Tailored Cement Systems with Enhanced Mechanical Properties Designed to Eliminate Sustained Casing Pressure in Development Wells

Oil and gas wells in the Barmer fields (Rajasthan, India) typically require a timeframe of five to seven days for well completion. The cementing process includes a wide range of challenges, including low fracture gradients, lost circulation, and sustained casing pressure (SCP). Because the baseline challenges were identified from cementing through completion phases, the target was to design a tailored, gas-tight, resilient, lightweight cement system to address wellbore integrity issues. The modelled simulations showed the rheological behaviour, equivalent circulating density (ECD), pumping rates, and maximum surface pressure, whereas the 3D model predicted the sweep efficiency of the pumped fluids. Elastomeric materials were incorporated into the designs to counter the stresses induced during well activities. Advanced laboratory testing was performed to ensure that these lightweight slurries met the requirements to address multiple issues by exhibiting suitable mechanical properties (based on finite element analysis (FEA) simulation output), gas-tight behaviour, and lost circulation curing capabilities. Three stable cement slurries were designed with the available set of additives to simplify operations. Elastomeric additives altered the mechanical properties of the set-cement sheath to provide greater resilience than conventional cement. More than 22 wells were cemented with a varied range of densities that were designed/modified with the available chemical additives, based on the severity of the depleted reservoir zones. To ensure completion of the full process (ranging from design to completion of the cement job), multiple verifications/checks were implemented. Quality control played an important part, and all new bulk blended batches were tested for mechanical properties. The wide range of densities and sensitivity tests of the cement system assured reliable implementation. The successful design and cemented completion resulted in the reduction/elimination of sustained casing pressure. SCP, which may have been a safety hazard, influences production rates and, in the worst case, could compromise the structural integrity of the well. Results indicated that more than 90% success was achieved in the targeted segment of the field, in terms of SCP in the B-annulus (after cementing and perforation of the wells) where the values were well below their maximum allowable limits. The returns to surface, excellent cement bond logs, microseismogram, circumferential visualization, and zonal isolation under lost circulation conditions further justified the performance of enhanced slurry designs.