天津城区奥陶系灰岩热储层酸化压裂增产试验研究

Test study of acidification fracturing stimulation in Ordovician limestone thermal reservoirs in the urban area of Tianjin

奥陶系灰岩热储是天津城区中深层地热的主要开采对象之一,但是在天津城区鞍山道断裂以西地区,奥陶系上覆地层保留相当厚度的石炭-二叠系地层,这种沉积环境下的奥陶系灰岩不利于地热流体联通与流动,影响热储层涌水量。以天津NK-28地热井为例,通过地球物理测井和地层岩屑录井,结合溶蚀试验、降压试验、反循环气举洗井等技术手段,进行了酸化压裂增产研究。试验结果表明:裂隙不发育且连通性差,以及地层地热流体补给不及时是该井产能过低的主要原因;经过酸化压裂增产后,其涌水量由68m^3/h提高到110m^3/h,地热井产能明显提高,可为类似地质条件下的地热资源开发提供了一定的参考依据。

Ordovician limestone thermal reservoir is one of the main middle-deep geothermal energy exploration sources in urban areas of Tianjin.In the western areas of Anshan Road Fault,there remains a relatively thick Permo-Carboniferous formation above the Ordovician limestone.Such a sedimentary environment is not favorable for the connectivity and flow of geothermal fluid in the Ordovician limestone thermal reservoir,usually reducing the outflow yield of geothermal wells.Taking a geothermal well(No.NK-28)in Tianjin as an example,acidification fracturing stimulation is carried out based on borehole logging,geophysical logging,the corrosion test,drop pressure tests,gas lift reverse circulation well washing and other technical methods.Test results show that a low productivity of the present geothermal well is mainly caused by the non-sufficient fracture formation,poor connectivity and recharge of fluid in thermal reservoirs.After a stimulation by acidizing fracturing,the outflow yield of geothermal water is greatly increased from 68 m^3/h to 110 m^3/h,which can provide positive references for the development of geothermal resources in similar geological areas.