黔西地区上二叠统龙潭组海陆交互相页岩气储层特征

为研究上二叠统龙潭组海陆交互相页岩气储层发育特征,基于黔西地区龙潭组参数井钻井资料,系统采集泥页岩样品,运用X-衍射分析、有机地化、扫描电镜、氮吸附、含气量测定及等温吸附等实验手段,开展储层特征研究。该区龙潭组泥页岩具有单层薄、层数多、总厚大的特点,矿物成分主要为黏土矿物和石英,黏土矿物含量较高;干酪根显微组分主体上为镜质组,均为Ⅲ型干酪根,有机碳含量整体上大于3.0%,镜质体反射率(R_o)平均为1.01%,有机质成熟度偏低;储层整体上为超低孔、超低渗,孔隙类型为粒间孔、粒内孔、有机质孔和微裂缝,发育大量纳米级孔隙,以中孔为主,主要为细颈广体的墨水瓶型孔和狭缝型孔,比表面积和总孔体积较大,孔隙分形维数大,相关系数高,表明泥页岩表面粗糙程度大,连通性差,非均质性强。泥页岩现场解吸总含气量较高,吸附性能较强,且互层的煤层含气量高,资源潜力较大;具备良好的页岩气发育地质条件和富集空间,可选取有效的储层改造技术进行合层开采。

Reservoir characteristics of marine-continental shale gas in Upper Permian Longtan Formation,western Guizhou province

The reservoir characteristics of marine-continental shale gas in the Upper Permian Longtan Formation in the western Guizhou province were studied using X-ray diffraction, organic geochemistry, scanning electron microscopy, nitrogen adsorption, gas content determination and isothermal adsorption analyses of shale samples from some characteristic wells. The shale in the Longtan Formation in the study area has a large overall thickness, but there are many layers and each layer is thin. The clay mineral content is the highest, followed by the quartz content. The vitrinite group is dominant in the kerogens, which are mainly of type Ⅲ. The TOC content is generally greater than 3.0%. The R_o value averages 1.01%, showing a relatively lower maturity, mainly at the gas generation peak. The reservoir has ultra-low porosity and ultra-low permeability. Intergranular, intragranular and organic pores as well as micro-fractures were observed. A large number of nano-scale pores and fractures were present. Meso-pores are dominant, shaped like narrow-necked and wide-body ink bottles or narrow pores. Large specific surface area, total pore volume, pore fractal dimension and correlation coefficient indicate that the shale has a rough surface, poor connectivity, and strong heterogeneity. The on-site analysis of shale finds high total gas content and strong adsorption, and the interbedded coal seams show high gas content, indicating a large resource potential. The geological conditions and enrichment space are favorable for shale gas in the study area, and effective reservoir reconstruction technology can be selected for coalbed mining.