1. Produced Water Reinjection Performance Joint Industry Project
TerraTek, Inc.
Triangle Engineering
Taurus Reservoir Solutions (DE&S)
E-first Technologies
Advantek International

2. A simple damage model for matrix PWRI injection (in soft sands and in general)
(Tony) Settari, D.A. Walters
TAURUS Reservoir Solutions Ltd.

3. Goal: To see if simple description of plugging can be developed which
Is capable of matching most matrix data
Is based on measurable parameters (as opposed to “type curve” matching) which can be related to lab data
Can simulate (or predict) effects of workovers
Is suitable for simulation models
Deliverable: Spreadsheet model for analysis of P, Q vs time data for inclusion in the Toolbox.

4. Model assumptions Steady state flow
Simple permeability vs throughput relation
Radial, currently single layer model
Piston-like injected water displacement
Fixed outside pressure and radius
Not specific to soft formations

5. Permeability model k/k0 = 1 /[ 1 +  (V/A )n]
k0 – initial (undamaged) permeability
K - damaged permeability
V - cum volume passing through area A
 - parameter (damage strength)
n - parameter (exponent)

6. Effect of  on permeability decline due to damage

7. Effect of n on permeability decline due to damage

8. Overall computational model

9. Data input and assumptions
Input both BHIP and rate, + basic reservoir data
Model honors BHIP (interpolates between entries) and calculates injection rate Qic.
Match the observed rate by changing damage parameters

10. Data input and assumptions
Workovers (acid treatments, filter changes) are described by:
Time and size of the job
Effectiveness (fraction of perm damage removed)
Skin and damage parameters after the job

11. Output from the model

12. Output from the model

13. Experience – Gulf of Mexico
5 wells, data from Wennberg (also SPE 38180)
All wells can be matched individually very well
Reasonable consistency in parameters
Ability to model workovers is the key

17. Experience – Elf 3 Initial time periods only
Some indication of fracturing based on skin needed
Good matches of both wells

19. Another data (anonymous)

20. Conclusions The model is surprisingly realistic, easy to match
Can be incorporated into more complex numerical simulators
May be easily made even more realistic:
Variable reservoir pressure
Multilayer model
Driven from rate and predicting pressures
Make physics more realistic (stripping of PW of solids), etc.
Fracture conditions?
May be worthwhile to do additional work