Exploration Case Studies

Stress Consistent Seismic Interpretation

4D Structural and Stress History

4D structural and stress history is dependent on quality seismic mapping. PSI’s 4DGeoStress software is a world first in promoting “stress consistent seismic interpretation”, the basis of more effective mapping. 4DGeoStress uses full structural history in 4D to determine the direction and magnitude of in-situ stress in 3D, for all pre-drill stress needs in the hydrocarbon exploration and production industries.

Pre-drill Stress Prediction

4D structural & stress history
Stress consistent seismic interpretation
Compressional events
Fault seal prediction
Prospect assessment
Effective geo-engineer interaction

Well Design
Minimise borehole collapse
Geological hazards
Multilateral & sidetrack design

Fractures & fraccing
Life of field management
Secondary recovering
Sand production
CO2 sequestration




Stresses in Rifts

The Early Miocene East African Rift (EAR) is the largest example of an active oil-productive rift system and a stress model for older hydrocarbon bearing rifts.


Compressional structures in rift basins are often ignored or explained as being caused by rotation into down-to-basin normal faults. The aim of this case study is to present a number of seismic reflection examples of compression in several rift lakes throughout the EAR, to link them to earthquake focal mechanism solutions and in turn to contemporaneous Pliocene to Recent upper crustal compression and lower crustal extension.


Earthquakes and seismically recognisable structures can be used to define SHD, the direction of the maximum horizontal component of compressional stress in a sedimentary rift or basin. As SHD is parallel with normal faults and perpendicular to reverse faults the accurate interpretation of fault throw, often varying with time, is crucial. The EAR provides the key.


SHM, the magnitude of SH (=SH/SV), can be quantified using Anderson Fault Stress States derived from stress consistently interpreted seismic reflection data within the upper crust. By mapping prospect and field scale compressional features and applying its 4DGeostress software, PSI is able to accurately determine SHD and SHM in 3D, pre-drill (refer to the PSI Snorre case study).



Snorre Oil Field, North Sea

The Snorre Oilfield in the North Sea links post-drill measured stresses and pre-drill seismically derived stresses.


The load (SV) and minimum horizontal (Sh) components of stress in many sedimentary basins can be determined from density logs and minifracs. The other mutually perpendicular component of the stress, the maximum horizontal stress component (SH) can only be estimated from a minifrac provided the rocks have negligible tensile strength.


The Direction and Magnitude of SH at a point (SHD and SHM) can be determined by interpretation of good quality 2D or 3D reflection seismic data. Here, seismically-derived stress information has been compared with drilling-derived data from the Snorre Field in the Norwegian North Sea.


This pre-drill determination of SHD and SHM is 3D, as opposed to dispersed points from individual wells derived post-drill, after problems, and at considerable cost. SHD and SHM (=SH/SV) can be accurately and quantitatively determined from seismic via isopach representations of the Anderson Stress States, using PSI’s patented technique and 4DGeoStress software.



Compressional Events in Extensional Basins

Plate Tectonics Plus (PT+)

2D mantle circulation based plate tectonics inadequately describes the complexity of global tectonics. PSI has added a time-varying vertical force to provide a 4D model which allows stresses to be predictable and quantifiable for petroleum exploration and production.


Anderson Thrust (Reverse) Fault Stress States within the grey earthquake intense areas are numerous and often unidirectional over large areas. These areas can be attributed to complex mantle movements by the theory of Plate Tectonics.


The enlargement of the Thrust Fault Stress States of South America (above right) reveals SHMax Direction (SHD) is north-south in the western Amazon Basin, at right angles to the east-west SHD’s along the length of the Andean margin. This indicates the compressional influence of the Pacific 6.8cm/yr, plate tectonic, ocean-continent subduction does not penetrate more than 1800km eastwards into the continental basement. The Amazonian and eastern South American, variable, non east-west SHD’s must be derived from a differing force or forces than plate tectonic collision.


Likewise, the variable SHD’s near the South Atlantic Ridge are not indicating east-west plate tectonic ridge push, also supported by the absence of subduction along the ridge-adjacent Eastern South American margin. Mantle circulation beneath the Atlantic is not the same as beneath the Pacific (confirmed by GPS separation rates).


Most of the non-grey shaded areas are responding to predictable, crustal curvature induced vertical forces above the less rigid movement of the mantle.



Pulsed Vertical Force

PSI’s time varying vertical force allows stress to be predictable and quantifiable, pre-drill.


The grey shading on the above World Stress Map indicates high earthquake activity attributable to 2D, horizontal stress, plate tectonic (PT) collision. The remaining continental and oceanic crust is also experiencing thrust faulting which is concentrated at crust cutting sources of weakness and formed by Earth surface curvature reduction, in 3D as PT+.


Mapping the compressional features formed during the Pliocene-Recent from interpreted reflection seismic in several basins reproduces the WSM stresses in detail. The repetition or pulsing of these globally synchronous compressional events since at least the Triassic can be seen on opposite sides of the globe in the plate tectonic “passive margins” of northwest Norway and NW Australia. The synchronous pulsing provides the basis for pre-drill stress prediction in sedimentary basins.