Hydraulic Unit Determination and Permeability Prediction Based On Flow Zone Indicator Using Cluster Analysis

Abstract

Abstract Classical discrimination of petrophysical rock types is based on subjective geological observations and on empirical relationships between permeability and porosity data. The Hydraulic Unit approach is a methodology for classification of rock types and prediction of flow properties, based on flow zone indicator that incorporates geological attributes of texture, mineralogy and the physics of flow at pore scale to discriminate distinctive hydraulic units. This paper presents a methodology for the determination of Hydraulics Units and permeability prediction using a cluster analysis technique due to a hydraulic unit's zonation process requires a rigorous statistical approach. MULTI-RESOLUTION-GRAPH-BASED CLUSTERING (MRGC) is a very powerful non-parametric algorithm which allows defining the optimal number of hydraulic units. The methodology was applied to Venezuelan Eocene sandstone reservoir integrating core data (flow zone indicator) and log data such as porosity, shale volume and caliper as an input data. Compared to previously classification, based on lithofacies information, it yielded to increased accuracy of permeability prediction and enhance reservoir description. All geological information available was integrated (core descriptions, image log, lithofacies, XRD, thin sections and SEM information) and five hydraulic units were identified, without any "a priori" subjective knowledge. A detailed characterization was achieved, determining rock properties (porosity and permeability) and SCAL properties (capillary pressure and relative permeability curves) by each rock type, which is an input data in the dynamic modeling of the reservoir. In order to verify this approach a nodal analysis was performed in an uncored well using all data available (buildup-flowing bottom hole, RFT-pressure data, petrophysical and fluid reservoir properties) obtaining and excellent match between real and predicted initial oil production.