集中采灌条件下碳酸盐岩热储群井示踪试验

地热回灌是实现地热资源可持续开发的有力措施,在世界各国已获得广泛应用,在地热资源的保护、减少资源浪费、延长地热井寿命以及减少环境污染等方面具有重要意义.天津是我国开展地热回灌比较成熟的地区之一,截至2019年底,天津市基岩裂隙型热储回灌率已达79.61％.大规模集中采灌条件下热储层渗流场的变化以及是否会影响热储温度已成为热储系统研究的前沿课题.本文以天津市东丽湖地区为例,选取1,5-萘磺酸钠作为示踪剂,在2018～2019年供暖期集中采灌期间开展了群井示踪试验,结果显示,供暖期内地热井开采量(或回灌量)、水温没有明显变化,水位除受正常采灌影响外没有明显变化,热储系统基本处于稳定状态;试验中示踪剂回收率极低,开采井和回灌井之间水力联系较差,有限的优势通道中的最大流速为448.42 m/d,优势通道的方向主要集中于北东向,与区内主要控热断裂沧东断裂及其次生断裂的发育方向一致;在现状开发利用模式下,不会造成该热储层温度的显著变化.这些认识对于指导北方古潜山碳酸盐岩热储的科学开发利用具有一定的现实意义.

Study on tracer test of carbonate geothermal reservoir under centralized pumping and re- injection conditions

Geothermal re- injection is a powerful measure to realize the sustainable development of geothermal resources, which have been widely used in various countries of the world. It is of great significance for the protection of geothermal resources, the reduction of resource waste, the extension of pumping well life and the reduction of environmental pollution. Tianjin is one of the earliest regions to carry out geothermal re- injection in China. By the end of 2019, the recharge rate of fractured reservoir of bedrock in Tianjin had reached 79. 61%. The change of seepage field of geothermal reservoir under large- scale concentrated pumping and re- injection, and whether it will cause the decrease of geothermal reservoir temperature have become the front research topic of thermal reservoir system. Taking Dongli lake area of Tianjin as an example, this paper selects 1, 5- naphthalene sulfonate sodium as tracer, and carries out the tracer test of well group during the central pumping and re- injection in the heating season from 2018 to 2019. The results show that there are no obvious changes in geothermal well pumping (or re- injection) and water temperature during the heating period, and the water level shows no obvious changes except under the influence of normal pumping and re- injection. The tracer recovery rate is very low in the test, which shows that the hydraulic connection between the pumping wells and the re- injection wells is poor, and the maximum flow velocity in the limited dominant channel is 448.42 m/d. The direction of the dominant channel is mainly concentrated in the north- east direction, and is consistent with the direction of Cangdong fault and its secondary fault, which is the main thermal- controlling fault in the area. Under the present exploitation and utilization mode, the temperature of the thermal reservoir will not change significantly. These conclusions are of practical significance for guiding the scientific development and utilization of carbonate reservoirs in the buried hills of north China.