Queen turned the tap to open Forties Field

Secrecy Part of North Sea Exploration Life

I have always counted myself to be one of those lucky geologists who became involved in a major petroleum province before it was discovered and stayed with it until it reached maturity.

The United Kingdom awarded its first round of offshore licences in the southern North Sea in 1964. BP was quickly off the mark and made the first gas discovery at West Sole the following year.

It was while this was drilling that I arrived on the scene – I had been appointed review geologist based in BP’s small East Midlands oilfields office, from where the North Sea operation was being run.

It was not an onerous job, as I had only three traded wells to review. (UK allows licensees six years before their data is released into the public domain and therefore companies acquire it by well trades.)

So secret was BP’s drilling operation that I was not allowed access to the well data. Nor was I allowed to see any maps; only the senior geologist had that privilege.

Data security was paramount but lacked a budget. I locked away my three sets of well logs with a hasp and padlock bought from Woolworths, while the senior geologist hid his West Sole material amongst the thousands of Coal Measure maps stored in eight large cabinets.

Retrieval presented problems – and some may still be there today!

Risking It All

Following the West Sole discovery I moved to London to undertake my review work amidst a small geophysical team that was struggling to interpret the analog seismic then being acquired.

Upper Permian salt diapirism masked reflections associated with the underlying Lower Permian reservoir, while the existence of multiples and problems of migration and velocity made depth conversion exceedingly tricky. Had the geophysicists not worked wonders, the West Sole well would have missed its target – as did a number of other exploration wells.

By 1966 exploration in the south was in full swing and others were soon making bigger gas discoveries than the 1.5 tcf West Sole field. Meanwhile BP took delivery of “Sea Quest,” the first North Sea semi-submersible rig, which would allow exploration to move into deeper waters to the north.

Early mapping of the 1962 seismic northward had identified an elongated basin running north-south up the center of the North Sea. The lines were widely spaced and the only decent reflector was thought to be the base of the Tertiary. It reached a depth of nearly 10,000 feet in the center of the basin (see map left), and from a structural point of view was completely featureless.

In 1965 the UK embarked on a second round of licensing, including some blocks in northern waters. BP was offered five of these, amongs them blocks 21/9 and 21/10, some 110 miles east of Peterhead. Of all that featureless seismic just one north-south line had shown a very slight turnover. Contouring indicated a nose plunging southeastwardly into the basin running through 21/9 and 21/10.

Throwing caution to the wind we accepted these blocks and the drilling obligation that went with them.

This was in October 1965, and before any gas had been discovered in the southern North Sea.

The water depth was around 400 feet, the sea was extremely hostile and there were no rigs available that could drill in such conditions. This was exploration by the seat of one’s pants.

We would never have got it through the board today now that risk assessment has been invented!

A Major Discovery

As things progressed in the south a tentative drilling program was taking place up north, both in British and Norwegian waters. Things were not encouraging. Over 50 wells had been drilled before Phillips made their major discovery at Ekofisk in Norwegian waters in December 1969. The race for North Sea Oil was on!

Almost simultaneously Amoco discovered oil in Palaeocene sands in 22/18 (Montrose/Arbroath field). Having contracted Sea Quest to drill this well it was very hard for them to keep the news secret from BP, much as they would have preferred.

By then I was regional geologist and was fully aware of what was going on at Arbroath. Fortunately we soon managed a well data exchange so that I no longer had to keep up the pretense of knowing nothing.

By now we had carried out new-fangled digital seismic across blocks 21/9 and 21/10 and the surrounding areas, and the results were encouraging because we had mapped a large low-relief closure. The Amoco well was of particular interest because Montrose was the first closure down the nose from 21/10 and, importantly, it was full to spill point.

Things were suddenly looking up but disaster nearly struck. One of our senior managers popped his head round my door after having had a convivial lunch with his Shell counterpart and said, “I don’t suppose there is any reason why we shouldn’t farm out 21/9 and 21/10, is there?”

I guess the expression on my face was answer enough and, fortunately, nothing more was heard of the idea.

Sea Quest quickly moved to drill 21/10-1 and, in October 1970 at a depth of just under 7,000 feet, it encountered oil bearing Palaeocene sands (just three feet from prediction; well done, geophysicists). Subsequent work showed we had 35 square miles of closure, an oil column of just over 500 feet and 4.4 billion barrels oil in place.

A field of major proportions had been discovered.

Pin-Point Accuracy

The decision to develop was taken immediately, despite the fact that no one knew quite how it could be done in what was then such deep water.

I remember a discussion about laying a pipeline to shore. Some thought it would collapse under the weight of water while others thought it would float to the surface. Such was the knowledge of offshore technology at that time. How things have changed in 40 years!

The field was given the name “Forties.” “Forties” is a fishing/meteorological area so called because it occupies a large part of the North Sea that is almost universally 40 fathoms (240 feet) deep. It was ironic that our Forties Field was discovered in the only part of that area that was around 400 feet deep!

Five years later the first of four production platforms was in place and drilling had commenced. The pipeline to shore had been laid (without collapsing or floating) and an operations HQ had been set up in Aberdeen, Scotland.

All was ready for Her Majesty the Queen to visit Aberdeen on Nov. 3, 1975, for a grand celebration – during which she pressed the button that allowed first oil to come ashore.

Full marks must go to the geophysicists whose painstaking work led to the discovery of the Forties structure.

For my part I felt much gratification at being the guy that stuck the pin in the right place on one of their maps.

