DISCUSSION ON RELIABILITY FOR CO-MINING THE COALBED GAS AND NORMAL PETROLEUM AND NATURAL GAS: ABSORPTIVE EFFECT OF DEEP COAL RESERVOIR UNDER CONDITION OF BALANCED WATER

Based on suggesting the problems for co-mining the coalbed gas and normal petroleum natural gas, the absorptive effect of the deep coal reservoir under the condition of the balanced water was studied using the physical simulating test with the analysis of the geological setting, and some new viewpoint were suggested. The results showed that the content of the balanced water in coal reservoir could be controlled by the combination of the strata temperature with the its burial depth and coal rank. The conditions of the deep strata could result in the difference of the absorption between the deep and sallow reservoirs. The relationship of the saturated gas-absorbing content to the burial depth of the reservoir could be reversed at a certain depth (named as the critical depth of absorptive saturation) in the strata, and the critical depth is varied with coal rank, which is deservedly derived from the co-action of the temperature-enhancing effect and self-characteristics of the deep reservoir. The match of the higher temperature with the flow pressure in the deep reservoir could be favorable of mining the coalbed gas, and, in another word, there is the reliability of co-mining the deep coalbed gas and petroleum natural gas. The difference of the absorption between the deep and sallow reservoirs could be radically derived from the double controls of the higher flow pressure and temperature in the deep reservoir.