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Abstract

Deviation from exploration for conventional, Albian age, clastic plays towards carbonate plays of a stratigraphic nature has prompted the use of plan view - horizontal seismic displays in the interpretation process as an additional means of data visualization enhancement.

Significant improvement in accuracy and speed have been attained with the use of horizontal displays in the mapping of minor lineaments and faults with no visible, or minor throw on vertical seismic sections. Mapping practices include work on horizontal slices and slabs, which can be either horizon or time consistent. This approach to seismic interpretation has allowed the inclusion of seismic Attributes, Spectral Decomposition, Edge detection, Coherence, Dip and Azimuth analysis, and other display enhancements into the interpretation process.

Carbonate plays of the Lower Cretaceous are of emerging interest as exploration targets. This type of play relies on fracture porosity, which is developed in close association with faults. Generally poor seismic data quality prohibits accurate fault identification on vertical sections. Here it has often been necessary to employ circumspect methods including the use of horizon volumes. These may even be based on vertically offset, but well defined marker horizons that approximate the curvature of the studied event. Methods of this nature have been employed in the identification of stratigraphic features such as the edge of a Lower Cretaceous oolite play proximal to the Minagish field in southern Kuwait.

Horizontal displays of seismic attributes were also used in the mapping of the extent of a flat spot in the Upper Cretaceous, and of a very shallow, Lower Miocene channel system in northern Kuwait. In the two latter cases it was extremely difficult to maintain lateral pick consistency among consecutive vertical sections.

We conclude that for these types of play, the level of accuracy attained in the interpretation of faults, stratigraphic features, i. e. onlap edges, channels and direct hydrocarbon indicators on horizontal data volumes, widely surpasses what can be reasonably achieved on vertical data displays. We anticipate that interpretation and study of horizontal seismic attribute and other signal enhancement displays will play an increasingly important role in the future subsurface mapping in Kuwait.

Introduction

Large amounts of information embedded in seismic trace data are not always readily visible on traditional, vertical amplitude sections. The underlying problem is the level of resolution apparent in the seismic data. Whether this is due to low consistency of detail or high levels of cluttering varies among data sets. Sensitivity to detail and demands of the task and quality of data at hand will determine the level of quality standards imposed on acquisition and processing parameters to be used.

Regardless of advances in data presentation and post-processing image enhancement, it is the underlying data quality that will ultimately determine the results of any interpretation. The data quality aspect extends from acquisition of raw data via signal processing to final display along with its various refinements. Early mistakes or bad practices can only rarely be repaired and never recovered in full. 3D seismic acquisition foot-prints can be softened at the processing stage, but not fully eradicated without compromising data content. This has particular relevance to fault resolution. Residual foot-prints are manifested as striations in the data that will interfere with real events of potential importance.