3D Seismic lnterpretation in Jarn Yaphour Field, Abu Dhabi
Authors: Abou Zeld Zaki S. , El Bishlawy Sherif H. 
Published: December 2007

A major 3D seismic project covering about 425 sq miles project coveringabout 425 sq miles [1100 kM] was conducted at Jarn Yaphour to define thestructural geometry, particularly faulting, better and to resolve stratigraphiccomplexities associated with the field's principal reservoirs. Datainterpretation included detailed geoseismic mapping of nine horizons andseismostratigraphic analysis of three intervals of interest. This paperdiscusses the interpretation techniques applied to the 3D seismic data, usingboth conventional and interactive methods, and the results achieved. Theproject, which has revealed extensive details about the structural andstratigraphic aspects of the Jarn Yaphour field, derived a reservoir-depthmodel for the Thamama Zone B, the main hydrocarbon-bearing reservoir. Thismodel and the seismostratigraphic anomalies identified suggested new areas toexplore.

Introduction

The Jam Yaphour field is a tectonically complicated, extensively faulted, northwest/southeast-trending, asymmetric, anticlinal structure in the easternpart of Abu Dhabi's coast (Fig. 1). Of the 10 wells drilled in the field, thelast two were based on the 3D seismic survey and proved the use of thetechnique.

Fig. 2 illustrates the stratigraphic succession in the area and the nineinterfaces selected for geoseismic mapping. The stratigraphic column iscomposed mainly of cyclic shelf carbonate/evaporite sequences with minorclastic sedimentation phases of shales and sandstones. Seals of differentcapacities are seen throughout the succession, which comprises lime mudstones, shales, and anhydrites.

The main reservoir in the field is the Thamama Zone B (Early CretaceousKharaib formation), which is oil- and gas-bearing. Secondary-orderreservoirs-the Thamama Zone A and the locally developed algal-coral facies ofthe Bab member-are found in the overlying Shuaiba formation.

Before the 3D seismic program, the Thamama Zone B showed pronouncedvariations in hydrocarbon/water contacts in wells reaching 183 ft [56 m]. Thissituation hindered implementation of an adequate field development program andwas the main reason for the 3D geoseismic project.

The project had many objectives.

The first was to define the structuralgeometry of the field. The second was to highlight stratigraphic featuresassociated with the algal-coral facies developed at the top of the EarlyCretaceous Thamama group and the potential shelf carbonates at the top of thepotential shelf carbonates at the top of the Middle Cretaceous Wasia group. Thethird goal was to derive a reservoir-depth model for the Thamama Zone B and toshow its impact on hydrocarbon entrapment. The last objective was to explainearlier well results and to assess future exploration/delineation plans. plans.3D High Resolution

To secure optimum temporal and lateral resolved images, field parameters andprocessing package were carefully selected. processing package were carefullyselected. Subsurface coverage in 41 × 82-ft [ 12.5 × 25-m] units improvedimaging by virtue of the two component fields in migration. One-and two-pass 3Dmigration techniques optimized lateral resolution. High vertical resolution wasattained through a comprehensive deconvolution testing program. A predictivedeconvolution approach and an ancillary frequency deconvolution technique wereapplied separately to satisfy the structural and seismostratigraphic analysisrequirements.

In the interpretation phase, the entire 3D seismic data set was loaded ontoan interactive workstation to allow analysis of each in-line, cross-line, andtime slices every 4 milliseconds, the sample rate of the data. The wide rangeof the 3D products and the use of the interactive system resulted in a networkof 16 random traverses along Tracks A through 0 and In-Line 4535 (Fig. 3). These tracks were selected to cross through important structural/stratigraphicfeatures, to provide additional ties, and to obtain better definitions ofsubtle fault patterns and main fault zones. The random patterns and main faultzones. The random traverses were produced in the form of regular verticalseismic sections, Hilbert-attribute displays, and seismic lithologicmodels.

Interpretation Techniques and Discussion

In addition to the large number of seismic data sets produced by the 3Dsurvey, geological information, wireline logs, and well-test data from ninewells (Wells JY-1 through JY-7, HW-1, and AT-1) were made available.

Time and Depth Structural Maps.

Synthetic Seismogram Ties. Borehole acousticdata in the form of check shots and sonic and density logs were available forall nine wells except Well HW-1, which lacked check shots. Syntheticseismograms were subsequently generated for each well to performseismogeological calibration, with perform seismogeological calibration, withgood matches being established by wavelet extraction studies.