In-depth water simulation strategies

Abstract

In-depth water diversion is a chemical EOR method that has been winning acceptance over the last years because of several reasons. One of them is the fact that sodium silicate, active component, is considered a green chemical. Moreover, this component has shown the ability to generate thermally activated plugs at far away distances from the wellbore improving oil recovery. This work aims to give further understanding of how to approach the simulation of silica gelation kinetics, by integrating experimental data to a novel simulation approach for this process and how it can be applied to industry needs.

The simulations are performed using a thermal-compositional reactive formulation in Stanford’s Automatic Differentiation General Purpose Research Simulator (ADG- PRS) based on a fully implicit approach. The motivations for selecting this method is the strong coupling between chemical and flow variables linked to drastic changes in permeability profile and the absence of methods in literature addressing this subject consistently. The implementation of the silicates reaction assumes an oligomerization reaction through a fourth-order reaction rate describing the deposition of solid silicate along the reservoir. The methodology followed in this document is structured in three chapters: calibration and study of kinetics, comparison with a previous study and field applications.

Validation of the model displays a match between core experiments and simulations. Results from this section suggest a strong dependence on upscaling of the reaction rate constant and encourage further research on this topic. Study of kinetics, from a simulation perspective, reveals that the process timescales and local domain play a major role in resolution. Numerical convergence of the solution was achieved for a two-meter grid along the flow direction and simulation timesteps below 1 day. Results from comparison with previous works show great differences in the formation of the in-depth silicate plug. The prescription of the equation as a solids deposition proposes more realistic results in terms of plug distribution and activation. Moreover, cumulative oil production improvements rounding 7% over a fields file, account for realistic figures. The application on channeled subsurface confirms the possibility of implementing the process on more realistic subsurface. A clear optimization of the water sweep around the plugged zones is evidently leading to improvements, rounding the percentage mentioned above. Contrary to expectations, after introducing a blockage, no major variation in flow towards producer’s perpendicular to the main channel are observed. In the geothermal applications, the generation of a plug helps to increase the thermal breakthrough time, extending the geothermal doublet lifetime.

The overall process has proved to be sensitive to parameters such as silicate concentration in solution, the volume of a pre-flush batch and the volumes of silicate solution injected. These factors give room for optimization of the process for future studies.