Flexisource WTS, eSource, Dual Near-Field Hydrophones, and Harmony
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Shearwater's Flexisource is a combination of multiple, overlapping sources, continuous recording and advanced de-blending techniques to separate the data into individual, non-overlapping shot records. Flexisource can be deployed with three or more source arrays providing opportunities for higher quality data or lower cost and faster acquisition.
Flexisource's continuous recording and de-blending allow shot overlap. The overlap, with de-blending, means that it is not necessary to sacrifice fold for efficiency. Shearwater's standard Flexisource acquisition configuration deploys 6-gun strings arranged in 3 two-string source arrays. Each array has lower energy output than a three-string array, but this is compensated for by the decreased time between shots. Moreover, a two-string array is closer to a point source in the crossline direction providing directionality benefits for out of plane energy.
If even greater energy is required, Flexisource can be deployed with up to 9-gun strings providing, for example, no compromise, triple source acquisition with each source having 3-gun strings. Alternatively, the additional gun strings provide you with the flexibility to go beyond 3 source arrays. All of Shearwater's source arrays have ultra-long, digital umbilicals meaning that we can deploy multiple sources in a wide tow configuration and ultra-wide tow streamer configurations with inline near offsets below 100m.
eSource Bandwidth-Controlled Seismic Source
Conventional marine airguns emit acoustic energy across a wide range of frequencies. However, the eSource airgun generates energy required for seismic imaging, while suppressing high-frequency energy outside the usable seismic bandwidth. This reduces possible effects on cetaceans and other marine mammals that are sensitive to seismic energy at higher frequencies.
The eSource can be configured to output energy at three different levels by swapping a single mechanical component. Depending on the mammal sensitivity and seismic imaging requirements, the seismic crew can quickly configure the source to the desired level. In addition, the eSource can be easily added to existing back-deck infrastructure and is compatible with existing vessels and source controllers, which significantly lowers the cost and risk of adoption.
Dual Near-Field Hydrophones
Marine source signature estimation using near-field hydrophone (NFH) measurements is a well-established procedure for accurate broadband de-signature of seismic data. In the case of a single NFH per source element, it is necessary to define a model for the propagation of sound from each source element. This requires knowledge of the precise layout of sources and receivers together with the reflectivity of the sea-surface. Using multiple hydrophone measurements removes both the need to model the ghost path, and to parameterize the sea-surface reflectivity. Improved methods for deriving marine seismic signatures using Dual Near-Field Hydrophones have recently been described in the literature, however, the ability to record these extra measurements is required. Shearwater is now able to record this data on a number of vessels and is continuing to expand this capability across the fleet.
Harmony is a new source from Shearwater with enhanced low-frequencies. It consists of modified airguns tuned for bubble frequency locking of the pressure wavefield (Hopperstad et al., US patent 9360578), with a resultant shift of half to one octave of the dominant frequency, depending on the reference source design.
Harmony uses the position of one standard sub-array and so is operationally very flexible. It can be used in multi-source designs or combined with itself to increase output, or in conjunction with traditional sub-arrays to create a desired output frequency spectrum, tuned for the survey objectives.