Several challenges are encountered when multi-zone intelligent water injection wells are to be deployed in a field with high contrast in well parameters such as injectivity indexes between individual zones or flow units. Some of these challenges include; selection of a common operating point (tubing intake pressure), estimating effective flow coefficients for interval control valve (ICV) choke settings, determining differential pressures that must be addressed through the ICV choking capability for individual zones and outlining an operations philosophy consistent with the objectives of the well.
Several authors have used Nodal analysis techniques and attenuated Inflow Performance Relationship (IPR) in designing and evaluating the performance of ICVs for single and multi-zone producing and injection wells. This paper combines this technique with sensitivity analysis to estimate flow coefficients for individual zones and investigates which control, surface or subsurface, is most suitable for a multi-zone water injection well for a given sample set of field data.
This paper outlines a number of set points and parametric optimization guidelines that can be used to determine optimal surface and subsurface settings for injection and flow control in intelligent water injection wells. Nodal analysis and attenuated IPR techniques applied to sample field data with high contrast in well zonal injectivity indexes indicates that for a certain range of field values and injection objectives applying only subsurface control (choking zonal ICV) could result in very high pressure drop across zones and cause equipment failure without providing superior injectivity.
Applying sensitivity analysis demonstrates that a blend of well head and ICV control can maintain desired injectivity and result in lower pressure drops that preserve equipment life. Reducing pump pressure typically reduces overall injectivity. Analysis can be extended to cover a wider range of uncertainties such as changes in fracture propagation pressure over time, etc., but these issues are not fully addressed in this paper.