Over 25000 oil and gas wells have been drilled in British Columbia. Since 2005 these wells have been increasingly gas wells, drilled horizontally and hydraulically fractured in the producing zone. Many of these wells leak and the primary issue is what is called a surface casing vent flow (SCVF). Here the gas finds a pathway from the horizontal part of the well upwards within the vertical surface casing to surface. Trudel et al. (2019) report that 28.5% of BC wells drilled from 2010 to 2018 report SCVF. Leakage occurs due to a poor seal of the cement in the annulus, which may be caused during or after placement. Therefore, all activities planned within the wellbore life should be carefully considered when designing a cement program as well integrity can be compromised during cement placement, well work-over operations or production. Thus, studying the sealing mechanism (primary cementing) is a topic of significant importance.Given the difficulties of downhole measurement/evaluation, many computational simulation studies of primary cementing fluid flows have been conducted. Based on the assumption of a narrow annular gap, Bittleston et al. (2002) reduced the problem to 2D and developed a gap-averaged model. Maleki et al. (2017) extended this model to turbulent and mixed flow regimes. Such models have been used extensively, both academically and industrially.&nbsp;Nevertheless, the geometry of a real well can be far more complicated, e.g. washouts and other irregularities. Thus, 3D simulations are useful to understand particular features of displacement flow. Here we present a numerical study of laminar miscible displacement flow in narrow, vertical, eccentric annuli.&nbsp;We have run a series of 3D numerical simulations in which the full Navier-Stokes equations and concentration advection equation are solved; a Volume of Fluid (VOF) method is used to capture the interface between the fluids.&nbsp;Comparisons of 3D against 2D gap-averaged (2DGA) model results show a range of interesting different phenomena, e.g. static layers, dispersive spikes, and instabilities. The predictions of 2DGA model are the same as the 3D results to a degree. In particular, they are consistent with each other well regarding of the evolving process, interface shape, etc. However, the main difference with the radially-averaged concentration colormap arise from dispersion on the scale of the annular gap: present in 3D but not captured in the 2D models. The differences are particularly evident close to the interface of fluids. From the recent research of Renteria et al. (2020), a variety of dispersive effects are the main discrepancy between experiments and 2DGA results as well. We give representative examples of the discrepancy and suggest methods for improvement of the 2DGA model.&nbsp;References:&nbsp;S. Bittleston, J. Ferguson and I.A. Frigaard, J. Engineering Mathematics, 43, pp. 229-253 (2002).A. Maleki, I.A. Frigaard, J. Eng. Math., 107, pp. 201-230, (2017).E. Trudel, M. Bizhani, M. Zare, I.A. Frigaard, J. Petrol. Sci. Engng., (2019).A. Renteria, I.A.Frigaard,&nbsp;J. Fluid Mech,&nbsp;905, (2020).

3d Simulation of Surface Casing Cementing: Dispersion Effects

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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