Abstract:This study is focused on two structures in the Baltic offshore region (E6 and E7 structures in Latvia) prospective for the geological storage of carbon dioxide (CO 2 ). Their CO 2 storage capacities were estimated recently with different levels of reliability. Petrophysical, geophysical, mineralogical and geochemical parameters of reservoir rocks represented by quartz sandstones of the Deimena Formation of Middle Cambrian in two wells and properties of Silurian and Ordovician cap rocks were additionally studie… Show more
“…These two rock samples have similar geochemical properties. Samples E6‐1 and E6‐3 were selected from two different depth intervals of the well E6‐1/84 (Table ), characterized by various lithological and petrophysical properties [ Shogenov et al ., ]. Sample E6‐2 (from the same depth as sample E6‐3) showed an increase in effective porosity and, contrary to E6‐3, petrophysical alterations after the experiment, thus proving the influence of rock heterogeneity on the obtained results.…”
Section: Discussionmentioning
confidence: 88%
“…Three‐dimensional geological models of the top of the Cambrian Series 3 Deimena Formation with location of the studied wells are shown (modified after Shogenov et al . [, ]).…”
Section: Introductionmentioning
confidence: 99%
“…Four geological structures, located onshore (South Kandava and Dobele) and offshore Latvia (E6) and Lithuania (E7) and serving as prospective CGS sites in the Baltic Region (Figure ), were previously described in detail by Shogenov et al . [, ]. All the studied structures are situated within the tectonically dislocated Liepaja‐Saldus zone of highs (Figure ).…”
Section: Introductionmentioning
confidence: 99%
“…The deepest Deimena Formation rocks occur in the offshore E7 structure (Figure ). This structure is also characterized by the highest temperature of 46°C and water salinity of 125 g/L [ Shogenov et al ., , ]. The shallowest offshore structure E6 shows a lower temperature (36°C) and the lowest salinity of Cambrian fluids (99 g/L).…”
Section: Introductionmentioning
confidence: 99%
“…The selected structures have an average porosity of 12–21%, permeability of 40–360 mdarcy, and mean reservoir thickness of 42–58 m. The average CO 2 storage potentials (conservative‐optimistic) of the Dobele, South Kandava, E7 and E6 structures were, respectively, 20–106, 25–95, 7–34, and 152–377 Mt. We estimated the E6 offshore structure as the largest suitable trapping structure prospective for CGS offshore Latvia with the highest CO 2 storage capacity [ Shogenov et al ., , ]. Based on unpublished exploration report data, stored in Latvian Environmental, Geology and Meteorology Centre (LEGMC), we have treated E7 as a Latvian offshore structure in our earlier publications.…”
The objective of this study was to determine the influence of the possible CO 2 geological storage in the Baltic Region on the composition and properties of host rocks to support more reliable petrophysical and geophysical models of CO 2 plume. The geochemical, mineralogical, and petrophysical evolution of reservoir sandstones of Cambrian Series 3 Deimena Formation and transitional clayey carbonate caprocks of Lower Ordovician Zebre Formation from two offshore structures in Latvia and Lithuania and two onshore structures in Latvia, induced by laboratory-simulated CO 2 geological storage, was studied for the first time in the Baltic Region. The geochemical, mineralogical, and petrophysical parameters were measured in 15 rock samples, before and after the alteration experiment. The diagenetic alterations of reservoir rocks were represented by carbonate cementation in the top of the onshore South Kandava structure, and quartz cementation and compaction, reducing the reservoir quality, in the deepest offshore E7 structure in Lithuania. The shallowest E6 structure offshore Latvia was least affected by diagenetic processes and had the best reservoir quality that was mainly preserved during the experiment. Carbonate cement was represented by calcite and ankerite in the transitional reservoir sandstones of very low initial permeability in the upper part of the South Kandava structure. Its dissolution caused a significant increase in the effective porosity and permeability of sandstones, a decrease in the weight of samples, bulk and matrix density, and P and S wave velocities, demonstrating short-term dissolution processes. Only slight geochemical changes occurred during the experiment in offshore reservoir sandstones. Minor dissolution of carbonate and clay cements, feldspar and some accessory minerals, and possible minor precipitation of pore-filling secondary minerals associated with slight variations in rock properties, demonstrating both short-term and long-term processes, were suggested. As a novelty, this research shows the relationship between diagenetic alterations of the Cambrian Series 3 Deimena Formation reservoir sandstones and their changes caused by the CO 2 injection-like experiment.
