While the shadow of doubt over global oil resource levels peaking anytime soon may have passed by for the oil industry, it is an undeniable fact that the world’s hydrocarbon reserves will not last forever.
Even with the shale boom in North America and the frequent discoveries announced in Iraq, current consumption levels have made it difficult for oil companies to maintain production levels against available resources.
The oil and gas industry has found many ways to deal with this massive challenge, feeding the world’s demand for energy is no easy task. Global energy demand in 2050 is projected to double or even triple from its 2000 level.
The growing role which natural gas will play in the world’s energy mix has been a major factor in allaying fears about reserve decline, deep drilling and subsea production have also made it possible for oil companies to tap into a massive wealth of resources that were formerly off-limits.
Despite the many innovative ways that the oil and gas industry has managed to find for new reserves to offset growing consumption levels, it is the companies that are developing new hydrocarbon recovery techniques that will save the day.
Mature fields worldwide account for a very large proportion of the world’s oil supply. Oil companies are continuing to look at methods in which they can prolong the lives of the fields they operate in order to ensure that the oil keeps flowing.
Tertiary Production, more commonly known as Enhanced Oil Recovery (EOR), is the generic term for techniques that can help to increase the amount of crude oil that can be extracted from an existing field. EOR relies on the reduction of surface tension or viscosity to encourage the flow of oil trapped in rocks.
This can be achieved through injecting chemicals (polymers or surfactants), gases (carbon dioxide, hydrocarbons or nitrogen), or steam into the reservoir.
The general consensus throughout the industry is that most primary and secondary production techniques can allow a company to extract approximately 30% of the hydrocarbons in an oil field. But the implementation of EOR techniques can increase this level to about 60%.
According to a report published by Royal Dutch Shell about the company’s developments in EOR techniques, a 1% increase in the global efficiency of hydrocarbon recovery would raise conventional oil reserves by up to 88 billion barrels, which is equivalent to three years of annual production at today’s levels.
Although the Middle East may be the world’s most bountiful hydrocarbon producing region, it is no stranger to EOR techniques. Countries like Saudi Arabia and Iraq may be decades away from needing to rely on such methods, but even these oil exporting powerhouses will eventually need to milk their reserves.
Other countries within the Gulf, also years from needing to implement EOR methods, have already started looking at ways they can extend the production capacity and lifetimes of their reserves.
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But only one country in the region has really defined itself as a market for EOR; the Sultanate of Oman. A country which features tough geological formations that hold relatively small amounts of heavy oil, Oman is one of the world’s most ideal locations to develop tertiary production techniques.
Under the stewardship of Petroleum Development Oman (PDO), the country really has come a long way to fulfilling that end.
The company’s strategy to develop EOR techniques has clearly paid its dividends. Last year, it broke its own production record to hit 1.24 million barrels of oil equivalent (boe) per day , a step up from its previous best of 1.21 million boepd in 2001.
Daily oil production now stands at around 566,305 barrels per day (bpd), and above the company’s long-term plateau target of 550,000 bpd. Daily production of non-associated gas stood at 582,500 boepd, and condensates at 92,500 bpd. The combined yield meant that the company had increased its aggregate production figure for its fifth consecutive year.
Currently, EOR techniques account for 3% of the company’s evolving portfolio, but this is expected to hit 16% by 2016 and 27% by 2021. The company currently has a total of six EOR trials in operation or in engineering execution.
Perhaps one of the most famous EOR projects in Oman is that which is taking place in Marmul. A 25 year old field which has only produced approximately 15% of the oil in place, Marmul has proven itself to be a challenging operation.
According to Shell, a water flooding scheme was installed to boost recovery, but due to the thickness of the oil, the water would simply bypass the reservoir instead of helping to increase yields.
PDO has since turned to polymer flooding; a scheme which involves treating injected water to remove impurities before mixing it with polyacrylamide, the substance is then injected into the reservoir under high pressure.
Shell reports that since 2010, PDO has been injecting about 100,000 barrels per day of the polymer solution into the reservoir, with the aim to increase oil production by 8,000 barrels per day and raise the recovery factor from 15% to over 25%.
The partnership between PDO and Shell has also led to the development of miscible gas flooding, a technique which can simultaneously increase reservoir yield while acting as a carbon storage mechanism. The Shell report explains that the gas acts as a solvent for the oil, the resultant solution has reduced viscosity and hence better flow characteristics.
Methane, liquefied petroleum gas, nitrogen and carbon dioxide are commonly used.
