Converting RTA Half-Lengths to Actual Non-Uniform SRV Half-Lengths

We wanted to highlight and share a paper we think everyone in tight unconventionals should read, namely URTeC 3719890, “Closing the Gap in Quantifying the Extension of Depletion: A Practical Workflow to Convert Analytical Fracture Half-Length to Actual Non-Uniform SRV” by Vivek Muralidharan and Soodabeh Esmaili. The paper addresses an important challenge in leveraging RTA in tight unconventionals, i.e. the discrepancy between “RTA resolved facture half-lengths” and “observed well-to-well interference” or “observed half-lengths”.

Difference between rectangular frac geometry and actual frac geometry

Rate Transient Analysis (RTA) is used in the oil and gas industry to understand the volume of oil and gas that can be extracted from a horizontal well, known as the Stimulated Reservoir Volume (SRV). This information is used to forecast and compare the performance of different wells. However, it has been observed that there can be significant differences between the SRV dimensions obtained from RTA models and the actual performance of the well, particularly when it comes to spacing decisions. This is often due to the assumption of a rectangular shape half-length in RTA models. To improve the accuracy of SRV dimensions for spacing decisions, the paper presents a workflow that translates rectangular geometries into an actual depletion profile, taking into account the non-uniform vertical depletion of the SRV. Without going into all the details, the paper argues that actual fracture geometries are not rectangular, but highly asymmetric in terms of shape. We like to call this a “droplet” shape. In addition, evidence is presented that the actual (maximum) half-length is ~4 times as large as the “RTA resolved half-length”. This is supported by pressure monitoring wells, with multiple gauges versus depth, and micro seismic data.

Comparison of gauge pressure drop to microseismic event counts

Author Vivek Muralidharan will hold a whitson webinar on this topic 10 May 2022 at 9 am Central Time (CT). Register →→→here←←←.

Want to learn more? Download the paper →→→here←←←.


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