沁水盆地煤储层孔隙差异发育主控因素

MAIN CONTROL FACTOR AFFECTING PORE DIFFERENTIAL DEVELOPMENT OF THE COAL RESERVOIRS IN QINSHUI BASIN

煤中孔隙的形态和结构特征强烈影响着煤储层的吸附、解吸、扩散及渗透性。为查明影响沁水盆地 高煤级煤储层孔隙系统差异发育的主控因素,对采自该盆地北、中及南部6个市县13个矿区的40余件样品进行了 详细解剖研究。应用对应分析方法发现煤相是该盆地煤储层孔隙系统在高煤层级阶段差异发育的主导控制因素, 而高煤级造就了该盆地煤储层孔隙系统总体上不利于煤层气产出的共同特征。煤相通过对该盆地高煤级煤储层 孔隙系统差异发育的直接控制而间接控制了储层吸附、解吸及渗流物性的优劣。在沁水盆地,活水泥炭沼泽相以 及森林泥炭沼泽相是形成有利储层的沉积环境,而干燥泥炭沼泽相一般难以形成有利的储层。由于沉积环境(煤 相)的剧烈频繁变迁导致了煤储层孔隙系统及相应的储层物性在纵向及横向上强烈的非均质性,给该盆地煤层气 的开发带来严重不利影响。

The adsorption, desorption, diffusion and permeability of coal reservoir are greatly affected by the shape and inner structure of the pores in coal. More than forty coal samples collected from thirteen coal mines in the north, central and south parts of Qinshui Basin were studied in detail so as to find out the main control factor affecting pore differential development of the high-rank coal reservoirs in the basin. Through investigating by use of correspondence analysis method, it was proved that the coal facies is the main control factor affecting pore system differential development of the coal reservoirs at high-rank stage in the basin and the high-rank coal has caused a common character of disadvantaging the coalbed methane's being produced from the pore system in the coal reservoirs overall. The coal facies might indirectly control the petrophysical properties as adsorption, desorption and permability of the coal reservoir through directly controlling its pore system differential development. In Qinshui Basin, the fresh-water peat swamp facies and forest peat swamp facies were the sedimentary environments of forming good reservoirs, but the drained peat swamp, fecies was difficult to form good reservoirs, in general. The severe and frequent changes in sedimentary environments (coal facies) led to the horizontally and vertically sharp inhomogeneities of the pore system and relevant petrophysical property of coal reservoir, which bring on a very disadvantageous influence on the coalbed methane development in the basin.