郑庄与樊庄区块高煤阶煤层气开发差异及其主控因素分析

摘要

查明高煤阶煤层气开发差异的主控因素对于实现效益开发意义显著.基于沁水盆地南部郑庄和樊庄区块高煤阶煤层气井生产特点对比,首次提出了储层流体可疏降系数以反映流体在煤层中疏降能力,探讨了地质、储层和流体等因素对高煤阶煤层气井气、水产出的差异控制并揭示了主控因素.结果显示:相对樊庄区块而言,郑庄区块煤层气井产气量低、产水总量大、解吸前排采时间长、气水产出比小,且地质和储层特点表现为地应力梯度高、地温梯度较高、煤厚较薄、煤层结构较复杂、裂隙较发育、渗透率较低、储层流体可疏降系数较小等.影响区块煤层气井产出差异的直接因素为渗透率和储层流体可疏降性,而控制渗透率的关键地质因素为地应力、控制储层流体可疏导性因素为煤储层本身特性.建议该区块有利区优选以寻找低地应力条件为主,针对高地应力区宜采取有利于地应力释放的储层改造措施.%Recognizing the major controlling factors of the difference for coalbed methane (CBM) development in high-rank coal can promote the benefits in the process of CBM development.Based on production characteristics contrast of CBM wells between Zhengzhuang and Fanzhuang blocks, we put forward a new dredging and pressure-drop index to reflect the difficulty level for fluid flow in coal coalbed during drainage, analyzed the differences of geology, reservoir and fluid factors between Zhengzhuang and Fanzhuang blocks, and discussed it's controlling factors on production differences.The results have shown that comparing with those of Fanzhuang block, the Zhengzhuang block has the lower gas production,higher water production, the longer water drainage time before CBM desorption and the lower radio of gas and water production, the higher geo-stress and geothermal gradients, the thinner thickness of coalbed and the more complex coal structure, the more well-developed fractures, the lower permeability, the smaller dredging and pressure dropping index.The direct factors that influence the production of CBM wells are permeability and the dredging and pressure-drop index of fluid in CBM reservoir, The major geological factors that controls permeability and the dredging and pressure-drop index of reservoir fluid are geo-stress and properties of coal reservoirs respectively.The low geo-stress should be taking into key account in optimization of sweat spot, and reservoir stimulation for CBM development in high geo-stress regions should take the geo-stress release into key measure.