从TR21孔抽水试验分析板桥凹陷东营组地热资源可采性

Recoverable Analysis of Geothermal Resources in Dongying Formation of Banqiao Depression through TR21-Hole Pumping Test

在天津地区板桥凹陷中,东营组储存有丰富的地压型地热流体资源,但开采水位降深大,导致勘查和开发比较困难。结合东营组孔隙结构条件及地压条件,对TR21孔抽水试验数据进行整理,认为东营组处于超压之中,存在启动水力坡度。经对0及3次降深抽水试验数据按迭代法拟合求解,求得启动水力坡度为1.16(1 160‰)、超压渗透系数为1.896 m/d。这表明东营组地热流体仅来源于下伏沙河街组超压储层,东营组可圈闭5.12～6.25 MPa的下伏地层超压,为下伏地层超压形成及本组超压保存提供了条件;超压渗透系数大于用渗透率求得的渗透系数(1.392 m/d),表明储层在超压作用下渗透系数增大的客观规律;储层超压及渗透系数的增大,为这一资源的开采提供了条件。

In Tianjin Banqiao depression, the Dongying Formation contains abundant ground pressure-type geothermal fluid resources. Because the exploitable water level is deep, both survey and development of the resource are difficult for local government. Combining with the pore structure and ground pressure of Dongying Formation, the authors analyzed the data of the pumping test of well TR21 and suggested that Dongying Formation is in overpressure condition, having a starting hydraulic gradient. By iterative fitting of the data from 0 and 3 stage drawdown pumping test, the calculated starting hydraulic gradient is 1. 16 （1 160‰）and the overpressure coefficient of permeability is 1. 896 m/d. These data indicate that the geothermal fluid of Dongying Formation receives recharged from the underlying overpressure Shahejie Fomation. Dongying Formation can trap underlying strata overpressure of 5.12 - 6.25 MPa which provides the probability for the formation of overpressure of underlying strata and the preservation of overpressure of the Dongying Formatiqn. The ovrpressure coefficient of permeabil!ty is higher than the one obtained（1. 392 m/d）by permeability, suggesting that the coefficient of permeability of geothermal reservoirs increases under overpressure conditions. The overpressure and increase of coefficient of permeability of the reservoir facilitate the exploitation of the resources.