S.H. Begg

Modelling the Effects of Shales on Reservoir Performance: Calculation of Effective Vertical Permeability

In this paper the authors present four methods of estimating the effective vertical permeability of a reservoir containing stochastic shales in both two and three dimensions. The methods vary in their accuracy, speed and range of applicability. The first is based on numerical simulation, the second is an analytical method, the third and fourth are based on calculating approximate streamline lengths. The methods give consistent results for similar models and are used to show that the effective vertical permeability is strongly dependent on the shale dimensions, shale fraction and layer thickness. It is also shown that the results of the two-dimensional models are inappropriate even when the megascopic flow is unidirectional.

Improving Investment Decisions Using a Stochastic Integrated Asset Model

This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s).

Handling risk and uncertainty in petroleum exploration and asset management: An overview

Uncertainties, and the business risks they generate, touch all aspects of the oil and gas industry. Being able to understand and quantify the risks and uncertainties, and knowing how to manage them effectively, contributes to well-founded business decisions, protects the value of projects and assets, and maximizes the value of company project portfolios. This article shows how different combinations of risks and uncertainties become relevant through the life cycle of an oil or gas field from exploration (main risk: absence of commercially viable hydrocarbons) through appraisal and development (main risks: aspects of effective project delivery) to field operation (main risks: delivery of promised reserves and value). This corresponds to a change in the relevance of uncertainties, which are mainly related to static volumetric issues early on, with dynamic factors coming to dominate later in field life. The specific risks related to individual assets need to be managed using mitigations or contingencies. By contrast, the overall risk exposure of the company (comprising many assets and potential projects) is managed by optimizing the portfolio of opportunities that are to be actioned. The 10 articles that follow in this thematic set cover risk and uncertainty across all stages of field life and from individual fields to portfolios. The articles discuss some of the latest technologies, modeling approaches, philosophies, and communication styles that can help make effective decisions to minimize risk exposure and maximize project and asset value.

Characterization of a Complex Fluvial-Deltaic Reservoir for Simulation

Lithotype is shown to be the main geological control on the spatial distribution of reservoir flow properties. The distribution of lithotypes is in turn controlled by lithofacies. Using core data, assemblages of lithotypes were grouped into major facies associations (MFA`s). Log signatures were used to pick MFA`s in uncored wells to provide conditioning data for a stochastic description of their interwell distribution using the sequential indicator simulation (SIS) technique. Deterministic correlation was not enforced. Characteristic object-models of the distribution of lithotypes within each MFA were then generated and converted to fine-scale poro-perm models using core-lug data. These models were upscaled to yield characteristic poro-perm distributions at the reservoir simulation scale. Finally, the MFA model was used as a template to distribute the upscaled poro-perm within the simulation model. The model history-matched rapidly and accurately, even though the wells were conditioned only to the MFA`s and not to foot-by-foot data. Multiple MFA realizations were generated to provide some understanding of the uncertainty in thickness and other rock properties between wells.