The successes of the Uvat project are impressive, especially against a backdrop of slower production growth across Russia as a whole and falling efficiency of exploration work.
In less than one year TNK-BP has managed to extract almost 2 million tons of oil from its new Eastern Uvat fields; the company has now begun developing Central Uvat, and in August is preparing to bring the Tyamkinskoe field on stream. These achievements are a great credit to TNK-Uvat’s geologists, who are applying advanced technologies and even developing new ones of their own. They have recently taken up a new technique known as commingled oil production.
TNK-Uvat’s deputy chief geologist, Alexander Prokhorov, explained to a Vslukh.ru correspondent that some fields contain not one, but several productive horizons. The law states that the oil companies have the right to operate such horizons jointly only if they can meter each reservoir separately — in short, if they can separate the production. However, this is very costly in terms of money and time.
The solution to the problem is commingled oil production, which makes it possible to develop two reservoirs at the same time via a single well, without drilling an additional grid or disconnecting the reservoirs. At the wellhead the flow-rates are measured and all the hydrodynamic tests are performed. Two reservoirs can therefore be brought on stream at the same time, doubling the flow-rate from a single well and boosting the oil recovery factor. Using conventional technology, the lower formation is developed first, before moving on to the upper reservoirs.
The catch, however, is that it is not possible to fully deplete the lower formation in practice: what happens is that when the flow-rate drops to 2—3 tons per day the well is deemed sub-commercial and the drillers move on to the overlying formation. With commingled production, even with a high water cut and production of just 2—3 tons from the lower reservoir, the more productive higher formation can be developed at the same time. “The technology is designed to tap all the reserves, maximize the recovery factor and improve the field’s economics”, noted Prokhorov.
Commingled production will be trialed at the Ust-Tegusskoe field, which has two productive reservoirs. The field’s development plan envisages drilling 40 wells into each of the reservoirs; if the pilot project is a success, it will be possible to achieve the same result with 40 wells as with 80, thereby cutting costs.
Prokhorov said that the first experimental well was spudded a few days ago and would take 30—32 days to drill. TNK-Uvat hopes to have some initial results in May. The plan is to drill two wells of this type at Ust-Tegusskoe in 2010. The company has so far signed a contact with Schlumberger and Baker Hughes to supply the necessary equipment, while KAC Deutag will perform the drilling work. The Christmas tree will be manufactured in Romania and downhole equipment sets are already being delivered.
This promising new technology came to Russia from abroad, but even there it is new and rarely used. Good results have been achieved from commingled production in Ethiopia and Ecuador. TNK-BP previously used a similar technology in the Orenburg region, but the wells there were fitted with sucker rod pumps rather than ESPs.
Another new technique, this time developed by TNK-BP geologists jointly with contractors from Tomsk, has also been given its Russian debut in the Uvat fields: at the Urnenskoe field, interference testing has been performed by injecting oil rather than water into the well. Developed for fields located far away from infrastructure, the technique involves making tight wellhead connections (to prevent oil spills or seeps) at the first well, measuring the flow-rate, running a line to the second well and pumping the oil to it instead of water.
According to Prokhorov, this prevented any deterioration in reservoir properties during the initial stages and provided the information needed to build a geological model. First used in the summer of 2007 at the Urnenskoe field, the new method proved that the field’s reserves and contours were bigger than the seismic had indicated (giving an increment of 3.5 mln tons of recoverable oil around the first cluster). It also enabled the geologists to design a reservoir pressure maintenance system and study the interaction between the wells. Other companies have now begun applying the technique.
The oilmen are keeping they eye on new ideas from local researchers and have set up working groups at various levels to look into the practicalities of applying new techniques. In Novosibirsk the company aims to apply a method of using reservoir pressure maintenance to boost recovery factors, and at the Kalchinskoe field hydraulic fracturing will be employed in reservoirs that were previously regarded as unpromising.
TNK-BP devotes a lot of attention to new technologies. “As a young company we can’t afford not to do this, because innovations are the future”, says Alexander Prokhorov. Thanks to new technologies the Uvat fields have achieved an average flow-rate of 100 tons – something that would have been considered fanciful not so long ago.