Techniques for Fast Screening of 3D Heterogeneous Shale Barrier Configurations and their Impacts on SAGD Production Behavior
Authors: Gao Chang , Leung Juliana Y. 
Published: March 2020

Steam-assisted gravity drainage (SAGD) recovery process is strongly impacted by the spatial distributions of heterogeneous shale barriers. Though detailed compositional flow simulators are available for SAGD recovery performance evaluation, the simulation process is usually quite computationally demanding, rendering their use over a large number of reservoir models for assessing the impacts of heterogeneity (uncertainties) to be impractical. In recent years, data-driven proxy has been widely proposed to reduce the computational effort; nevertheless, the proxy must be trained using a large data set consisting of many flow simulation cases that is, ideally, spanning the model parameter spaces. The question remains: is there a more efficient way to quickly screen a large number of heterogeneous SAGD models? Such techniques could help to construct a training data set with less redundancy; they can also be used to quickly identify a subset of heterogeneous models for detailed flow simulation. In this work, two particular distance measures, flow-based and static-based, are formulated to quantify the similarity among a set of 3D heterogeneous SAGD models.

First, to formulate the flow-based distance measure, a physics-based particle tracking model is employed: Darcy's law and energy balance are integrated to mimic the steam chamber expansion process; steam particles that are located at the edge of the chamber would release their energy to the surrounding cold bitumen, while detailed fluid displacements are not explicitly simulated. The steam chamber evolution is modeled, and a flow-based distance between two given reservoir models is defined as the difference in their chamber sizes over time. Second, to formulate the static-based distance, the Hausdorff distance is employed: it is often used in image processing to compare two images according to their corresponding spatial arrangement and shapes of various objects.

A suite of 3D models is constructed using representative petrophysical properties and operating constraints extracted from several pads in Suncor's Firebag project. The computed distance measures are used to partition the models into different groups. To establish a baseline for comparison, flow simulations are performed on these models to predict the actual chamber evolution and production profiles. The grouping results according to the proposed flow- and static-based distance measures match reasonably well to those obtained from detailed flow simulations.

Significant improvement in computational efficiency is achieved with the proposed techniques. They can be used to efficiently screen a large number of reservoir models and facilitate the classification of these models into groups with distinct shale heterogeneity characteristics. It presents a significant potential to be integrated with other data-driven approaches for reducing the computational load typically associated with detailed flow simulations involving multiple heterogeneous reservoir realizations.