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From Static to Dynamic Interpretation of Subsurface Data - A Change of Paradigm*
By
Dietrich H. Welte1, Bjorn Wygrala1, and Thomas Hantschel1
Search and Discovery Article #40058 (2002)
*Adapted for online presentation from the article by the author in AAPG Explorer (May, 2000), entitled “Static Interpretation Now Dynamic.” Appreciation is expressed to the author and to M. Ray Thomasson, former Chairman of the AAPG Geophysical Integration Committee, and Larry Nation, AAPG Communications Director, for their support of this online version.
1IES Integrated Exploration Systems, Juelich, Germany (www.ies.de; [email protected])
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General StatementThe most widespread
source for subsurface data is 2-D and, increasingly, In petroleum exploration and production it is an essential requirement to understand these past geological processes - especially petroleum generation and migration - which determine whether or not a trap contains hydrocarbons. Hence, it is crucial to understand the dynamics of relevant processes responsible for the present day geological conditions. As modeling of geological processes relies entirely on a subsurface database and related, intelligently structured data archives (often called data models), it is essential that the numerical simulation is linked as closely as possible to these data sources. This is easily achieved by direct binary access to seismic data and interpretation tools like OpenWorks, GeoFrame, SeisWorks, IESX, etc. It is common practice to organize and store subsurface data in more or less sophisticated data archives that can be screened and manipulated electronically. An electronic data archive enables information to be exchanged, reviewed, and thereby enriched and updated. Even the most refined interpretation utilizing advanced interpretation software and databases, however, produces static information for stratal terminations, seismic facies, lithofacies and property distributions, etc. Such static data archives can be brought to life - and at the same time generate a great deal of added value - by dynamically modeling the geological processes behind it.
Static to Dynamic Process (Figures 1 and 2) The conversion of static data to a dynamic process interpretation starts with a rigorous analysis of the stratigraphic time record of the sedimentary column and by assigning absolute ages. In this way an absolute time sequence of critical geological events is derived and a conceptual geological process model is created, forming the backbone of the dynamic process interpretation and the chain of logics for a computer model. A petroleum system
includes the entire hydrocarbon source, carrier, and accumulation
system, and the goal must be to reconstruct the entire geological
history of a petroleum system, from its origin to the present. The main
focus must be on the location and The modeling of the petroleum system; i.e., the numerical simulation of the relevant processes, rigorously follows the geological time axis. The principal concepts and methods of this kind of modeling are well established in existing basin modeling techniques. It commences with the deposition and compaction of the oldest stratigraphic units at the bottom of the system and works its way upward through younger and younger events to the present day. The resulting dynamic modeling requirements mean that our models must be able to take most important changing factors through geologic time into account. These include:
Software programs
today can provide all of this functionality. Petroleum migration
processes can be modeled in two dimensions (2-D) along geological cross
sections, but any attempt to quantify hydrocarbons in a simulated system
must be based on three dimensional (
Simulation runs that reconstruct the
geological history of a petroleum system inclusive of multi-phase
migration modeling should typically be performed in several hours on a
normal workstation or workstation cluster. Such “short”
Overpressure zones can be fairly well
predicted by geological process modeling, so the technology can even
help to improve seismic interpretations, for instance, with respect to
selecting the right seismic interval velocities in overpressure prone
regions. The new simulation technology enables regional scale
This kind of Procedure and LogisticsToday a complete array of technological facilities is already available to extend “classical” but static subsurface data interpretations into dynamic process modeling in a sequential manner - firstly seismic interpretation, and secondly process modeling. The next step is to extend the integration of the various technologies and data types to create even more value by adding synergies. It is the provision and availability of proper interfaces between the relevant software packages and intelligent tools interactively to manipulate original data and results on both sides. This step, without any doubt, will dramatically accelerate the application of more intelligent (dynamic) data interpretation tools. The
cost of this type of dynamic interpretation compares favorably with, for
instance, the cost of sophisticated seismic |