Cemented Horizontal Production Liners in Challenging Conditions
With bottom hole temperatures in excess of 250 oF, and total measure depth exceeding 20,000 feet, cementing production liners in the Williston Basin is a challenge. The target producing intervals are the Bakken and Three Forks formations. These wells are drilled underbalanced using brine to optimize penetration rates. Due to the high temperatures, long laterals, and slim hole design; fluid design is critical to the well.
A spacer system that provides excellent hole cleaning, even in low shear rate environments is a must. Pump rates are minimized during the job due to liner hanger restrictions, and tool operational requirements. The spacer must also be thermally stable and be tested to ensure that excessive fluid static gel strength is not developed when the spacer is static during the job.
The cement must be able to withstand being pumped at high temperatures, sitting static while the liner is set, and then being circulated to surface. The cement must have excellent anti-settling properties to ensure a consistent cement sheath throughout the lateral.
ALTCem’s CD Spacer was optimized to the wellbore utilizing CEMPRO+ modeling software. The spacer’s fluid compatibility was examined in the laboratory, between the both the spacer and well fluid as well as the spacer and cement. This was done to ensure there were no undesirable changes in rheology when the fluids were intermixed.
ALTCem P50-31 is a uniquely designed cement with a post-set expansion agent for excellent bond, silica flour to combat strength retrogression, and a synthetic cement retarder to provide optimal cement placement. Its low fluid loss prevents dehydration when circulated past the liner hanger assembly. To ensure successful cement placement and job completion, the cement was designed to have a working time that allowed the cement to sit static for one hour without a significant increase in fluid viscosity.
A Williston Basin operator switched to ALTCem, and successfully completed an entire pad with cement circulated off the liner top on each well. The volumes circulated back were indicative of 100% drilling fluid removal, ensuring a complete cement sheath and proper zonal isolation.