Gas Productivity Enhancement By Wettability Alteration Of Coalbed Methane Reservoirs

Although oil and natural gas have a large proportion of China’s energy consumption, the proportion of coal is still China’s largest energy Source. Coal and energy are fossil fuels, exploitation has a considerable risk and safety issues. since the1834French Isaac first in the world recorded gas outburst occurred,the coal industry of he world’s major coal mining countries have undergone varying degrees of gas outburst disasters,so in China.from the current situation Gas outburst is still one of the the key security of coal production, so the Country strongly support the Policy of Coalbed Methane exploitation before gas production mining, and a substantial increase in research in improving the efficiency of methane (CBM) mining, the China National Petroleum Corporation also joined the field of gas exploration and research. Effective prevention and treatment of an important technical means to protect mine production safety and improve mine economic benefits, the gas outburst, coal mining is to solve the outstanding issues of deep coal mining, gas is one effective means. The main issue is how to substantially improve the gas extraction rate and extraction ratio.The study of China’s coal-bed methane reservoir bases on the characteristics of low pressure and low permeability. analyzed and summarized the existing methods and techniques of coal seam gas extraction rate and extraction rate were.By molecular simulation methods, the nature of the gas wetting the surface of the alteration agent simulation, calculation intermolecular interactions, changes in interfacial tension and contact angle data of the corresponding three-component system for screening good wetting alteration performancemolecular Design. Successfully synthesized according to the results of molecular simulation, the design of gas-wetting alteration agent, and the measured contact angle and other related performance parameters, in good agreement with experimental results and simulation data.Since the use of Li-Horne model greatly simplifies the traditional calculation method, water permeability kw and capillary pressure Pc can be easily worked out through the experimental study of the two-phase system imbibition.Through mercury injection experiment, we can infer that coal fractures contribute the most to the coal porosity with the matrix for a small contribution. By comparison1#coal sample most easily inject and withdraw mercury than2#coal sample and3#coal sample.2#coal sample has strongest heterogeneity,3#coal sample the weakest. Pore radius distribution and the fractal dimension have accordant results, showing the larger the fractal dimension, the stronger the heterogeneity. Brooks-Corey model and Purcell model are also used the preliminary calculations for the wet phase permeability and non-wet phase permeability.Preliminary study on the dynamic prediction method of gas extraction, gas extraction volume and dynamics of many factors, mainly permeability, relative permeability, fracture development, and measures; gas extraction dynamic fitting and prediction theoryand methods, however, very difficult, is still a huge challenge; existing analysis results show that the Li-Horne, the formula can be fitted well with the fracturing coalbed gas extraction volume with the time change.