Geophysics, Metaphysics, and the Independent Geologist

This abstract is for a talk given in Houston, TX at the July 15, 2004 SIPES Luncheon.
Geophysics, Metaphysics,and the Independent GeologistJohn F. Parrish
Abstract:Finding and producing subsurface hydrocarbon reservoirs requires an adept combination of the arts of interpretation, geophysical science, geological science, and engineering. Each of these aspects is necessary; however, all of them may not be enough. What else does the classical artist, scientist, or engineer bring to bear on this problem?
A recent article (Henry, 2000) in The Leading Edge declares that "The primary goal of seismic interpretation is to make maps that provide geologic information (reservoir depth structure, thickness, porosity, etc.)." Is this a statement of the art of interpretation, the science, or the engineering? It is None of the above! It is a philosophical meta-statement about the purpose of seismic acquisition, processing, and interpretation. Several articles from the January 2004 issue of The Leading Edge can be used to exemplify this philosophical dimension of geosciences applied to upstream oil and gas business.
Reservoir characterization uses elements from geology, geophysics, petrophysics, and rock physics. A philosophy (meta-geoscience?) is needed to apply the business and economic constraints. For example, seismic sections reveal an impedance image of the subsurface which can be compared with well logs of sonic and density observations. However, economic constraints generally limit logging to observation like gamma-ray and resistivity that more closely related to fluid and formation properties. Comparisons of such non-impedance logs to seismic are appropriate when structure controls the hydrocarbon trap. Stratigraphic control requires impedance, plus dip, offset, and velocity. In order to more fully characterize reservoirs these seismic and well log observations should be supplemented with dynamic estimates like absorption, pore pressure, and reservoir variability.
There are no good or bad well ties. Ethics and Esthetic criteria determine "fit for purpose" comparisons. Recognizing and characterizing hydrocarbon reserves are the result of the geoscientist-engineer''s imposition of esthetic criteria combined with scientific and artistic rules. Quantitative comparisons require auditable processing of seismic data together with well logs that yield elastic properties. The comparisons should be weighted by time gates, space (location), and frequency.
A self-consistent philosophy of reservoir characterization, including well to seismic comparisons, must ask the following meta-geosciences questions:1. WHY do you want to compare seismic with a well measurement?2. WHAT observations are available?3. WHERE are the well (path), the logging interval, and the corresponding seismic?4. HOW were the various elements modified to enhance the comparisons?5. WHO has established the esthetic criteria of good vs bad?6. ARE there additional observations that will add both scientific-interpretative value and economic value to a reservoir characterization?
Biography: John F. Parrish is a licensed Professional Geoscientist (Geophysics #5073) in Texas and is currently serving the GSH as First Vice President. He is also Program Chairman for SIPES (Society of Independent Professional Earth Scientists). As an independent consulting geophysicist (PeriSeis Company), since leaving Shell (SEIP) E&P Technology in 1999, he has consulted on seismic interpretation patents, ocean bottom cable patents, vector fidelity, and provided geophysical advice for processing data from the Gulf of Mexico, Brazil, West Africa, Red Sea, and other areas. He is a member of SEG, AAPG, EAGE, ASEG, GSH, and HGS. His interests include 3D deconvolution, relative entropy deconvolution, quantitative signal processing for seismic imaging, quantitative comparison of seismic with well log synthetics, suppression of multiple interference, and processing/interpretation pitfalls. John F. Parrish received an S. M and a Ph. D. in Physics from Massachusetts Institute of Technology. For 30 years, he worked on diverse projects within Shell Oil Company. He has served Shell as land party-chief, inventor (several patents), technological prognosticator, geophysical programming supervisor, and chief geophysicist of Pecten Geophysical Company (a start-up processing subsidiary of Shell Oil Company). In 1996, John received the Shell E&P Technology Company Achievement Award as a member of the Shallow Water-Flow Control Team (URSA #4). He has processed or interpreted seismic data from both land and marine plays in the U.S.A. (including Alaska and Gulf of Mexico), Brazil, West Africa, and China.