Session: 11-04-03 Well Cementing Theory & Practice

Paper Number: 128385

128385 - Well Leakage: Effects of Centralization and of Controlling Cement Shrinkage 

Primary leakage pathways for surface casing vent flows are widely acknowledged to be via micro-annuli that form along the cement-casing and cement-formation interfaces. These microannuli are quite variable due to irregularities in the primary cementing process, e.g. caused by uncontrolled annulus eccentricity. At the most basic level, eccentricity affects shrinkage azimuthally. Additionally, the wall shear stresses experienced during primary cementing are larger in the wide part of the annulus than the narrow. Wall shear stress governs the mud removal and residual layer thickness around the annulus. Thus, azimuthal variation is a natural occurrence whenever the primary cementing is eccentric. 

Here we combine stochastic and physical models to study the effects of this microannulus variability due to eccentricity, on the squeeze cementing efficiency. We study the effects of different penetrations of squeeze cement slurry into different microannuli. The cement directly affects subsequent gas leakage along the microannulus and hence emissions. We compare distributions of leakage flow rate before and after the squeeze operation. This is repeated for different operational scenarios representing reduced variability of the microannular gap and reduced mean gap. These scenarios might result from better control of annulus eccentricity and from improved cement blends (e.g. controlling shrinkage). We present preliminary results from our analysis.

Presenting Author: Mahdi Izadi University of British Columbia

Presenting Author Biography: Mahdi Izadi

Authors:

Mahdi Izadi University of British Columbia
Elizabeth Trudel University of British Columbia, Okanagan
Ian Frigaard University of British Columbia