New Thermally Responsive Cement for Heavy Oil Wells

Abstract

Canada’s oil sands are one of the world’s largest hydrocarbon resources. The initial volume of crude bitumen in place is estimated to be approximately 260 billion cubic metres with 11 percent or 28 billion cubic metres recoverable under current economic conditions. Continually improving economics, bolstered by recent higher crude oil prices, has resulted in the International recognition of the vast potential of Canada’s oil sands. Based on publicly announced development plans through to 2015, over C$60 billion could be invested in numerous projects to develop the oil sands. Various factors have to be considered to select the proper cement for zonal isolation of thermal recovery heavy-oil wells. First the cement should be flexible enough to withstand the stresses which occur when casing expands during the heating up of the well. To reduce these stresses, the cement thermal expansion coefficient should be similar to the thermal expansion coefficient of the casing. Finally, cement mechanical properties should not degrade during the whole steam injection process, i.e. when it is subjected to extremely high temperatures (up to 350 degC) for extended periods of time. Specifically in Canada, the majority of the steam injection wells are drilled in shallow sandstone formations. This requires the cement to have high flexibility to resist the stresses. Moreover, during steam injection, a reaction between the sandstone formation and the cement sheath may occur, impacting the cement matrix and hence changing its properties. This paper describes the application of a new thermally responsive cement for zonal isolation of heavy oil wells in Canada. This system is designed to have excellent strength, flexibility and thermal properties even upon interaction with sandstone formations. It minimizes the mechanical stresses exerted on the cement sheath during steam injection, thus reducing the risk of loss of well integrity. The numerical simulations performed with these long-term material properties (six months of exposure to 350 degC) for typical Canadian heavy oil wells conditions predict reliable and durable zonal isolation under these extreme conditions. These simulation results are confirmed by several field applications in wells which have not leaked after months of steam injection.

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

“…LS2 formulation in this case). Such findings corroborate those of Tomilina et al (2012) and Guo et al (2015).…”

“…It can be seen that latex addition into cement slurry not only increases the flexibility of the cement sheath, but also its thermal expansion coefficient thereof causing it to deform further when subjected to temperature variations. Similar conclusions were found by Tomilina et al (2012). Tables 2 and 3 summarize the mechanical and thermal properties of the casing, sheaths and formations considered in the parametric analyses.…”

“…Several cement slurry formulations (Cain, 1966;Goodwin and Crook, 1992;Carpenter et al, 1992;Dean and Torres, 2002;Myers et al, 2005;Boukhelifa et al, 2005;Stiles, 2006;Bezerra et al, 2011;Tomilina et al, 2012;Teodoriu et al, 2013;De Andrade et al, 2014;Albawi et al, 2014;Pernites and Santra, 2016;Bu et al, 2017) have been studied to improve the mechanical behavior of cement sheaths in oil wells. Such studies revealed the great influence of the thermomechanical properties of the casing, the cement and the formation on damage occurring within the cement sheath.…”

“…Strength, flexibility and thermal properties have been pointed out as key issues (Thiercelin et al, 1998;Bosma et al, 2000;Dean and Torres, 2002;Myers et al, 2005;Stiles, 2006;Tomilina et al, 2012;Yuan et al, 2013). Such mechanical properties can be enhanced by mixing the cement slurry with various additives (Pedersen et al, 2006;Pernites and Santra, 2016;Broni-Bediako et al 2016), and in particular with latex, which has been shown to be promising for this purpose (Dean and Torres, 2002;Pavlock et al 2012).…”