Steam injection is a fundamental method for enhanced oil recovery (EOR) wherein the wells are drilled and steam is injected to heat the crude oil in the formation to help reduce viscosity and improve oil recovery. The best practices for zonal isolation in the Baghewala field in India are discussed in detail. For desired zonal isolation, cement should maintain long-term stability once placed. Pressure and temperature changes can cause failure within the set cement.
An effective annular seal designed in these wells will be exposed to high temperature, cyclic stresses, and potentially corrosive environments caused by the injection of high-temperature steam into the wellbore. The design stage should go beyond cement placement, compressive strength, and gas-migration prevention. The solution is rooted in the synergy between diagnostic tools and engineered cement systems. Such design methodology was developed to address the challenge of the loss of zonal isolation caused by changes in the wellbore that can stress the cement sheath and cause destabilization at any point during the life of the well.
Specific to the cyclic steam injection in the Baghewala field, a cement system was designed to address the following challenges: Achieving cement returns to surface without fallbackHelping ensure the cement system is thermally stable at the maximum expected temperature (i.e., no strength retrogression, radial cracking, debonding, etc.)Achieving a good cement bond throughout the open and cased holesHelping prevent wellhead growth during steam injectionEncountering different types of formations (halite, anhydrite, sand, and carbonate) in this fractured reservoirUsing a cement slurry designed to avoid strength retrogression of set cement during exposure to high-temperature injection
Proprietary 2D hydraulics, finite element analysis (FEA), and 3D displacement simulators are analytical tools designed for simulations or investigative modeling to simulate fluid properties and slurry placement during operations. Additionally, they help reduce the need for costly remediation and positively affect the long-term cement sheath integrity by assessing and addressing issues before they become problematic.
More than 10 wells were successfully constructed with no issues reported during/after cyclic steam injections, which is endorsed by excellent cement bond logs. This helped minimize multiple potential risks and ultimately maximize production.
The cement design technology associated with FEA simulations and analysis provides the ability of the set cement to expand and contract in sync with the well's fluctuating temperature, reducing stress on the cement sheath. This occurs because these cement systems have approximately the same thermal expansion properties as the steel casing. Unlike conventional cement, particles can expand and contract thermally, thus reducing cement-sheath stress six times more than conventional systems.