Applying 3-D Seismic Multi-Attribute Analysis and Unsupervised Seismic Facies Classification Techniques in Jurassic Carbonate Depositional Sequences, Onshore Saudi Arabia

Wharton, Stanley R.¹; Lawrence, Paul ¹; Gregory, Arthur ¹; Bakhiet, Abdelfattah ¹
(1)Saudi Aramco, Dhahran, Saudi Arabia.

Jurassic carbonates represent some of the most productive reservoirs in Saudi Arabia. The main challenge associated with prospecting for these carbonate reservoirs is reservoir heterogeneity. This heterogeneity is caused by depositional history with tectonic, stratigraphic and diagenetic influences. To assess the heterogeneity of these reservoirs, a 3D seismic multi-attribute analysis and a neural network seismic facies classification analysis, were applied to an area near a large intra-shelf basin.

Seismic attribute volumes generated from input data from a 2D chronostratigraphy model, were combined to generate seismic facies 3D block volumes, to analyze the seismic stratigraphy and stratal associations, of the depositional sequences at the Oxfordian stage. Seismic facies 3D block volumes were visualized and sliced to define the geometry of prograding clinoforms within a highstand system tract. Waveform classification analysis of a key horizon revealed distinct lateral facies changes between carbonate shoal and distal basinal areas. A proportional slicing technique applied at the top of the sequence, revealed a strike-dominated depositional setting for the shoal facies, and a dip-oriented depositional setting for the basinal deposits. Electrofacies from well log data corroborated the seismic facies distribution with sporadic grainstone deposits located in a shoal belt, and poorer facies in the intra-shelf basin.

Application of multi-attribute analysis and unsupervised seismic facies classification, to assess the seismic stratigraphy and the seismic facies variations, proved beneficial in defining favorable broad carbonate facies belts. Use of a chronostratigraphy model, selected seismic attributes and associated data-conditioning procedures, helped in analyzing heterogeneity of the carbonate sequences.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.