Abstract
A study on geobody architecture and petroleum potential of the Yowi Field has been carried out by integrating well logs and 3D seismic data. The objectives of this study include: The determination of the lateral continuity of key horizons; identification of gross geobody distribution and architecture; and the petroleum potential of the field. Well log correlation shows that key horizons are continuous and laterally extensive across the field. Eleven sand horizons displaying majorly stacked upward-coarsening regressive log profile with high net-to-gross ratio towards the eastern flank of the field have been mapped within 7000ft thick (2333 m) interval. A depth structure map generated over the N5.2 sand reveals a structural saddle; an elongate four-way dip closure having two structural culminations. Further analysis using 3D seismic attributes revealed four facies distribution patterns. The Root-Mean-Square (RMS) and Variance attributes were applied to identify subtle lithological variations as indicated by its high and low amplitude anomaly. Four facies depositional patterns recognized from amplitude trends include: Dispersed facies pattern; linear/parallel facies profile; discrete/isolated pattern and meandering configuration. Architectural elements inferred from these amplitude distribution patterns include: Beach-barrier-shoreface depositional profile (about 7077ft (2355 m) in length, 1476ft (490 m) width on the eastern flank and 783ft (260 m) width on the west flank); deep sea channel morphology, chaotic/dispersed turbidite sands and stratigraphic pinchouts. Areas with highest Root-Mean-Square (RMS) amplitude values represent porous and sand-prone prospective units; whereas sections characterized by low amplitude reflections may be interpreted as deposits resulting from pelagic or hemi pelagic sedimentation, or a mud-rich and water-bearing facies. The structural closures form sites for hydrocarbon accumulation in the field. 3D seismic horizon slices remain the best amplitude displays for gross facies identification, selection of optimum drilling locations and for measuring facies architecture.
Highlights
The application of 3D seismic volume attributes to image subsurface geologic features has been in use for more than four decades
The aim of this study is to evaluate facies distribution pattern within the study area and adjacent fields using 3D seismic volume attribute and to establish the lateral continuity of key horizons across the field
The gross thickness of the reservoir ranges from 111ft to 345ft with a layer-cake architecture and large lateral extent
Summary
The application of 3D seismic volume attributes to image subsurface geologic features has been in use for more than four decades They are valuable analytical tools for lithology prediction, identification of various depositional elements, structural analysis and characterization of reservoirs. It has been used to predict the distribution of geobodies within the YOWI Field and adjacent areas This family of attribute is derived from amplitude computation and is useful in facies interpretation, stratigraphic mapping and reservoir studies. Using modern computer power and automation certain seismic features give a direct reflection of subtle subsurface stratigraphic elements that are relevant to hydrocarbon entrapment This is the secret behind most of the discoveries made in recent times in many sedimentary basins across the world
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