AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Applying Innovative Production Modelling Techniques to Quantify Fracture Characteristics, Reservoir Properties and Well Performance in Shale Gas Reservoirs
(1) DeGolyer and MacNaughton, Dallas, TX.
(2) Lucid Reservoir Technologies, Austin, TX.
(3) Object Reservoir, Houston, TX.
Gas rates from shale wells are comparable to those of conventional wells as a result of rapidly-evolving horizontal drilling and well stimulation technologies. However, an understanding of the factors controlling production rates and recoveries lags behind the knowledge derived from decades of gas production from conventional reservoirs. Specific difficulties include: a) incomplete knowledge about the characteristics of staged hydraulic fractures in horizontal wellbores, b) petrophysical property uncertainties, and c) an inability to distinguish between hydraulic fracture and reservoir contributions from production data alone.
In order to more accurately characterize reservoir and hydraulic fracture properties from well performance, a workflow has been developed that effectively integrates variable quality data from a variety of sources. This workflow applies analytical techniques designed specifically for shale gas wells followed by as-needed numerical modeling. The analytical techniques can be applied to multiple wells through time to a) identify groupings of like-performing wells, b) detect wells with anomalous behaviors, c) develop hypotheses about production mechanisms, and d) choose specific wells for more detailed analysis and numerical modeling.
Numerical modeling is important for understanding complex reservoir mechanisms, quantifying well performance, and optimizing completions. Conventional numerical models typically use finite-difference grids, but these are neither sufficiently complex nor sufficiently flexible for shale gas reservoirs. For this reason, a finite-element modeling technology has been applied that places a large number of closely-spaced nodes near hydraulic fractures “where all the action takes place” in the early life of a well. The finite-element technique also allows complex fracture geometries to be modeled.
This workflow, incorporating analytical and numerical solutions, has been applied to multiple shale gas projects, including industry consortia in the Haynesville (US) and Montney (Canada) shales and individual operator projects in the Woodford (US), Horn River (Canada), and Marcellus (US) shales. Through the application of these techniques, fracture and reservoir properties have been characterized and uncertainty associated with forecasted well performance has been reduced.