Primarily intended for use in the oilfield industry, the OFITE Static Gel Strength Measurement Device (SGSM) is designed to measure the gel strength development of cement after pumping operations have ceased. The unique design of the SGSM, combined with the advanced data acquisition software, provides users with a true mechanical static gel strength measurement.
The SGSM is an accessory for the OFITE UCA (Ultrasonic Cement Analyzer). When used together, these two instruments give users a complete picture of the setting characteristics of cement slurries. Having the ability to both condition and analyze cement slurries allows the SGSM to mechanically measure the gel strength development rate of slurries that are subjected to a comprehensive range of downhole conditions; up to a maximum pressure of 20,000 psi and a maximum temperature of 204°C (400°F).
The classic van bob configuration of the SGSM conditions the cement slurry at speeds up to 150 RPM, while still supplying the necessary mixing energy defined by industry standards such as API and ISO. Users can set multiple temperature ramps and conditioning speeds to accommodate different testing environments.
After conditioning the slurry, the SGSM goes into a static period while gel strength builds. Then the measuring period begins and the paddle rotates at 0.01 rpm (0.001 rad/sec). A transducer in the head assembly measures the amount of resistance supplied by the gel formation. The user can adjust the static period, measuring period, and the rotational speed during the measuring period.
Static Gel Strength is measured at user-defined intervals throughout the test and recorded in an Excel Spreadsheet. At the end of the test, the software generates a graph of gel strength formation over time. The software will then interpolate the data and draw a trend line through the recorded gel strength peaks. The software uses this data to calculate the time it takes for the gel strength to build, also known as the transition time.
The SGSM was designed to be maintained with simple hand tools. Reducing the amount of work required to maintain the system encourages users to follow a regular maintenance schedule, ensuring that the test results are consistent and reliable.
The key to the success of the OFITE SGSM is in the simplicity of its design. When coupled with the capabilities of the associated UCA to measure the compressive strength of slurries, the OFITE SGSM is able to provide a complete picture of the setting characteristics of cement.
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Patent No. 9,612,232.