In an ongoing attempt to learn more about subsurface conditions before and during production, service companies and operators have explored a wide range of technologies. One technology, that allows for transmission of subsurface data back to the surface, is the installment of fiber optic cable behind casing. Fiber optic cable not only provides subsurface data conditions affecting production, but it serves as a highway for data transmission in seismic surveys, as well as, monitoring production information itself along the entire length of the cable. We will expand on methods used to preserve this installment of the fiber optic cable by identifying its location behind casing. Circumferential ultrasonic scanning techniques have been used for many years to inspect the casing itself, and cement behind the first string of casing. These techniques offer a better inspection of channeling, or partial vertical void in cement behind first string of casing, than just your standard radial cement bond tool. Cement and Casing Inspection have been useful services of the ultrasonic scanning services, but it isn’t without limitations, whereas this scanning tool has a shallow depth of investigation. Traditionally, standard cement bond logs are used in conjunction with the circumferential ultrasonic scanning services to examine the bond index, and to offer some additional understanding of the cement bond to casing, as well as cement to formation bond. In that shallow ultrasonic scan, is where this publication will demonstrate the value added of locating the fiber optic cable, but it is not without some uncertainty. To reduce some of that uncertainty, a pulsed-eddy current system, which uses an arm-mounted pad sensor that contacts the inside of the first casing string, utilizes pulsed-eddy current technology to accurately locate the position of the fiber optic cable mounting clamps. Detecting the location of the clamps, offers great insight into oriented perforation, but as this publication will demonstrate, the fiber optic cable can meander in between those clamps. The circumferential ultrasonic scanning service offers visibility of the meandering of that fiber optic cable, in between clamps, and when used in combination with the pulsed-eddy current system, this creates an integrated service that reduces the probability of perforating the installment of the fiber optic cable. Purpose of this paper, will be, to demonstrate the use of the impedance data, gained from the circumferential ultrasonic scanning tool, in combination with the fiber optic clamp location from the pulsed-eddy current tool, to locate the fiber optic flatpack between clamp locations. However, there are limitations in the location of the fiber flatpack, as in, gaps between flatpack and casing, and/or lack of cement coverage. The final product will include the depth location of clamps, station degrees of fiber loop, degrees of fiber flatpack location, and level of confidence by interval shading. This information will give customers greater confidence in the execution of oriented perforation procedures, without damaging fiber optic cable flatpack.
Evaluation of a pulsed eddy-current system for subsurface flaw detection
