About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


13th Annual Convention Proceedings (Volume 1), 1984
Pages 241-254

Seismic Estimation of Point-Bar Sands Using Simple Modeling Procedures

Robert Dennison


A seismic Previous HitreflectionNext Hit with an anomalous low frequency character has been mapped in the Ibul Field area of South Sumatra. The mapped configuration of this anomalous Previous HitreflectionNext Hit forms a linear pattern, and portions of this anomaly coincide with point bar sands as determined from core and log data. Recent drilling on this seismic anomaly has produced oil from several wells located off-structure and below the Ibul Field oil-water contact.

Seismic modeling of this anomaly was carried out in an attempt to understand its significance. A personal computer with a memory capacity of 2000 bytes was used for this model study.

Synthetic seismograms were first generated. From the initial work it was apparent that to properly estimate the composition of the seismic trace it was necessary to estimate the wavelet as closely as possible. Misleading conclusions are frequently the result when an assumed wavelet is used in synthetic seismogram work.

The wavelet was estimated from the seismic trace and well logs using Fourier Transforms of the time domain acoustic impedance, and the seismic trace. The conclusion of the synthetic seismogram study was that the low frequency anomaly is the result of a strong second cyle Previous HitreflectionTop from the overlying Basal Telisa Limestone interfering with reflections generated from stacked point bars in the upper part of the Talang Akar. Synthetic seismograms were generated from a simple geological model composed of a flat, massive limestone overlying a simple sand wedge. Comparisons were made between the wedge model and the stacked seismic data to predict sand thicknesses.

At the Ibul-46 location, 75 feet of point bar sands were predicted, and after the well was drilled the log showed two sands (net thickness of 58 feet) seperated by 20 feet of shale. The upper sand contains hydrocarbons.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24