--> Abstract: AVO Applications in New Exploration Areas of Saudi Arabia, by E. F. Chiburis; #90987 (1993).

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CHIBURIS, EDWARD F., Saudi Aramco, Dhahran, Saudi Arabia

ABSTRACT: AVO Applications in New Exploration Areas of Saudi Arabia

AVO techniques have been routinely used and heavily relied upon in Saudi Arabia for the last nine years in reducing the risk of exploration prospects and in delineating the lateral extent of hydrocarbon distribution. During the last four years, the majority of the successful applications has been in the new Central Arabian exploration areas; prior to these latest efforts, all AVO work had been confined to eastern Saudi Arabia and the Arabian Gulf.

The specific AVO technique employed continues to be that developed by Chiburis (1984, 1987) in which (1) target peak amplitudes in each gather arepicked interactively and normalized trace-by-trace to a reference event (or to an rms window if a suitable reference cannot be found); (2) the ratios are then conditioned to provide a two-sided distribution from which least-squares curve fits are made to determine an AVO trend; and (3) the trends are then compared along the line to note the relative changes in AVO behavior. In this way, most of the causes of amplitude distortion can be removed or minimized without recourse to complex or undeterminable correction schemes.

After an initial discovery oil well in 1988 in Central Arabia, the AVO technique was brought to bear on successfully delineating the lateral distribution of oil in the field. The technique was then used to predict the occurrence and nonoccurrence of hydrocarbons (gas or oil) for numerous other prospects throughout a region of about 500 km in extent.

Except for those seismic lines having signal-to-noise ratios too low to confidently analyze, the AVO technique was successful in 26 out of 27 confirmed cases, the one failure being due to an attempt to analyze a target event overlying an angular unconformity. It is of interest to point out that, after the first discovery well in the region, all AVO analyses were made and the results presented prior to the drill.

The intent of this presentation is to present several of the more interesting case histories in which AVO has been instrumental in predicting the occurrence and in determining the lateral distribution of hydrocarbons in Saudi Arabia; in one notable case, the fluid type (gas) was also predicted. Also to be discussed are the offset ranges, processing considerations (and dangers), and limitations of the technique.

Therefore, under the right conditions and with suitably analyzed data, AVO is continuing to demonstrate its value as an important innovative adjunct to aggressive exploration and exploitation programs.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.