Hydrocarbon generation characteristics, reserving performance and preservation conditions of continental coal measure shale gas: A case study of Mid-Jurassic shale gas in the Yan'an Formation, Ordos Basin
Hydrocarbon generation characteristics, reserving performance and preservation conditions of continental coal measure shale gas: A case study of Mid-Jurassic shale gas in the Yan'an Formation, Ordos Basin
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陆相煤系页岩气生烃特征、储集动态及保存条件——以鄂尔多斯盆地延安组中侏罗统页岩气为例
DOI：
10.1016/j.petrol.2016.06.031
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发表时间：
2016
影响因子：
--
通讯作者：
Liu Haiyan
中科院分区：
文献类型：
--
作者：
Wang Dong-dong;Shao Long-yi;Li Zhi-xue;Li Ming-pei;Lv Dawei;Liu Haiyan
与海相页岩气相比，陆相页岩气的研究较少。鄂尔多斯盆地是中国北部侏罗纪陆相含煤盆地之一。多口探井揭示了该盆地中侏罗统延安组页岩气资源的存在。延安组是该盆地的煤系，以硅质碎屑岩和厚煤夹层为主，页岩主要发育在河流、湖泊和湖泊三角洲环境中。页岩为多层砂岩和煤岩，平面分布不稳定。具有单层厚度小(0.1微米至34.77微米)，总累积层厚度大(高达380微米)的特点。页岩总有机碳含量中高(0.24%~5.82%)，未成熟-成熟阶段热演化程度较低。天然气主要为生物成因，热成因相对较少。矿物学研究表明，该页岩的脆性矿物含量较低，粘土矿物含量较高。孔隙类型以溶孔、粒间孔、粒内孔和微裂缝为主，有机孔很少。孔渗率低，储集层非均质性明显。该陆相页岩含气量低，以吸附相为主。该盆地的页岩气一般封闭在地下水流动封闭带内，地下水矿化度相对较低。页岩和页岩气的发育特征也受沉积相控制，湖相发育有利生烃条件、储集性能和天然气保存条件，其次为湖泊三角洲相，河流相条件相对较差。尽管陆相陆相煤系的页岩气资源潜力低于海相，但陆相煤系中的页岩气、煤层气、煤层气和致密砂岩气常常并存，这可能支持更具远景的能源前景。因此，对陆相盆地的页岩气、煤层气和致密砂岩气进行综合勘探和协同开发，可能是综合利用陆相煤层气的理想途径。
Shale gas in nonmarine facies has attracted less interest compared with the marine facies. The Ordos Basin is one of the Jurassic nonmarine continental coal basins in northern China. Several exploration wells have revealed the existence of shale gas resources in the Middle Jurassic Yan’an Formation in this basin. The Yan’an Formation is the coal-measures in this basin, dominated by an intercalation of siliciclasitcs and thick coals, and the shales were mainly developed in the fluvial, lacustrine and lacustrine delta environments. The shales are multi-inerlayered with sandstones and coals, and have an unstable horizontal distribution. characterized by a small thickness of individual layer (ranging between 0.1 m and 34.77 m), and large thickness of the total cumulative layers (up to 380 m). The shales have intermediate to high contents of total organic carbon (ranging from 0.24% to 5.82%) and low thermal evolution degree in an immature-mature stage. The gas is mainly of biogenic origin, with relatively small fraction of thermogenic origin. The mineralogy investigation revealed that the shale have a lower content of brittle minerals and a high content clay minerals. The pore types are dominated by dissolution pores, intergranular pores, intragranular holes and micro cracks, and few organic holes can be seen. The porosity and permeability are low, with significant reservoir heterogeneity. The gas content in this nonmarine shale is low, dominated by adsorption phase. The shale gas in this basin were generally/enclosed within the groundwater flow closure zones, where the groundwater salinity is relatively low. The development characteristics of the shale and shale gas were also controlled by the depositional facies, and the conditions for hydrocarbon generation, reservoir performance, and gas preservation, can be favorably developed in the lacustrine facies, followed by the lacustrine delta facies, while the conditions in the fluvial facies are relatively poor. Although the resource potential of shale gas in the nonmarine continental coal-measures is lower than that of the marine facies, the shale gas, coal, coalbed methane, and tight sandstone gas often coexist in the continental coal basins which may support a more prospect energy scenario. Therefore, comprehensive exploration and collaborative development of the shale gas, coalbed methane and tight sandstone gas in the continental basin may be an ideal way to synthetically utilize the continental coal-measure gases.