Romanian CCS Demo Project-static Modeling Activities for Storage Sites in in Oltenia Region

Abstract

Storage pre-feasibility study for the Romanian CCS Demo Project, CCS team has performed static modeling activities for the two sites selected in “Zone 1” and “Zone 5”. These activities were split in two steps for each site: structural modeling and property modeling.The data available at the time of the building of the static models consisted of the following:241 2D seismic lines across the entire Turceni area, 58 wells with some associated logs, of which notably -16 in “Zone 1”, of which 9 are “deep wells” (crossing the entire Sarmatian sequence) and 44 in “Zone 5”, of which 16 are “deep wells”. Some of these wells are shallow wells according with the TD and according with the bottom hole formation (they drilled only the upper part of the Sarmatian). All the others are deep wells, they have drilled almost the entire Sarmatian sequence, some of them found the Tertiary base. In the ‘wells with logs’ groups there are 16 deep wells and 28 shallow wells in Zone 5, 9 deep wells and 7 shallow wells in Zone 1 respectively. Using the logs, geological markers from the wells and all the geological information from the bibliography, technical reports and other sources, the Sarmatian deposits have been divided into several layers (Sa2, Sa3, Sa4, Sa5, Sa5a, Sa6, Sa7, Sa8), each of them characterized by different characteristics as can be seen on the wells correlations.The seismic lines have been acquired and processed according with the different technologies according with the available methods from the time when they have been acquired. In the area there are seismic lines acquired from 1973 till 2005. Some of the old seismic data have been reprocessed later on but due to the quality of the raw data the quality of the processed seismic lines did not improve too much. The Sarmatian deposits are characterized by parallel, horizontal seismic horizons with good continuity and variable amplitude according with lithological and fluid content changes.The faults are developed on different seismic lines but was very difficult to correlate from a line to another and in such a way to define if it is a fault with major importance and extension or is very local ones. Some of faults are developed only in the tertiary sequences that means that these are formed by gravitational processes done by differential compaction of lithological columns with different thickness which in general decrease in net slip in the upper part. Such kind of faults have a local development and because they affected an unconsolidated or poor consolidate geological formations they are close faults and not create an open space and in general these faults are formed above the uplifted blocks or a prominent high of the relief.Most of these wells have lithological marker information (well tops) and resistivity logs (including SP). However these logs have not been made available. One well has a GR log, 2 wells have a sonic log, 2 wells have a neutron log; 7 wells have checkshot information. While the seismic coverage appears sufficient to build a structural model with a reasonable level of detail for this stage, it is evident that the scarcity of petrophysical information is likely to affect the reliability of the property models. The static model from zone 1and zone 5 have been created using: fault modeling, pillar gridding, make horizons, make zones, layering, facies calculation, scale up well logs, facies modeling, properties modeling.The facies modeling, reflects the knowledge of the depositional environment of the site. The “regional” (depositional) facies respects the assumptions of the source rock and sedimentation direction; the methods chosen to model the lithofacies (“newfacies”), conditioned to each of depositional facies types defined above, appear adequate for the environment distribution of petrophysical properties (porosity and permeability) has been modeled separately for each facies type (petrophysical model conditioned to facies model). This is the recommended way to capture the lithological variations previously modeled.The source for these properties is normally the corresponding upscaled well logs. However, this is apparently not the case for the static models reviewed here: only the minimum and maximum values for each facies type were input in the petrophysical modeling process.Using the static model created for the two zones, 1 and 5, two injection areas have been selected for CO2 injection. The selection of these CO2 injection areas took in consideration the lithological content of geological formations from Sarmatian deposits, depth of the reservoirs, the existence of a proper seal rocks above the reservoirs.