Features of Adjusting the Frozen Soil Properties Using Borehole Temperature Measurements

The paper examines the theoretical issues of using borehole temperature survey data to control a frozen wall formed around the sinking mine shafts of the Nezhinsk mining and processing plant potash mine. We consider adjusting the parameters of the mathematical model of the frozen soil based on temperature measurements in boreholes. Adjustment of the parameters of the mathematical model (thermophysical properties of the soil) is usually carried out by minimizing the discrepancy functional between the experimentally measured and model temperatures in the temperature control boreholes. An important question about the form of this functional and the existence of minima remained after the previous studies. The study aimed at this question included analysis of heat transfer in two horizontal layers (sand and chalk) for two shafts under construction using artificial ground freezing. It was shown that the discrepancy functional minimum under certain conditions moves over time or is nonunique. This phenomenon results in ambiguity in adjusting the mathematical model parameters in the frozen soil to fit the borehole temperature survey data. At the stage of the frozen wall growth, the effective thermal conductivity in the frozen zone can be determined ambiguously from the temperature measurements in the boreholes—its value can change over time. At the stage of maintaining the frozen wall, the solution turns out to be dependent on the ratio of effective thermal conductivities in the frozen and unfrozen zones.

Existence of High Temperature Geothermal Resources in the Igneous Rock Regions of South China

Large areas of Yanshan period granites with high heat production values (3–10 μW/m3) and mantle plume around Hainan province co-exist in Igneous Rocks Regions of South China (IRRSC). Surface manifestations are mainly warm/hot springs with temperatures below 90 °C and no typical phenomenon of high temperature resources have been observed. The main objective of this paper is to discuss the existence of high temperature geothermal resources and their possible locations under this kind of geothermal and tectonic background by analysis of high temperature heat sources, borehole temperature measurement, and reservoir temperature estimation. Two possible partial melts of the magma chamber were detected as high temperature heat sources in the Southern Leizhou Peninsular and North Hainan Island at a depth of 8–15 km. Other low resistivity zones in the upper crust are more likely caused by fluid in the formations or faults but not high temperature heat sources. This was also verified by borehole temperature measurement in these two areas, with maximum formation temperatures of 211°C and 185°C found, respectively. Reservoir temperatures from fluid geothermometers show lower temperatures of between 110–160°C for typical geothermal fields over the IRRSC but not in the Southern Leizhou Peninsular and Northern Hainan Island. In all, high temperature geothermal resources may be found in the Southern Leizhou Peninsular and on Northern Hainan Island.

Reply to Discussion on ‘Borehole temperature log from the Glasgow Geothermal Energy Research Field Site: a record of past changes to ground surface temperature caused by urban development’ by Watson and Westaway 2020 (SJG, 56, 134–152, 2020).

Watson and Westaway (2020) (WW) quantified subsurface temperature variations caused by anthropogenic climate change and urban/industrial development in Glasgow, using temperature data from the Glasgow Geothermal Energy Research Field Site (GGERFS) well GGC-01 (at site G-10; Fig. 1), noting implications for the thermal physics of this site. Monaghan, Manning and Shipton (2021) (MMS) have queried points, noted in passing by WW, on other aspects: the GGERFS purpose, location, design, heat resource, and cost.

Inversion results appended with estimates from vegetation changes in assessment of Ground Surface Temperatures for the Amazon Region, Brazil

Estimates have been made of ground surface temperature (GST) variations for 25 localities in the region of Manaus (province of Amazon in Brazil) making use of both forward and inverse models. The work is based on analysis of borehole temperature logs as well as remote sensing data concerning changes in vegetation cover. Results of functional space inversion (FSI) of borehole temperature data reveal the occurrence of a cooling event, with a decrease in temperature of slightly less than 1oC, for the period of 1600 to 1850 AD. This episode coincides roughly with the period of “little ice age” in the southern hemisphere. It was followed by a warming event, with magnitudes varying from 2 to 3oC, that lasted until recent times. Integration of these results with estimates based on changes in normalized index of vegetation cover (NVDI) of the last decade points to continuation of climate warming over the last decade. This event is found to be prominent in areas of deforestation in central parts of the Amazon region.

