The UK is committed to transition to a low-carbon economy requiring significant reduction of greenhouse gas emissions to net zero by 2050. In nearly all scenarios emission reductions are characterized not only by energy demand reductions, but also the decarbonization of electricity and new energy systems. Geothermal energy has considerable potential to decarbonise heating, deep geothermal systems (>100m depth) can provide up to 300 Exajoules of heat – sufficient to deliver a minimum 100 years of heating to the entire UK .
The development of geothermal energy systems has not been widespread and has in part been hindered by the high capital costs associated with drilling deep wells. Reducing the exploration risk is vital to lowering the entry barrier for investment in geothermal energy. One very promising geothermal play is the Lower Carboniferous (Dinantian) Limestone (LCL), which has potential for supporting large-scale geothermal (heating) developments in several UK regions .
Pore space connectivity within the subsurface is a key control on achievable water flow rates (yields) from geothermal reservoirs and hence on geothermal prospectivity . In carbonate rocks, residual primary porosity and intergranular hydraulic conductivity are generally very low, and permeability is created by secondary processes (karstification, dolomitisation, faulting/ fracturing). These processes are controlled by the depositional, diagenetic (burial and uplift), structural history of, and the evolution of pore-fluid chemistry within, these carbonate rocks,
By combing outcrop studies, data from onshore exploration wells and experimental work, this project aims to come to a process-based understanding of interactions between fluid flow and water-rock interaction to assess rates and distributions of dissolution under geothermal reservoir conditions. This project has the prospect to reduce geological uncertainties of geothermal carbonate reservoirs through enhanced understanding of how different permeability elements (e.g. karstification, dolomitisation, fault/fracture networks) control fluid flow within the buried limestone over relevant length scales. Outcomes have direct application to reducing risks in geothermal prospects and can be applied to CO2 storage in carbonate reservoirs and cap-rock integrity of carbonate rocks.