Probabilistic Performance Forecasting for Unconventional Reservoirs with Stretched-Exponential Model

Abstract

Reserves estimation in an unconventional-reservoir setting is a daunting task because of geologic uncertainty and complex flow patterns evolving in a long-stimulated horizontal well, among other variables. To tackle this complex problem, we present a reservesevaluation workflow that couples the traditional decline-curve analysis with a probabilistic forecasting frame. The stretched-exponential production decline model (SEPD) underpins the production behavior. Our recovery appraisal workflow has two different applications: forecasting probabilistic future performance of wells that have production history; and forecasting production from new wells without production data.For the new field case, numerical model runs are made in accord with the statistical design of experiments for a range of design variables pertinent to the field of interest. In contrast, for the producing wells the early-time data often need adjustments owing to restimulation, installation of artificial-lift, etc. to focus on the decline trend. Thereafter, production data of either new or existing wells are grouped in accord with initial rates to obtain common SEPD parameters for similar wells. After determining the distribution of iv model parameters using well grouping, the methodology establishes a probabilistic forecast for individual wells.We present a probabilistic performance forecasting methodology in unconventional reservoirs for wells with and without production history. Unlike other probabilistic forecasting tools, grouping wells with similar production character allows estimation of self-consistent SEPD parameters and alleviates the burden of having to define uncertainties associated with reservoir and well-completion parameters.

Reserves Estimation for Coalbed Methane Reservoirs: A Review

“…This will benefit in the calculation of the estimated ultimate recovery (EUR) for the individual wells. [63] The stretched exponential decline model can be calculated from the following equation:…”

A Critical View of the Current State of Reservoir Modeling of Shale Assets

“…When applied to shale wells DCA has many shortcomings. Several authors (Boulis 2009, Cheng 2010, Mattar 2008, Johnson 2009, Can 2012, Ikewun 2012) have come up with interesting techniques to overcome some of the well-known shortcomings of DCA, but nevertheless, many facts remains that make the use of Decline Curve Analysis suboptimal.…”