A Study On Correction Method For The CBM Horizontal Well Logging Environment Effect

As China’s CBM exploration continued to improve, the impact on the CBM horizontal well logging environment can not be ignored. The shallow buried coal seam, the development of micro pore and crack, which are effected of mud invasion easily. In addition, the mechanical low strength of the coal, which leads to collapse easily in the process of drilling, expanding was particularly prominent.. Horizontal well logging is not only affected by the borehole diameter, salinity, temperature and mud cake and clearance and other environmental factors, and the horizontal well conditions, influence of anisotropy on the measurement results will be greatly enhanced. The gravity will cause the tool eccentricity; invade the asymmetric distribution of sedimentary detritus layer and at the lower side of the borehole. Expanding, anisotropy, intrusive, tool eccentricity and cuttings bed and other environmental factors will lead to CBM horizontal well logging curve to produce different degree of distortion, distortion of the original form of logging curve is of many environmental factors influence the results, the influence of specific environmental factors which are large, which distinguish difficultly. If you can use a method to identify the CBM horizontal well logging environment influence factors, and according to the main environmental impact of inversion correction of CBM exploration and development is of great significance.Summarizing the predecessors’ mechanism and environmental impacts of logging calibration method, on the basis of summed up the conventional CBM horizontal well logging response characteristics. According to the different kinds of coal and rock and coal rank statistical analysis of the horizontal well logging response characteristics of coal seam. The density logging, acoustic logging, resistivity log analysis of influence factors are carried out on the CBM horizontal wells. the differences of CBM vertical wells and horizontal wells are compared in the natural gamma ray log and three porosity and resistivity logging, and find out the influence factors of CBM vertical wells and horizontal wells, and also through comparative analysis the influence factors of vertical and horizontal wells in coal bed gas, which is obtained both by the eccentric, mud invasion, anisotropy, rock and layer thickness effects. According to the influencing factors of CBM horizontal well resistivity logging environment, this paper uses the finite element method and conducts the numerical simulation of coal bed methane horizontal well logging to the horizontal well environmental factors identification. And uses fuzzy mathematics for CBM horizontal well logging identification of the primary and secondary factors. The impact on the environment mapping calibration factors, the optimal fitting, with a large number of fitting formula instead of plot, the formula of the program, realized the computer automatic environmental effect correction.The coal seam has obvious "four high and four low" characteristics in the logging curve. the resistivity curve of the existence of the ash is susceptible to influence of surrounding rock. Ash content makes resistivity and gamma ray logging all change, and the natural gamma value is lower than the conventional coal sandstone. The coal rank, coal and rock of different types of statistical analysis of response characteristics horizontal well are no obvious regularity. The resistivity of the borehole and surrounding rock and invasion correction chart are mapped, after automatic correction, the correction results meet the actual work requirements.