Subparallel thrust and normal faulting in Albania and the roles of gravitational potential energy and rheology contrasts in mountain belts

The active tectonics of Albania and surrounding regions, on the eastern margin of the Adriatic Sea, is characterized by subparallel thrust and normal faulting which, we suggest, is likely to be related to gravitational potential energy contrasts between the low-lying Adriatic Sea and the elevated mountainous areas inland. We calculate the magnitude of the force which the mountains and lowlands exert upon each other as a result of this potential energy contrast. It is likely that this force is largely supported by shear stresses on faults, and if so, the average stresses are less than ∼20 MPa. Alternatively, if the mountains are supported by stresses in the ductile part of the lithosphere, the stresses are likely to be ∼80–240 MPa in magnitude. The mountains of Albania are significantly lower than other ranges, such as the Peruvian Andes, which are thought to be extending in response to potential energy differences, and we discuss the relation between Albania and these other, higher, mountain belts from the perspective of differences in lithosphere rheology. We suggest that the lowlands of western Albania and the Adriatic Sea may have been weakened through time as a result of the deposition of large thicknesses of sediment, which lead to heating of the crystalline basement, a reduction in the potential energy contrast that could be supported by the lowlands, and so normal faulting in the mountains of eastern Albania

Measurement, Monitoring and Verification: Enhanced Oil Recovery and Carbon Dioxide Storage

This report assesses the differences between monitoring technology requirements for CO2 storage in a saline or depleted hydrocarbon reservoir and in a hydrocarbon reservoir, when CO2 injection is used for enhanced oil recovery (EOR). First order factors dictating technology choice including geological and geographic parameters are assessed before addressing differences introduced by the choice of process (EOR or storage). A brief review of the most common monitoring technologies suitable for use in either CO2 storage operations or in CO2-EOR projects are found to not vary significantly, however the measurements and analysis do. Specific differences are highlighted, however, it is found that the largest differences in monitoring technology usage is not process related, rather it is controlled by site specific geology and geography. Where differences do exist due to process choice it is shown to be largely related to the level of characterization, baseline assessment, likely infrastructure in place and pressure management during operations. No specific different technologies or monitoring strategies are recommended for EOR over CO2 storage in either saline or depleted oil and gas reservoirs. Rather, it is recommended to assess the local site- specific conditions of any CO2 injection project including the geology, geography and the level of knowledge and understanding of the reservoir and then to build a risk based approach to selecting the appropriate monitoring technologies and deployment strategies.This report assesses the differences between monitoring technology requirements for CO2 storage in a saline or depleted hydrocarbon reservoir and in a hydrocarbon reservoir, when CO2 injection is used for enhanced oil recovery (EOR). First order factors dictating technology choice including geological and geographic parameters are assessed before addressing differences introduced by the choice of process (EOR or storage). A brief review of the most common monitoring technologies suitable for use in either CO2 storage operations or in CO2-EOR projects are found to not vary significantly, however the measurements and analysis do. Specific differences are highlighted, however, it is found that the largest differences in monitoring technology usage is not process related, rather it is controlled by site specific geology and geography. Where differences do exist due to process choice it is shown to be largely related to the level of characterization, baseline assessment, likely infrastructure in place and pressure management during operations. No specific different technologies or monitoring strategies are recommended for EOR over CO2 storage in either saline or depleted oil and gas reservoirs. Rather, it is recommended to assess the local site- specific conditions of any CO2 injection project including the geology, geography and the level of knowledge and understanding of the reservoir and then to build a risk based approach to selecting the appropriate monitoring technologies and deployment strategies

Layer spreading and dimming within the CO2 plume at the Sleipner Field in the North Sea

The CO2 plume at Sleipner has been imaged on 3D seismic surveys as a series of bright sub-horizontal reflections. Nine discrete CO2 rich layers are inferred to have accumulated between a series of intra-reservoir mudstones beneath a substantial reservoir topseal. Time-lapse changes in reflectivity and in the lateral extent of these layers provide useful information about CO2 flow within the reservoir. The deepest CO2 layers within the growing plume have acoustically dimmed, stopped growing, and some have shrunk. Shallower layers have continued to grow. A combination of numerical flow models and analytical solutions of layer spreading yields useful insights into plume development. The observed seismic dimming and shrinkage of the deeper layers are, at least in part, caused by a reduction in the amount of CO2 trapped in the deeper plume. This is probably due to increases in the effective permeability of thin intra-reservoir mudstones. These changes reduce net flux of CO2 into the deeper layers of the plume with a corresponding increase of CO2 flux towards the top of the reservoi