1. From 2D Seismic to Hydrodynamic Modelling A Complex Study of Turbidites in a Petroleum-Bearing Basin
Marcell Lux, hydrogeologist engineer
Tamás György Krusoczki, hydrogeologist engineer
MOL Plc., Eurasian Exploration & Production
ISZA, Tatabánya, 31 March 2012

2. Outline of The Presentation
Objectives
Geology
Hydrogeology
Hydrodynamic conditions
Hydrodynamic modelling
Results, conclusions, implications
Summary

3. Objectives Summarizing and assessing geology and hydrogeology
Construction of a hydrodynamic model to simulate natural flow system
Finite difference method (Processing Modflow 7)
Finite element method (FEFLOW 6.0)
Assessment of the hydrodynamic system
Data: HC wells (well log and core analyses, DSTs) 2D seismic, literature
Comparison

4. Geology Neogene sub-basin Surroundings uplift during basin subsidence
Deltaic depositional system
Assessed late-miocene formations:
Basal marls
Pro-delta turbidites
Distal (main emphasis, possible tight gas reservoir)
Proximal (several conventional HC accumulations)
Delta slope

5. Seismic interpretation – Master seismic section
Onlap reflection ending
Deltaic sediments
Distal turbidites: hummocky clinoform internal reflection pattern
TWT

6. Seismic interpretation – Mapping
Structure map of distal turbidites top
Isopach map of distal turbidites

7. Hydrogeology Delta slope, basal marls: regional aquitards
Proximal and distal turbidites: regional aquifers
Porosity and permeability decreases with depth -> lower in depocenter, greater on flanks
Permeability map of distal turbidites

8. Hydrodynamic conditions
A moderately super-hydrostatic zone is followed by a strongly overpressured regime
Transition within proximal turbidites, distal part is highly overpressured
Flow is mainly directed upward
Faults play an important role in the dissipation of overpressures
Fluid potential map of basal marls

9. Model grid of the finite element method (Vogt, 1993)
Hydrodynamic modelling
4 confined layers, each layer is divided into 3 sub- layers to enhance vertical resolution
Geometry from well data and seismic interpretation
Effective porosity and hydraulic conductivity from parameter distribution maps
Ratio of vertical and horizontal hydraulic conductivity determined from available core analyses
Hydraulic head data from DSTs
Fixed head cells at top and bottom
Steady-state flow -> Permanent model
Finite difference method and finite element method
Model grid of the finite difference method (Chiang and Kinzelbach, 1999)
Model grid of the finite element method (Vogt, 1993)

10. Hydrodynamic modelling – Hydraulic cross sections I.
Flow is directed upward
Horizontal component toward deep grabens
Potentiometric „mounds” above basement highs
Finite element method: congestion of equipot. lines
Finite difference method
Finite element method

11. Hydrodynamic modelling – Hydraulic cross sections II.
Finite difference method
Finite element method

12. Hydrodynamic modelling – Flow velocities, access times
Hydraulic gradient map
Acces time from bottom to top of modelled space: t = years
Average vertical flow velocities: (1÷6) ×10-9 m/s
Average hydraulic gradients: I = 0,8-3
Extremely high hydraulic gradients, still low flow velocities -> very low permeability!
Acces times

13. Hydrodynamic modelling – Hydraulic trapping
Stagnation point?
Hydraulic trap?
Deep part of the basin: insufficient data -> high uncertainty
Coincidence of different flow systems is unlikely
(Fetter, 1994)

14. Hydrodynamic modelling – Overpressure prediction
Hydraulic head (pressure) values correspond to every single point of the modelled space
1000 m equipotential surface is approx. 100 bar (10 MPa) overpressure

15. Summary Results: Improvements may include:
Geological overview of the basin, more detailed investigation of distal turbidites
Systematic hydrogeological description of the basin’s deeper formations
Characterizing the hydrodynamic system based on a hydrodynamic simulation
Fluid potential maps
Hydraulic cross sections
Access times
Flow velocities
Identification of a possible stagnation point
No significant discrepancy between finite difference and finite element method
Improvements may include:
Using seismic attributes to refine geological and hydrogeological model
More detailed structural geological investigations
Advantages of finite element method can be utilized better
High-resolution quantitative well log analysis

16. Thank You For Your Attention!