No abstract

Turpan-Hami Basin is a typical low coal rank coal bearing basin in China, with coal resources accounting for 50% of the total low coal rank resources. Structural evolution of the basin plays important controlling roles to generation；Fan delta and braided delta deposit systems are thick and stable sedimentary systems which are favorable for coal beds development；Hydrogeological condition is a major force for the adjustment and construction of coal-bed gas reservoirs.

China is rich in CBM resources, but so far, some production wells present low production and rapid decline trend. In addition to these objective factors such as low permeability and complexity of geological structure of CBM reservoir, there is still the most important problem during the exploitation techniques that is the lack of understanding to dynamic variation character of CBM reservoir permeability, which leads to the unreasonable work of depletion for coalbed methane.Using P&M model and parameters from 3# coal seam of Shanxi Formation, Permian system in Qinshui basin, the permeability variations of this block (first decline, then ascend, reaching 2.8 times of initial permeability at the end) were analyzed, revealing good depletion prospect of this CBM field, and pointed that the higher Young's modulus is, the more obvious matrix shrinkage is and the higher gas saturation is, the more favor for permeability improvement through sensitivity analysis. Finally, two suggestions were proposed, (1) add the 'permeability variations' to the parameters for CBM block select, which may find the "innate" in the late development of the poor condition of properties easy to improve, develop potential for larger blocks. (2) Adjust and optimize the depletion method (amplitude and frequency of bleeding, pressure reduction) according to the permeability variation characters discussed in this paper

Coalbed Methane(CBM) production enhancement for single wells is a big problem to CBM industrialization. Low production is due to insufficient gas generation by thermogenic. Luckily, Biogenic gas was found in many areas and its supply is assumed to improve coalbed methane production. Therefore, microbial simulation experiment will demonstrate the effectiveness of the assumption. From microbial simulation experiment on different coal ranks, it is found that microbes can use coals to produce biogas under laboratory conditions. With different temperatures for different experiments, it turns out that the gas production at 35 °C is greater than that at 15 °C, indicating that 35 °C is more suitable for microbes to produce gas. According to quantitative experiments, adding exogenous nutrients or exogenous bacteria can improve CBM production. Moreover, the production enhancement ratio can reach up to 115% under the condition of adding exogenous bacterial species, while the ratio for adding nutrients can be up to 144%.

To support remaining economic recoverable reserves and undeveloped reserves compliant with SEC rules, different types of recovery analogous reservoir sequences need to be established. Based on the SEC reserves estimation standards and the actual development characteristics of the oilfield, a classified and optimal evaluation method of analogous reservoirs, which can select a reasonable analogous reservoir fast, has been proposed. This method mainly includes 7 steps to select analogous reservoirs. With practical application in an oilfield, this method has obtained good effects. Selection results can cover all the typical reservoir blocks, and it provides a reliable basis for analogizing the target reservoir in the future. The method herein could provide a new method to select analogous reservoirs based on SEC, and it can be widely used in other oil fields.