Do Oil Wells Re-Charge Themselves?

There have been numerous reports in recent times, of oil and gas fields not running out at the expected time, but instead showing a higher content of hydrocarbons after they had already produced more than the initially estimated amount. This has been seen in the Middle East, in the deep gas wells of Oklahoma, on the Gulf of Mexico coast, and in other places. It is this apparent refilling during production that has been responsible for the series of gross underestimate of reserves that have been published time and again, the most memorable being the one in the early seventies that firmly predicted the end of oil and gas globally by 1987, a prediction which produced an energy crisis and with that a huge shift in the wealth of nations. Refilling is an item of the greatest economic significance, and also a key to understanding what the sources of all this petroleum had been. It is also of practical engineering importance, since we may be able to exercise some control over the refilling process. _Recharging of Oil & Gas Fields

RigzoneOf course we all understand the concept of "repressurising oil fields" using gas injection and other means.

As the oil or natural gas in a formation is produced, the hydrocarbons remaining in the reservoir may become trapped because the pressure in the formation has lessened, making production either slow dramatically or stop altogether.

...gas injection is used on a well to enhance waning pressure within the formation. Systematically spread throughout the field, gas-injection wells are used to inject gas and effectively sweep the formation for remaining petroleum, boosting production.... gas injection can serve as an economical way to dispose of uneconomical gas production on an oil reservoir. While in the past, low levels of natural gas that were produced from oil fields were flared or burned off, that practice is discouraged in some countries and against the law in others.

...Gas Injection, Gas Lift & Gas Miscible Process
Although the terms are sometimes interchanged, gas injection and gas lift are two separate processes that are used to increase production. While gas injection is a secondary production method, gas lift is a type of artificial lift.

Artificial lift is another way to increase production from a well by increasing pressure within the reservoir. The main types of artificial lift include gas lift and pumping systems, such as beam pumps, hydraulic pumps and electric submersible pumps.

While gas injection is achieved by injecting gas through its own injection well, gas lift occurs through the production wells. In gas lift, compressed gas is injected down the casing tubing annulus of a production well, entering the well at numerous entry points called gas-lift valves. As the gas enters the tubing at these different stages, it forms bubbles, lightens the fluids and lowers the pressure, thus increasing the production rate of the well.

Furthermore, a type of EOR employed on a well in the tertiary production process, a gas miscible process can be used to increase production. The difference in this recovery method is that the gases introduced into the reservoir are not naturally occurring. In a gas miscible process, carbon dioxide, nitrogen and LPG are injected into the reservoir. _Rigzone Gas Injection

Most of the oil in existing wells remains underground, waiting for people to become smart enough to retrieve it. Better enhanced oil recovery techniques will inevitably be developed to extract more and more of the residual hydrocarbon -- until it is no longer economical to do so. Then the remaining oil will wait for further developments.

Thomas Gold argues (here and here for example) that oil wells are charged and re-charged with new oil & gas from below. He claimed that most new hydrocarbons are generated deep in the crust, rising into geological traps at several different depths for particular parts of the crust. That is the abiogenic theory of hydrocarbon production, which is supported by astronomical data and by lab data simulating conditions in the deep crust and upper mantle.

Rapid charging of oil fields -- such as is suggested here -- would require deeper secondary reservoirs under pressure, feeding into the primary reservoirs as they are depleted.

There is another way in which oil & gas fields are re-charged -- via the biogenic production of oil & gas. But biogenic production via geologic heat and pressure is generally a much slower method of re-charging than Gold's abiogenic method. But it inevitably occurs all the same. Biogenic oil is a renewable resource, but it is renewable on a different time scale than humans generally use.

And yet, there is a way in which biogenic oil can "rapidly" recharge a depleted oil field. In the case of multiple communicating oil reservoirs at different depths, heat, and pressure, a deeper biogenic reservoir could re-fill a more superficial reservoir at variable rates, depending upon a number of factors. Oil & gas migrate upwardly, when given the opportunity. In this case, instead of "turtles all the way down," it is "oil & gas reservoirs all the way down." ;-)

Biogenic Oil FormationThis image illustrates the conventional idea of biogenic formation of oil. Imagine it taking place over and over again, during the 3 billion + years that photosynthetic life has been converting CO2 into various biological carbon polymers, layer stacked upon layer etc etc . . . . .

Abiogenic Hydrocarbons Forming in the Mantle

This image illustrates the likely abiogenic formation of hydrocarbons in the upper mantle. These hydrocarbons then can migrate upward into the crust, and become trapped under impermeable minerals. Abiogenic hydrocarbons almost certainly mix with biogenic hydrocarbons.

Abiogenic hydrocarbons are also modified in various ways by deep crust microbial populations. In other words, the predominately short-chain abiogenic hydrocarbons from the mantle can be converted to longer chain hydrocarbons on the way up.

