Study On Adaptability Of Coalbed Methane Special Technology Well In Wuwei Basin

The exploration and development of coalbed methane has just started in Wuwei basin. Currently, for coalbed methane exploration project, the level of geological knowledge is low, there is no depth study on mechanical properties about coal rocks, the understanding of properties and mechanical characteristic was not abundant, so the development program for Wuwei basin was not clear. In order to provides theoretical support for matching technology of special technology wells, it is necessary to research special process and optimize it, then carry out test research about mechanical characteristic of coal rocks.This paper researched wellbore instability combining with geological characteristics and analyzed the suitability of special process well on rock mechanics parameters, physical parameters and geological features based on mechanics experiments of coal rocks. This paper aimed to research coalbed during the Carboniferous Taiyuan in Wuwei basin, has done deep study on geological characteristics, rock mechanics parameters, physical parameters, wellbore stability and so on, then established physical and mathematical models. Last optimize a wellbore trajectory which is suitable for coalbed in Wuwei basin. This paper mainly research work and results are as follows:Rock mechanics characteristic analysis and assessment. This paper got rock strength parameters, elastic parameters, tensile strength, vertical and horizontal velocity through rock mechanics experiments. There is a conclusion that special process wells is suitable for Wuwei district, besides, these parameters are useful for analysising wellbore stability.This paper has analysised the geological conditions, the work area has simple structure, less faults and stratigraphic gentle, the coalbed has low porosity and low permeability with a micro-cracks and cleats.Then, this paper did log interpretation to analysis physical parameters, at the same time, provided basic parameters for optimizing wellbore parameters.Calculation model of ground stress was established based on rock mechanics parameters of well W-1and W-2, wellbore rock stress was calculated under different borehole trajectory parameters. This paper determined the mud window width through analysing the three pressure traverse and draw a conclusion that Wuwei district is suitable for drilling horizontal wells, furthermore, provided parameters for optimizing wellbore trajectory.This paper optimized parameters for special process wells through mathematical model and designed wellbore trajectory which is suitable for Wuwei district combining with related design principles based on the best borehole azimuth for horizontal wells.