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

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

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.

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

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)

Effect of  on permeability decline due to damage

Effect of n on permeability decline due to damage

Overall computational model

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

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

Output from the model

Output from the model

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

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

Another data (anonymous)

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