“…These two rock samples have similar geochemical properties. Samples E6‐1 and E6‐3 were selected from two different depth intervals of the well E6‐1/84 (Table ), characterized by various lithological and petrophysical properties [ Shogenov et al ., ]. Sample E6‐2 (from the same depth as sample E6‐3) showed an increase in effective porosity and, contrary to E6‐3, petrophysical alterations after the experiment, thus proving the influence of rock heterogeneity on the obtained results.…”
Section: Discussionmentioning
confidence: 88%
“…Three‐dimensional geological models of the top of the Cambrian Series 3 Deimena Formation with location of the studied wells are shown (modified after Shogenov et al . [, ]).…”
Section: Introductionmentioning
confidence: 99%
“…Four geological structures, located onshore (South Kandava and Dobele) and offshore Latvia (E6) and Lithuania (E7) and serving as prospective CGS sites in the Baltic Region (Figure ), were previously described in detail by Shogenov et al . [, ]. All the studied structures are situated within the tectonically dislocated Liepaja‐Saldus zone of highs (Figure ).…”
Section: Introductionmentioning
confidence: 99%
“…The deepest Deimena Formation rocks occur in the offshore E7 structure (Figure ). This structure is also characterized by the highest temperature of 46°C and water salinity of 125 g/L [ Shogenov et al ., , ]. The shallowest offshore structure E6 shows a lower temperature (36°C) and the lowest salinity of Cambrian fluids (99 g/L).…”
Section: Introductionmentioning
confidence: 99%
“…The selected structures have an average porosity of 12–21%, permeability of 40–360 mdarcy, and mean reservoir thickness of 42–58 m. The average CO 2 storage potentials (conservative‐optimistic) of the Dobele, South Kandava, E7 and E6 structures were, respectively, 20–106, 25–95, 7–34, and 152–377 Mt. We estimated the E6 offshore structure as the largest suitable trapping structure prospective for CGS offshore Latvia with the highest CO 2 storage capacity [ Shogenov et al ., , ]. Based on unpublished exploration report data, stored in Latvian Environmental, Geology and Meteorology Centre (LEGMC), we have treated E7 as a Latvian offshore structure in our earlier publications.…”
The objective of this study was to determine the influence of the possible CO 2 geological storage in the Baltic Region on the composition and properties of host rocks to support more reliable petrophysical and geophysical models of CO 2 plume. The geochemical, mineralogical, and petrophysical evolution of reservoir sandstones of Cambrian Series 3 Deimena Formation and transitional clayey carbonate caprocks of Lower Ordovician Zebre Formation from two offshore structures in Latvia and Lithuania and two onshore structures in Latvia, induced by laboratory-simulated CO 2 geological storage, was studied for the first time in the Baltic Region. The geochemical, mineralogical, and petrophysical parameters were measured in 15 rock samples, before and after the alteration experiment. The diagenetic alterations of reservoir rocks were represented by carbonate cementation in the top of the onshore South Kandava structure, and quartz cementation and compaction, reducing the reservoir quality, in the deepest offshore E7 structure in Lithuania. The shallowest E6 structure offshore Latvia was least affected by diagenetic processes and had the best reservoir quality that was mainly preserved during the experiment. Carbonate cement was represented by calcite and ankerite in the transitional reservoir sandstones of very low initial permeability in the upper part of the South Kandava structure. Its dissolution caused a significant increase in the effective porosity and permeability of sandstones, a decrease in the weight of samples, bulk and matrix density, and P and S wave velocities, demonstrating short-term dissolution processes. Only slight geochemical changes occurred during the experiment in offshore reservoir sandstones. Minor dissolution of carbonate and clay cements, feldspar and some accessory minerals, and possible minor precipitation of pore-filling secondary minerals associated with slight variations in rock properties, demonstrating both short-term and long-term processes, were suggested. As a novelty, this research shows the relationship between diagenetic alterations of the Cambrian Series 3 Deimena Formation reservoir sandstones and their changes caused by the CO 2 injection-like experiment.
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