川中地区栖霞–茅口组地热资源评价探讨

Geothermal Resource Evaluation of the Middle Permian Qixia-Maokou Formation in the Central Sichuan Basin, China

关键词:  川中地区  栖霞-茅口组  热储特征  体积法  地热资源评价

Key words:  Central Sichuan Basin  Qixia-Maokou Formation  Thermal reservoir characteristics  volume method  geothermal resource evaluation

摘要:

含油气盆地在勘探和开发中，拥有大量的地质、地球物理和地球化学数据，对地质构造和地热储层有着全面的认识，在地热能开发利用中具有得天独厚的优势。四川盆地作为中国重要的含油气盆地，同样富含水热型地热资，该文在收集相关资料、总结以往油气勘探成果的基础上，确定了川中地区地温梯度大部均在24℃/km以上，大地热流大部均在60 mW/m²以上，为四川盆地相对高值异常区。考虑到热储温度及埋深是地热开发是否具有经济效益的重要因素，重点选择埋深相对较浅（3000～6000 m）、热储温度相对较高（65～155℃）和热储相对较厚（280～380 m）的川中地区栖霞-茅口组热储进行地热资源潜力评价。研究中，基于盆地地层参数建立三维地质模型，结合现今地温场、岩石热物性参数，利用一维稳态热传导方程计算得到栖霞-茅口组内部温度分布，最后利用体积法计算得到栖霞-茅口组的地热资源强度和资源量。研究表明，川中地区栖霞-茅口组热储温度为65～155℃，地热资源总量为3.01×10²¹ J，折合标准煤1030.25亿吨；可开采地热资源量2.03×10²⁰ J，折合标准煤206.5亿吨。且根据川中地区地热资源特征，提出了优先以研究区中东部为中心开展中低温地热发电、地热干燥、地热农业等综合开发利用和地热梯级利用示范工程的建议，为未来的油气废弃井的二次利用及油田地热开发打下基础。

Abstract:

In the exploration and development of petroliferous basins, there are a large number of geological, geophysical, and geochemical data. They comprehensively understand the geological structure and geothermal reservoirs and have unique advantages in developing and utilizing geothermal energy. As an important petroliferous basin in China, Sichuan Basin is also rich in hydrothermal geothermal resources. Based on collecting relevant data and summarizing previous oil and gas exploration results, it is determined that most of the geothermal gradients in the Central Sichuan Basin are above 24 ℃/km and most of the terrestrial heat flow is above 60 mW/m², which is a relatively high-value anomaly area in Sichuan Basin. Considering that the geothermal reservoir temperature and buried depth are important factors for the economic benefits of geothermal development, the geothermal reservoir of Qixia-Maokou Formation in central Sichuan Basin with relatively shallow buried depth (3000 ~ 6000 m), relatively high geothermal reservoir temperature (65 ~ 155 ℃) and relatively thick geothermal reservoir (280 ~ 380 m) is selected to evaluate the potential of geothermal resources. In the study, a three-dimensional geological model is established by using different strata thickness parameters. Combined with the current geothermal field and rock thermal physical parameters, the temperature distribution in the middle of the Qixia-Maokou Formation is calculated by using a one-dimensional steady-state heat conduction equation. Finally, the geothermal resource intensity and resource quantity of the Qixia-Maokou Formation are calculated by using the volume method. The results show that the geothermal reservoir temperature of the Qixia-Maokou Formation in central Sichuan is 65 ~ 155 ℃, and the total geothermal resource is 3.01 × 10²¹ J, equivalent to 103.025 billion tons of standard coal. Exploitable geothermal resources 2.03 × 10²⁰ J, equivalent to 20.65 billion tons of standard coal. According to the characteristics of geothermal resources in the Central Sichuan Basin, it is proposed to give priority to the central and eastern parts of the study area to carry out comprehensive development and utilization of medium and low-temperature geothermal power generation, geothermal drying, geothermal agriculture, and geothermal cascade utilization demonstration projects, laying the foundation for the secondary utilization of abandoned oil and gas wells and geothermal development in oil fields in the future.