Search

Subsea control systems utilize electric and/or optical communication channels within subsea optical distribution systems for redundant, duplex telemetry between topside facilities and subsea control systems. Downhole fiber optic sensing (DFOS) systems utilize the same subsea optical distribution systems for establishing transmission paths between the same topside facilities and downhole sensing fibers. To date, subsea fiber optic control and sensing systems have been operated on independent subsea optical distribution systems. This redundancy introduces complexity and cost into the overall subsea optical distribution system required for subsea developments. We describe the systems that combine fiber optic communications for subsea control systems and downhole fiber optic sensing systems into the same subsea optical distribution system. This enables simultaneous operation of communications between the topsides and subsea control module, and the topside interrogation of multiple downhole fiber optic sensors while preserving dry-tree equivalent sensing performance.

Topside distributed acoustic sensing (DAS) of subsea wells requires advanced optical engineering solutions to compensate for reduced acoustic bandwidth, optical losses, and back reflections that are accumulated through umbilicals, multiple wet- and dry-mate optical connectors, splices, optical feedthrough systems, and downhole fibers. To address these issues, we introduce a novel DAS solution based on subsea fiber topology consisting of two transmission fibers from topside and an optical circulator deployed in the optical flying lead at the subsea tree. This solution limits the sensing fiber portion to the downhole fiber, located below the subsea tree, and enables dry-tree-equivalent acoustic sampling frequencies of more than 10 kHz while eliminating all back reflections from multiple subsea connectors above the tree. When combined with enhanced backscatter single-mode fiber, this gives rise to a DAS interrogation system that is capable of providing dry-tree-equivalent acoustic sensing performance over the entire length of the subsea well, regardless of the tie-back distance. It also enables the same spectral-based DAS processing algorithms developed for seismic, sand control, injector/producer profiling, and well integrity on dry-tree wells to be applied directly to subsea DAS data. The performance of this subsea DAS system has been validated through a series of laboratory and field trials. We show the results of the tests and discuss how the system is deployed within subsea infrastructure.

Recent deployments of subsea optical distribution systems and single-fiber optical feedthrough systems have enabled distributed acoustic sensing (DAS) of subsea wells to augment existing electric pressure and temperature sensing systems. Following recent developments of multi-fiber optical feedthrough systems enabling multiple downhole fibers, we describe the concepts for all-optical downhole sensing solutions that combine distributed acoustic and temperature sensing (DAS/DTS) with discrete fiber Bragg grating (FBG) sensing of pressure and temperature gauge arrays while minimizing impact on subsea optical distribution. Since DAS, DTS, and FBG sensing operates at different optical wavelengths, we combine them via a wavelength division multiplexer (WDM) so they are distributed via the the same subsea fiber topology. This subsea fiber topology involves two transmission fibers in the umbilicals and subsea distribution systems to a remote and passive optical multiplexer and circulator assembly deployed in the optical flying lead (OFL) or optical feedthrough system (OFS) of the subsea tree. This enables the down-going transmission fiber to be split into three sensing fibers which are coupled to three downhole fibers via a multi-fiber optical feedthrough system: one fiber for DAS and DTS sensing, and two fibers for FBG sensing of pressure and temperature gauge arrays. The circulators enable dry-tree equivalent pulse repetition rates, regardless of the tieback distance, and via another remote wavelength division multiplexer (WDM), recombine the backscatter light from multiple downhole fibers into the up-going transmission fiber. This pure backscattered light can be selectively amplified prior to entering the receiver arms of the DAS, DTS, and FBG interrogators. The dry-tree equivalent sensing performance implies that the variety of DAS, DTS and pressure and temperature algorithms developed for reservoir and well diagnostics can be equally applied straightforward to DAS, DTS, and FBG-based pressure and temperature data acquired from subsea wells.

Topside interrogation for distributed acoustic sensing (DAS) of subsea wells for vertical seismic profiling (VSP), well integrity, and sand control requires optical engineering solutions to compensate for the insertion losses and back reflections accumulated through umbilicals, multiple wet- and dry-mate optical connectors, splices, optical feedthrough systems, and downhole sensing fiber and wet mates. Moreover, the acoustic bandwidth is inherently limited by the total length of the sensing fiber. To obviate these problems, we describe a subsea fiber topology with two ultralow loss transmission fibers from the topside to a remote optical circulator deployed in the optical flying lead at the subsea tree. This limits the sensing fiber portion of the total fiber length to the fiber located below the remote circulator, and eliminates all back reflections from the multiple subsea connectors above the remote circulator. The receiver arm in the DAS interrogator only senses pure backscatter light from below the circulator. The pulse repetition rate is only constrained by the fiber length below the remote circulator, thus enabling dry-tree equivalent acoustic bandwidths of 10+ kHz regardless of the tie-back distance. This yields significant signal-to-noise ratio (SNR) improvement via stacking and selective amplification, while further enabling sensing of high-frequency acoustic events occurring inside or in the vicinity of the wellbore. A fiber with enhanced back-reflectance is deployed in both the upper and lower completions inside a triple-tube cable design that provides a hydrogen-permeation barrier to delay onset of hydrogen-induced attenuation. Results from various laboratory and field trials are shown to validate system performance.

Introduction: A common approach at differentiating acute ischemic stroke (AIS) from stroke mimics (SM) is medical history and clinical presentation. However, combination of certain clinical symptoms and signs are more associated with SM than with AIS. Identifying these clinical features during “Code Stroke “would help clinicians to raise high suspicion to identify SM and thus prevent futile IV thrombolysis. Hypothesis: A predictive model will identify a combination of signs and symptoms associated with SM. Methods: A retrospective cohort over a 4-year period was used to construct a predictive model with recursive partitioning. Results: During the study period, out of 1467 “Code Stroke” activations, 508 patients were eligible for IV thrombolysis. After initial analysis of 43 “Code Stroke” clinical features, we identified 11 signs and symptoms that were significantly different in AIS and SM patients: age, systolic blood pressure, atrial fibrillation (AF), being on antithrombotic at presentation, similar admissions in the past, seizure at onset, headache at presentation, encephalopathy, focal neurological symptoms, NIHSS and old stroke on head CT. Using a predictive model analysis, headache at presentation, absence of focal symptoms, and seizure at onset significantly predicted of SM. A high predictive value of 92%, (CI: 88-95%) for SM included: i) headache at presentation, ii) no headache without focal symptoms, iii) no headache with at least one focal symptom and seizure at onset. While a low SM predictive value of 29% (CI: 23-35%) included no headache at presentation with at least one focal symptom and no seizure at onset. Conclusion: Our study found that among other symptoms, headache, absence of focal symptoms, and seizure at onset have strongest association with SM during “Code Stroke”. Study results further need to be validated in prospective cohort.

Although the ethical use of hypnosis is a topic of utmost importance, there are few studies assessing professional hypnosis users' views regarding questions of hypnosis ethics. This survey of 121 members of the American Society of Clinical Hypnosis (ASCH) investigated respondents' attitudes toward a number of timely issues of ethics and standards of practice. This study also assessed attitudinal differences held by physicians, dentists, and psychologists. This analysis revealed a number of significant differences between groups. Supplemental analysis by source of primary hypnosis training revealed few differences.