Stark, Tracy J.¹
(1) STARK Research, Plano, TX

ABSTRACT: Using a Relative Geologic Time Volume to Identify Stratigraphic Features

This poster paper will address three questions: 1) What is a Relative Geologic Time volume? 2) How is it generated? and 3) How is it used to identify stratigraphic features? 
A Relative Geologic Time Volume (RGT volume) has the same dimensions and coordinates as the seismic data volume, but instead of seismic amplitude, each sample contains an estimate of relative geologic time. Relative geologic time, as used in this context, implies that we know if a data sample A is younger or older than a data sample B, but we cannot say (until a calibration step is performed) how much older of younger A is than B. In an RGT volume a constant amplitude surface will have a constant relative geologic time and therefore will be a seismic horizon. 
There are many ways to generate an RGT volume. The most straightforward method is to perform a standard horizon interpretation and assigned a constant value (that approximates the geologic age of the horizon) to each interpreted horizon. The RGT volume is then populated by interpolating values between the picked horizons. Another way to generate an RGT volume is to unwrap the instantaneous phase as discussed by Stark at the 2003 SEG convention. 
Seismic amplitude along a surface of constant relative geologic time is analogous to Henry Posamentier’s “Proportional Slice” or Hongliu Zeng’s “Stratal Slice”. The use of these types of displays for identifying stratigraphic features is well documented. Software will be demonstrated that uses an RGT volume to provide an interpreter the ability to interactively display a stratal slice by dragging the mouse over a seismic display. When coupled with a volume visualization package, constant relative geologic time units can also be investigated for stratigraphic features.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.