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Visualizing Rock Properties from the Gulf of Mexico

Exploring for Hidden Pay with Rock Properties


H. Roice Nelson, Jr., Geophysical Development Corporation


Understanding geophysical rock properties is key in order to accurately tie seismic and well data in the Gulf of Mexico.  In this clastic environment, rock-property analysis provides a mechanism for integrating pore-fluid and lithologic distributions to stratigraphic models.  Analyses include Vp and density trends (maps and volumes) for sand and shale in the regimes above and below the onset of abnormal pressure, depth to the first-occurrence of abnormal pressure, sand-volume distribution, and other rock properties that contribute to a better understanding for finding hidden pay - the invisible remaining hydrocarbons.  To realize these goals, it is essential to have a statistically significant set of data adequately resolving the variations in geologic trends. 


The objective is to enable explorers to make rapid amplitude and AVO judgments about hydrocarbon prospects.  Seventy-plus rock properties have been derived from GDC’s proprietary well log database.  This paper demonstrates how these data are being evaluated and being made available for specific geographic areas called TILES.  Each of the 27 GDC Tiles™ defined for the offshore Gulf of Mexico include about 100 wells, key rock property maps, and half a dozen signature well studies.  These signature well studies include digital well log suites, wet and gas case synthetic offset gathers, synthetic offset gather incident angle plots with 15, 30, and 45 degree traced across the display, and synthetic angle stacks for 0-15, 15-30, and 30-45 for both wet and gas cases.  Although initial work is in the Gulf of Mexico, the Tile concept is designed to support explorers anyplace in the world.


Since the data are digital, they can be evaluated on interactive workstations as a natural extension to prospect generation workflow.  SpotFire™, a PC-based data mining software package, is used to look at trends in Rock Property Space, and to identify interesting anomalies.   An AVO toolkit built by Dr. Fred Hilterman, named TIPS™ (Toolkit for Integrating Petrophysics and Seismic), is used to model anticipated AVO response.  These software packages will mature to allow explorers to access, model, and correlate measured rock properties with proprietary in-house seismic and borehole information.  Regional trends and trend curves from individual well studies become rock property analogs and allow interactive prediction of seismic AVO response for a prospect or exploration idea.  The data and tools are easy to learn, understand, and use.  They allow an explorer, a geotechnical expert, or a manager to determine anticipated AVO response for a new prospect quickly and easily.  User-specified rock-property volumes can be generated to enhance understanding of the hydrocarbon system .  Given these volumes and paleo horizons, the explorer can extract Sand Vp, Sand Vs, Sand Density, Shale Density, Normal Incidence Reflection Coefficient, or other rock property values along a horizon or between horizons in order to study spatial lithologic and fluid changes. These studies are interactive, where interactive means one finds the answer before forgetting the question.


The value of visualizing rock properties hinges on the ability to predict how rock properties vary. With quality rock-property data and easy to use toolkits, one can determine what data and exploration tools should be used to find the hidden reserves.  This is accomplished by comparing the properties of a proprietary prospect to pre-identified regional trends.  This type of work allows explorers to be more informed and better prepared – resulting in a competitive advantage in identifying hidden pay.


H. Roice Nelson Jr. has been Vice President Interpretation-Business Development for Geophysical Development Corporation since April, 2004.  During his 34 years in the Oil Industry he has also been founder or co-founder of numerous companies and organizations.  Some with well known names, such as Landmark Graphics Corporation and the University of Houston’s Allied Geophysical Laboratory.  His major oil company experience comes from Mobil and Amoco where he was a geophysicist.  He graduated from the University of Utah with a BS in Geophysics and Southern Methodist with a MBA.  He has published 181 technical  articles since 1973 and co-organized 8 SEG Research Workshops.  Roice is also a Honorary Member of the Houston Geophysical Society, and an active member of  AAPG, GSH, SEG, and World Future Society. 


He can be reached at (713) 782-1234 x271 or by e-mail Roice