First EAGE CO2 Geological Storage Workshop

Estonia, Latvia and Lithuania have strong economic links and coordinated environmental policy. They are situated within common Baltic Sedimentary basin. The smallest of the three countries Estonia with 1.3 mln population produces the highest CO2 emissions mainly due to oil shale used for energy production. Geological conditions in three countries are different, resulting in zero potential for CO2 geological storage (CGS) in Estonia located at the shallowest part of the Baltic sedimentary basin, low CGS potential in Lithuania located at the deepest part of the basin and high CGS potential of Latvia containing large uplifts as the potential traps for CO2 storage. Alternative approaches are suggested for Estonia and Lithuania, focusing on the mineral trapping of CO2. The immobilization of CO2 by the alkaline watered ash and ash transportation water from flue gas formed by shale combustion is a prospective option in Estonia. The serpentinites abundant in the crystalline basement is a prospective rock media for CO2 immobilization in Lithuania. The other CGS option for Estonia and Lithuania is a transportation of CO2 to the Latvian structural traps. Solubility and mineral trapping in the Baltic saline aquifers have large potential which could be considered for future decades.

Iran, with a record of over one century of oil production, is currently one of the major oil producing countries of the world. Several of the old fields have been depleted to an uneconomical level of production which requires significant amount of natural gas for re-injection so that currently over 100 million cubic meters of natural gas is re-injected daily to maintain or enhance oil production to an economical level. It is estimated that in order to maintain oil production, over 200 million cubic meters of natural gas will be needed daily by 2015. However, due to the increased level of domestic and export demands for natural gas, IOR, EOR with natural gas is prohibitive and therefore portions of this amount of natural gas can be substituted by carbon dioxide. In the other hand, CO2 emission increased from 240 MM ton per year in 1994 to 382 MM Ton in 2006 which 40% of this emission is related with stationary sources like power plants and industries. According to the fact that part of CO2 can be remain in reservoir in IOR/EOR projects. The CO2 storage capacity was studied for IOR/EOR project in Iran. 20 main mature oil fields were considered and so many factors same as reservoir pressure, temperature, depth, geological condition, exist faults, crude density, crude viscosity and crude composition were considered at first step. Then suitable reservoirs have been chosen. In the case of Oil and gas reservoirs, the fundamental assumption is that the volume previously occupied by the produced hydrocarbon becomes, by and large, available for CO2 storage. Consistent with the resource- reserves pyramid concept, both theoretical and effective CO2 storage capacities are calculated according to formation volume factor, reservoir area, thickness, porosity and water saturation. Water saturation changes that can affect storage capacity, was simulated by formula obtained from laboratory test in carbonated reservoir and according to oil displacement. Conclusion illustrates that more than 16 Giga ton CO2 equivalent 20 years current annual emission of Iran power plants, can be stored in selected reservoir in south of Iran.

The present paper proposes a new methodology for identifying and exploiting through internet various documentary sources, that may be relevant for CO2 storage sites. It describes a knowledge communication scenario resting on a software platform, which enables communication and cooperation between various internet services. Several knowledge communication issues are examined such as vocabulary extraction from texts or maps geographical area identification, semantic analysis of geological terms. The proposed solution rests on the definition of adequate domain ontologies and on semantic annotation. It has the advantage of allowing a goal-oriented and largely automated document search.

Using state of the art survey planning and modeling tools, we investigate the possibility of employing marine controlled-source electromagnetic (CSEM) surveys in the monitoring of carbon dioxide sequestration. As a site example, we use the CO2 injection from the Sleipner Øst gas field into the Utsira formation in the North Sea. The injection plume inferred from 3D seismic surveys is used, together with well information and a priori geological knowledge, to build resistivity models for CSEM modeling. We find that the time-lapse change in the CSEM response would have been well above CSEM-acquisition noise levels in both 2001 and 2006. The combination of CSEM and seismic methods, which have a complementary dependence of their response on residual brine saturation, can yield an improved resolution of the CO2-distribution. In addition, CSEM methods are sensitive to the bulk volume of a resistor, also complementary to the superior resolution in seismics. We therefore would expect CSEM monitoring to become a valuable addition to the current monitoring program.

