火烧铺煤矿多层叠置含煤层气系统发育规律

Development Laws of Multiple Superimposed CBM System, Huoshaopu Coalmine

根据研究区前期钻孔资料,结合最新的煤层气参数井相关资料,剖析了该区煤层气地质赋存条件,分别从煤质、含气性分布、解吸—吸附特征、孔隙—裂隙特征及渗流特征等5个方面对煤储层物性的垂向规律进行了分析,同时借鉴多层叠置含煤层气系统理论对该区煤层气系统进行了划分。结果显示:伴随着煤层埋深的增加,煤储层化学性质表现为规律性的波动变化,原煤灰分与硫分呈现出在煤层上部递减,中部递增,下部递减,并最终趋于稳定的趋势;不同层位煤层的平均含气量呈波动变化,综合煤储层化学性质及含气量变化,大致以12号、22号煤层为界,初步可划分为3个旋回序列,且在同一个旋回序列内表现为随埋深增大含气量逐渐升高的规律,当埋深达到一定深度(基本为24号煤层埋深处)时含气量基本趋于稳定;研究区内煤储层孔隙主要为微小孔,孔隙类型主要为连通性较好的开放孔,这对于煤层气的渗流产出比较有利;煤层气参数井试井结果显示:主采煤层压力系数自顶部至底部呈现先降低后升高,最终趋于稳定的趋势。综合考虑上述因素,结合地层层序格架最大海泛面相关知识,将该研究区煤储层划分为3个独立的含煤层气系统。

On the basis of not only previous drilling data but also the latest information from CBM parameter wells, we at first analyzed complicated geological environments of CBM reservoirs in Huoshaopu Coalmine, then summarized the vertical relationship between five properties or characteristics(coal property, gas-bearing property, desorption-adsorption characteristics, pore-fissure characteristics, and percolation characteristics) and petrophysical property, at last subdivided these reservoirs through multiple superimposed CBM system. Results show that in these reservoirs,(1) along with an increase of burial depth, chemical properties assume regular fluctuation, such as, a gradual decrease of both raw coal ash and sulfur contents at the upper and lower whereas a progressive increase at the middle, finally showing the trend towards stability;(2)the average gas content appears fluctuation in different reservoirs.And taking No. 12 and No.22 seams as boundary, there are three cyclic successions divided according to chemical properties and gas-content change. Within the same succession, some variation is found, for instance, gas content increasing with burial depth, however gas content tending towards stability when a certain burial depth(identical to burial depth of No. 24 seams); and(3) pore is dominated by micropore and its type is mainly open pore with better connectivity, which is more favorable for CBM percolation. It is demonstrated from well parameters that, for the main reservoirs,pressure coefficient presents the trend from the top to the base,firstly down, then up, finally towards stability. In addition, combined with some knowledge on maximum flooding surface, we classified these reservoirs into three independent CBM-bearing systems.