This paper was a repeat presentationat the SPE Middle East Oil Technical Conference and Exhibition held in Bahrain, 3-6 April, 1993.

Abstract

Nowadays, the seismic reflection is playing an increasingly significant rolein the development of oil fields in addition to the detection of hydrocarbontraps of even greater stratigraphic and structural complexity.

This paper presents and describes an integrated method using seismic and well data to predict, quantity and map the porosity variations within four reservoirs in the Thamama Group in two structures named "A" and"B" and located offshore Abu Dhabi.

The seismic and well data were processed and aimed to produce a Noise free sections presenting a high Signal-to-Noise ratio. The data were processed in a True-Amplitude and a Zero-Phase sections were produced providing a good matching with the well data. These Zero-Phase sections were inverted to an Absolute Acoustic Impedance sections which were calibrated with the impedance logs generated at the wells.

The different factors that may affect the porosity in the four studied reservoirs were investigated and a relationship between the porosity and the acoustic impedance was established.

This relationship along with the calibrated absolute impedance sections were used to produce porosity maps for the Thamama reservoirs.

After the completion of this study, two wells were drilled in this area and the results are in general satisfactory. The comparison between the predicted and real petrophysical reservoir parameters can be summarised as follows:

Depth : error about 0.7% H (thickness x porosity): The average error for all the studied reservoirs in the two wells is about 10%.

INTRODUCTION AND OBJECTIVES

This study was carried out by the Compagnie Generale De Geophysique (CGG) in 1987/1988 with the contribution and under the Supervision of ADMA-OPCO.

The area of the study is located offshore Abu Dhabi, as indicated in Figure-1.

This study covered two structures "A" and "B".

The first exploration well drilled on the Structure "A" was in 1981and it was a discovery. The oil-bearing reservoirs occur in the Thamama Group Lower Cretaceous age. The first well in the nearby Structure "B" was drilled in 1989 and discovered oil in the Thamama zones I, II and IV.

The main objective of this study was to evaluate the potentialities of the different reservoirs in the Thamama Group.

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