Comments (0)


Historical Highlights

Historical Highlights - Peter J. Walmsley

Peter J. Walmsley, MBE, spent his entire working career with BP and its associated companies until 1981, when he was recruited to the UK Department of Energy to become director general, Petroleum Engineering Division, with responsibility for all things technical, ranging from geology to the safety of divers. He retired in 1989. During his time with BP he served in the Middle East and Trinidad before returning to the UK to work on the North Sea. He became exploration manager, Aberdeen, prior to returning to London as deputy chief geologist. He was honored with the MBE (Member of the Order of the British Empire award) by Her Majesty the Queen in 1975 for his part in the discovery of the Forties Field. He now lives in retirement in Surrey with his wife, Edna.

Historical Highlights

Historical Highlights - Hans Krause

Hans Krause is an AAPG Honorary Member, Distinguished Service Award winner and former chair of the AAPG History of Petroleum Geology Committee.

Historical Highlights

A History-Based Series, Historical Highlights is an ongoing EXPLORER series that celebrates the "eureka" moments of petroleum geology, the rise of key concepts, the discoveries that made a difference, the perseverance and ingenuity of our colleagues – and/or their luck! – through stories that emphasize the anecdotes, the good yarns and the human interest side of our E&P profession. If you have such a story – and who doesn't? – and you'd like to share it with your fellow AAPG members, contact the editor.

View column archives

Image Gallery

See Also: Book

Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 4457 Book
Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 8373 Book
Alternative Resources, Structure, Geochemistry and Basin Modeling, Sedimentology and Stratigraphy, Geophysics, Business and Economics, Engineering, Petrophysics and Well Logs, Environmental, Geomechanics and Fracture Analysis, Compressional Systems, Salt Tectonics, Tectonics (General), Extensional Systems, Fold and Thrust Belts, Structural Analysis (Other), Basin Modeling, Source Rock, Migration, Petroleum Systems, Thermal History, Oil Seeps, Oil and Gas Analysis, Maturation, Sequence Stratigraphy, Clastics, Carbonates, Evaporites, Seismic, Gravity, Magnetic, Direct Hydrocarbon Indicators, Resource Estimates, Reserve Estimation, Risk Analysis, Economics, Reservoir Characterization, Development and Operations, Production, Structural Traps, Oil Sands, Oil Shale, Shale Gas, Coalbed Methane, Deep Basin Gas, Diagenetic Traps, Fractured Carbonate Reservoirs, Stratigraphic Traps, Subsalt Traps, Tight Gas Sands, Gas Hydrates, Coal, Uranium (Nuclear), Geothermal, Renewable Energy, Eolian Sandstones, Sheet Sand Deposits, Estuarine Deposits, Fluvial Deltaic Systems, Deep Sea / Deepwater, Lacustrine Deposits, Marine, Regressive Deposits, Transgressive Deposits, Shelf Sand Deposits, Slope, High Stand Deposits, Incised Valley Deposits, Low Stand Deposits, Conventional Sandstones, Deepwater Turbidites, Dolostones, Carbonate Reefs, (Carbonate) Shelf Sand Deposits, Carbonate Platforms, Sebkha, Lacustrine Deposits, Salt, Conventional Drilling, Directional Drilling, Infill Drilling, Coring, Hydraulic Fracturing, Primary Recovery, Secondary Recovery, Water Flooding, Gas Injection, Tertiary Recovery, Chemical Flooding Processes, Thermal Recovery Processes, Miscible Recovery, Microbial Recovery, Drive Mechanisms, Depletion Drive, Water Drive, Ground Water, Hydrology, Reclamation, Remediation, Remote Sensing, Water Resources, Monitoring, Pollution, Natural Resources, Wind Energy, Solar Energy, Hydroelectric Energy, Bioenergy, Hydrogen Energy
Desktop /Portals/0/PackFlashItemImages/WebReady/book-s59-Carbon-Dioxide-Sequestration-in-Geological-Media.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 5827 Book

See Also: Bulletin Article

We describe the structure, microstructure, and petrophysical properties of fault rocks from two normal fault zones formed in low-porosity turbiditic arkosic sandstones, in deep diagenesis conditions similar to those of deeply buried reservoirs. These fault rocks are characterized by a foliated fabric and quartz-calcite sealed veins, which formation resulted from the combination of the (1) pressure solution of quartz, (2) intense fracturing sealed by quartz and calcite cements, and (3) neoformation of synkinematic white micas derived from the alteration of feldspars and chlorite. Fluid inclusion microthermometry in quartz and calcite cements demonstrates fault activity at temperatures of 195degC to 268degC. Permeability measurements on plugs oriented parallel with the principal axes of the finite strain ellipsoid show that the Y axis (parallel with the foliation and veins) is the direction of highest permeability in the foliated sandstone (10–2 md for Y against 10–3 md for X, Z, and the protolith, measured at a confining pressure of 20 bars). Microstructural observations document the localization of the preferential fluid path between the phyllosilicate particles forming the foliation. Hence, the direction of highest permeability in these fault rocks would be parallel with the fault and subhorizontal, that is, perpendicular to the slickenlines representing the local slip direction on the fault surface. We suggest that a similar relationship between kinematic markers and fault rock permeability anisotropy may be found in other fault zone types (reverse or strike-slip) affecting feldspar-rich lithologies in deep diagenesis conditions.
Desktop /Portals/0/PackFlashItemImages/WebReady/Bulletin-hero-2013-07jul.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 5694 Bulletin Article

See Also: Energy Policy Blog

Crude oil and natural gas infrastructure problems, from pipeline oil spills to train derailments and fires, have been in the news recently. Though these problems are not new, public concern is growing. Think tanks and government agencies have been considering the problems and potential solutions for some time and are now reporting the results of their studies. Here are reports of one oil and one natural gas infrastructure study.
Desktop /Portals/0/PackFlashItemImages/WebReady/Oil-and-natural-gas-infrastructure-challenges-03mar-17-2015-hero.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 16886 Energy Policy Blog