| Two sets of rich-organic shale including the Hongshuizhuang Formation of Mesoproterozoic Jixian System and the Xiamaling Formation of Daijian Syetem which are developed in Yanshan area.The distribution characteristics and reservoir physical parameters of the shale are unclear,and the preservation conditions are not implemented,the favorable area of shale gas is need to be further clarificated..Based on fully collecting and collating all kinds of oil and gas geological data and the literature in the study area,field geological survey was carried out in Xuanhua-Huailai,Chengde-Kuancheng of Hebei province,as well as drilling core observation and experimental analysis of well Jiyuan-1,Jiqian-1 and Jing-101.The paper studied geological conditions of shale gas accumulation including the development environment,regional distribution characteristics,organic geochemical characteristics,mineral assemblage characteristics,pore permeability characteristics,shale gas preservation conditions and other geological conditions of the rich-organic shale of the Hongshuizhuang Formation and the Xiamaling Formation.Furthermore,the comprehensive information superposition method is applied to preliminarily predict the favorable area of shale gas in the study area.The Hongshuizhuang Formation and the Xiamaling Formation of middle proterozoic in Yanshan area are mainly developed in the sedimentary environment including lagoon,sand-mud flat and semi-open sea,and the accumulative thickness of hydrocarbon source rocks is relatively large.Among them,the subsidence center of the Hongshuizhuang Formation is located in Beijing Miyun-Hebei Xinglong,with a maximum thickness is about 180 m,and the subsidence center of the Xiamaling Formation is located in Hebei Huailai-Xuanhua,with a maximum thickness of more than 450 m.The organic kerogen types of the black shale in the Hongshuizhuang Formation and the Xiamaling Formation is in Yanshan area are mainly type I kerogen,and the the organic carbon content is higher overall,of which the Hongshuizhuang Formation is 0.06%~6.10%,with an average value of 2.84%,the Xiamaling Formation is 0.09%~16.7%,with an average value of 1.67%.The thermal evolution degree of the two sets of shale is lower overall,the Hongshuizhuang Formation is 1.01%~4.2%,with an average value of 1.32%,and an Ximaling Formation is 1.03%~2.03%,with an average of 1.23%.The shale mineral composition is dominated by quartz(average value of 48.0%)and clay minerals(average value of 41.49%),and the clay minerals are dominated by the Iraqi/Mongolian mixed layer.The shale reservoir storage space types mainly include micro-nano-scale pores such as micro-cracks and mineral dissolution pores.The shale permeability of the two groups is mostly less than 0.01 mD,and the shale porosity of the Hongshuizhuang Formation is mainly distributed in 2%~4%.The porosity of the Ximaling Formation shale mostly exceeds 2%,indicating that the two sets of shale in the study area have good reservoir conditions.The results of isothermal adsorption simulation show that the shale with a large organic carbon content of the Hongshuizhuang Formation and the Ximaling Formation have stronger adsorption performance for shale gas.The shale of the Hongshuizhuang Formation and the Xiamaling Formation has good self-sealing performance,and the conditions of the top and bottom of the shale interval are generally good,and late hydrocarbon generation of shale and little damage from late tectonic activities.Therefore,shale gas in the study area has better preservation conditions on the whole.The Hongshuizhuang Formation in the stable structural belt in Chengde-Kuancheng of Hebei province,and the Xiamaling Formation in the stable structural belt in Hebei Zhuozhou-Beijing Fangshan-Mentougou-Changping and Hebei Lanqiyingzi are preliminary predictions for the shale gas favorable area. |
