天津市古潜山奥陶系岩溶裂隙发育规律研究

Research on karst fissure development pattern of the Ordovician buried hills in Tianjin

奥陶系在天津平原区是具有开发前景的基岩热储,但是在开发过程中发现,该层岩溶裂隙发育极不均匀,富水性相差较大,给施工带来一定的难度,严重阻碍着地热资源的开发进程。为此,对全市近百眼揭露奥陶系地热井的资料进行对比分析,对不同构造单元奥陶系一、二类裂缝发育和原始出水量情况进行统计,总结其岩溶裂隙发育规律。研究结果表明:岩溶裂隙多分布于灰岩较纯的马家沟组,泥质灰岩较发育的亮甲山组和冶里组次之;在埋深小于2 300 m的地区,奥陶系裂隙发育随地层厚度的增大而增大;上覆地层为新近系和中生界的岩溶裂隙发育厚度大于上覆地层为石炭系的;双窑和潘庄凸起岩溶裂隙较发育,富水性较好;张性断裂附近岩溶裂隙最发育。据此可知,岩溶裂隙多分布在张性断裂附近、灰岩较纯的马家沟组,以及埋深较浅、上覆地层为新近系和中生界的凸起区,这些地区富水性较好,可为地热开发提供可靠依据。

Ordovician is a promising bedrock thermal reservoir in Tianjin Plain. However, during the process of development, it is found that the karst fractures in this stratum are very uneven and the aquosity is quite different, which may bring difficulties to the construction and seriously hinder the development of geothermal resources. Therefore, the data of nearly 100 Ordovician geothermal wells in this city were compared and analyzed, and the development of Ordovician type I and type II fractures and the original water output in different tectonic units were statistically analyzed to summarize the development law of the karst fissure. The results show that the karst fissures are mainly distributed in Majiagou Formation with relatively pure limestone, followed by Liangjiashan Formation and Yeli Formation with relatively developed argillaceous limestone. In the areas with burial depth less than 2 300 m, the fissure development of Ordovician System increases with the increasing of formation thickness. The thickness of karst fissures in the overlying strata of Neogene and Mesozoic is thicker than that in the overlying strata of Carboniferous. The karst fissures in Shuangyao and Panzhuang uplifts are well developed and water-rich. Karst fissures are most developed near tensional faults. According to this, karst fissures are mostly distributed near tensional faults and Majiagou Formation with pure limestone, mainly uplift areas with shallow burial depth and Neogene and Mesozoic overlying strata. These areas are rich in water, which can provide reliable basis for geothermal development.