GeoDict Hysteresis for Oil-Water Setups GeoApp

The Hysteresis for Oil-Water Setups GeoApp is a specialized GeoDict application for digital rock physics and digital Special Core Analysis (SCAL). It simulates oil‑water two‑phase flow directly on 3D digital rock structures, covering the complete hysteresis cycle—from primary drainage and imbibition to secondary drainage—under different wettability conditions.

This GeoApp enables users to compute capillary pressure‑saturation curves, relative permeability, and fluid distribution across the entire hysteresis loop. Unlike traditional laboratory SCAL, which typically provides only macroscopic curves, the digital approach allows direct visualization of oil and water distribution, connectivity, and flow paths within the true 3D pore space.

Key Features

Complete Hysteresis Cycle Simulation – The GeoApp simulates the full sequence of two‑phase displacement processes: Primary Drainage (oil displacing water), Spontaneous and Forced Imbibition (water re‑entering and displacing oil), and Spontaneous and Forced Secondary Drainage (oil re‑entering to displace water).

Mineral‑Scale Wettability – Users can assign different contact angles to different mineral surfaces, enabling realistic representation of water‑wet, oil‑wet, and mixed‑wet conditions.

Rock Aging – After primary drainage, partial aging of mineral surfaces in contact with oil can be simulated, affecting subsequent imbibition and secondary drainage behavior.

Capillary Pressure‑Saturation Curves – The GeoApp records capillary pressure, oil saturation, and water saturation at each pressure step, and combines results from drainage, imbibition, and secondary drainage into a single hysteresis curve.

Relative Permeability – From the 3D fluid distribution at selected saturation states, effective permeability of each phase is computed, yielding relative permeability as a function of saturation.

Corey and LET Models – Discrete relative permeability results can be fitted to continuous functions using industry‑standard Corey or LET models, ready for integration into reservoir simulators and history matching workflows.

Key Input Parameters

Users can define the following parameters to tailor the simulation to their specific rock and fluid system:

Fluid Types – Specify the two immiscible fluids (oil‑water, water‑air, or other pairs)

Contact Angle – Defines wettability of rock surfaces (water‑wet, oil‑wet, mixed‑wet)

Fluid Viscosity – Viscosity values for both fluids

Interfacial Tension – Controls capillary effects together with contact angle

Digital SCAL Workflow

The GeoApp provides a predefined, automated workflow that replaces traditional laboratory SCAL with a faster, non‑destructive digital alternative:

3D Rock Image (µCT or other) → Image Segmentation → Digital Rock Model → Select Hysteresis Stages → Define Fluid & Wettability Parameters → Run Two‑Phase Flow Simulation → Obtain Capillary Pressure Curves, Relative Permeability, and 3D Fluid Distribution

Key advantages of the digital SCAL approach include:

Non‑destructive – No physical core samples are consumed

Reproducible – Same model can be re‑run under different conditions

Faster – Weeks of lab work reduced to days

Direct Visualization – Observe fluid distribution and flow paths in 3D pore space

Multiple Scenarios – Test different wettability, fluid properties, and boundary conditions on the same sample

Official Example: Gildehauser Sandstone

A validation study on Gildehauser sandstone demonstrates the GeoApp's capability. The simulation used a voxel length of 4.4 µm and a model size of 900 × 900 × 566 voxels. The initial contact angle was set to 40°, while the aged contact angle was 140°. The computed irreducible water saturation was 15%, and residual oil saturation was 42%. The computation required approximately 20 hours, using about 95 GB of memory on 32 parallel cores with GeoDict 2025.

The simulation produced the complete hysteresis capillary pressure curve, imbibition relative permeability curves, and 3D velocity distributions for relative permeability calculations.

Typical Applications

Reservoir Characterization – Analyze capillary pressure, relative permeability, and wettability behavior

Production Forecasting – Derive relative permeability from pore‑scale structure

Enhanced Oil Recovery (EOR) Studies – Evaluate different wettability and displacement scenarios

SCAL Validation – Compare digital results with laboratory SCAL data

Data Gap Filling – Generate parameter studies when experimental data is limited

Required GeoDict Licenses

Running the Hysteresis for Oil‑Water Setups GeoApp requires:

Essential Module: SatuDict – for computing saturation‑dependent material properties including capillary pressure, drainage, imbibition, relative permeability, and resistivity index

Commonly used supporting modules include:

ImportGeo‑Vol – for importing and segmenting 3D rock images

PoroDict – for pore structure analysis

MatDict – for solid phase analysis

The specific module combination depends on the data source and research objectives.