Strong and Silent Type
In 1993 PGS was getting ready to launch its latest 3D seismic ship, the Nordic Explorer, towing up to 5 seismic streamers – almost twice as many as its competitors. Acquisition Manager Einar Nilsen was at Langsten yard on the west of Norway, when he saw a pale gray vision of the future: the mysterious Marjata, a Norwegian navy spy ship. This delta-shaped maritime Mata Hari was designed to lie quietly and listen for Russian submarines in the Arctic. Extremely stable and broad in the beam, she was built to withstand top-ice but all that space had other potential in Einar’s mind. He met the designer Roar Ramde and explained a bit about multi-streamer seismic operations. Then he got on the phone to the PGS head office to tell them that the holy grail of seismic had been found. Within a few weeks, PGS agreed to build the first two seismic Ramforms, tying the design indelibly to the PGS brand. Since then we have continued to evolve the Ramform design and built a lot more. This continues to be the best design in the world for seismic survey ships.
Ocean Bottom Seismic (OBS) is one of the best technologies not to make it big in seismic. Pressure and velocity sensors collocated in the same cable are placed on the seafloor, well out of the weather window, offering clearer 3D images in shallow water and obstructed areas, and more effective multiple attenuation. PGS attempted repeatedly to get the idea to work in the mid-1990s, with towed and dragged arrays, using two sensors 2C and four sensors 4C (FourCe) before dropping out of the field in 2005. Unfortunately, the market was too small to make it a profitable business. Though OBS fans insist that its time will come, this technology has so far failed to thrive. Processing remains a challenge, especially the converted waves and operational efficiency is low compared to modern towed streamer operations. Technologists still like the science, but economists are not keen on the ROI.
Stand Up and Be Counted
Using the vertical cable method, strings of seismic receivers were suspended vertically in the water column, held at the surface by submerged floats and fixed to the seabed by anchors. In theory, the 3-dimensional receiver grid allowed endless flexibility in acquisition geometry, both azimuth and offset. It seemed ideal for smaller complex surveys, especially in obstructed areas. However, the model was difficult to emulate in real life, as currents twisted the perfect lines into less desirable formations. The market never materialized. Just one customer was interested in sponsoring this technology.
August 2002, Norsk Hydro transferred its share of Production License 038 in the North Sea to PGS. PL 038, otherwise known as the Varg field, was considered to be on its last legs, with increasingly watery extractions and declining reserves. PGS had a particular interest in keeping production going, as we were the owner of the floating production facility on site, FPSO Petrojarl Varg. Our management team believed that better seismic data and a new production plan could significantly extend the life of the field. It was a hunch that paid off. PGS bought the field for 1 Norwegian krone. Recoverable reserves on Varg more than doubled following the drilling of two new wells, based on the industry’s first commercial MAZ survey and inspired work from the PGS reservoir team. Pertra, the business created from this venture, was sold for NOK 1.5 billion.
Ghostbusters – part 1
In 2001 PGS financial woes meant non-essential activity ground to a halt. The development of GeoStreamer® was in its early days and its results were far from stellar at this stage. Nevertheless, PGS management calculated that the potential upside of making this work was worth the risk and voted to protect the program. Six years later the new ghost busting technology took the industry by storm and launched the broadband seismic revolution, opening up a host of new development opportunities.
Need for Speed
In 2010 PGS launched the PGS hyperBeam®, a unique combination of beam migration and immersive visualization. The beam machine slashed months off the time from survey to production by reducing cycle times for velocity modeling from months to minutes. Rapid depth imaging and model building brought the interpreters, geologists and engineers closer to the processing team.
Ghostbusters – part 2
In 2011 PGS expanded on its de-ghosted GeoStreamer receiver technology with a time and depth-distributed source, designed to avoid all ghost effects on the emitted source signal spectrum. Complementary signals emitted by sub-sources in the array allow the source ghost effects to be removed, permitting the recovery of much richer low and high-frequency signal information.
Who says Resistance is Futile?
After the turn of the millennium, there was a buzz in the air around electromagnetics. EM was touted as the panacea for dry holes. A single sweep of data would determine the content of the reservoir before drilling. PGS leaped into the fray, initially pouncing on a budding alternative technology called multi-transient electromagnetic. It was a learning experience and education can be expensive. Though MTEM did not fulfill its early promise, the drive to find an efficient electromagnetic solution continued. In 2012 using a towed streamer and source, PGS introduced a brand new EM solution that combines data quality and unbeatable operational efficiency.
Under the Ice
Developed in the early 1990s, the remotely operated marine vibrator has been described as the next big thing in seismic for over two decades. Twenty years on, it is equally flushed with promise but still on the test bench. As exploration advances towards the poles, its developers are hoping that inertia will thaw. The marine vibrator could yet tip the balance in arctic and ice-bound exploration. It also promises a range of other exciting potential benefits, from low-frequency signals to multiple, flexible source arrays.
Permanent seismic monitoring has enormous potential, but our industry has been slow to adopt it on a grand scale. One problem is the reliability of electronics over the producing life of a field. The PGS OptoSeis® solution draws on the longevity of fiber optics to measure dynamic reservoir properties. Currently in operation on a part of the Jubarte field off Brazil.