Achieve complete zonal isolation—verified with bond logs—and no sustained casing pressure (SCP) for the 8-in hole section of a high-temperature exploration well.
Drilling with water-based mud (WBM) left severe washouts up to 15 in, which reduced mud removal efficiency. In addition, centralization was limited, and the exploratory nature of the project meant the frac gradient was unknown, leading to uncertainty about pumping rates. A prior well cemented conventionally under similar conditions in the same reservoir had a poor bond log.
The proposal included CemPRIME Scrub engineered scrubbing spacer enhanced with surfactants and mutual solvents to help thin and remove mud in the washouts; a formation integrity test (FIT) to assess safe cement placement rate; pumping at a high displacement rate (1,400 L/min as determined from the FIT); minimal mud yield point of 14 lbf/100 ft2.
The spacer train and cement were pumped as designed. Top of cement reached the planned depth with a successful 3,000-psi pressure test and excellent cement bond across the section.
For a cementing operation in an exploration well with severe washouts, CemPRIME Scrub engineered scrubbing spacer with chemical wash and good cementing practices helped Sonatrach achieve excellent bond logs with top of cement as designed.
