Multi-Scale Characterization and Modeling of Heterolithic Tidal Systems, Offshore Mid-Norway

Abstract

The Lower Jurassic Tilje Formation on the Halten Terrace, offshore mid-Norway, forms an important reservoir in a number of hydrocarbon fields. A high volume fraction (80 percent) of the formation is heterolithic in nature, showing various styles of sandstone-mudstone intercalated bedding at several scales. The depositional model is based on a general facies classification scheme applicable to all fields. The stratigraphic interval discussed was deposited in a narrow basin during overall rising relative sea level as a tide/wave-dominated, mud-rich delta with well-developed prodelta, delta-front, and estuarine-type distributary- channel facies. The main heterolithic deposits are found in the prodelta, delta-front, and distal parts of the estuarine- type distributary-channel-mouth areas, whereas relatively "clean" facies occur in medial areas of these distributaries.

Lithofacies associations are modeled in 3D using stochastic, object-based methods, and the heterolithic architecture at the lithofacies scale is modeled using a process-based sedimentary architecture tool. Multiple data sources (core, log, and outcrop-analogs) are used to establish a data-rich procedure for estimating the effective reservoir properties within a step-wise upscaling procedure. Our results show the importance of integrating multi- scale data with good sedimentary models to accurately estimate reservoir properties in these heterolithic formations. We derive effective property functions (for example k_v/k_h) for different facies and identify important reservoir flow units using flow simulations of stochastic realizations.