How to initialize the dynamic model with tilted OWC surface while achieving stability condition
In summary, there are many oil reservoirs have been reported with tilted OWC surfaces that are confirmed by both water saturation log profiles and downhole pressure managements. Nevertheless; due to simulation tools limitations, many of those reservoirs their dynamic models have been designed either to eliminate deep oil saturation from the volumetric calculation or its introduced as immobile oil saturation to achieve stable dynamic model.
Even though there were alot of discussions about the deep oil if its mobile or immobile, and why should be introduced into dynamic models? However, from reservoir engineering point of views, that deep saturation oil would be an excellent subject for EOR’s projects, which need to be captured in dynamic/sector models for further assessment and studies.
Study Options:
Most of the old subsurface studies models are ignoring the deep oil saturation volume in view its wasn’t simple to addressed it into dynamic models, although it has been volumetric calculated in the static models. Furthermore; most of those studies dynamic models were initialized with shallowest FWL’s flat depth surfaces where whatever below that FWL’s flat depth surfaces have been removed from dynamic model STOOIP’s calculation.
Nevertheless, in the recent studies there were attempts to introduced deep oil volumes in the dynamic models by using negative drainage capillary pressures curves (Pc’s curves) to initialize dynamic models with kind of enumeration approach to allows simulators to calculate deep oil volumes as part of total STOOIP’s, but that deep oil volumes has been designed to be immobile i.e. (by using residual oil saturation values close to oil saturation, which does not allow any drops of the deep oil to be recovered with objective to achieve stable dynamic model)
New Proposal:
Following to those problems, a new concept to initialize dynamic models at stable equilibrium condition with tilted OWC’s surface while present deep oil as mobile fluid has been tested through “FAST-TRACK approach to design Pc's curves” that is showing excellent results based on readjustment capillary pressure curves in very practical way.
The used model was initialized using tilted OWC surface with 173 ft in elevator height and ran it for 200 years as stability test. the model reported with 2.5 Billion STOOIP and average permeability of 100 mD. It's worth to mentioning that, all the static model drops of oil saturation was captured in dynamic model without using negative capillary pressure curves. The dynamic model showed only 0.6 pai change in pressure historically with running time steps of 1 year continued i.e. (very stable model).
Consultant Reservoir Engineer
6 年Depending on the precise reason for the titled contact, I can see at least two other potential approaches that might achieve this. First, it would be possible to literally simulate the tilt by applying a numerical aquifer to the edge of the model, and then running the model as a restart of this case as the point of initialisation.? Second, it is also possible to define saturation together with pressure directly in initalising the model coupled with quiescence.? A more complex saturation model can be used to calculate the saturation directly in the static model and it can be taken across to the dynamic model. I have seen both approaches adopted on carbonate fields so perhaps you can elborate on why this approach is better or preferred than either of these other two?
Audit/Finance chez Audit
6 年ya si djamel il faut d'abord la stabilité moral puis chercher achieving stability.Bonne journée?
Sr. Geologist & Geomodeler | Reservoir Characterization, Geomodelling
6 年Thanks for sharing, such kind of experiments leads to new understanding. it is important to first differnetiate between FWL and OWC before concluding a tilted OWC. Undetected fault /stratigraphic boundary can give apparent tilted OWC. Mis-interpretation of paleo water contact as present day contact etc.?
Oil & Energy Professional | Geoscientist | Exploration | Development | Upstream | Geo Modeling | FDP | Asset Management | New venture | Seismic |
6 年Upto what gradient do we consider case to be? ?qualified? for Tilted OWC. Generally we? go for a misconception,? as different OWC means diff reservoirs. Is there any clear line of delineation pls. share
Principal Reservoir Engineer (Simulation)
6 年One of my objective is to share the possible simple solution with RE’s community of a problem that might be considered so complex and time consuming, although it has toke one day of my time by redesign saturation tables.