Smart Retarder for Cementing Systems with Accelerated Set and Gel Strength Properties with Potential for Improved Operational Safety

Abstract

Cement retarders available in the market include the traditional lignosulfonates and synthetic copolymers. Commonly, lignosulfonates lack batch to batch reproducibility which hinders formulation consistency. Both lignosulfonates and synthetic polymers will retard the set of cement. However, their chemistry dictates that they also slow down setting time which increases waiting on cement time, thus increasing rig costs. This paper proposes a new smart cement retarder that overcomes these traditional negatives. A number of polymers were designed and synthesized aiming for a chemical able to retard the set of cement while also acting as an accelerator once the cement slurry was in place. These polymers were tested for cement retardation performance using a high-pressure high-temperature (HPHT) consistometer. Static Gel Strength Analyzers (SGSA) measurements were used to determine compressive strength development as well as static gel strength development while curing under downhole temperature and pressure conditions. The new smart cement retarder delivers cement retardation in the 125 - 350°F temperature range and can be used at higher temperatures using a co-retarder. This unique material delivers an accelerated set and attains 500 psi compressive strength very quickly which minimizes waiting on cement time. In addition, this new retarder builds static gel strength rapidly and minimizes gel transition time. Upscaling to field application, the top of the cementing column takes the longest to set. By having this inbuilt accelerator into the system, it allows the top of the column to set as fast as possible gaining the needed compressive strength at the weakest point of the cement column. This should ensure the quality of the cement job in comparison with conventional retarders with significant operating cost savings. The new smart cement retarder will simplify cementing formulations due to its flexibility in dosage range of the retarder within the slurry and improve the quality of the cement jobs. As a result, the proposed smart cement retarder can help with minimizing risk of failures during production and possibly improving safety.

Synthesis and Evaluation of Highly Inhibitory Oil Well Cement Retarders with Branched-Chain Structures

“…After the injection of the cement slurry, gelation of the cement slurry initiated as the hydration reaction proceeded, transforming from a liquid fluid state that could transmit hydraulic pressure to a solid state with measurable compressive strength. − When the static gel strength was less than 48 Pa, the cement slurry could transfer hydraulic pressure. Gas channeling would not occur in the wellbore under overbalanced pressure conditions.…”

Influence of Various Nanomaterials on the Rheology and Hydration Kinetics of Oil Well Cement

“…Low temperatures can cause long wait-on-cement times due to the extended setting time and late strength build-up due to the delay in cement hydration kinetics, which can compromise well integrity. A long wait-on-cement time causes an extended drilling time and, as a result, increased operational cost [13,14]. Mostly, inorganic salts such as calcium chloride (CaCl 2 ) have been used as conventional accelerators; however, these can increase the permeability of the set cement, potentially affecting the robustness of the hardened cement [15].…”