Investigation on Migration Law of CBM with Low Permeability in Well Group Combined with Heat Injection Mining

Abstract

In order to obtain migration rules of low permeability coal-bed methane(CBM) in well group combined heat injection mining, a coupled thermal-solid-fluid mathematical models of CBM was established based on theory of heat transfer, elastic mechanics, seepage mechanics and rock mechanics. Combined with the geological parameters of the 3# coal seam of the Shanxi formation, the finite element software was adopted to stimulate seepage rules in the process. The temperature, stress and gas pressure variation were drawn after 10d heat injection, 100d mining in different well grid. The results show that the average velocity of heat transfer is 1.57m/d, and after 10d heat injection, the effective area of heat injection is in the 35m range of central well. With the increase of well number and the decrease of well-bore spacing, the action of well group interference is strengthened, the reservoir pressure drop is more quickly, the gas desorption area is increased and the production of well is promoted significantly in certain production area and mining time. The production of CBM in the 20m well-bore spacing of 7 well is 2.01 times that of the 5 well 30m interval.