Effect of Dynamic Loading on Wellbore Leakage for the Wabamun Area CO2-Sequestration Project

Abstract

The most viable options for permanent removal of carbon dioxide (CO 2 ) from the atmosphere include large-scale injection of CO 2 from stationary sources, such as coal-fired power plants and heavy-oil production, into brine-filled formations. One of the main risks identified with storing CO 2 in the subsurface is the potential for leakage through existing wells penetrating the caprock. The wellbore system has several components that can fail and create leakage pathways, including type and placement of wellbore casing and cements, completion method, abandonment, and wellbore expansion or contraction by changes in temperature and pressure. Of the 1,000 wells in the study area near Wabamun Lake, Alberta, 95 wells penetrated the immediate caprock above the proposed Nisku injection formation and were identified as potential leakage pathways. The leakage risk of these wells was evaluated on the basis of knowledge of the well design, current well status, and historical regulations in the area. Only four wells, for the subset of 27 wells studied, were identified as requiring workover, which was less of a problem than anticipated. To evaluate the risk of creating leakage pathways by thermal and pressure changes caused by CO 2 injection, a 3D finite-element model was built by use of poroelastoplastic material models for cement and formation. Multistage simulations for casing/cement and cement/ formation interactions with temperature-enabled elements were conducted. A parametric study of cement properties was conducted to investigate cement design and its mechanical properties for injection wells. The simulation results indicated that thermal cooling might reduce near-wellbore stresses, which would increase the risk of integrity loss in casing/cement and cement/ formation. The parametric study revealed that the risk of debonding and tensile failure would increase with increasing Young's modulus and Poisson's ratio of the cement under dynamic-loading conditions. In addition, low mechanical cement strength would increase the risk of shear failure in the cement.

Well integrity for CO2 injection from ships: Simulation of the effect of flow and material parameters on thermal stresses

“…The latter has been demonstrated to be a real problem in both laboratory and field studies (Carey et al, 2007;Crow et al, 2010;Kjøller et al, 2016), and is a major concern when it comes to CO 2 well integrity. The integrity of the interfaces between cement-casing and cement-rock is most severely threatened in situations where the well is exposed to strong temperature variations (Manceau et al, 2015;Nygaard et al, 2014;Bois et al, 2010). In this paper we seek to uncover when such critical situations can occur during CO 2 injection.…”

Carbon dioxide sequestration in underground formations: review of experimental, modeling, and field studies

“…• Increasing risks associated with CO 2 leakage over the storage period. Nygaard et al (2014) studied the effects of dynamic loading on wellbore leakage. They specified approximately 1000 wells in the Wabamun zone (near Wabamun Lake, Alberta, Canada) to determine the leakage pathway of CO 2 .…”

Numerical simulation of the thermomechanical behavior of cement sheath in wells subjected to steam injection

“…The three Mohr circles corresponding to the unconfined behavior of the three cement slurry formulations, i.e., SS, LS1 and LS2, are first determined based on the results of the compressive tests conducted as described before. The Mohr-Coulomb failure envelopes of the cement slurries are obtained using friction angles varying from 20°to 30°to account for the uncertainty associated with this parameter (Ferla et al, 2009;Nygaard et al, 2014;Zhang et al, 2015). The resulting Mohr circles and failure curves are shown in Fig.…”