Hydraulic fracturing and horizontal drilling have catalyzed the recent United States (US) hydrocarbon production "renaissance," spearheaded by unconventional asset development. The increase in oilfield activity, however, has exposed groundwater contamination as a potential environmental concern associated with the use of these two technologies. Government and state agencies have revisited regulations to help ensure well integrity, but operational success is currently limited because of tool deployment and centralization issues in horizontal wellbores.
The combination of acoustic logging and conveyance technologies with field engineering insight has created a unique solution to well integrity monitoring in horizontal well intervals. Various successful logging services have been performed in wells producing from the Marcellus shale play in Pennsylvania.
A well operator needed to determine proper cement placement between different fracturing stages to avoid unwanted fluid movement throughout the wellbore annulus. The logging tool string, composed of ultrasonic scanning and cement bond log (CBL) tools, was transported through the horizontal wellbore using a tractoring device.
Tool centralization, which is critical to accurate operation of acoustic tools, is difficult to achieve in horizontal wellbores because of the influence of gravity and friction forces. This challenge was overcome by integrating centralization equipment for additional tool support while maintaining wireline tension limits.
This case study discusses the operational background and challenge, creation of this innovative tool setup, and the effects this service will have on performing successful well integrity monitoring in additional unconventional horizontal wells.