Pressure-Monitoring Technique Uses Sealed Wellbore Pressure as Source

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199731, “Monitoring the Pulse of a Well Through Sealed Wellbore Pressure Monitoring: A Breakthrough Diagnostic With a Multibasin Case Study,” by Kyle Haustveit, SPE, Brendan Elliott, SPE, and Jackson Haffener, SPE, Devon Energy, et al., prepared for the 2020 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, 4-6 February. The paper has not been peer reviewed. A pressure-monitoring technique using an offset sealed wellbore as a monitoring source has led to advancements in quantifying cluster efficiencies of hydraulic stimulations in real time. Sealed wellbore pressure monitoring (SWPM) is a low-cost, nonintrusive method used to evaluate and quantify fracture-growth rates and fracture-driven interactions during a hydraulic stimulation. The measurements can be made with only a surface pressure gauge on a monitor well. To date, more than 1,500 stages have been monitored using the technique. The complete paper reviews multiple SWPM case studies, collected from projects in the Anadarko and Permian Delaware basins; this synopsis will concentrate on the concepts behind, and the validation of, the technique. Introduction SWPM is performed on a well that acts as a closed system. The well cannot be connected to a formation through perforations or other types of access points; the casing must be sealed. Uncompleted wells can be used if the shallowest perforations are isolated from the formation. In an existing producing well, a plug must be set above the shallowest perforations to create a closed system from the top of the plug to surface where the pressure measurement is recorded. The wellbore should be filled with low-compressibility fluid (e.g., completion brine) to amplify the pressure response created during monitoring. Fractures intersecting the sealed wellbore cause local deformation, which results in a small volume reduction in the closed system (system being the fluid volume inside of the casing) and generates a discernible and distinct pressure response. Pressure can be recorded either using a surface gauge or a downhole gauge. Multiple sealed wellbores can be used as monitor wells for a single treatment well, allowing for a more-detailed understanding of fracture growth rates during a stimulation. The field execution of SWPM is simple and does not require any tools to enter the wellbore. A surface gauge provides the necessary data needed to evaluate the fracture interactions with the monitor wellbore. There is no need to alter zipper operations if sealed wellbores are available. The main restriction SWPM introduces to operations is the necessity to leave new wellbores, designated as monitors, unprepped by not opening toe sleeves or shooting perforations for Stage 1 until monitoring of the offset treatment wells is complete. Because the pressure response in the monitor well is a result of a fracture intersection at the wellbore, the method reduces the uncertainty related to the location of the monitor point commonly associated with other offset pressure-monitoring techniques.