High Density Foamed Cement Application for Channeling and Behind-the-Casing Flows Minimization in the Production Zone

This article describes the application of relatively high-density foamed cement for cementing wells in the Volga and Urals region. Good cementing practices with high density or conventional density cement slurry is required to ensure mud displacement in fluid saturated intervals of reservoir formations (Benge et al; 1982). With this requirement met, the cement column should circumferentially cover the annulus at this very interval which is exposed to the highest loads. However, due to limited physical and mechanical properties of conventional cement slurries in both liquid and solid state, in certain cases conventional slurries do not solve the problems encountered by the Customer, namely elimination of annular flow between the casing and cement sheath. High-density foamed cement is considered as an improved alternative to conventional cement slurries, and results in a high quality and durable sealing of gas and oil saturated production zones for the life of the well. Proprietary software and process equipment are used for the mixing of the foamed cement slurry with a variety of foaming properties. This process enables the use of a base cement slurry with higher density (up to 2.1 g/cm3) for delivering foamed cement slurries in a wide range of densities. To avoid possible cross flows behind the casing, pilot tests were conducted, where a conventional cement slurry (1.80–1.90 g/cm3) was replaced with a high-density foamed cement slurry with equivalent density with a foam quality of approx. 10% making the cement sheath elastic with improved adhesion to both the casing string and the formation (Spaulding et al; 2018). Pilot tests, incorporating the cementing of several production casings, were conducted where only foamed cement slurries with various foam quality were used in the entire cementing interval. No conventional (non-foamed) cement systems were used in these cases.