Assessment of Possibilities to Use Captured Co2 in the Western Black Sea Area

Abstract

In order to define the offshore solution, the first step was to identify the ports along the Danube which have the necessary infrastructure to facilitate the transport of CO2 by ship to the Black Sea. 17 ports have been identified, from which 11 are only fluvial, 3 are fluvial-maritime, and 3 maritime. The offshore solution considers transporting captured CO2 from the Oltenia region for utilization in the Black Sea. At the current knowledge level, the most favorable region for CO2 geological storage is Histria Depression. This depression comprises five hydrocarbon fields (discovered so far) located on an NW-SE alignment on its northern flank. These fields are: •Lebada Est, discovered in 1980, with oil in Albian and Upper Cretaceous rocks and gases in Eocene deposits; •Lebada Vest, discovered in 1984, with oil in Albian, Upper Cretaceous, and Eocene reservoirs; •Sinoe, discovered in 1988, with oil in Albian reservoirs; •Delta, discovered in 2007, with oil in Albian reservoirs; •Pescarus, discovered in 1999, with oil in Upper Cretaceous (Cenomanian) reservoir. From these fields, only Lebada East and Lebada West can be used for CO2-EOR operations and CO2 storage purposes. These fields already have injection wells that are used for enhanced recovery operations (not involving CO2). The East Lebada deposit was discovered in 1980, following the development and exploitation of the associated oil and gas deposit between July 1984 and January 1991, on three production platforms. Initially, the deposit has produced in May 1987, in its eastern part, in natural mode. Secondary exploitation by water injection began after about 2 months. There are defined 3 deposits, superimposed vertically, cantoned in Albian reservoirs, Upper Cretaceous and Eocene. In the oil field, of the Albian age, East Lebada, two porous-permeable zones were divided, separated by two compact zones. The productive area comprises only the upper porous-permeable range. West Lebada deposit was discovered in 1984 with the 82 Lebada West Probe that produced oil and associated gases from two Albian collectors. The drilling program comprised 9 production wells and 2 injection wells, production starting in April 1993. During the operation, it was found that apart from the two A3 and A4 collectors belonging to Albian, there is another dated collector on top of them. Vraconian, a distinct hydrodynamic unit, characterized as a narrow-band gas field of crude oil. Within the Albian formation, four porous-permeable intervals were separated, characterized by different porosity values. The A3 and A4 layers, the productive ones, are located in the upper part of the Albian and have medium to good porosity and permeability values. The ranges noted A1 and A2 are located in the lower part of the Albian and have very small porosities and permeabilities. The mechanism of the trap is complex with both structural and stratigraphic components. A combination of factors acts in the formation of the A4 layer trap, namely: an erosional truncation to the west, tapering to the north, structural to the east, and facies compaction to the south. On the structure of the Lebada Vest deposit was identified a crude oil field with a primary gas head, enclosed in Eocene detritus rocks. The Eocene reservoir contains two porous-permeable layers E3, E4, with average porosity and good respectively. The closure of the E4 layer trap is made by erosion and erosion truncation in the east and by compaction in the west. The closure of the E3 trap is achieved by erosion and erosion truncation in the East and North and by structural closure and facies change in the West and South. The screen of the two layers E4 and E3 is represented by the Oligocene clays. Within the Black Sea, the major structural unit that accommodates oil reservoirs and potential storage structures and the only structure investigated so far from the CO2 storage perspective are Histria Depression. The oil reservoirs that can be used for injection and utilization of captured CO2 for EOR are Lebada Vest and Lebada Est, Sinoe, Portia, Pescarus, and Delta.