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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 2. (February)

First Page: 314

Last Page: 314

Title: Carbonate-Anhydrite Facies Determination by Quantitative Previous HitSeismicNext Hit Stratigraphy in Paradox Basin: ABSTRACT

Author(s): Richard F. Wadleigh, Jr., John A. Ward

Article Type: Meeting abstract

Abstract:

Recent advances in Previous HitseismicNext Hit acquisition and processing techniques have greatly improved the usable bandwidth and signal-to-noise ratio of Previous HitseismicNext Hit Previous HitdataNext Hit collected in the Paradox basin. Historically, the irregular terrain coupled with shallow velocity gradients limited the usable stratigraphic thin-bed resolution to near 60 Hz. Analysis of filtered sonic logs of the upper Ismay formation suggests that even with 100-Hz Previous HitseismicNext Hit Previous HitdataNext Hit, carbonate porosity will not be represented seismically as an individual low-velocity trough on wavelet-processed Previous HitdataNext Hit. Conventional Previous HitseismicNext Hit stratigraphy attempted to interpret these zones based on a qualitative study of synthetic seismograms.

The purpose of this paper is to evaluate an inverse method of calibrating Previous HitseismicNext Hit Previous HitdataNext Hit by the integration of quantitative analysis of filtered sonic logs from bore-hole Previous HitdataNext Hit with seismically derived sonic logs (Seislogs). The Seislog Previous HitdisplayTop has a horizontal scale in transit time and a vertical scale in depth. In this format it is possible to compare quantitative variations observed on the Seislogs with changes derived in model studies that relate filtered velocity on sonics to lithologic variation.

This paper discusses the application of this method in an upper Ismay field (Patterson Canyon), located in San Juan County, Utah. The field is currently producing oil from a porous carbonate algal-mound facies, which in filtered-sonic logs is typified by a decrease in both velocity and thickness when compared to the anhydrite facies. When the carbonate facies becomes tight, there is a transit-time decrease and an apparent increase in thickness. The anhydrite facies sonically has the lowest transit time and also is the thickest facies. It is important to note that a limestone with intercalated clastics may have exactly the same sonic response as the porous carbonate facies. The distribution of these facies in map view provides the key to differentiation of the two types of low velocity response in this trend. The porous carbonate facies is typically narrow and lenticular in contrast to the more sheetlike clastic carbonate facies.

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