Oil

Exceptions to the rule

Reservoirs more than 5,000 meters below the surface were long considered impossible to develop. It was generally accepted that, crushed under thousands of meters of geological strata, they were bound to be unsuitable for production. Yet between 1999 and 2007, more than 20% of the world's new reserves were discovered deep below the Earth's surface. When certain reservoirs were shown to be exceptions to the rule and to harbor potential, Total became a key player in developing them. Back in 1986, when we acquired an interest in the acreage in the U.K. sector of the North Sea in which the Franklin field had just been discovered at a depth of 5,300 meters, our experts were convinced it could be brought on stream. Meanwhile, our geoscientists had a "hunch" that a similar field existed in a neighboring block. Their intuition was rewarded by the discovery of the Elgin field in 1991. It was the start of a far-reaching industrial adventure.

An unrivalled feat

Like all very deep reservoirs, Elgin/Franklin is a high-pressure (1,100 bar)/high-temperature (190° C) formation. Because of the geological complexity of very deep strata, pressures can vary abruptly as you drill through the reservoirs. There is a very real risk of serious damage to the geological formations or of oil or gas eruptions. In addition, starting at 180° C, the heat disables the electronic systems that provide real-time analysis of the geological structures being drilled. It took ten years of R&D for Total to successfully drill six wells in each field, pulling off the feat of bringing Elgin/Franklin on stream in 2001. The Elgin/Franklin development, the largest high-pressure/high-temperature project in the world, remains an exploit unrivalled to this day.

A record and a world first

Since coming on stream, Elgin/Franklin remains a choice proving ground for demonstrating our state-of-the-art expertise in deeply-buried reservoirs. To make the site's facilities cost effective, we made the bold move of transporting production from Glenelg, a nearby gas and condensate field discovered in 1999, to Elgin/Franklin. The gamble paid off in 2006, when a 7,300-meter-long step-out well was drilled from the Elgin platform. Its target, located at a depth of 5,600 meters, was a reservoir with a temperature of 200°C and a pressure of 1,150 bar. An extreme drilling operation, it set a record in the North Sea.
The ultimate challenge for our drilling teams was drilling a new well into the Franklin reservoir several years after it was brought on stream, to continue its development. Yet at the time the field first began producing, this option was considered unfeasible because of the enormous pressure differences between the untapped and developed areas. This endeavor, too, was crowned with success, when an infill well was drilled in the high-pressure/high-temperature reservoir in 2007 - a world first!

A vast subject for research & development

 Why do some reservoirs have potential despite their deepness and what are the factors that helped preserve them? Geologists are the ones who will have to answer this tough but critical question, the only way to identify the best potential targets for very deep exploration. Locating fields across more than 5,000 meters of sediment also challenges conventional seismic methods. As distance increases, the ultrasound image of the subsurface fades and only the use of innovative methods for seismic data acquisition and image processing allows us to "see" that deep. Temperatures close to 300° C at a depth of more than 6,000 meters and pressures of over 1,500 bar require the development of new techniques and drilling tools and the qualification of new materials that can help wells withstand this below-ground inferno over long periods of time. This vast area of R&D will serve in the future for the potential development of other deep fields discovered by Total, such as Victoria in the North Sea, Incahuasi and Itau in Bolivia, and Maharaja Lela/Jamalulalam in Brunei. In 2008, the sultanate saw two successive discoveries below producing reservoirs, one by means of a 5,858-meter well, the deepest ever drilled in a high-pressure/high-temperature formation in Brunei.