Controlled-Source Electromagnetics (CSEM) provides a new method of far-field flowback monitoring. We used this method in the Permian Basin to map frac fluid during flowback after a three-well hydraulic fracture stimulation, leading to an improved understanding of large- and small-scale changes within the reservoir.
Fracture network characterization in shale is a difficult task that is further complicated by a wide range of operational concerns. Past operations have required months or years of production data gathering, resulting in significant delays. However, monitoring the flowback that occurs between stimulation and well activation can help determine early production rates and predict long-term rates.
Challenge
A client operating in the Permian Basin required frac fluid mapping during flowback after a three-well hydraulic fracture stimulation. The purpose was to identify changes in the reservoir and map those changes to potential future production.
ESG Solution
We used a large-scale, surface-based, multi-receiver CSEM approach to record and analyze electrical signals induced in the frac fluids. A grounded dipole transmitter was placed directly above the central horizontal well of three parallel neighboring wells, and we placed an array of 161 receivers on the surface of the three wells to record the frac fluid response signal.
Several days after flowback began, we recorded the flowback response signals in three-hour intervals over the course of 13 days. This time-lapse recording showed us spatial and temporal electrical conductivity and fluid movement within the fractured reservoir. Chemical tracers were also included in the frac fluid during stimulation to confirm mapped fluid locations and movement (shown in Figure 2).
Figure 3 shows time-sequential frames of the flowback response during the monitoring period. The increase indicates areas of significant change from initial conditions. Much of the monitored portion of the reservoir shows a flowback response, with the bulk of the signal response being due to Wells 22 and 23.
