Integration of well log-derived facies and 3D seismic attributes for seismic facies mapping: A case study from mansuri oil field, SW Iran

Abstract

The recognition and mapping of rock facies is a pivotal step in reliable reservoir characterization and planning development operations. The present study aimed to present a practical workflow by integrating three-dimensional (3D) seismic attributes and well-log facies analysis to determine the spatial distribution of electrofacies rock types of the Oligo-Miocene Asmari reservoir in Mansuri oilfield located in the southwestern part of Iran. The workflow begins with integrating well logs, core data, and geological information from the selected ‘key wells’ to build an electrofacies model, which could help reservoir facies to be classified and estimated in the cored and uncored wells, respectively. In addition, a group of 3D seismic attribute volumes derived from amplitude, frequency, and time characteristics of the post-stacked 3D seismic data were identified to specify the heterogeneity of the vertical and lateral rock facies within the reservoir. Additionally, the seismic attributes were analyzed using unsupervised and supervised learning techniques to identify seismic facies. The extraction of the seismic facies at multiple-well locations within the 3D classified volumes demonstrated that the supervised neural network learning method, as compared to the unsupervised approach, could more accurately estimate the desired seismic facies. The results of the ultimate rock facies maps of different vertical slices in the Asmari reservoir indicated that electrofacies with good reservoir quality were best developed on the top of the reservoir, mostly with NW-SE elongation at the crest line of the structure. The applied workflow allowed the localities of the buried sand channels to be identified and mapped. Accordingly, seismic facies mapping shed light on the spatial heterogeneity and quality of the reservoir, which could be used to guide the development drilling for optimal recovering of the unswept hydrocarbons.