A practical workflow for performance prediction of low permeability reservoirs

Abstract

The Society of Petroleum Evaluation Engineers (SPEE) recently released ‘Monograph 4 – estimating ultimate recovery of developed wells in low-permeability reservoirs’ (hereafter called ‘Monograph 4’; SPEE 2016). This paper outlines a practical engineering workflow enabling companies to evaluate unconventional plays developed with horizontal multi-stage fractured wells consistent with the principles summarised in Monograph 4. This workflow has many applications including assessing potential acquisitions, defining new plays, evaluating competitor results, corporate budget processes, long-term business planning, portfolio management and reserves certification. The workflow, developed and refined over several years, has proven effective in large-scale applications. It enables engineers to readily identify and assess flow regimes, estimate the time to boundary dominated flow and estimate the flow patterns of boundary dominated flow for large groups of wells. The workflow also allows the engineer to deal with changing well designs and completion techniques. Throughout the workflow, the geological, engineering and statistical methods described in Monograph 4 are used. This provides the foundation to define and create representative type curves, yielding statistically reliable estimates of expected ultimate recovery (EUR) and production forecasts for asset evaluation with an accompanying characterisation of the confidence of these estimates. A case study demonstrating application of this workflow and a summary of results are presented. Potential sources of error in the technical analysis and application of type curves are identified; the technical and commercial impacts of these errors are highlighted. By allowing the evaluator to focus time and attention on the details of the technical analyses, companies can achieve a quicker, more in-depth analysis of the development of these large-scale unconventional resource projects.