Microbially enhanced CBM well production rate technology and its application

In order to evaluate the microbially enhanced coalbed methane (CBM) well production rate technology, an experimental study was performed on the gas generation through microbial coalbed degradation by adding a certain amount of coal and the nutrient solution prepared with produced coalbed fluid into the anaerobic bottle. The effective microbial community density of nutrient solution was 3-6 orders of magnitude higher than that of the produced coalbed liquid. Gas production per milliliter of nutrient liquid was 2.84 mL.After the coalbed microbes were activated by the nutrient solution, N2, H2 and CO2 were the dominant products with lower CH4 content at the early stage of reaction. With the proceeding of reaction, CH4 content increased gradually. The X-ray diffraction suggests the structural changes of coal micro-crystal. It is indicated that the interaction between microbes and coal allows for the generation of biogas and the degradation of coal composition, thereby improving the coalbed permeability. And consequently, methane desorption is promoted and CBM well production is increased. After the laboratory experiment, field pilot test was conducted in one well time by injecting 230 m3 microbial fluid. Before the treatment was made, average daily gas production rate of this well was 16.81 m3 and average casing pressure was 0.09 MPa. After the treatment was made, its average daily gas production rate was 75.13 m3, average casing pressure was 0.35 MPa and cumulative gas production was 14 100 m3. At present, this well is at stable production stage. Obviously, the purpose of enhancing CBM well production rate by microbe injection is reached.