The monitoring of CO2 storage in fractured reservoirs (depleted hydrocarbon field or brine aquifers) requires the study of the impact of fracturation and fluid substitution on seismic data. Seismic data can provide information about the additional compliance due to the fractures and to the fluids through the analysis of seismic azimuthal anisotropy and the introduction of a rock physics model providing a realistic description of fractured media (where porosity, multiphasic fluid phases, inherent seismic anisotropy, the presence of multiple sets of fractures and their connection with porosity can be considered). Seismic methods by themselves cannot fully describe fracturation and must be associated with other methods through an integrated approach. First, borehole and outcrop geological information can give the upper limit of the fracture density expected at depth in the same formation. Second, rock mechanics helps understanding the fracturation state at depth.

Electrical resistivity tomography ERT survey performance in boreholes BRT is studied by numerical forward and inverse simulations to test its sensitivity to changes induced by CO2 injection and migration. Compared with seismic, BRT has lower resolution, but its permanent installation and continuous time-lapse monitoring make it an economical alternative. ERT applications in CO2 storage in saline aquifers are powerful in quantifying intrinsic property changes with time due to the strong contrast between resistive (supercritical) CO2 and conductive saline water reservoir. The resolution of ERT-time lapses is enhanced by applying a constrained inversion with exact apriori geological/structural information on the subsurface from seismic and log data. Our numerical 2D and 3D modelling reveals the capability of BRT techniques to map CO2 plumes and changes as a function of thickness, concentration and electrode configuration as well as modelling and inversion constraints. Some configurations are more favoured due to their better spatial resolution and lower artefacts.

CO2 emissions monitoring is one of the rising problems in a CO2 underground storage site. In this framework OGS has tested a simple methodology addressed to control the hypothetic CO2 emissions from an underground storage facility by direct airborne measurements. The study also investigates the economical aspects of such an activity. The test has been carried out using a low cost single engine IFR certified aircraft where an air sampling system, able to measure the CO2 concentration in the air, has been mounted on; a pseudo regular flight pattern has been adopted at an altitude of 2000 ft above the studied area, located in the North Eastern part of the Adriatic seashore and including some small dimension towns. In real time the system collected the position of the aircraft, the air pressure, temperature, relative humidity, wind direction and CO2 concentration values. A specific approach for data reduction to a "datum" altitude has been investigated and successfully applied. The trend of anthropic CO2 concentration has been studied, as the base for the computation of a first primitive diffusive model of CO2 flux in the air and nearby the ground. The test demonstrated the feasibility of the method.

This study aims to investigate the effects of the capillary and solubility characteristics of the CO2-brine-rock systems on CO2 injectivity and storage capacity numerically. The general-purpose numerical simulator for multicomponent, multiphase fluid flow, TOUGH2 is used as numerical tool. The EOS module, ECO2N which considers the fluid system consisting of CO2 and brine is incorporated to TOUGH2 for the dynamic phase changes during the transport. A generic axissymmetric 2D aquifer model is created. Two distinct capillary pressure models are used. A CO2 injection rate of 60 kg/s is assured in three injection blocks from the bottom of the model. Due to the high solubility of CO2 into brine, the effect of the capillary forces on injectivity is determined to be less pronounced compared to inert gases. Another important effect of the solubility is on the critical gas saturation which decreases below the determined values of relative permeability curves. The increasing salinity of the aquifer brine increases the effect of the capillary forces on the injectivity. Because of the salting out effect less amount of CO2 dissolves in the brine. The salt precipitation is found to be another factor influencing the injectivity negatively.

One of the main challenges facing industrial scale storage of CO2 in saline aquifers will likely arise from pressure build up in the storage formation and displacement of brine. The study presented here examines two mitigation strategies for limiting the rate and magnitude of over-pressure development by producing and re-circulating brine in the storage system. The analysis is performed using a reservoir modelling tool applied to a multi-aquifer storage system.