Assessing Arctic Ground Surface Temperatures from Borehole Temperatures and Paleoclimatic Model Simulations

<p>The surface temperature response to changes in our planet’s external forcing is larger at higher latitudes, a phenomenon known as polar amplification. The Arctic amplification has been particularly intense during the last century, with arctic-wide paleoclimatic reconstructions and state-of-the-art model simulations revealing a twofold arctic warming in comparison with the average global temperature increase. As a consequence, Arctic ground temperatures respond with rapid warming, but this response varies with snow cover and permafrost processes. Thus, changes in arctic ground temperatures are difficult to reconstruct from data, and to simulate in climate models.</p><p>Here, we reconstruct the ground surface temperature histories of 120 borehole temperature profiles above 60ºN for the last 400 years. Past surface temperature evolution from each profile was estimated using a Perturbed Parameter Inversion approach based on a singular value decomposition method. Long-term surface temperature climatologies (circa 1300 and 1700 CE) and quasi-steady state heat flow are also estimated from linear regression through the depth range 200 to 300 m of each borehole temperature profile. The retrieved temperatures are assessed against simulated ground surface temperatures from five Past Millennium and five Historical experiments from the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3), and the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archives, respectively.</p><p>Preliminary results from borehole estimates and PMIP3/CMIP5 simulations reveal that changes in recent Arctic ground temperatures vary spatially and are related to each site’s earlier thermal state of the surface. The magnitudes of ground warming from data and simulations differ with large discrepancies among models. As a consequence, a better understanding of freezing processes at and below the air-ground interface is necessary to interpret subsurface temperature records and global climate model simulations in the Arctic.</p>

Borehole logging and temperature measurements with the MARUM-MeBo sea bed drilling technology: Recent developments and scientific applications

<p>The MARUM-MeBo sea bed drilling technology is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen (Freudenthal and Wefer, 2013). Presently two drill rigs are in operation for drilling and coring down to more than 70 m (MARUM-MeBo70) and 200 m (MARUM-MeBo200), respectively. The robotic drill rig with the required drill tools is deployed on the seabed, where the drill string for conducting coring is assembled during the drilling operation. In addition to wireline core barrels a temperature probe can be used for measuring formation bottom hole temperature at discrete drilling depths by pushing the probe about 15 cm into the base of the bore hole. The temperature is logged for about 10 – 15 minutes in order to allow for dissipation of the frictional heat generated during pushing and equilibration to formation temperature. When the temperature measurement is completed, the probe is recovered out of the drill string and the drilling operation can be continued.</p><p>The trip out of the drill string after reaching the target drill depth can be used for logging of the geophysical properties within the borehole and the adjacent formation. A memory logging tool is lowered into the drill string with the sensor part penetrating through the drill bit. When the drill string is tripped out the probe is raised together with the drill string inside the borehole and conducts the geophysical measurements. This method called “logging while tripping” is especially suitable for unconsolidated sediments and logging in unstable borehole conditions, since the drill string stabilizes the borehole above the sensor part during the logging operation. For the MeBo drill rigs we have spectrum gamma ray, magnetic susceptibility, dual induction and acoustic probes available. The latter is also equipped with a temperature sensor for measuring borehole temperature. </p><p>In this presentation we show examples from MeBo drilling campaigns where core drilling, borehole logging and formation temperature measurements where combined. A focus of this presentation is the analysis of borehole temperature measurements during trip out. We investigate how geothermal flux and lithological changes (i.e. thermal conductivity) influence the bore hole temperature measurement by modeling the temperature evolution within the borehole during drilling and trip out.</p><p>  </p><p>References:</p><p>Freudenthal, T and Wefer, G (2013) Geoscientific Instrumentation, Methods and Data Systems, 2(2). 329-337. doi:10.5194/gi-2-329-2013</p>