Flood Management with floodOPT

For many mature fields, significant optimization potential may exist without introducing new wells. The goal is to achieve patterns that are more balanced and minimize fluid recycling. However, until now there has been no easy way to identify injection patterns or areas of inefficiency beyond standard surveillance and tie back to reservoir simulation. FloodOpt is a tool that assists the reservoir engineer to manage large water floods by re-balancing well rates from streamline-generated data.

Prices for the history matching add-on to studioSL, and our other products can be found here.

For the theory behind floodOPT see Thiele, M.R. and Batycky, R.P.; "Using Streamline-Derived Injection Efficiencies for Improved Waterflood Management," SPEREE April 2006, Vol 9, No 2, pp187-196 (SPE84080-PA).  Click here for the original 2003 presentation.

Features

floodOPT is based on either a surveillance or simulation run.

  • Any number of producers and injectors can be included along with individual well rate targets.
  • Field level water injection or oil production target.
  • Automatically pass rate targets back to 3DSL (or Eclipse) for forecasting in a simulation model.
  • Export rate targets to Excel.

From Streamlines to Flux Pattern Maps to Injection Efficiencies

One powerful aspect of streamline simulation is the ability to create a snapshot of how the reservoir is connected at any instant in time, and how much fluid is allocated between injector/producer pairs. Because a 1D transport problem (e.g. water displacing oil) is solved along each streamline connecting an injector to a producer, it is possible to related injected water volumes to off-set oil production down to a well-pair level. This novel information leads to the idea of injection efficiencies, which in turn can be used to manage flood more effectively.

Streamlines between injectors (blue) and producers (red) at time T.

Flux Pattern map derived from the streamlines.

 

Since a transport problem is solved along each streamline connecting an injector-producer pair, the injection efficiency of a well pair can be defined using the individual phase rates known at either end of the bundle of streamlines between the well pair. The injection efficiency, which is defined simply by as the ratio of off-set oil production to water injected. Note the following about the injection efficiency:
  • There is an injection efficiency for each well pair (connection) as well as for each active injector in the field. The offset oil production (numerator) must be calculated using the information from the well allocation data supplied by the streamlines. On a per-injector basis this is the IEplot within studioSL (left).
  • The injection efficiency defined in Eq. 1. is a ratio of rates and therefore represent an instantaneous metric. However, the equation applies just as well to cumulative volumes (conformance plot).
  • The definition of an efficiency can be extended to any type of injected and produced volumes and therefore can be used for gas injection as well as WAG injection.

Injection Efficiency Definition.

Flux Pattern map derived from the streamlines.

Once the injection efficiency is known for each well-pair, water can be re-allocated towards efficient connection and removed from more inefficient once. The strategy is implemented via a weighting function that is user defined (for details see: Thiele, M.R. and Batycky, R.P.; "Using Streamline-Derived Injection Efficiencies for Improved Waterflood Management," SPEREE April 2006, Vol 9, No 2, pp187-196.)

 
floodOPT Workflow within studioSL

studioSL offers a convenient way to apply floodOPT to a 3DSL run for flood management purposes and forecasting. The starting point is a 3DSL simulation with an acceptable well-level history match (see more about history matching "here). The well-level history match is an important component of any reliable forecast. Since floodOPT uses well-pair injection/production information, an acceptable well-level history matching is an important pre-requisite for applying the workflow. The basic steps in a floodOPT workflow are:

  1. Select a 3DSL base run (history matched) from which to start the floodOPT workflow.
  2. Select wells for which rate changes are desired. Set constraints as necessary (min/max injection/production targets). Set parameters for the weighing used in translating well-pair efficiencies into rate increases/decreases.
  3. Calculate new rates to use for forecast run.
  4. Decide on time step to take before updating target rates again. Return to 2.

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1) To create a floodOPT project, right-click on a 3DSL simulation node in the projects window, and then select the New floodOPT Project action off of the drop down menu.
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2) R-click on the workflow project node and select the Open action to choose wells for which new target rates are to be calculated. Optionally, set min/max well rate constraints and/or field constraints as well as the specific form of the the weighting function used as part of the floodOPT algorithm.

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3) The Plot Rates action runs floodOPT and plots old and new rates as either a bar plot or a cross plot. It also possible to view the weighting function.
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4) To automate the procedure of creating new rates, including them in to a 3DSL input file, re-running 3DSL, creating new rates again...etc, studioSL offers an automatic way of forecasting using floodOPT. Decide on the length of the forecast period, how often target rates are to be updated using floodOPT, and how large of a time step 3DSL should take.
An example workflow
The example that is outlined, step-by-step in the user manual, is available for download here.