二氧化碳羽流地热系统的碳封存经济分析

【研究目的】 二氧化碳羽流地热系统（CPGS）在取热的同时可实现CO₂地质封存,在碳达峰与碳中和背景下,CPGS碳封存的经济性是众多学者关注的要点。【研究方法】 以松辽盆地泉头组为例,采用数值模拟方法对比分析了注入压力、井间距与回注温度对热提取率的影响,在供暖情景下,计算了CPGS供暖效益与碳封存成本,并与常规水热型地热系统供暖效益进行了对比。【研究结果】 受携热介质转变与热突破影响,CPGS开采井温度呈现“降低-稳定-降低”的趋势,其中井间距对开采井温降影响显著,井间距越小开采井温降越明显;热提取率与回注压力呈现正相关性,与回注温度呈现负相关性,井间距对热提取率影响不显著;CPGS与常规水热型地热系统相比,采热量呈现“高-低-高”三个阶段,其中回注压力越小、回注温度与储层温度越接近,实现CPGS较水介质多采热能所需的时间越短。【结论】 仅考虑CO₂价格与取热效益,供暖收益抵消部分碳封存成本后,井间距对CO₂封存单位成本影响最为显著,井间距越小,CO₂封存单位成本降低越迅速,在注采井间距300 m条件下,持续开采30 a后CO₂封存单位成本可降至160元/t。

Economic analysis of carbon storage in CO2 plume geothermal system

This paper is the result of the geothermal geological survey engineering. Objective]The CO₂- plume geothermal system (CPGS) can achieve geological CO₂ storage during heat extraction. Under the background of carbon peaking and carbon neutralization, the economics of CPGS carbon storage attracts much attention. Methods] Taking the Quantou Formation in the Songliao Basin as example, the influence of injection pressure, well spacing and reinjection temperature on the heat extraction rate were analyzed by numerical simulation in this paper. In addition, the benefit of CPGS and the cost of carbon storage were calculated and compared with conventional hydrothermal geothermal systems. Results]Results show that the temperature of mining wells in CPGS exhibits a trend of "decrease-stabilization-decrease" due to the transformation of heat-carrying medium and thermal breakthrough. Typically, the well spacing has a significant impact on the temperature drop of the mining well. Smaller the well spacing contributes to larger temperature drop of the mining well. The heat extraction rate has a positive correlation with the reinjection pressure and a negative correlation with the reinjection temperature. The influence of well spacing on the heat extraction rate is limited. Compared with the conventional hydrothermal geothermal system, CPGS has three stages of heat recovery, namely, high, low and high stages successively. A low reinjection pressure and a close reinjection temperature with the reservoir temperature helps to shorten the time required for the CPGS to recover a similar heat energy with the water medium. Conclusions]Taking the price of CO₂ and the benefits of heat extraction into account only, the well spacing has a dominating impact on the unit cost of CO₂ storage after the heating revenue offsets part of the cost of carbon storage. Small well spacing contributes to quick decrease of the unit cost of CO₂ storage. The unit cost of CO₂ storage can be reduced to 160 yuan/ton after 30 years of continuous mining when the well spacing is 300 m.