CO2 soil flux baseline at the technological development plant for CO2 injection at Hontomin (Burgos, Spain)

Abstract

a b s t r a c tFrom the end of 2013 and during the following two years, 20 kt of CO 2sc are planned to be injected in a saline reservoir (1500 m depth) at the Hontomín site (NE Spain). The target aquifers are Lower Jurassic limestone formations which are sealed by Lower Cretaceous clay units at the Hontomín site (NE Spain). The injection of CO 2 is part of the activities committed in the Technology Development phase of the EC-funded OXYCFB300 project (European Energy Program for Recovery -EEPR, http://www.compostillaproject.eu), which include CO 2 injection strategies, risk assessment, and testing and validating monitoring methodologies and techniques.Among the monitoring works, the project is intended to prove that present-day technology is able to monitor the evolution of injected CO 2 in the reservoir and to detect potential leakage. One of the techniques is the measurement of CO 2 flux at the soil-atmosphere interface, which includes campaigns before, during and after the injection operations.In this work soil CO 2 flux measurements in the vicinity of oil borehole, drilled in the eighties and named H-1 to H-4, and injection and monitoring wells were performed using an accumulation chamber equipped with an IR sensor. Seven surveys were carried out from November 2009 to summer 2011. More than 4000 measurements were used to determine the baseline flux of CO 2 and its seasonal variations.The measured values were low (from 5 to 13 g m −2 day −1 ) and few outliers were identified, mainly located close to the H-2 oil well. Nevertheless, these values cannot be associated to a deep source of CO 2 , being more likely related to biological processes, i.e. soil respiration. No anomalies were recognized close to the deep fault system (Ubierna Fault) detected by geophysical investigations. There, the CO 2 flux is indeed as low as other measurement stations. CO 2 fluxes appear to be controlled by the biological activity since the lowest values were recorded during autumn-winter seasons and they tend to increase in warm periods. Two reference CO 2 flux values (UCL 50 of 5 g m −2 d −1 for non-ploughed areas in autumn-winter seasons and 3.5 and 12 g m −2 d −1 for in ploughed and non-ploughed areas, respectively, in spring-summer time, and UCL 99 of 26 g m −2 d −1 for autumn-winter in not-ploughed areas and 34 and 42 g m −2 d −1 for spring-summer in ploughed and not-ploughed areas, respectively) were calculated. Fluxes higher than these reference values could be indicative of possible leakage during the operational and post-closure stages of the storage project.

Developments since 2005 in understanding potential environmental impacts of CO2 leakage from geological storage

“…Low baseline fluxes from 5 to 13 g m −2 d −1 were recorded by extensive surveys at Hontomin in northern Spain (Elío et al, 2013) with few outliers. There was greater variability at other sites with a summer range of around 5-55 g m -2 d -1 at Lacq-Rousse (Lescanne et al, 2011) and much higher July 2001 results from Weyburn (median=48 g m…”

Setup of a large-scale test field for distributed soil gas sensors and testing of a monitoring method based on tomography

“…Therefore, mostly direct observation methods were applied. There are different technologies and methods for surface and near-surface monitoring which include soil and vadose zone gas sampling [24], CO 2 detectors, laser systems and Light Detection and Ranging (LIDAR), soil flux monitoring based on accumulation chambers and micrometeorological eddy flux monitoring [1,7,19], and monitoring of tracers [12,27]. Beside direct monitoring methods fluid-rock interactions [8] were studied, surface deformation monitoring [28] was performed, and geoelectric measurements were applied in the shallow subsurface [10,13].…”

Groundwater Contamination Studies by Environmental Isotopes: A review

“…Examples of such applications include investigations in carbon cycle and flux (e.g., [50][51][52][53]), chemical weathering (e.g., [54]), degassing from thermal and cold springs (e.g., [55,56]), volcanic-hydrothermal systems (e.g., [57,58]), and, as a relatively new field, geochemical trapping in CO 2 injection (carbon capture and storage (CCS)) projects (e.g., [59][60][61]). …”