Search Results (2)

A conceptual model is presented of two MW-scale low enthalpy mine water geothermal heat pump schemes that are being developed in Tyneside, UK. The Abbotsford Road scheme (54.955° N 1.556° W) is operating (as of May 2021) at 20–30 L/s, abstracting groundwater (and heat) from an unmined Coal Measures Upper Aquifer System (UAS) and reinjecting to the deeper High Main Aquifer System (HMAS), associated with the High Main (E) coal workings and the overlying High Main Post sandstone. A similar scheme, 700 m away at Nest Road (54.959° N 1.564° W), abstracts at 40 L/s from the HMAS, recovers heat from the mine water and reinjects the thermally spent water to deeper workings associated with the Hutton (L), Harvey-Beaumont (N) (and possibly other) coal seams, termed the Deep Mined Aquifer System (DMAS). The three aquifer systems are vertically discontinuous and possess different hydraulic (storage, transmissivity and continuity) properties that would have been near-impossible to predict in advance of drilling. At the sites, 10 boreholes were drilled to obtain five usable production/reinjection boreholes. Development of mine water geothermal energy schemes thus carries a significant project risk, and also a potential ongoing maintenance burden related to iron hydroxide scaling. These do not preclude mine water geothermal as a useful low carbon heating and cooling technology, but the involvement of skilled hydrogeologists, hydrochemists, mining and groundwater engineers is a pre-requisite. Full article

CO₂-induced reactions in low salinity aquifers overlying CO₂ storage sites are of interest to understand potential reactions or impacts in the possible case of a leak. Previous investigations of overlying aquifers in the context of CO₂ storage have focused on pure CO₂ streams, however captured industrial CO₂ streams may contain ancillary gases, including SO₂, O₂, NOx, H₂S, N₂, etc., some of which may be more reactive than CO₂ when dissolved in formation water. Eight drill cores from two wells in a low salinity sandstone aquifer that overlies a target CO₂ storage complex are characterised for porosity (helium, mercury injection, or micro CT), permeability, and mineral content. The eight Hutton Sandstone cores are variable with porosities of 5.2–19.6%, including carbonaceous mudstones, calcite cemented sandstones, and quartz rich sandstones, common lithologies that may be found generally in overlying aquifers of CO₂ storage sites. A chlorite rich sandstone was experimentally reacted with CO₂ and low concentrations of SO₂ to investigate the potential reactions and possible mineral trapping in the unlikely event of a leak. Micro CT characterisation before and after the reaction indicated no significant change in porosity, although some fines movement was observed that could affect permeability. Dissolved concentrations of Fe, Ca, Mn, Cr, Mg, Rb, Li, Zn, etc., increased during the reaction, including from dissolution of chlorite and trace amounts of ankerite. After ~40 days dissolved concentrations including Fe, Zn, Al, Ba, As and Cr decreased. Chlorite was corroded, and Fe-rich precipitates mainly Fe-Cr oxides were observed to be precipitated on rock surfaces after experimental reaction. Concentrations of Rb and Li increased steadily and deserve further investigation as potential monitoring indicators for a leak. The reaction of chlorite rich sandstone with CO₂ and SO₂ was geochemically modelled over 10 years, with mainly chlorite alteration to siderite mineral trapping 1.55 kg/m³ of CO₂ and removing dissolved Fe from solution. Kaolinite and chalcedony precipitation was also predicted, with minor pyrite precipitation trapping SO₂, however no changes to porosity were predicted. Full article