Session: 11-04-02 Well Cementing Theory&Practice-2

Paper Number: 104944

104944 - Squeeze Cementing, a Mathematical Model for Cross Flow Filtration 

Squeeze cementing is a process of fundamental importance in oil & gas wellconstruction and production. In this operation, a cement slurry is pumpedinto void spaces in defective sections of a wellbore, to isolate the borehole fromadjacent geological zones and to prevent undesired fluid migration along the welloutside the casing, i.e. repairing cracks, fractures, debonding and microannuli.The pathways that the injected slurry is expected to fill are mainly long andnarrow conduits. The cement slurry in existing oilfield models is usually treatedas a homogeneous fluid, typically represented by a Herschel-Bulkley rheology.However, the small scales of the conduits in squeeze cementing, as well as therange of specialized cements and other fluids used, necessitate considering themulti-phase nature of the injected material.This paper proposes a novel mathematical framework for modeling the squeezecementing process, in which the cement slurry considered as a viscoplastic sus-pension displacing a preflush fluid under a constant pressure. The model takesinto account particle migration effects, maximal packing effects for jamming, andthe local shear-dependent rheology of the suspension. The model allows us toexplore different stoppage mechanisms that combine bulk yield stress effects, en-hancement by the solids fraction, and modifications by particle migration. Themodel considers the transition of a particulate flow into a packed bed formation(above a percolation threshold), together with the possibility of interstitial flowand leak-off. In addition, the rheology of the preflush can lead to interestingdispersioneffects.Our approach is a continuum model based on the Suspension Balance Model(SBM) approach. We use this to model slurry penetration in long ducts as aconstant pressure difference in different scenarios. This work discusses the solidconcentration, the flow, the placement of the slurry, and the stoppage of thesuspension in various scenarios over relevant parameter ranges. We show thatthe transversal distribution of particles in yield stress fluids can be nonmonotoneadjacent to unyielded regions and predict depleted layers close to the wall.

Presenting Author: Mahdi Izadi University of British Columbia

Presenting Author Biography: PhD student

Authors:

Mahdi Izadi University of British Columbia
Ian Frigaard University of British Columbia
Seyed Mohammad Taghavi Laval University