High Frequency Pressure Based Downhole Monitoring System Implemented in Mexico Land Assets

Abstract The positive pressure increase effect from a displacement plug hitting the landing collar is often a signal for the end of cement displacement. Occasionally the plug is damaged by frictional wear, chemicals, and temperature, however displacement can also be affected by the mud compressibility, a complex value dependent on the downhole conditions (rheology, density, temperature, etc.) and pump efficiency, which are never truly 100 percent efficient. Using a high frequency pressure monitoring system, it is possible to detect the location of the wiper plug when passing through each casing joint as it produces a pulse that can be detected in real time, even as the displacement plug fins are worn away with friction. Controlling displacement volume is crucial for the cementing job as overdisplacement of cement can complicate the isolation of the string cemented due to contaminated cement pushed up into the annulus and under-displacement may result in extra drill out time and therefore nonproductive time in both scenarios. Testing of a novel cement displacement method by measuring pressure at high frequencies to see the pulses generated by the displacement plug passing through the casing joints consisted of validating the technology to an accuracy of one casing joint or around 12 meters. The Mexico Land analysis has shown that on average, 45 m of cement is left above the retention collar, or 45 meters of cement that was never planned to be left inside the casing. The technology demonstrated great success where casing joints have a positive internal diameter change. By combining the measurements of displacement volume and pressure pulses produced as the plug passes through a casing joint, a more accurate measurement of the wiper plug location is achieved versus conventional displacement methods.