Dual Sensor Towed Streamer: From Concept to Fleet-Wide Technology Platform

Abstract

discuss the lessons learnt from the roll out of dual-sensor technology in PGS' fleet.T he launch of the dual-sensor towed streamer technology in 2007 is seen by many in the industry as the most important milestone in marine seismic technology in the last decade. The introduction of the technology triggered a significant interest and demand for broader bandwidth seismic data and increased the industry-wide awareness of the geophysical benefits of such broadband data for both frontier exploration and production monitoring in mature basins. It also resulted in the rapid development of new acquisition and processing technology, both concerning the source and receiver side, as well as changes to seismic vessel design and equipment. The geophysical benefits of broadband data and the availability of up-and down-going wavefields as part of the dual-sensor deghosting methodology are now routinely exploited throughout the entire seismic value chain, including seismic imaging and reservoir characterization.After the first 2D dual-sensor survey in 2007, which was quickly followed by the first 3D acquisition commencing on New Year's Eve 2008, PGS has steadily converted its seismic fleet from hydrophone-only to dual-sensor streamers. The pace of the technology roll-out has been largely driven by the life-cycle of existing streamer inventory and the equipment needs for newly launched seismic vessels as part of an ongoing fleet renewal process. The fleet-wide roll-out of dual-sensor technology will finally be completed in the 4 th quarter of 2015 with the upgrade of the last Ramform vessel. Given the scale and complexity of replacing and industrializing a complete acquisition platform, there have naturally been significant lessons, some of which we will be sharing in this article. We will also discuss some of the acquisition and processing technologies that have been developed and/ or adapted in order to fully utilise this new marine seismic technology platform. Robust ghost removal for deeper streamer towTo be successful in today's challenging E&P environment, petroleum geoscientists must detect and properly image increasingly complex reservoirs by resolving the fine detail of ever smaller hydrocarbon accumulations. High quality seismic data plays a key role in this task and is of great significance in the effort to reduce overall E&P risk. The demands placed on modern seismic data are multifold, but critically the data needs to enable the identification and delineation of leads/prospects based on pre-stack seismic and to quantify key reservoir properties to increase the probability of successfully separating lithology-fluid facies. All of these goals must be achieved in 3D using all the dimensions of the seismic data, mainly pre-stack, and later on 4D (time-lapse). It has been well understood for some time that data richer in both low and high frequency information would form the optimum input for improved reservoir delineation and high-resolution imaging and that improvements in the signal-to-noise ratio of the recorded data ...

Acoustic Pressure and Particle Velocity for Spatial Filtering of Bottom Arrivals

“…In recent years, VS have also been used on towed streamers for the elimination of surface reflections (ghosts); however, details of these developments have limited publicity as they contain commercially sensitive information. It was also concluded that VS allowed us to operate surveys closer to the bottom, increasing the signal-to-noise ratio (SNR), hence enhancing the system seismic imaging performance [23], [24]. Recently, the usage of mobile platforms for seismic geophysical surveying, mainly those where the streamers are installed in AUVs, is subject of attention, in particular in the European project WiMUST [25].…”

Improved HSEQ and survey efficiency demonstrated with a new remotely operated streamer cleaning tool

“…In 2011, a new version was introduced that is also able to pass three-wing birds. SCUs were initially used only during line changes and no data recording, but the introduction of a noise removal algorithm has enabled online operation which has now become standard (Widmaier et al, 2015). Although this device has served us well, its usage depends on allowable workboat weather.…”

Development and Testing of a Dual Accelerometer Vector Sensor for AUV Acoustic Surveys

“…In sea surveys in particular, water-bottom cables with such sensors have been used for the attenuation of water-column reverberations [ 11 ]. In recent years, vector sensors have been used on towed streamers for the elimination of surface reflections (ghosts) [ 12 ], however details of these developments have limited publicity as they contain commercially sensitive information. A further advancement in marine geo-acoustic surveys is the replacement of the ship-towed streamers with sensors either towed or carried by Autonomous Underwater Vehicles (AUV).…”