Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Integrated Reservoir Characterization of Barnett Shale Gas: Defining the Stratigraphic Influences on Production
(1) ConocoPhillips, Houston, TX.
(2) School of Earth Sciences, Stanford University, Stanford, CA.
Many factors related to completions and operations affect production from shale-gas reservoirs, and these parameters typically change from well to well. Similarly, shale property variations are observed at different scales: from basin to basin, within a basin, along a single wellbore or within a single core. Seldom are there attempts to correlate these stratigraphic variations to variations in gas production. We report here the results of analyses that show how variations in stratigraphic parameters (e.g., thickness and depositional facies) affect gas production from the Barnett Shale in the core area of the Fort Worth Basin. Our results are based on a four-stage approach: 1) establishment of a regional stratigraphic framework, 2) definition of architectural elements, 3) construction of 3-D geocellular models that capture facies and physical property variations, and 4) statistical correlation of production to stratigraphic variables. Here, we focus on the latter two steps.
After establishing the stratigraphic framework and defining architectural elements, we integrated core and wireline log data to predict petrofacies, including predictions of TOC and calcite contents, for wells to be used in geocellular models. Next, 3-D geocellular models were created for areas that represent different depositional settings for the Barnett. Stratigraphic variations (e.g., pinchout of the Forestburg Limestone) can be clearly observed and quantified within the 3-D models. Production data for 600+ wells were collected and averaged to mitigate the impact of completion and operational differences for individual wells. The averaged production values show very good correlation with modeled properties such as TOC and calcite. For example, average 5-year production for wells drilled in the best portion of our study area, an area where the Barnett is relatively thin, is approximately 50% higher than the production from areas where the Barnett is thickest. These stratigraphically controlled production differences are primarily due to changes in the amount of gas generated (thickness and richness of the source rock), potential for gas storage (i.e. porosity in organic matter), and the presence of frac barriers that prevent portions of the Barnett from being stimulated.