Controlled Source Electromagnetics (CSEM) is used to monitor and image a three well zipper frac operation. We examine the interaction between the completions operation and a fault zone at reservoir depth.
Using two grounded dipole transmitter lines and 350 receiver locations, 27 frac stages were monitored in the Anadarko basin for three horizontal wells. Our broadband signal is transmitted before the start of the frac stage, during the frac stage, and after the frac stage is completed. This allows us to establish a baseline image prior to the start of the frac stage and to generate a response throughout the frac. The electromagnetic data collected provides a direct measurement of the conductivity change in the subsurface caused by the hydraulic fracturing process and from this we infer fluid movement.
This case study presents the effects of a fault at reservoir depths that is intersected by the three wells and examines the possible effects of formation heterogeneities on frac fluid migration. Images produced by our CSEM method illustrate the lateral extent of the fluid, fracture azimuth, and identify reservoir heterogeneities. In addition, unlike microseismic, the CSEM method records signal generated from fluid flow in natural fractures as well as those fractures created by hydraulic pressure. As a result, CSEM allows us to infer fluid propagation and location to gauge frac behavior near and away from the fault where the fault zone is seen possibly acting as a sink and barrier. CSEM monitoring of a frac operation not only serves as a tool for monitoring and fracture diagnostic, it can also be used to identify geologic controls that can affect reservoir stimulation.
Recreational and private pilots are regularly exposed to potentially hazardous noise levels during flight training sessions and recreational flying. For the first part of this study, light airplane noise was recorded during recurrent 1.5-hour flight training sessions. Measurements were made at the level of the pilot’s left and right shoulders (using dosimeters). Data demonstrated that changing inflight operations and power adjustments were associated with specific acoustic patterns. Noise levels (Leq) ranged from 76 dBA to 96 dBA during flight. The second part of this study examined the effect of the noise on subjective and objective measures of the pilot’s auditory function. Measurements were made before and immediately after flight training sessions. Pure-tone audiometric thresholds, middle-ear absorbance and click-evoked otoacoustic emissions did not show significant changes from pre- to post-flight. Although inflight noise levels are potentially hazardous, the use of an aviation headset acted to mitigate the risk of hazardous exposure. Future research directions include measurements in diverse aircraft and across longer flight durations.
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