Investigation of Cement Slurry Design and Sources of Quality Impacts in High Rate Gas Wells (A Case Study)

Cementing oil and gas wells is a critical stage of well completion. Cement integrity can be frustrated if the slurry design does not meet the specific requirements of the well. A poor cementing job can fail in providing the required isolate zones and induce costly remedial cementing operations. Improper isolation between producing zones can lead to ineffective stimulation treatment, mislead reservoir evaluation, annular communication with unwanted well fluids. Parameters such as pumping schedule, casing standoff, pre-flushes and cement slurry design have significant effects on zonal isolation. In one of Iranian offshore gas wells 7 liner string was run and cemented in high pressure-high temperature (HPHT) down-hole condition. The cement sheath was evaluated with ultrasonic imager tool and cement bond log. Having closely evaluated the logs, poor cement bonding in the annulus was approved and an investigation of sources of quality impact was commenced. This article presents a narrow analysis of the tests, evaluations and improvements made which led in a quality jump and also examines the effects of detailed considerations in cementing a high pressure-high temperature gas well, such as slurry properties. As a consequence, the design has to be selected according the requirement otherwise several pitfalls may occur after cement job.

Keywords:

Cement sheath , Cement Bond Log , Zonal isolation , HPHT Wells , Producing zone