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Collaborating Authors
Results
Abstract The laboratory testing described here can be seen as the first step in investigating potential thermal effects leading to the creation of a leakage pathway at or in the vicinity of a CO2 injection well. The occurrence of thermal stresses in metal casing, cement and formation can lead to either one or more of these materials developing cracks, or debonding between pairs of materials at their interface. A first investigation is thus concentrating on the rock immediately above the injection reservoir; this sealing rock is most often some variant of shale formation. Here we look at the required temperature contrast between the injected CO2 (or for that matter any other liquid) and the shale formation, in order to initiate tensile fracturing due to the development of tensile stresses exceeding the rock's tensile strength. Finite element simulations suggest that significant fracturing may occur for a temperature contrast of 80° C. An accompanying series of laboratory tests showed that for the chosen shale specimen, fracturing should only be of concern for much higher temperature contrasts.
- North America > United States > New Mexico > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- North America > United States > Colorado > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
Abstract A coupled simulator based on the MDEM fracturing code and the TOUGH2 reservoir simulator was used to study propagation of hydraulic fractures in a naturally-fractured formation under isotropic and anisotropic in-situ stress conditions. Offset of a propagating hydraulic fracture by a pre-existing natural fracture was observed in some of the simulations. In others, the hydraulic fracture was found to cross a natural fracture without any offset. A mesh-dependence was observed: changing the mesh geometry from regular to irregular affected the fracture pattern, even though the mesh resolution was approximately the same. The mesh dependence particularly affected the fracture pattern observed under isotropic in-situ stress field. The results of the study are of importance for practical application of hydraulic fracture simulation, in particular in gas shale reservoirs.
Near-Well Integrity and Thermal Effects: A Computational Road from Laboratory to Field Scale
Lavrov, A. (SINTEF Petroleum Research) | Torsæter, M. (SINTEF Petroleum Research) | Albawi, A. (Norwegian University of Science and Technology) | Todorovic, J. (SINTEF Petroleum Research) | Opedal, N. (SINTEF Petroleum Research) | Cerasi, P. (SINTEF Petroleum Research)
Abstract Integrity of the near-well area is crucial for preventing leakage between geological horizons and towards the surface during CO2 storage, hydrocarbon production and well stimulation. The paper consists of two parts. In the first part, a finite-element model of earlier laboratory tests on thermal cycling of a casing/cement/rock assemblage is set up. It is demonstrated that radial tensile stresses contributing to annular cement debonding are likely to develop during cooling of such an assemblage. The results of the modeling are in agreement with the results of the earlier laboratory experiments, with regard to the temperature histories, CT data, and location of acoustic emission sources. In the second part of the paper, a computational procedure is developed for upscaling of data about rock damage obtained from CT, to a finite-element model of flow in porous media around a well. The damaged zone is shown to dominate the flow along the axis of a compound specimen (a hollow cylinder of sandstone filled with cement). Implications for leakage along an interface between cement and rock in-situ are discussed.
- Asia (0.93)
- North America > United States > Texas (0.68)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.36)