Study Compares Methods To Measure Static Gel-Strength Development

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31348, “Comparing Oilwell Cement Static Gel-Strength Development by Ultrasonic and Intermittent- and Continuous-Rotation Measurement Methods,” by Shameed Ashraf, Rahmad H.M. Husin, and Awang Rizalman, Schlumberger, et al. The paper has not been peer reviewed. Copyright 2022 Offshore Technology Conference. Reproduced by permission. _ Cement-sheath integrity preventing interzonal communication is closely related to static gel strength (SGS). API Standard 65-2 puts importance on the critical gel strength period (CGSP) measurement, which begins when the critical static gel strength (CSGS) is developed and ends when 500 lbf/100 ft2 is attained. The three methods accepted in the industry to measure SGS development are continuous and intermittent rotation, followed by ultrasonic measurement. A laboratory-based study is presented in the complete paper that compares these measurement methods. SGS Measurement Methods Continuous-Rotation Device. The continuous-rotation device used for direct SGS measurement is equipped with a pressure vessel capable of maintaining the set temperature and pressure that simulates actual cementing conditions. The paddle drag created by the continuous movement is converted and measured as SGS by means of correlation. Intermittent-Rotation SGS Device. This device keeps the cement slurry to be evaluated in a static condition inside a pressure vessel at controlled temperature and pressure. The device features a torque-sensing arrangement that obtains the intermittent rotating paddle value. This measured torque value is used to calculate the SGS using correlations related to paddle dimensions. Ultrasonic Method. An ultrasonic device can estimate the SGS of a concrete slurry under high-pressure and high-temperature conditions using an acoustic ultrasonic mechanism based on the attenuation of the acoustic wave communicated through the slurry during the hydration process. The ultrasonic cement-analyzer configuration estimates the acoustic speed, whereas the SGS analyzer measures the signal through the slurry. Thus, the SGS analyzer joins an implanted framework that performs computerized gel analysis. When data collection is complete, investigation of the information calculates the SGS values as a function of time. The authors compared the results obtained by this SGS system with information acquired from the tube rheometer device and shearometer and found them to have similar findings. Testing Methodology The methodology included the cement-slurry formula and the preparations followed by the device settings for each assessment type. Two different paddle configurations are used for the continuous-rotation method. As a result, four types of equipment evaluation are made for each slurry, two for the continuous-rotation type, one for the intermittent-rotation type, and one for the ultrasonic type.