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

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.

Research Status of Synthetic Oil Well Cement Retarder

: Oil well cement retarder is an additive that can extend time for thickening cement slurry, which can ensure the safety of cement. At present, the oil well cement retarder is mainly composed of synthetic materials, which are mainly divided into three major categories: compound polymer, AMPS polymer and non-AMPS. In this paper, the research status of synthetic oil well cement retarder in recent years is reviewed, and its shortcomings and development trends are analyzed. It is pointed out that the shortage of synthetic retarder mainly lies in problems, including large temperature sensitivity, small temperature application range, abnormal thickening curve, great influence on high temperature settlement stability and cement stone strength development. The development direction of oil well cement retarder is mainly focused on developing intelligent retarder and degradable retarder to meet the cementing needs of oilfields and ensure cementing effect increasing steadily.

PURIFICATION OF PHOSPHOGYPSUM FOR USE AS CEMENT RETARDER BY SULPHURIC ACID TREATMENT

Phosphogypsum is a by-product of the wet phosphoric acid production. In this study, chemical compositions of phosphogypsum waste (PG) in Hai Phong diammonium phosphate plant (DAP1) and Lao Cai diammonium phosphate plant (DAP2) in Vietnam were surveyed for the purpose of gypsum recovery by P2O5, F removal to meet TCVN11833 for use treated gypsum as cement retarder. Studies of impurities P2O5, F, TOC removal by sulfuric acid 10 % at 28 0C was presented. The results found that the combination of a low concentration of sulfuric acid treatment, washing, lime neutralizing, and thermal treatment was successful in Phoshogypsum treatment for use as cement retarder. The cement test proved that treated PG could partially replace natural gypsum as a retarder.Keywords: phosphogypsum treatment, phosphorus pentoxide removal, calcium sulfate transition phase, cement retarder.

Synthesis and retarder mechanism study of a novel amphoteric composite high temperature-resistant retarder for oil well cement

An amphoteric composite polymer (hereinafter referred to as PAADM) as high temperature-resistant cement retarder was prepared byin situintercalated polymerization method with AMPS, AA and DMDAAC as monomers, and modified montmorillonite as an active polymerization filler.