煤层气井压降规律与排采参数关系分析

煤层气区块排采制度以现场经验为主，与区块的地质条件及开发现状结合较少。压降漏斗的扩展形态是煤层气井地质特征和开发方式的具体表现形式，利用压降规律建立合理的排采制度是煤层气田科学开发的关键环节。将压降漏斗横向上的压降半径和纵向上的压降大小比值称为压降漏斗表征系数，分析认为压降漏斗表征系数越大，单井产气量越大。以保德区块试验区为例，通过Eclipse建模及Matlab画图工具箱分析了3种不同煤层渗透率、地下水流体势及试验区井组间干扰对压降漏斗表征系数的影响后，建立了合理放气套压与合理压降速率等排采参数与压降漏斗表征系数的函数关系式，计算了滚动开发区C1~C13井的合理放气套压以及S1~S12井的合理压降速率，结果表明理论计算排采参数值与生产实际值差值越小的井，单井产气量越高，表明该方法建立的煤层气井排采参数计算方法可靠，可指导见套压未放气井和见气井的合理排采，为煤层气区块的定量化排采提供理论依据。

Analysis on the relationship between pressure drop laws and production parameters of CBM well: A case study on the Baode Block

The production systems of coalbed methane (CBM) blocks are mainly based on field experience but less on the geological conditions and development status of the blocks. The extension form of pressure drop funnel is the specific manifestation of the geological characteristics and development mode of CBM well, so formulating a rational production system based on pressure drop laws is the key link for the scientific development of CBM fields. The ratio of the lateral pressure drop radius to the vertical pressure drop value of pressure drop funnel is defined as the representation coefficient of pressure drop funnel. It is deemed that the higher the representation coefficient of pressure drop funnel is, the higher the single-well CBM production is. The pilot area of Baode Block was taken as an example. The effects of three coalbed permeabilities, groundwater fluid potential and interference between well groups of pilot area on the representation coefficient of pressure drop funnel were analyzed by virtue of Eclipse modeling and Matlab drawing toolbox. Then, the functional relation between production parameters (reasonable casing releasing pressure and reasonable pressure drop rate) and the representation coefficient of pressure drop funnel was established. Finally, the reasonable casing releasing pressure of Well C1-C13 in the progressive development area and the reasonable pressure drop rate of Well S1-S12 were calculated. It is shown that the smaller the differences between the theoretically calculated production parameters and the actual values of a well are, the higher its single-well CBM production is. That the proposed CBM production parameter calculating method is reliable and can provide the guidance for the rational production of wells with casing pressure but no gas releasing and those with gas breakthrough, as well as the theoretical basis for the quantitative production of CBM blocks.