How to pick your Free Water Level and Hydrocarbon Water Contact
The Free Water Level is a horizontal surface of zero capillary pressure.
The FWL is the level fluids would separate out in a very wide borehole.?It is the intersection point of formation pressures. In very high porosities the FWL is the start point for Sw vs. Height function.
The Hydrocarbon Water Contact is the height where the pore entry pressure is sufficient to allow hydrocarbon to start invading the formation pores. This depends on the local porosity and permeability and is therefore a surface of variable height.
Typical scatter plot when you plot Sw vs. Height.?Low porosity formation is fully water saturated for hundreds of feet above the FWL.?There is one FWL but multiple HWCs.
When you replace Sw by the Bulk Volume of Water the data collapse to a simple function independent of porosity and permeability.
Two constants completely describe the distribution of fluids in your reservoir!
Dividing the BVW function by porosity gives you multiple SWH functions showing the HWC as a function of porosity.
For fields comprising of gas, oil and water you need a FWLG for the gas interval and a FWLO for the oil interval.
Petrophysicist
2 年Watch the SPWLA recording of this presentation https://www.youtube.com/watch?v=7D11BFuPvo8
Principal Reservoir Engineer (Simulation)
3 年Steve Cuddy how to identify FWL in case of existing title OWC surface?
Petrophysicist
3 年SPWLA paper?https://www.dhirubhai.net/posts/steve-cuddy-84780210_the-bvw-sw-vs-height-function-activity-6868542400042803201-3RN9
Geological Advisor at CNOOC International
3 年Good Stuff Steve!
Occasional consultant chez Retired, Self-Employed
3 年Using BVW instead of Sw is certainly a good idea. One step further is to use a J function. However this analysis is still a bit simplistic in my view: - in a number of cases the FWL is not a horizontal plane (giant fields exist thanks to this) - in a number of cases (not necessarily the same) the equilibrium at discovery is not the result of one simple drainage and thus is not reflected by drainage Pc - it is very frequent to have hydrocarbon saturation under the FWL - given the nature of migration it could almost be argued it should be a base case