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3-D Seismic Classification - An Efficient Approach to Identify Prospective Targets in South Louisiana [Abstract]
The land/water Transition Zone (TZ) in South Louisiana is characterized by intensive salt tectonics, complex fault systems, and broad geographic and stratigraphic distribution of productive reservoirs. Even though the Transition Zone's production history is long and prolific (nearly 100 years with over 90 Tcf of gas and 7.6 Bbbl of oil produced), regional studies and recent discoveries confirm that this productive trend still has significant potential. Definition of drilling targets for production and exploration generally requires months of seismic interpretation to identify and interpret the horizons of interest, extract and analyze seismic attributes corresponding to petrophysical properties, and assess the potential and risks. Very often, it may take a year for a new player to define top infill development and exploration opportunities in a large area due to the complex geology of South Louisiana and the large number of potentially productive horizons. Even for experienced players, successfully unlocking these opportunities depends on whether or not explorationists can significantly reduce cycle time, increase efficiency, and lower risk in defining drilling targets. In meeting this challenge, an innovative approach was developed to effectively identify prospective targets in South Louisiana. Combining multiple attribute 3-D seismic classification analysis with the existing Transition Zone database and studies, it is now feasible to identify top drilling targets in a matter of weeks instead of months.
3-D seismic classification is a breakthrough technology to determine the three-dimensional distribution of pore fluid, lithology, and faults/fractures from multiple seismic attribute volumes. This technique provides an innovative, timesaving solution for identification and definition of drilling targets, especially in areas with multiple pay zones and complex geology.
A 3-D seismic classification analysis was performed in a 50 square mile area surrounding an existing field in South Louisiana. The purpose of the study was to identify top drilling targets within and adjacent to this field. Five seismic attribute cubes were generated from conventional seismic data and used as the input for classification: conventional seismic; acoustic impedance; reflection strength; instantaneous frequency; and trace decomposition. A seismic classification method was used to define classes of fluid (oil, gas, or water) and lithofacies (sand versus shale) based on knowledge of well log and production data. Using cross-plot discriminant analysis, extra classes were defined based on data cluster distribution, separating classes based on their degree of risk. The generated class cubes provide the distribution of prospective targets while the associated distance cubes provide quantitative estimation of risk. Volume visualization and interpretation techniques are used to identify and define the location and extent of prospective features. More focused interpretation and risk analysis provide top drilling targets for new drill, reentry and/or recompletion opportunities to complete a workflow that lasts just a few weeks.
This breakthrough seismic interpretation technology is much more cost effective, reduces cycle time and results in more accurate risk assessment than current seismic interpretation and classification techniques. Exploration opportunities can be more quickly and systematically identified to optimize E&P activities, especially in areas where clients have found bright-spot anomalies alone to be unreliable hydrocarbon indicators. For both existing and new TZ players, application of this technique can result in significant reduction in time and money. The potential savings to individual companies could exceed hundreds of thousands of dollars.
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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
Data and Consulting Services, Houston Solution Center, 1325 S. Dairy Ashford, Houston, TX 77077
Copyright © 2003 by NOGS (The New Orleans Geological Society)