging materials which wilder application and then propose a new type plugging material, comparing the performances of several materials such as high temperature and pressure, the strength changes after immersion though the laboratory test. The new plugging material has a better effect on solving the leakage problem, can effectively improve the success rate of plugging though field application.The leakage to be relieved and the plugging success rate to be substantial improved of Ludong-Wucaiwan area though the research of leak-proof and plugging above and field application, whether the leakage times of each well or the leakage volume greatly lower than before. Of course, some technology which also needs further testing in the field can be verified, for example, the controlled pressure drilling resolve the role of fractured leakage of carboniferous.