Oil companies have traditionally used improved oil recovery (IOR) methods, such as water and gas injection or additional wells, to squeeze out more reserves. Enhanced oil recovery (EOR), which targets immobile oil trapped in the pores, is considered a less mature technology, but is being increasingly tested on the Norwegian shelf.
Low Shear Polymer Injection
The most popular method being studied by most licensees on the Norwegian shelf is polymer flooding, according to the Norwegian Petroleum Directorate’s Petroleum Resources 2014 report. Polymer flooding works by using chemicals (polymers) that increase the viscosity of injection water or block pore channels so that additional oil can be displaced. The technique speeds up oil production.
However, there are several challenges with polymer flooding, a technique which requires handling large quantities of chemicals and control of produced water. One is that polymers are very sensitive to shear and get destroyed in the injection process. The result is less effective flooding operations.
Norwegian company Typhonix is currently leading a NOK 15 million Petromaks 2 research project together with French oil company Total that tests Typohonix’ Pump and Typhoon Valve for low shear injection of polymer. The swirling flow within its cyclone-based choke and control valve reduces shear forces and the level of turbulence compared to conventional valves.
“The industry has seen degradation rates of up to 50% due to shear,” says Ole Jørgen Engelsvoll, Typhonix general manager. “We want to reduce that significantly by developing low shear equipment for use in connection with injection.”
The technology will be tested at both Typhonix’ lab in Varhaug near Stavanger and Total’s lab in France during the project period 2013-2015. Although polymer flooding has not been used offshore in Norway much because of environmental restrictions, it is regarded worldwide as one of the most important EOR chemical methods in sandstone reservoirs, according to Typhonix. Statoil for example has been using polymer flooding on parts of the Total-operated Dalia oil field offshore Angola.
First Well Stimulation Tanker
Another way to enhance recovery is by injecting sodium silicate into wells. Under the right conditions, a plug forms and directs the injection water into new undrained areas. Statoil has conducted laboratory tests on preventing water flow with sodium silicate gels in 2008-2009, followed by a field trial in one well on the Snorre field offshore Norway in 2011. Last year, the company successfully completed a pioneer large-scale field test from Siri Knutsen, a converted oil shuttle tanker.
The conversion by Knutsen OAS and Halliburton marked a technological milestone in many ways. It was the first time an oil shuttle tanker was rebuilt into a well stimulation vessel and it was also the largest ship used for stimulation. The vessel pumped 37,000 tons of sodium silicate into the wells -- a significant lift compared to conventional well stimulation vessels, according to Kjetil Skrettingland, Statoil pilot project manager at Snorre.
“Sodium silicate gels have been used in other parts of the world on a smaller scale to make near wellbore restrictions,” says Skrettingland. “This is an old chemical that dates back to ancient Egyptian times. It has been used to bind soil and improve water quality in rivers. But we are using it in a new way and in a large scale.”
Statoil selected the Snorre wells for the pilot project because of their relatively isolated location in the reservoir. This property helps assure that proven changes to the flow pattern are not caused by changes in other wells. There is also a main channel or “thief zone” between the wells where a considerable amount of the injection water flows.
“Production response measurement is ongoing,” says Skrettingland. “Production response from tracer injections shows promising results that indicate a significant alteration of the flow pattern has been achieved.”
Another well stimulation technique being studied is looking to replace hydraulic fracturing, a costly technique in the US. Stavanger-based Fishbones has developed a technology that extends titanium needles in the hole liner to penetrate tight oil reservoirs. The protrusions resemble a bony fish spine poking into the rocks.
Fishbones has received funding from the Research Council of Norway’s DEMO 2000 project in 2012 to test the technology on a consolidate chalk project including pilot well installation. It was also the recipient of Offshore Northern Seas’ SME Innovation Award this August.
The company successfully installed its well stimulation system inside the EnerVest Operating L.L.C. C.B. Jones well in Texas this April. The liner string was fitted with Fishbone’s subs and Backbone open hole anchors, which penetrated the tight limestone formation in the Austin Chalk with Fishbone’s extended needles. Acid was jetted through the needles into the carbonates.
The system represents a technological breakthrough because it not only offers a more time efficient alternative to traditional hydraulic fracturing methods, but also brings environmental benefits by using 95% less fluids. Instead of spending days and hiring hydraulic frac trucks to lift oil recovery, Fishbones’ method takes just hours.
The technology has proved so promising that is has already attracted the interest of Statoil Technology Invest, which announced this June it had taken an 11% ownership interest in Fishbones’ private placement. Statoil was part of the North Sea research cooperation Joint Chalk Research, which managed the pilot project in Texas, along with BP, Shell, ConocoPhillips, the Danish North Sea Fund, DONG, ENI, Hess, Maersk, and Total.
“Fishbones has a unique and cost-effective technology to increase production from challenging reservoirs, and implementation will provide great benefits for Statoil,” said StåleMyhre, STI investment director. “In addition, the downside risks of the technology are low compared to competing technologies."
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