Study On Admixtures For Calcium Aluminate Phosphate Cement Useful To Seal CCS Wells

Abstract

Conventional Portland cement is known to degrade under the attack of CO 2 . The failure is caused by formation of CaCO 3 which in the presence of wet CO 2 can leach as calcium bicarbonate Ca(HCO 3 ) 2 . This way, channels for further ingress and migration of carbon dioxide are created. Recently, a new binder system based on calcium aluminate phosphate cement has been developed which exhibits outstanding CO 2 resistance and temperature stability up to 320 °C. Main limitation of this novel binder system is a lack of additives to retard and control the water loss from the aqueous slurry.In our study, we first present an effective retarding admixture for this cement. Comparison of four different retarders (boric acid, tartaric acid, calcium lignosulfonate and butylene triamine pentamethylene phosphonic acid) revealed that only a combination of boric and tartaric acid at the specific ratio of 2.7:1 (wt./wt.) retards hydration of this cement long enough to guarantee a pumpability time of over 6 h at a pressure of 200 bars and a temperature of 80 °C.Testing of numerous fluid loss additives showed that conventional admixtures based on polyvinyl alcohol, cellulose ether or polyethylene imine do not prevent water loss. This lead to the conclusion that neither film forming additives nor synthetic polymers which physically plug cement filtercake pores will work sufficiently in this specific cement system. Thus, polymers which control fluid loss by adsorption within the pores of the filtercake were probed. This approach proved to be successful. Application of a fluid loss additive based on acrylamide tert-butylsulfonate (ATBS) produced excellent fluid loss control, even at 80 °C. The mechanism behind this performance was found to be reduction of filter cake permeability by adsorption of the high molecular weight polymer onto the positively charged surfaces of cement hydrate phases. Interaction of this admixture with the binder and its working mechanism are presented in detail.

Comprehensive Review of Sealant Materials for Leakage Remediation Technology in Geological CO2 Capture and Storage Process

“…On the basis of these mechanisms, non-Portland cement, and composite cement have been gradually developed. Calcium-aluminate cement, , sulfate-aluminate cement, − and calcium phosphate-aluminate cement − are all non-Portland cements and could be alternatives when being applied in the CO 2 storage process. Compared to conventional Portland cement, these three types of materials have less content of CaO, and many other components such as Al 2 O 3 and P 2 O 5 were added to prevent them from easily reacting with CO 2 like conventional Portland cement .…”

Effects of Thermal Shocks on Integrity of Existing and Newly-Designed Sealants for Ccs Applications

“…These characteristics make it attractive in the construction of future wells for CCS. Dugonjic-Bilic et al (2011) tested the performance of a sealant composition based on CAC with a retarder in a CO 2 environment. They found that the ability of their composition to control water loss is suitable in CCS applications.…”

Associative Microgels, New Self Adaptive Systems to Control Fluid Loss in Well Cementing

“…Many polymeric additives are combined in cement slurry designs to control the properties of the cement slurry and ensure an even placement against the rock formation (Nelson and Guillot 2006, Bilic et al 2011, Cadix and James 2021. Fluid loss and rheology control additives are critical from this perspective to maintain the homogeneity of the slurry, prevent settling and retain water within the slurry as it is being pumped under high differential pressure against a porous rock formation.…”