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Collaborating Authors
Results
The Effect of Casing Eccentricity on the Casing Stability Analysis of a Wellbore Drilled in Gas Hydrate Bearing Sediments
Salehabadi, Manoochehr (Heriot-Watt University) | Jin, Min (Heriot-Watt University) | Yang, Jinhai (Heriot-Watt University) | Ahmed, Rehan (Heriot-Watt University) | Tohidi, Bahman (Heriot-Watt University)
Abstract Conductor pipe is a surface casing installed in the first few hundred meters in deepwater drilling operations (tens of meters in onshore operations) and it is used to prevent borehole collapse (and protect unconsolidated surface formations against washing out by drilling mud). Gas hydrate bearing sediments found typically near to the seafloor in deepwater environments are very soft and unconsolidated formations. Hole enlargement and wash-out are problems during the drilling these types of formation. As a result, the casing eccentricity is inevitable in the case of borehole washout (in particular if there are not enough centralizers placed on the casing). The circulation of hot drilling mud during subsequent drilling operations or production of hot hydrocarbon after completion of the wellbore will dissociate gas hydrates in the formation behind the casing. Water and gas resulted from gas hydrate dissociation cannot flow away if the permeability of the formation is very low causing high pore pressure to trap behind the casing. The trapped pore pressure in combination with the casing eccentricity may endanger the stability of the casing depending on the magnitude of trapped pore pressure, degree of casing eccentricity and the mechanical strength of the casing. As a result, the development and drilling operations in deepwater environments can be challenging if there are gas hydrate bearing sediments. In this communication, a numerical model is developed using a finite-element code in order to analysis the casing stability of the wellbores drilled in gas hydrate bearing sediments. The model is used to analysis the casing stability of the wellbore under uniform and non-uniform loadings. The non-uniform loading is introduced in the model by considering the presence of eccentric casing together with the pore pressure increase due to gas hydrate dissociation. The results of the model show that the casing eccentricity is an important issue in the casing stability analysis of the wellbores drilled in gas hydrate bearing sediments in deepwater environments. The higher degree of casing eccentricity, the higher the magnitude of stress generated in the casing during subsequent operations, which may lead to casing collapse
- Europe > Norway > Norwegian Sea (0.25)
- North America > United States > Texas > Harris County > Houston (0.15)
Static and Dynamic Estimates of CO2 Storage Capacity in Two Saline Formations in the UK
Jin, Min (Heriot-Watt University) | Pickup, Gillian (Heriot-Watt University) | Mackay, Eric (Heriot-Watt University) | Todd, Adrian (Heriot-Watt University) | Monaghan, Alison (British Geological Survey) | Naylor, Mark (University of Edinburgh)
Abstract Estimation of CO2 storage capacity is a key step in the appraisal of CO2 storage sites. Different calculation methods may lead to widely diverging values. The compressibility method is a commonly used static method for estimating storage capacity of saline aquifers: it is simple, easy to use and requires a minimum of input data. Alternatively, a numerical reservoir simulation provides a dynamic method which includes Darcy flow calculations. More input data are required for dynamic simulation, and it is more computationally intensive, but it takes into account migration pathways and dissolution effects, so is generally more accurate and more useful. For example, the CO2 migration plume may be used to identify appropriate monitoring techniques. Two typical saline aquifer storage sites were analysed using both static and dynamic methods. One site has a comparatively simple geology, while the other has a more complex geology. For each site both static and dynamic capacity calculations were performed. CO2 injection for 15 years was followed by a closure period lasting thousands of years. The proportion of dissolved CO2 and the proportion immobilised by pore scale trapping were calculated. The results of both geological systems show that the migration of CO2 is strongly influenced by the local topography of the upper surface of the aquifer formation. The calculated storage efficiency for the first site varied between 0.5% and 1% of total pore volume, depending on whether the systems boundaries were considered open or closed. Simulation of the deeper, more complex geological system gave storage capacities as high as 2.75%. This work is part of the CASSEM (CO2 Aquifer Storage Site Evaluation and Monitoring) integrated study to derive methodologies for assessment of CO2 storage in saline formations. Although, static estimates are useful for initial assessment, we demonstrate the value of performing dynamic storage calculations, and the opportunities to identify mechanisms for optimising the storage capacity.
- North America (1.00)
- Europe > United Kingdom > England (0.46)
- Geology > Geological Subdiscipline > Geomechanics (0.94)
- Geology > Rock Type (0.68)
- Oceania > Australia > Western Australia > Ashmore Cartier Territory > Timor Sea > Bonaparte Basin > Londonderry High > Vulcan Basin > Eclipse Field (0.89)
- Oceania > Australia > Western Australia > Ashmore Cartier Territory > Timor Sea > Bonaparte Basin > Bonaparte Basin > Vulcan Basin > Eclipse Field (0.89)
- North America > United States (0.89)
- North America > Canada (0.89)
- Reservoir Description and Dynamics > Storage Reservoir Engineering > CO2 capture and sequestration (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Health, Safety, Environment & Sustainability > Environment > Climate change (1.00)
- Facilities Design, Construction and Operation > Unconventional Production Facilities > CO2 capture and management (1.00)