Abstract
Under conditions of heavy oil thermal recovery, cement sheaths often suffer high-temperature performance degradation and CO2 corrosion. The performance of Class G oil well cement commonly used for cementing, deteriorates significantly at high temperatures and in CO2 environments, which can easily cause accidents. By contrast aluminate cement (CAC), at the same time, has good high-temperature resistance and corrosion resistance. Therefore, this study explored the mechanical properties and permeability of CAC with a high-temperature stabiliser cement slurry system (C1), pure CAC slurry system (C2) and Portland cement with sand cement slurry system (C3) before and after corrosion at 50, 300, 400, 500, and 600°C. The micromorphology, hydration products and pore structure of the cement paste before and after corrosion were analyzed using scanning electron microscopy, X-ray diffraction, thermogravimetry and nitrogen adsorption specific surface area and pore diameter analysis; additionally, the hydration mechanism of CAC under high temperatures and in CO2 environments was explored. The results show that the degree of degradation of the mechanical properties of C1 cement slurry system at high temperatures and under CO2 corrosive environments is significantly lower than that of the C3 cement slurry system. At a curing high temperature of 400°C, the maximum strength of the C1 cement paste reached 36.39 ± 0.37 MPa. The addition of a high-temperature stabiliser improved the mechanical properties of CAC at low temperatures, reduced the formation of C3ASH4 in the cement paste at high temperatures, and improved the strength of the cement paste after high-temperature curing. Compared with the C3 cement slurry system, the C1 cement slurry system had better high-temperature resistance and corrosion resistance and was more suitable for application under conditions of a burning reservoir in heavy oil thermal recovery.
Highlights
With the deepening of oil and gas exploration and development to complex strata, some special oil reservoirs have attracted increasing attention from the petroleum industry, among which the exploitation of heavy oil has become an interesting topic in recent years (Yue et al, 2013)
This is because contrast aluminate cement (CAC) hydration is considerably affected by temperature (Ukrainczyk and Matusinović, 2010; Klaus et al, 2013), and the strength development is unstable at low temperatures
The C1 cement slurry contains high-temperature stabiliser, which promotes the hydration of cement, and its filling effect improves the compressive strength of the cement paste
Summary
With the deepening of oil and gas exploration and development to complex strata, some special oil reservoirs have attracted increasing attention from the petroleum industry, among which the exploitation of heavy oil has become an interesting topic in recent years (Yue et al, 2013). The recovery methods for heavy oil primarily include steam driving and oil layer burning. Burning oil layer is the first thermal oil recovery technology used to develop heavy oil (Askarova et al, 2020). CO2 gas produced after high-temperature oxidation is extremely corrosive in the presence of H2O in the oil layer. The CO2 corrosion in oil well cement is mainly caused by the dissolution of CO2 gas present in the oil layer in water, formation of corrosive carbonic acid (H2CO3), and chain reaction between bicarbonate (HCO3−) and the hydration product of cement paste formed at high temperatures to form calcium carbonate (CaCO3) crystals (Zhang et al, 2021a; Zhang et al, 2021b). The original structure of the cement paste is destroyed, leading to the failure of the cement sheath isolation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