Finally, there is the ocean crustal tectonic activity which feeds a constant supply of partially processed organic material to the deep crust and mantle via constant subduction of ocean crust beneath continental crust. This is a slow but steady pipeline which supplies feedstock for production of oil & gas on a constant basis. The Earth's huge gas hydrate resource likely owes a great deal to this tectonic process.

Methane Clathrate Exploratory Research in Alaska

One intriguing idea for the simultaneous recovery of energy and sequestration of global warming gas is proposed by the transformation of methane hydrates to carbon dioxide hydrates with the injection of liquid CO2. Here we use molecular dynamics simulations to show that the replacement can take place without melting of the network of hydrogen-bonded water molecules. Depending on the distance to the interface between the liquid CO2 and solid clathrate hydrate, we find that the replacement occurs either via direct swapping of methane and CO2 or via a transient co-occupation of both methane and CO2 in one cavity. Our results suggest that, with a careful design of the operation condition, it is possible to replace methane from methane hydrates with CO2 in the solid phase without much change in the geological stability. _ACS Abstract

ACS
A team of American and Japanese researchers are in Alaska this month to test a new method of extracting methane hydrates from rich Arctic resources. They intend to inject CO2 into the hydrates in hopes that the waste gas will replace the more valuable methane in the ice cage, freeing up the methane for extraction and use.

This month, scientists will test a new way to extract methane from beneath the frozen soil of Alaska: they will use waste carbon dioxide from conventional wells to force out the desired natural gas.

...The test will use the Ignik Sikumi well, which was drilled on an ice platform in Prudhoe Bay last winter. Specialized equipment has been installed, including fibre-optic cables to measure the temperature down the well, and injection pipes for the CO2. “None of this is standard equipment; it had to be built to design,” says Boswell.

...During the test, the researchers will inject nitrogen gas into the hydrate deposit to try to push away any free water in the system, which would otherwise freeze into hydrates on exposure to CO2 and block up the well. The next phase is to pump in isotopically labelled CO2, and let it ‘soak’ for a week before seeing what comes back up. This will help to test whether the injected carbon is really swapping places with the carbon in the hydrates. Finally, the team will depressurize the well and attempt to suck up all the methane and carbon dioxide. This will also give them a chance to test extraction using depressurization — sucking liquids out of the hydrate deposits to reduce pressure in the well and coax the methane out of the water crystals. “We’ll continue to depressurize until we run out of time or money, and see how much methane we can get out that way,” says Boswell. _Nature

Methane, trapped in an icy cage of water molecules, occurs in permafrost and, in even greater quantities, beneath the ocean floor. It forms only under specific pressure and temperature conditions. These conditions are especially prevalent in the ocean along the continental shelves, as well as in the deeper waters of semi-enclosed seas (see graphic).

World reserves of the frozen gas are enormous. Geologists estimate that significantly more hydrocarbons are bound in the form of methane hydrate than in all known reserves of coal, natural gas and oil combined. "There is simply so much of it that it cannot be ignored," says leading expert Gerhard Bohrman of the Research Center for Ocean Margins... _DerSpiegel

As humans devise more and better ways to utilise methane in place of crude oil, it makes sense to learn how to extract the richest reserves of methane in the crust.

We do not yet know how much of the methane resource originates abiotically in the mantle -- and thus can be theoretically seen as "renewable methane." It is likely to be substantial. And thanks to the giant tectonic plate mechanism, with ongoing subduction of organics-rich oceanic crusts under continental crusts, biogenic methane is, to a large extent, renewable as well -- on an extended time scale, and on a continuous basis. Where do you think most of these methane hydrates came from in the first place? No matter. There are a lot more where those came from.

More Shale Oil than First Believed & Gas That's Cleaner than Wind

EIA Shale Reserves via Brian Wang
North America is glutted with shale gas. But the new energy boom in mainland North America is shale oil -- a much more profitable play. New discoveries of rich shales in the middle of the US high plains are drawing a lot more attention, because these shales appear to be loaded with oil.

The Niobrara Shale formation covers parts of four western states – Wyoming, Colorado, South Dakota and Nebraska...Geologists have known about the oil in Niobrara for about 80 years. But no one ever thought it could be recovered economically… until now. Like the Barnett, Fayetteville, Marcellus, Haynesville and Bakken – the Niobrara is another shale play that’s been known about for some time.
But it’s only recently that some of the major exploration and production companies shifted capital and drill rigs to explore the Niobrara.
And it’s only since the advent of hydraulic fracking and horizontal drilling that it’s possible for this formation to be exploited for the oil and natural gas it contains.
According to El Paso County assessor Mark Lowderman, there have been over 2,200 leases signed with oil companies since 2009.

...A September report from the U.S. National Petroleum Council (NPC) said that U.S. shale oil reserves are “proving to be much larger than previously thought.” The NPC indicated that shale oil production could rise to as much as three million barrels per day “depending on access to new plays and continued technology development.”
That’s significant, but still nowhere near enough to wean the country off foreign oil. But it’ll provide a significant chunk of our current consumption of 19 million barrels per day.

