Well cementing and integrity

We study all aspects of well cementing: primary cementing, plug cementing, squeeze cementing, for both construction and decommissioning. Although our core expertise is fluid mechanics, we also study applied mechanics topics and well leakage: causes, statistics and prediction. The overall aim is to develop complete knowledge and engineering know-how that can be targeted at environmental improvements in industrial performance, both for new wells and in the decommissioning of old wells.


Consequences of poor well integrity do not respect national and jurisdictional borders. We work collaboratively with active research groups, in Canada and internationally. Our research has received sponsorship from federal, provincial and industrial sources including the following: NSERC, SLB, BCOGC, BCOGRIS, PTAC, CNRL, Sanjel, Geonomic, Norwegian Research Council, Sintef, CFI/BCKDF. Transparent high quality public research is needed to understand complex processes. Solving problems and improving performance are multi-faceted, ranging from the deeply technical to managerial and behavioral. Collaboration with industry, regulatory bodies and other interested stakeholders is needed to affect change.

Primary cementing

In primary cementing we have extensively studied displacement flows in annuli, looking at the effects of standoff (eccentricity), inclination, casing movement flow rate and fluid rheology on the ability to remove drilling mud and steadily displace annular sections.

  • We have developed two dimensional gap-averaged (2DGA) models of annular cementing displacements in laminar regimes, and analogous models for turbulent and transitional flow regimes. In addition, we have developed simplified models for laminar flows of foamed cementing in annuli.
  • We are currently supplementing our laminar 2DGA models with detailed three dimensional 3D studies and are improving the 2DGA approach to model gap-scale dispersion.
  • We have modeled downward displacements in the casing, over all flow regimes and including the effects of buoyancy and rheology. The aim of all this is to predict the degree of mixing between 2 fluids, in the absence of a plug being used.
  • We have developed estimates for the speed of the displacement front and the displacement efficiency, in various situations.
  • We have studied pipe flows where a fluid with large yield stress is displaced by a much less viscous Newtonian fluid, e.g. water though gelled drilling mud. This leads to residual layers on the walls and various instabilities.
  • We have looked closely at displacement flows in simplified sections of the annulus (plane channels), to study the formation of residual mud layers due to mechanical factors, i.e. formation of a wet micro-annulus.
  • We have investigated the effects of washouts on annular cementing flows, both in the mud conditioning and removal phases.
  • We have studied displacement flows in irregular sections of horizontal data using caliper data to give typical metrics for the unevenness and using an elliptic description for the borehole cross-section.
  • We have studied fluid driven mechanisms for gas invasion to occur during post-placement and studied how invasion can be influenced by cement rheology.
  • We have looked at the possibility of using chemically reactive spacer systems to improve displacement efficiency through the instigation of local instability and mixing.
  • We are exploring the effects of casing rotation on improving displacement in horizontal wells
  • We are exploring systematic irregularity in annuli, e.g. axially periodically varying geometries
  • We are exploring density unstable/reverse circulating cementing.
  • We are modelling casing centralization, in order to predict

With our experimental setup, we have:

  • Studied Newtonian and non-Newtonian laminar displacement flows down inside the casing, over a range of inclinations.
  • Extensively studied horizontal laminar displacements flows with Newtonian and shear-thinning fluids.
  • Extensively studied vertical laminar displacements flows with Newtonian and shear-thinning fluids.
  • Performed experiments on density unstable/reverse cementing
  • Studied turbulent displacement of yield stress fluids by washes and viscous spacers, in strongly eccentric horizontal annuli.
  • Studied the effects of a cuttings bed blockage on the above turbulent displacement flows.
  • Performed experiments with a rotating inner pipe to explore the effects of casing rotation on displacement.
  • We are currently refitting the laminar annulus in order to study systematic borehole irregularities (ellipticity and axial periodic variations)

Remedial cementing and well leakage

  • We have critically reviewed P&A practices and associated statistics in BC
  • We have reviewed the incidence of well leakage in Western Canada, in particular BC where wells drilled in the past 20 years are mostly similar.
  • We have developed a well leakage model that considers different leakage pathways to surface and calibrated this using leakage data from BC. A dry (shrinkage) micro-annulus model that varies in aperture both along the well and azimuthally, is able to effectively represent the distribution of leakage in the intermediate range of rates (1-10 m3/day). Higher leakage rates result from wet micro-annuli and channeling defects during cement placement. Super-leakers (>100 m3/day) likely require some combination of these effects, together with other unexpected operational anomalies, e.g. shallow gas, low top of cement, etc.
  • We have critically reviewed P&A practices and associated statistics in BC
  • We have reviewed the incidence of well leakage in Western Canada, in particular BC where wells drilled in the past 20 years are mostly similar.
  • We have developed a well leakage model that considers different leakage pathways to surface and calibrated this using leakage data from BC. A dry (shrinkage) micro-annulus model that varies in aperture both along the well and azimuthally, is able to effectively represent the distribution of leakage in the intermediate range of rates (1-10 m3/day). Higher leakage rates result from wet micro-annuli and channeling defects during cement placement. Super-leakers (>100 m3/day) likely require some combination of these effects, together with other unexpected operational anomalies, e.g. shallow gas, low top of cement, etc.
  • Squeeze cementing: we have developed a physical model for the penetration of a cement slurry into a variable aperture micro-annulus, where the arrest is caused by the slurry yield stress. This model has been coupled with our stochastic model for the micro-annulus thickness. Individual perforations show a large variation of penetration behaviors. We have introduced different metrics to describe this variation: minimal penetration radius Rmin, void fractions H1,void and H3,void
  • Using a stochastic approach we have modelled different squeeze cementing operations in typical BC wells, predicting the distributions of Rmin, H1,void and H3,void
  • Taking a characteristic BC well we have also been able to predict leakage rate distributions both before and after a given squeeze operation.
  • We are developing new physical models of the squeeze operation, including particle migration in the cement slurry, the transition from slurry to filtration/packing in a perf, pressure effects of the wellbore, particle jamming and capillary pressure effects.
  • In plug cementing, we have studied the stability of plugs that are set off-bottom addressing the question of what physical properties are needed in order for viscous pills and cement slurries to remain stationary after placement with a less dense fluid beneath.
  • In near horizontal wells we have estimated the distance that a plug may slump. We have performed similar estimates for horizontal annuli, e.g. a chemical packer
  • We have performed experiments to study the post-placement stability of cement plugs set off-bottom. These experiments confirm that the design criteria for static stability developed earlier are valid.