Abstract: Xuzhou area features a widespread distribution of high-quality thermal reservoirs, such as carbonate and metamorphic rocks, indicating significant potential for deep geothermal resources. However, fundamental research on their formation conditions remains insufficient. This study, drawing on previous research and drilling data, provides a comparative analysis of the formation conditions for geothermal resources, including "source, pathway, reservoir, and caprock", across different tectonic units. It delineates prospective areas for deep geothermal resources, explores the accumulation mechanisms of deep geothermal energy, constructs a genetic model for deep geothermal systems, and identifies favorable areas for exploration. The research results show as follows. (1) The deep geothermal resource potentials across different tectonic units, from highest to lowest, are Fengpei fault block, Pizhou-Suining fault block, Tan-Lu fault zone, and Xuzhou-Jiawang fault block. (2) Geothermal temperatures in depressions are generally higher than those in the uplift areas within Xuzhou area. In the areas where Meso-Cenozoic fault depressions are developed, such as the Fengpei fault block and Tan-Lu fault zone, the geothermal gradient ranges from 2.0 ℃/hm to 3.2 ℃/hm. In contrast, the geothermal gradient is typically less than 2 ℃/hm in uplift areas including the Xuzhou-Jiawang and Pizhou-Suining fault blocks. The structural configuration alternating uplifts and sags within the depressions leads to the redistribution of heat flow, with the uplift areas exhibiting higher thermal conductivity and thus better conditions for heat accumulation. (3) Different types of reservoir-cap assemblages exhibit distinct heat accumulation conditions. Within the Fengpei fault block, the Huankou and Jing’an sags are characterized by dual caprock layers creating heat insulation, along with multiple stacked reservoirs (Neoarchean metamorphic rocks, Cambrian Zhangxia Formation and Ordovician Majiagou Formation carbonates), resulting in the most favorable heat accumulation conditions. In the Pizhou-Suining fault block, the Pantang and Sihu sags are characterized by reservoir-cap assemblages of Mesozoic-Cenozoic clastic rocks and Qingbaikou System dolomites. The significant differences in physical properties between the reservoir and caprock lead to heat concentration at their interface, yielding less favorable conditions for heat accumulation. (4) In the Fengpei fault block, crust-mantle uplift has occurred, and concealed magmatic bodies at depth provide a heat source. The intersection of deep major faults nearly EW-trending and NNW-trending forms efficient water-conducting channels. The reservoirs develop karst. The low thermal conductivity clastic rocks and coal measures have a strong insulation effect. These conditions result in a geothermal system predominantly driven by heat conduction, with thermal convection playing a supplementary role. (5) The northern Changdian Town, located within Huankou sag of the Fengpei fault block, sits atop an anticlinal structure bounded by normal faults. This area experiences heat flow convergence and sufficient groundwater recharge. The reservoir is buried at depths ranging from 3 000 to 4 000 meters, making it favorable for development and an advantageous area for deep geothermal resource exploration in Xuzhou area.

Key words: deep geothermal energy, Xuzhou area, karst geothermal reservoir, heat accumulation mechanism, favorable exploration area

摘要： 徐州地区碳酸盐岩、变质岩等优质热储分布广泛,深层地热资源潜力良好,但形成条件等基础研究薄弱。结合前人研究成果、钻探资料,对比分析不同构造单元的"源、通、储、盖"等地热资源形成条件,圈定深层地热远景区,探讨深层地热的聚集机制,构建深层地热的成因模式,优选深层地热资源勘探有利区。研究结果表明:①徐州地区不同构造单元的深层地热资源潜力由高到低依次为丰沛断块、邳州—睢宁断块、郯庐断裂带和徐州—贾汪断块。②徐州地区坳陷区的地温普遍高于隆起区,丰沛断块和郯庐断裂带等中生代—新生代断陷发育区的地温梯度为2.0~3.2 ℃/hm,徐州—贾汪断块和邳州—睢宁断块等隆起区的地温梯度普遍小于2.0 ℃/hm,坳陷内的隆-凹相间构造导致热流再分配,凸起区的热导率高,聚热条件好。③不同类型储-盖组合的聚热条件各异。丰沛断块内的欢口凹陷和敬安凹陷具有双盖层隔热和多套储层(新太古界变质岩、寒武系张夏组和奥陶系马家沟组碳酸盐岩)叠置的特点,聚热条件最佳;邳州—睢宁断块内的潘塘凹陷和四户凹陷等具备青白口系白云岩、中生界—新生界碎屑岩的储-盖组合,且两者物性差异大,交界处热量汇集,聚热条件次之。④丰沛断块表现为壳-幔隆升,深部存在隐伏岩浆岩体供热,近EW向和NNW向的深大断裂交汇形成了良好导水通道,储层岩溶发育,低热导率碎屑岩与煤系的隔热作用强,由此形成以热传导为主、热对流为辅的复合深层地热系统。⑤在丰沛断块欢口凹陷内,常店镇北部位于被正断层夹持的背斜构造之上,该地区热流汇集,地下热水补给充足,储层埋深为3 000~4 000 m,有利于开发,是徐州地区深层地热资源勘探的有利区。

关键词: 深层地热, 徐州地区, 岩溶热储, 聚热机制, 勘探有利区