We replace the traditional correlation+grid+geostats steps by a constrained physics-based depositional process model to define realistic geobodies fitting the well data. The body's boundaries will be the support for the reservoir grid geometry. The body's intrinsic properties will be the support for the rock properties distributions.
In input, we take the well litho-facies data, the depositional environment (like river-dominated delta) and constraints (like valley geometry from seismic data), and optionally a eustatic sea-level curve correlated to the parasequences boundaries.
Stochastically construct a sequence of deposition using processed-based objects controlled by the iteratively modeled topography, sea-level, and litho-facies intervals.
Use bodies boundaries to construct a reservoir grid preserving flow barriers.
Use bodies intrinsic to inform grain size in grid cells.
What do we not need: No variograms, no complex parameters as typically required by other processed-based systems (sediment input, diffusion, etc.), no detailed well markers correlation.
What do we need: the depositional environment and some of its geometrical constraints, the range of dimensions of deposition bodies in analogs, the litho-facies interpretation (lithology & depositional setting, see SEPM definition), and the eustatic sea-level curve correlated to the parasequences.
The standard method to construct reservoir models is a three-step process: first, correlate well picks, second construct a stratigraphic grid, and then use geostatistics to fill in property values.
Different problems exist with this method:
1. The correlation of markers across many wells is sometimes very difficult.
2. The creation of the grid to honor the stratigraphy can be very challenging.
3. Creating realistic sedimentary geological models is laborious with today's technology.
4. The size of the grid cells being set, the models' spatial heterogeneity can be lost including thin flow barriers.
5. Broken flow barriers or lack of spatial heterogeneity can lead to an overstatement of reserves.
Copyright Next-Shot LLC. All rights reserved.