RETINA Simulation Case Studies



Model Description
The case is an Iranian offshore oil field located beneath the Karg island in Persian Gulf. Production from this field started in 1972. The history matching model of this field was delivered to ESTD in an agreement between IOOC and ESTD aimed at validating and certifying RETINA Simulation™. The model is dual porosity with some single porosity layers (DPNUM). It is an under-saturated reservoir with a moderate aquifer as its boundary condition. during these years 8 oil producing wells are activated. More details about the model are described at the Table. The model is simulated with RETINA SimulationTM and results from “ECLIPSE E100 2010.1 32-bit” are used for comparison and validation. The two simulators were allowed to select their own time steps as they see fit and no special tunings were defined. The main restriction on time step size is the frequency of input history rates which is almost every one month. The results from these two simulators for this case study are compared from two aspects: accuracy and speed.

Model Type Black Oil dual porosity with DPNUM
No. of active cells 211410
No. of active wells 8
Model run duration 24 years
Special model Black Oil dual porosity with DPNUM


Accuracy
Figure 1 and 2 show the comparison between RETINA Simulation™ and ECLIPSE 100™ for one of the wells only for the reason of confidentiality of data. All the results match almost perfectly and this is the case for all the other wells and vectors. The selected well is the first producing well and hence has more results through the simulation.

Simulation result Max. of relative difference
Field average pressure (FPR) 0.051%
Field oil production rate (FOPR) 0.000025%
Field gas production rate (FGPR) 0.5%
Field water production rate (FWPR) 4.7%
Wells gas production rate (WGPR) 0.83%
Wells water production rate (WWPR) 5.1%
Wells bottom-hole pressure (WBHP) 0.98%
Wells average block pressure (WBP9) 0.78%
Aquifer rate 2.7%


Speed
As it is seen in figures 3 and 4, RETINA Simulation™ can take larger time steps in this model and therefore it has less simulation run time. RETINA Simulation™ is usually more stable and can get larger time steps in the case of dual porosity models with tight matrices and high conductive fractures. This is due to a better linear solver pre-conditioner used in RETINA Simulation™ . Hence, in this case (as a typical dual porosity model), we expect a better performance compared to ECLIPSE 100™. More detail on speed comparison is explained in the following sections. 1 - Simulation elapsed time in seconds. This is the time taken to run the model from time 0 to the specified simulation time (days). Figure 3 shows that RETINA Simulation™ has less elapsed time and can run the model almost two times faster than ECLIPSE 100™. RETINA Simulation™ takes 16615.70 seconds where ECLIPSE 100™ needs 27185.98 seconds to run the entire model. RETINA Simulation™ solves the model with 957 time steps and 5499 non-linear iterations and ECLIPSE 100™ with 7588 time steps and 42587 non-linear iterations. 2 - Time step size Figure 4 is the comparison of time step size between RETINA Simulation™ and ECLIPSE 100™. It is clear that the report step size (time at which the well rates are entered for the model) is the limiting factor for time steps in RETINA Simulation™ in most of the time steps; whereas ECLIPSE 100™ faces trouble taking large time step in the size of report step size. Average size of time steps in RETINA Simulation™ is 21.69 days where ECLIPSE 100™ has the average of 5.34 days time steps. From the accuracy comparison it is evident that, large time step sizes do not lead to higher time truncation error in RETINA Simulation™.

More Cases
Open the RETINA Simulation™ case studies from here . Following reservoir types as case studies are available.
  1. Tight Carbonate
  2. Conventional Field
  3. Heterogeneous Sandstone
  4. Naturally Fractured
  5. Layered Structure