73- www. energy- future. com 5.4- Technology: pushing boundaries temperature rises. That causes the ball to spring apart into something much bigger - something that is either too big to flow through the rock pores or gets tangled up with other exploding Bright Water chains and forms a blockage. Stop thief! What's good about a blockage? The reser-voir contains so- called thief zones, areas into which water preferentially rushes ahead of the rest of the flood, bypassing valuable pockets of oil before breaking out through the produc-tion wells. In the past, thief zones have gen-erally been isolated with the insertion of phys-ical barriers downhole - mechanical plugs, patches, polymer gels or cement. But none of these penetrates very deeply into the thief zones and the injected water can often find its way into the thief zones by other routes. Bright Water, says Cockin, has the poten-tial to plug thief zones automatically. " The fantastic thing is you don't have to have de-tailed knowledge of what the problem is," he says. " It's like putting something in a bi-cycle's inner tube that automatically finds punctures and fixes them." Low- salt diet BP has also been experimenting with changing the salinity of the water it uses to flush oil out of the reservoir. Its LoSal technology, it believes, may be able to add something like 1 billion barrels of proved re-serves around the world. Conventionally, the water used in floods is saline; reservoirs are often injected with sea-water, because they're offshore or close to seawater supplies. " The classical approach is that the salinity of the water doesn't make any difference," says Cockin. " But we've dis-covered that it does." BP has run several tests that involve tak-ing a rock sample from a well and recreat-ing reservoir conditions - temperature and pressure - in a laboratory, before perform-ing a water flood on the sample with low-salinity water. " We've studied over 20 differ-ent rock types and, as long as it's a sand-stone reservoir, in every case we get more incremental oil out," says Cockin. The com-pany's best result has been a 40% improve-ment over a high- salinity flood. About 60% of BP's oil production comes from water floods, and that is set to climb to 80% by 2010, so anything the company can do to improve water flood perform-ance will have a significant impact on over-all recovery. The lateral thinking doesn't stop there. Microbes, which exist naturally in reservoirs and are capable of surviving high tempera-tures and pressures, have potential too. By in-jecting bugs into reservoirs and feeding them, or adding nutrients to stimulate those naturally occurring in reservoirs, their metabolic activ-ity can be manipulated to give rise to by- prod-ucts such as polymers, surfactants and gas. In turn, these can help trapped oil to move more freely. Micro- organisms can also degrade the oil itself, reducing the viscosity of heav-ier oil so that it can flow from the rock pores. Nanotechnology, meanwhile, could one day revolutionise production. ?? When Bright Water reaches a specific warmer temperature, it expands tenfold, popping like popcorn Courtesy BP Frontiers magazine
74- www. world- petroleum. org 5.5- Technology: pushing boundaries Go with the flow - or cause the flow yourself Shale gas - natural gas held in rock formations with extremely low permeability - doesn't flow well. Unless it's given a helping hand There's good news and bad news about natural gas held in shales deep below the earth's surface. The good news is that exploration in the US is proving that many shales contain very large volumes of ex-ploitable gas The bad news is that although shale is the earth's most common sedimentary rock, only a small proportion is suitable as a poten-tial hydrocarbon source. Most muds, when they're deposited, don't contain high levels of organic source material; even when they do, the organic material usually gets oxi-dized before it can be buried. Only in cer-tain low- oxygen environments does the or-ganic material survive intact for long enough to provide a potential hydrocarbon source. And even when hydrocarbons are present, it hasn't always been possible to get at them. Fine- grained shale formations are character-ised by low permeability, which impedes the flow of gas ( or liquids), making shale an inef-fective petroleum reservoir rock. Get them moving But oil firms and oil field services com-panies have developed special production technologies to get them moving. The two main techniques - horizontal drilling and hydraulic fracturing - have been around since the 1950s, but recent refinements have made their use more technically effi-cient and more economic. In simple terms, both techniques improve the contact be-tween the well and the reservoir. Hydraulic fracturing - known as fracing ( pronounced fracking) - involves the use of powerful pumps at the surface to inject a fluid into the reservoir, typically water with a friction- reducing chemical additive that allows it to be pumped into the formation at faster rates. That pressure fractures the rocks around the well, forcing open new Conventional or unconventional? Conventional oil and gas: crude oil and natural gas that is produced by a well drilled into a geological formation in which the res ervoir and fluid characteristics per-mit the oil and natural gas to flow read-ily to the well bore ( as defined by the US Department of Energy's statistic arm, Energy Information Administration). The gusher of folklore is the most productive of this type of well. Unconventional hydrocarbons: any other type of crude oil and natural gas. If it's oil, it might be thick and viscous - and won't flow on its own. The biggest deposits are: Canada's so- called oil sands, containing remaining established reserves of bitumen of 173 billion barrels; and Venezuela's ex-tra- heavy oil Orinoco Belt, containing ul-timate recoverable resources of 272 bil-lion barrels. That puts Venezuela's uncon-ventional oil resources marginally ahead of Saudi Arabia's conventional oil reserves, which are estimated at around 264 billion barrels ( although Saudi Arabia's crude oil is much better quality and much easier and cheaper to get out of the ground). But reserves could increase. What is re-coverable depends on technology, which is improving all the time. Total resources in Alberta and Venezuela, mostly unrecover-able with today's technology, are several times higher. Shale gas is unconventional because it requires special technology to develop it. ??