Investigation into the thermal regime of lithosphere is an essential part of geothermal research. The thermal state of lithosphere can be expressed as the vertical distribution of temperature. It has been found that the thermal regime of lithosphere can control the heat flow distribution and the geothermal mechanism of local geothermal fields. In this work, equilibrium temperature logs were obtained from 27 wells, and thermal conductivity and heat generation data were collected from 148 rock samples from different wells. Besides, 55 high-quality terrestrial heat flow values were extracted. Based on these data, the distribution of heat flow across Xiong'an New Area was mapped. Later, the thickness of the thermal lithosphere in Xiong'an and the deep crustal temperature were analyzed using the one-dimensional steady-state heat conduction equation. The crustal structure beneath this area was derived from the seismic wave velocity profile, and it was then used to illustrate the connection between the geothermal fields’ heat sources and regional tectonic setting. The results indicate that high heat flow is mainly distributed around the basement uplifts, such as Niutuozhen uplift and Rongcheng uplift. The average heat flux in the study area is 70.5 mW/m², higher than the 61.5 mW/m² in mainland China. The temperature-depth profiles show great temperature variation across the new area. At the depth of 40 km, the crustal temperature ranges from about 750°C to 1100°C. Despite the large temperature variation, this area shows high thermal state. The temperature variation with depth may be attributed to the heat flow variability and the high thermal state may be caused by the large residual heat flow from the lithosphere boundary. The average reduced heat flow in the new area is high at around 44.35mW/m², which is associated with the high thermal state of this area.

Geothermal energy has been recognized as an important clean renewable energy. Accurate assessment of geothermal resources is an essential foundation for their development and utilization. The North Jiangsu Basin (NJB), located in the Lower Yangtze Craton, is shaped like a wedge block of an ancient plate boundary and large-scale carbonate thermal reservoirs are developed in the deep NJB. Moreover, the NJB exhibits a high heat flow background because of its extensive extension since the Late Mesozoic. In this study, we used the Monte Carlo method to evaluate the geothermal resources of the main reservoir shallower than 10 km in the NJB. Compared with the volumetric method, the Monte Carlo method takes into account the variation mode and uncertainties of the input parameters. The simulation results show that the geothermal resources of the sandstone thermal reservoir in the shallow NJB are very rich, with capacities of (6.6–12) × 10²⁰ J (mean 8.6 × 10²⁰ J), (5.1–16) × 10²⁰ J (mean 9.1 × 10²⁰ J), and (3.2–11) × 10²⁰ J (mean 6.6 × 10²⁰ J) for the Yancheng, Sanduo and Dai’nan sandstone reservoir, respectively. In addition, the capacity of the geothermal resource of the carbonate thermal reservoir in the deep NJB is far greater than the former, reaching (9.9–15) × 10²¹ J (mean 12 × 10²¹ J). The results indicate capacities of a range value of (1.2–1.7) × 10²¹ J (mean 1.4 × 10²² J) for the whole NJB (<10 km).

Doublet system has been widely used in the geothermal system heat extraction, which mainly involved the hot groundwater extraction and geothermal water reinjection into the underground thermal reservoir. Many factors can influence the thermal reservoir performance, such as the production or injection mass flow rate, injection fluid temperature, and lateral well spacing. In this study, taking the specific heat capacity varying with the formation temperature, the rock porosity, and permeability variations into consideration, a three‐dimensional thermo‐hydraulic coupled numerical model was established to assess the influence of heat capacity variation with formation temperature and other correlation parameters on the sandstone and carbonate thermal reservoir performance over a period of 40 years. Results show that the influence of specific heat capacity variation on the thermal reservoir performance was less than the rock porosity variation and less than the rock permeability variation. On the other hand, the influence of the above three parameter variations is more significant on the sandstone reservoir than the carbonate formation, in which the specific heat capacity variation hardly made any difference for the carbonate thermal reservoir, but for the sandstone reservoir, the specific heat capacity and its temperature variation can yield a 1.3 K decreasing for the average output temperature and a 0.02 × 10⁷ W decreasing for the average energy production rate over the 40 years. Finally, in this case, the temperature and energy production rate from the production well is higher after considering the rock porosity variation no matter for the sandstone or the carbonate. But the result may be opposite after changing the initial and boundary conditions or parameter selection. The influence of rock permeability variation on the thermal reservoir performance was also studied, which can produce a decreasing 10.1 K for the average output temperature and 0.19 × 10⁷ W for the energy production rate over the 40 years.

Seven steady-state temperature profiles are logged in the Harbin Area, Northeast China. The temperature data illustrate high conductive thermal gradients with a mean value of 4.78°C/100 m. Temperature maps at depths of 1000, 1500, and 1800 m are represented. The present temperature field is cooling southeastward, with the highest thermal gradients being observed at the junction zone between the Central Depression and the Southeast Uplift of the Songliao Basin. The recoverable heat is calculated using a volumetric method and Monte Carlo simulation. The mean value for recoverable heat from the detailed exploration area around the Harbin Area is 1.052 × 10¹⁹ J (3.59 × 10¹¹ t standard coal). Geological controls on the present temperature fields are discussed.

The thermal structure of the lithosphere is key to understanding its thickness, properties, evolution, and geothermal resources. Cratons are known for their low heat flow and deep lithospheric roots. However, present-day cratons in East China have geothermal characteristics that are highly complex, with variable heat flow values, diverging from the typical thermal state of cratons. In this study, we conducted a detailed analysis of the geothermal geological background of the cratons in East China, summarizing the thermal state and tectono-thermal processes of different tectonic units, calculating the temperature at various depths, and discussing differences in temperature and thermal reservoirs at different depths. The observed lithospheric thermal thickness within the North Jiangsu Basin and the Bohai Bay Basin is notably reduced in comparison to that of the Jianghan Basin and the Southern North China Basin. The phenomenon of craton destruction during the Late Mesozoic emerges as a pivotal determinant, enhancing the geothermal resource prospects of both the Bohai Bay Basin and the North Jiangsu Basin. Our findings contribute significantly to the augmentation of theoretical frameworks concerning the origins of heat sources in global cratons. Furthermore, they offer invaluable insights for the methodical exploration, evaluation, advancement, and exploitation of geothermal resources.