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SINTEF developing new oil-drilling tool concept for small reservoirs; exploiting “dwarves” close to giants

Researchers at SINTEF Petroleum Research in Norway are developing a new drilling tool that may enable the production of oil from small pockets lying close to large fields on the continental shelf. The oil-bearing strata on the Norwegian shelf probably contain many thousands of small oil-filled pockets, and reservoir experts believe that there is as much oil left out there as has been produced from all the major discovered fields together.

If we explore and drill in the traditional manner, many small reservoirs will remain unprofitable and undisturbed. But if we can drill across to some more of them from existing wells, costs will be significantly reduced, and such “dwarf” reservoir close to the giants will become worth exploiting. This will be a very efficient way of enhancing oil recovery rates.

—Jan David Ytrehus, SINTEF project manager

The most important characteristic of the newly developed mole is very visible; it has one “row of teeth” more than other drilling tools. Although the equipment is still on the drawing board, the researchers have used a 12 meter-long model of an oil-well to show how it will work by recreating the imprints—spiral grooves—that the extra teeth would leave in the wall of the well. These grooves are the reason for the expectations that surround the new tool.

  1. All drilling for oil is based on the use of drilling fluid. This has several functions, among them cooling of the drill-bit.
  2. The pressure of the drilling fluid also prevents the well from collapsing and allowing gas to flow into the wellbore during drilling. But it must not be too high; if it were, the drilling fluid would flow out of the well and disappear into the pores of the reservoir formation.
  3. The drilling fluid is kept under a certain additional pressure in order to keep it circulating so that it carries the drill cuttings up to the surface. Traditional drilling requires such high extra pressure that a lot of drilling fluid would flow into depleted reservoirs if the branch wells were drilled from existing wells, so this potential method is insufficiently exploited.
  4. The new drilling tool can get by with lower additional pressure than normal drilling equipment because its extra row of teeth (side-cutters) create spiral grooves in the wall of the well, which makes the removal of drilling cuttings more efficient.
  5. Thanks to the low extra pressure, loss of drilling fluids becomes less of a problem, and this is what has given rise to hopes that the new tool can be used to drill out from existing wells.
Click to enlarge.

Tests in the well model have shown that the grooves improve the efficiency of cleaning out the wellbore; i.e. the removal of drilling cuttings. Ytrehus says that the team believes that the new tool will make it easier to drill branches from existing wells out to nearby pockets of oil.

One of Norway’s experts in petroleum research who is very interested in small unexploited reservoirs is Hans Borge, who directs the Department of Petroleum Technology at the University of Stavanger. Borge believes that the Norwegian continental shelf houses anywhere between 1,000 and 100,000 pockets of hydrocarbons.

According to Borge, the greatest challenge lies in knowing exactly where these small deposits are to be found. He also points out that combined exploration and production wells will usually be a sensible strategy for Norway to adopt in the hunt for pockets of oil.

Suppose that there are 10,000 such pockets. If we conservatively assume a price of US$60 per barrel, these contain oil worth NOK 20,000 billion [US$3,500 billion]. Now that would be come to several “sovereign wealth funds”! But using traditional technology, it would easily need NOK 20,000 billion to produce that oil. And that is simply not realistic.

—Hans Borge

Borge estimates that 1% of the pockets lie less than one kilometer from a reservoir already in production. Although a single percentage may not sound like much, Borge says, there is good reason to believe that in that1%t of pockets lies oil worth several hundred billion kroner.

No matter which Norwegian oil-field you are on, there will always be small unexploited reservoirs in the vicinity.

—Hans Borge

If the new drilling tool meets the expectations raised by the laboratory results, Ytrehus believes that drilling out to pockets up to a kilometer from current wells—if not even further—is possible.

Ytrehus says the new tool has been given a good reception by both the offshore and service industries. SINTEF intends to industrialize the new system by establishing a company for this purpose.


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