The use of fiber-optic-sensing technology for the evaluation of completion efficiency, primary cement sheath integrity, and offset well interference has become more prevalent in recent years. In addition, the use of a fiber-optic cable for microseismic monitoring as opposed to traditional wireline-conveyed geophones was recently introduced. Various fiber deployment methods have been developed over the years to allow operators to make rapid decisions in real-time based on distributed acoustic sensing (DAS), distributed temperature sensing (DTS), and microseismic data, all provided by a small fiber- optic cable deployed in the well and monitored at surface via sophisticated interrogation equipment.
Historically, fiber-optic cables were deployed in a permanent configuration, strapped to the production casing, in a manner similar to a standard control line, and deployed with the casing prior to cementing. Permanent fiber has become simpler and cost effective over time and provides valuable near wellbore information - and there are continuous developments to keep reducing that cost and complexity. Some operator focus has been less on the monitoring of the completion efficiency metrics and more on understanding the cross well interference data provided from fiber. As a result, operators have looked to other, temporary-type deployment options for fiber.
Two typical temporary deployments are via coiled-tubing and an armored fiber-optic cable. For the first method, a fiber-optic cable is fed into a coiled-tubing reel and then deployed downhole to monitor the strain when the well is impacted or closely impacted by a hydraulic fracture from an adjacent well. An armored fiber-optic cable deployment is similar to electric wireline in that it is installed in the well during pump down or with a wireline tractor.
Both these options are viable and readily available; however, they include supplementary expenses in terms of equipment required to convey the fiber into the well. In addition, the surface footprint required during the conveyance and monitoring phases of the operation is substantial with crane(s), a coiled-tubing unit or wireline unit, and associated on-location equipment required during the job. Figure 1 depicts a wireline-conveyed fiber operation in conjunction with fracturing operations. Additional equipment in the form of a wireline truck and extra crane are highlighted in yellow. In contrast, a wellsite where disposable fiber is being deployed is shown in Figure 2. Once the fiber is landed, the pump units are removed and only a trailer and crew pickup remain on-site.
Figure 1 Typical fracturing operation, wireline-conveyed fiber
Figure 2 Typical offset well monitoring wellsite, disposable fiber
This paper will discuss a new, low-cost option now available to conduct cross well monitoring and microseismic evaluation of offset completions using a disposable optical fiber that requires minimal equipment to deploy into the wellbore, reduces surface impact during the operational phase, provides quality strain information with excellent quality microseismic data when compared to other fiber-optic deployment methods, and is able to be disposed of at the conclusion of the operation with no detriments or impediments to the completion of the well it has been deployed in. This fiber was successfully deployed for the first time in the Marcellus Shale for Chesapeake Energy with minimal operational disturbance and reduced costs when compared to similar technologies. It was demonstrated to provide valuable data for the purposes of understanding the impact of hydraulic fracturing on far-field communication and evaluating both the temporal fracture response and zonal impact caused by structural changes across the lateral.
