Numerical Geology: Predicting Depositional and Diagenetic Facies From Wireline Logs Using Core Data

Abstract

SPE Members ABSTRACT: To exploit a reservoir, the geological model must accurately define the depositional environment and the effects of diagenesis on the pore network. Current methods for establishing the geological model of a field usually require subjective, qualitative interpretation of geological and petrophysical data. A method - Numerical Geology - has been developed that greatly reduces the subjectivity in geological modelling efforts. This method also allows geological attributes to be quantified and predicted. Numerical Geology involves the integration of petrophysical, petrological and geological data with wireline log responses. The geology of "Hydraulic or Flow Units" intervals with similar hydraulic characteristics is described using conventional sedimentology, petrography and core analysis data. These data are translated into a matrix of geological indices classified according to hydraulic unit profile of the section. Hydraulic units are then predicted for uncored sections based on their unique log signatures that are obtained from cored sections. By combining predicted hydraulic units profile with the matrix of geological indices for each flow unit, profiles of geological attribute~ are derived. The prediction reliability of hydraulic units is calculated based on the uniqueness of log signatures for each flow unit. Therefore, the confidence level for geological predictions can be assigned to estimated profiles of geological attributes. This eliminates much of the subjectivity from future geological interpretations and predictions. INTRODUCTION: Hydrocarbon reservoirs are heterogeneous and nonuniform. However, these nonuniform and heterogeneous systems are made of multiple homogeneous groups - Hydraulic Units. The basis for this grouping is similarity in flow characteristics which are affected by–grain size–sorting–texture (packing, angularity, grain shape, homogeneity) P. 507^