Siemens researchers collaborating with the Russian oil company Rosneft have developed an enhancement to a conventional technique for boosting extraction of oil from wells. Rosneft tested the procedure at 27 oil wells and succeeded in increasing the flow by an average of 17 tons per day. Using the conventional approach, the wells produced only 8.6 additional tons.
The average recovery factor worldwide for oil wells is between 35 and 40% of a total deposit. Only around 10% of the petroleum is initially channeled by natural reservoir pressure into boreholes (primary phase of production). From there it is pumped to the surface for further processing.
Secondary production uses a variety of techniques to increase the yield to the average recovery levels, such as injecting water, gas or steam to increase the pressure in the well. Hot steam and gases such as carbon dioxide also lower the viscosity of the oil.
Engineers from Siemens and RN-Ufanipineft—a research institute operated by Rosneft in the city of Ufa near the Ural mountains—developed an efficient, cost-effective method for increasing the oil-flow rate in the near–borehole zone of an oil reservoir.
The method is based on a long-applied technique for cleaning oil wells using an acid solution to dissolve impurities, such as calcium, gypsum, and barium sulfates, which are found in oil-bearing sediments and would otherwise block the flow of oil into the borehole. The reservoir is first flooded with the solution, which is then pumped out and the affected rock is washed with water. Without this treatment, which is normally carried out once every two to five years, the product extracted from roughly one million boreholes, which yield 30 billion barrels annually worldwide, would be around 30% less.
However, application of the acid is imprecise and inefficient, as part of the solution disappears into layers of sediment where it isn’t needed.
The new technique uses foam pumped into the bore hole in the first step to seal off most of those areas of the underground reservoir that don’t need to be cleaned, but which nevertheless soak up large amounts of the solution in conventional applications. The acid mixture subsequently introduced into the well flows to points where obstructions are waiting to be dissolved.
Use of the sealant also reduces the amounts of chemicals required for the cleaning process, saving money and reducing the environmental impact.
Siemens now wants to work with Rosneft on projects for the extraction of oil from oil shale. A corresponding feasibility study is now in progress.