贵州省织金、纳雍地区煤储层物性特征研究

Characteristics of coal reservoirs in Zhijin and Nayong regions,Guizhou province,China

为了探讨织金、纳雍地区煤层气的勘探开发潜力,运用各种测试手段从孔、裂隙系统角度研究了该区煤储层物性特征,分析了煤储层的聚气能力、渗流能力及其控制因素.研究后认为该区煤变质程度高,煤储层吸附能力强,对煤层气的吸附聚集较为有利;而煤储层渗流能力低,仅局部地区存在高渗条件,不利于煤层气的产出;煤储层物性特征受控于该区复杂的构造条件,前燕山期的深成变质作用使得煤岩吸附能力增强,渗流能力下降,而燕山期强烈的构造运动使得断裂带附近的煤储层吸附能力和渗流能力整体增大,改善了局部地区煤储层物性特征.研究结果表明:织金、纳雍地区煤储层孔隙中以吸附孔为主,吸附孔隙百分比为50.61%～89.71%,吸附能力较强;而煤储层渗流孔隙百分比仅为21.14%,且煤岩显微裂隙密度普遍低于100条/9cm2,裂隙连通性较差,煤储层的渗透率相对较低;强烈的构造活动产生了大量的断层,地下的岩浆热液通过断层向上侵入,使得局部地区煤的变质程度迅速增加,同时产生大量的孔裂隙,改善了断层发育区附近煤储层的孔渗条件,后期的矿化作用充填了部分孔裂隙,一定程度上控制了煤储层物性,不利于后期的煤层气开发.

In order to Nayong regions, a se exp t of ore the production potential of coalbed methane （CBM） in testing methods were used to research the characteristics of coa ijin and 1 reservoirs from the angle of pore and fracture systems, and the adsorption and seepage capacities as well as their controlling factors were analyzed in this paper. It is considered that high degree of metamorphism of coal in the study areas and high gas adsorption capacities of coal reservoir are favorable for the adsorption and accumulation of the CBM; the low seepage capacities of coal reservoir and hypertonic conditions of local area are not conducive to the output of the CBM. The physical properties of coal reservoirs are controlled by complex geological factors. The burial metamorphism in the pre-Yanshan stage has resulted in the increase of the coal adsorption capacities and decrease of the seepage capacities; furthermore, the intense tectonic move- ments in the Yanshanian period have enhanced the coal adsorption capacities and improved the seepage capacities of the coal reservoirs that are near the fault zone. The results show that the pore structures of the samples in Zhijin and Nayong regions are dominated by adsorption pores, and the range of the adsorption pores is up to 50.61^--89.71~, resulting in the high adsorp- tion capacities. In contrast, the seepage pores poorly developed with an average content of 21.14%. In addition, the density of the microfraetures is generally less than 100 per 9 cm2 ,and the connectivity between the microfractures is relatively poor, which has reduced the permea- bility of the coal reservoirs. Faults are well developed in the districts with intensive tectonic movements, and the intrusion of magma in faulting zones not only sped up the coal metamor- phism, but also formed massive bility of coal the porosity CBM. reservoirs near the and permeability of pores and fractures, which improved the porosity and permea- fault zone. On the contrary, the later mineralization reduced the coal reservoirs, making it difficult for the output of the