The objective of the proposed three-year effort will be to develop a fiber-optic sensing system capable of real-time simultaneous distributed measurement of multiple subsurface, drilling, and production parameters. A proven and breakthrough technology that enables the harmonic-free interrogation of thousands of grating-based distributed interferometers along an optical fiber will be leveraged for long distance, distributed acoustic measurements, and integrated with a novel optical sensing fiber to obtain distributed subsurface electromagnetic field measurements. A novel multi-material, measurand-specific, optical fiber will be fabricated and integrated with the sensing system to enable the distributed and real-time measurement of multiple parameters simultaneously with ultrahigh sensitivity, high frequency, and reliability at depths and temperatures beyond that of current monitoring technologies.
Virginia Polytechnic Institute and University, Blacksburg, VA 24061
Sentek Instrument LLC., Blacksburg, VA 24060
It has been estimated that the recovery efficiencies are on the order of 20% in gas-rich shale reservoirs and less than 10% in liquid-rich plays. Critical knowledge gaps in the understanding of subsurface hydraulic fracture geometry and optimal completion/stimulation strategies continue to limit the most efficient recovery of Unconventional Oil and Gas (UOG) resources. Limitations of currently available technologies to characterize and monitor relavant subsurface features present a major obstacle to understanding the in situ nature of hydrocarbon occurrence and the resultant flow properties of the stimulated reservoir as well as controlling the stimulation and production.
Next-generation logging tools that can image radially from the borehole with high resolution, seismic sensor arrays to monitor stress near the wellbore, and methods to remotely characterize fluid flow are actively sought to assure efficient production. Although several schemes (such as wireless data telemetry, electronics-based technologies, and fiber optic sensors) have been investigated, insufficient performance has limited their widespread efficacy in UOGs. Furthermore, the use of more than one of these technologies to obtain the necessary information further complicates the deployment and is often not feasible because of the stark difference in operating principles and integration procedures. There is a clear need for innovative and breakthrough technologies for improved subsurface characterization, visualization, and diagnostics to fill data gaps in big data analytics to inform decision making and improve ultimate recovery of UOG plays.
The project will demonstrate a ground-breaking technology to view the subsurface with unprecedented clarity, enable real-time facture diagnostics, and optimize drilling and production via the rapid, distributed, and simultaneous measurement of subterranean seismic and electromagnetic phenomena. A one-of-a-kind distributed fiber optic acoustic sensing system will be coupled with a transcendent magnetic fiber optic sensing fiber that will provide seismic and electromagnetic measurements with contrast, spatial resolution, and functionality not yet realized by other techniques. It is envisioned that the simple, minimally invasive, compact, and cost-effective approach will aid in the ultimate recovery from UOG resources and optimal use of the Nation’s subsurface resources, particularly for the small profit margins and fast turnaround time required for decision-making at these sites.
In this second year of the project, the research team’s efforts are focused on the fabrication and evaluation of multi-material sensing fibers. Stable designs and techniques were successfully developed to reliably fabricate single mode fibers with a number of nickel and Metglas™ cladding wires. Continuous lengths (>500 meters) of acryalted coated sensing fibers were produced with relatively low attenuation (~10 dB/km at 1550 nm) and high tensile strength (>50 kpsi). Fiber Bragg grating (FBG) sensors were also fabricated in sensing fibers with 2 nickel cladding wires via femtosecond laser inscription. In parallel efforts, Sentek constructed DASNova™ interrogators with 2 and 5 meter spatial resolution, that wil be used to evaluate the acoustic and magnetic field response of selected sensing fiber samples.
Finite Element Analysis (FEA) 2D models were developed and theoretical modeling was performed with commercial modeling software, such as COMSOL V4.2a, to evaluate the influence of the fiber design parameters (magnetostrictive wire spacing, number and size) on the response to magnetic field exposure . The high quality magnetostrictive models were refined with a 1e-9 geometric tolerance, new bottom-up meshing techniques, and benchmarked material property additions to demonstrate the ability of the sensing fiber with Ni and Metglas® cladding wires to sense magnetic fields much lower than 1 mT.
Laboratory scale test facilities were designed and constructed to characterize the response of prototype sensing fibers in a simulated environment. Laboratory soil box test beds with 2 and 5 meter lengths were commissioned with capabilities to exposure the sensing fiber to controlled magnetic fields up to 10 mT, temperatures up to 150ºC, and acoustic fields of varied frequencies. In addition, a DASNova™ sensing cable was successfully deployed in a 60 meter trench to evaluate its response upon exposure to 20 unique acoustic sources.
Phase 1 – DOE Contribution: $466,512
Phase 2 – DOE Contribution: $518,593
Phase 3 – DOE Contribution: $514,895
Planned Total Funding – DOE Contribution: $1,500,000
Phase 1 – Performer Contribution: $125,000
Phase 2 – Performer Contribution: $124,999
Phase 3 – Performer Contribution: $125,001
Planned Total Funding – Performer Contribution: $375,000