The Harweel cluster of fields in Oman have become the grounds for miscible sour gas flooding.
The Harweel cluster contains more than 60 wells drilled into reservoir structures characterised by 100 metre thick carbonate stringers, says the report by Shell.
These slabs of carbonate rock lying at depths of 2.505 km are salt encased and contain light sour oil.
During the first phase of the project, when production levels were about 18,000 bpd, miscible gas containing 3-4% hydrogen sulphide and 10-15 % carbon dioxide was injected into the Zalzala field to confirm the viability of miscible sour gas injection. By April of last year, the project was online, producing some 25,000 bpd, well ahead of schedule.
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But last year, also saw the development of thermally assisted gas oil gravity drainage (TAGOGD) recovery mechanisms in Oman as well. Naturally fractured reservoirs create difficulties for all EOR techniques, especially where the production of heavy oil is concerned.
At the Qarn Alam field, the TAGOGD method is used to inject steam directly into the fractures of the reservoir. The steam acts as radiators to heat the rock and reduce the viscosity of the oil by up to 100 times, according to Shell. The thinner oil flows more readily from the matrix rock into the fractures and then drains by gravity into an oil rim.
One of the key advantages of the TAGOGD scheme is that the number of wells required to heat the reservoir is considerably lower when compared with conventional steam flooding.
According to PDO, this was the first time that such a technique had been attempted in a carbonate field anywhere in the world. The technique is estimated to increase recovery by 20-35% from a field was otherwise operating at a recovery factor of 3-5%.
But no analysis of developments in enhanced oil recovery in Oman can go without a look at what has taken place in Amal West. At the end of last year, the Amal West Solar Steam Generation Pilot, the largest plant in the world to use such technology, started producing steam to be injected downhole.
Developed by GlassPoint Solar, the project focuses the sun’s energy with the use of lightweight, reflective mirrors to boil produced water that is then fed directly into PDO’s existing steam distribution network and used as a thermal EOR method to extract heavy oil.
Unlike traditional solar-steam projects, GlassPoint installs the bulk of its equipment inside a glasshouse. By protecting its mirrors from the harsh desert environment, in particular the sandstorms, the company is able to use more lightweight mirrors and equipment.
This means that an operator does not have to rely on heavy steel and concrete installations to ground what is effectively a field of metallic sails against the wind.
“We cost about a third of a conventional oil site trough, one third of the capital expenditure,” says Rod MacGregor, CEO and founder of Glasspoint.
“The weight of the mirror system is a tenth of that, so a conventional system will be about 30 kilograms per square metre, we weight about 3 kilograms.” In the remote regions of Oman where logistics are a serious concern, such cost differentials can make a huge difference. The GlassPoint system has really emerged as a project that is perfectly suited for Oman.
“We were looking at what you need to make solar EOR successful, and you need three things. Heavy oil, abundant sunshine, and a shortage of alternative fuel. Anywhere those three things are present is a good opportunity for us,” says MacGregor.
Naturally, Oman has all three. The success of GlassPoint’s system has been recognized throughout Oman’s EOR market. The project produces a daily average of 50 tonnes of emissions-free steam that feeds directly into existing thermal EOR operations at PDO’s Amal West.
The 7MW system is in regular operation and recently passed its first performance acceptance test since coming online, exceeding contracted steam output by 10%.
“The GlassPoint system is proving it can reliably fuel thermal EOR with solar power while reducing the need to burn natural gas. This solar EOR solution provides for an economically viable and environmentally sustainable long term resource to develop Oman’s heavy oil portfolio, while saving valuable natural gas resources for use in other gas-dependent industries,” says Restucci.
By incorporating solar steam, PDO reduces the amount of natural gas used for steam injection. With Oman’s already limited supply of natural gas, this not only saves the country money, but it allows for the gas to be diverted towards industries that can create more local employment for Oman.
“You don’t burn gas to create the steam, that means the gas can be used for something else, that something else is usually job creation,” says MacGregor. “So you give the gas to a local industry and create jobs with it, you can use it for power generation, desalination, but job creation seems to be at the top of the list.”
In numbers:
– 60% Recovery Industry experts say that EOR techniques can increase oil recovery from fields to this much
– 25,000 bpd Production rates at the Harweel cluster of fields in Oman after the implementation of miscible gas injection techniques.
– 50 tonnes The GlassPoint Solar steam project in Oman is producing a daily average of this much steam.
