Evaluation Of Geothermal Resources In Target Block Of Bohai Bay Basin

At present,China is generally at an important stage of rapid economic and social development.Energy resources are scarce,environmental pressure is huge,and the surplus of non-renewable energy such as oil is declining.Geothermal as an important part of renewable energy is potentially improving.The multi-stage tectonic movement in Bohaiwan basin has led to the development of multiple sets of source,reservoir,and cap rocks.Among them,the Qingfeng karst thermal reservoir in the southern shear structure area of the Bohai Bay Basin contains highly potential geothermal resources.Beside the large amount of geothermal resources,the He Paleogene Dongying Formation and the Neogene Guantao Formation in the Dongying Hekou area heat storage are also important oil field operation areas,but the evaluation of geothermal resources is not sufficient.In this paper,the primary objective is to evaluate the geothermal resources of the target block.Through the analysis of its geothermal geological conditions,a three-dimensional geothermal conceptual model of the block is established.A variety of methods are used to evaluate the geothermal resources,determine quantitatively the type of geothermal system in the target block,and predict the geothermal"sweet spot"of the target block.The results show that the karst heat storage in Qingfeng area experienced compression-relaxation from the Triassic to the Indosinian-Yanshan movement period before the deposition of the Lower Paleogene.Hence,forming a series of fractures and cracks,which are the main factors and dominant channels leading to the enrichment and migration of geothermal water;the conceptual model of the geothermal system in the block was established.The fluid migration and temperature changes in the research block were analyzed.It was found that the fluid velocity in the fault was greater than the average velocity of the entire formation,which was close to the fracture.In the“one injection,one production”mode,the whole formation temperature does not change much.The average temperature of the fault on the side away from the geothermal well is higher than the thermal storage temperature,and it is less affected by the water injection well.When the thermal storage is in the non-recharge period,the thermal storage temperature needs 5 years to recover.The geothermal resources and recoverable geothermal resources calculated by the thermal storage volume method are 3.41×10¹⁷ and 5.12×10¹⁶ J,respectively,the standard coal are 1.17×10⁷and 1.75×10⁶ t;the geothermal resources and recoverable geothermal resources calculated by the numerical simulation method are 2.45×10¹⁸ and 8.49×10¹⁶ J,respectively,the standard coal are8.37×10⁷ and 2.90×10⁶ t.Based on relevant data and numerical simulation,we predicted the geothermal"sweet spot"of the target block from reservoir geological conditions and temperature conditions.The sweet spot area is located in the Xiamajiagou formation of Ordovician reservoirs.This paper systematically evaluated the geothermal resources of the study area,and provided important reference data for the later geothermal exploitation and utilization in the area.