...Keep an eye on the Niobrara. It’s another hot new play in shale oil, and could be a significant contributor to U.S. oil production in the years ahead. _InvestmentU_via_GWPF

In the meantime, the glut of North American natural gas will be waiting for technologists and entrepreneurs to develop new uses and new markets. And why not? According to Matt Ridley, natural gas is cleaner than big wind energy:

The gas well requires no subsidy – in fact it pays a hefty tax to the government – whereas the wind turbines each cost you a substantial add-on to your electricity bill, part of which goes to the rich landowner whose land they stand on. Wind power costs three times as much as gas-fired power. Make that nine times if the wind farm is offshore. And that’s assuming the cost of decommissioning the wind farm is left to your children – few will last 25 years.

Decided yet? I forgot to mention something. If you choose the gas well, that’s it, you can have it. If you choose the wind farm, you are going to need the gas well too. That’s because when the wind does not blow you will need a back-up power station running on something more reliable. But the bloke who builds gas turbines is not happy to build one that only operates when the wind drops, so he’s now demanding a subsidy, too.

...The International Energy Agency reckons there is quarter of a millennium’s worth of cheap shale gas in the world. A company called Cuadrilla drilled a hole in Blackpool, hoping to find a few trillion cubic feet of gas. Last month it announced 200 trillion cubic feet, nearly half the size of the giant Marcellus field. That’s enough to keep the entire British economy going for many decades. And it’s just the first field to have been drilled.

...The best thing about cheap gas is whom it annoys. The Russians and the Iranians hate it because they thought they were going to corner the gas market in the coming decades. The greens hate it because it destroys their argument that fossil fuels are going to get more and more costly till even wind and solar power are competitive.

...Wind cannot even help cut carbon emissions, because it needs carbon back-up, which is wastefully inefficient when powering up or down (nuclear cannot be turned on and off so fast). Even Germany and Denmark have failed to cut their carbon emissions by installing vast quantities of wind.

...To persist with a policy of pursuing subsidized renewable energy in the midst of a terrible recession, at a time when vast reserves of cheap low-carbon gas have suddenly become available is so perverse it borders on the insane. Nothing but bureaucratic inertia and vested interest can explain it. _Matt Ridley_via_HotAir_via_ GWPF

Both articles linked above are worth reading in their entirety. One item of note in Matt Ridley's article on shale gas, is the anticipated bonanza of natural gas at the continental margins. When these discoveries start coming, they are likely to eclipse all the news of discoveries of other types of energy. Why? Because for billions of years, oil has been forming under sediments beneath the oceans, then being inevitably moved toward continental margins to be subducted into the mantle, under the continental margins. It is at those subduction points where hundreds of millions of years worth of oil & gas -- particularly gas -- are likely to be made available for exploitation -- with an ongoing conveyor belt of unlimited and renewable production on the way. For as long as life on earth continues, and the tectonic machinery of the planet operates.

Deep Earth Hydrocarbons of Abiotic Origin

Scientists at Lawrence Livermore National Laboratory used supercomputers to simulate what would happen to carbon and hydrogen atoms buried 40 to 95 miles beneath the Earth’s crust, where they would be subjected to prodigious pressures and temperatures.

They found at temperatures greater than 2,240 degrees F and pressures 50,000 times greater than those at the Earth’s surface, methane molecules can fuse to form hydrocarbons with multiple carbon atoms. Interactions with metal or carbon sped up the fusion process, the researchers said. These conditions are present about 70 miles down, according to an LLNL news release. _PopSci

PO
A team of scientists and engineers from UC Davis, Lawrence Livermore Labs, and Shell Projects and Technology have created sophisticated simulations which demonstrate that methane can be polymerised to multi-carbon chains under conditions similar to those in the deep crust and mantle of Earth. (Published in PNAS)

...hydrocarbons of purely chemical deep crustal or mantle origin (abiogenic) could occur in some geologic settings, such as rifts or subduction zones said Galli, a senior author on the study.

"Our simulation study shows that methane molecules fuse to form larger hydrocarbon molecules when exposed to the very high temperatures and pressures of the Earth's upper mantle," Galli said. "We don't say that higher hydrocarbons actually occur under the realistic 'dirty' Earth mantle conditions, but we say that the pressures and temperatures alone are right for it to happen.

Galli and colleagues used the Mako computer cluster in Berkeley and computers at Lawrence Livermore to simulate the behavior of carbon and hydrogen atoms at the enormous pressures and temperatures found 40 to 95 miles deep inside the Earth. They used sophisticated techniques based on first principles and the computer software system Qbox, developed at UC Davis.

They found that hydrocarbons with multiple carbon atoms can form from methane, (a molecule with only one carbon and four hydrogen atoms) at temperatures greater than 1,500 K (2,240 degrees Fahrenheit) and pressures 50,000 times those at the Earth's surface (conditions found about 70 miles below the surface). _PO

More information in an earlier AFE posting