Leonard LeBlanc Houston Once all economically recoverable oil and gas reserves are produced, does the global hydrocarbon finding machine simply grind to a halt, it's technology of no value for other functions? Not likely! There are at least three other challenges, two affiliated with the ocean environment, that can absorb this extensive expertise and technology in the decades to come. Hydrates recovery:

Apr 1st, 1996

Leonard LeBlanc

What happens after oil and gas recovery
is no longer economic?

Once all economically recoverable oil and gas reserves are produced, does the global hydrocarbon finding machine simply grind to a halt, it's technology of no value for other functions? Not likely! There are at least three other challenges, two affiliated with the ocean environment, that can absorb this extensive expertise and technology in the decades to come.

  • Hydrates recovery: Methane gas hydrates are widespread on the ocean floor up to a depth of 200 meters below the seabed. Scientists have estimated that the organic carbon bound up in seafloor hydrates is twice that found in all recoverable and non-recoverable oil, gas, and coal deposits on earth.

  • Seawater mineral extraction: Seawater contains large and small concentrations of common and rare minerals. The technology of seawater mineral recovery and separation has been little explored, because land-based mineral extraction has been easy. This may not always be true.

  • Deep mineral mining: The recovery of rare minerals deep underground also is not feasible today, principally because surface-mined minerals are still available. Once accumulations accessible by mining begin to disappear, then deep recovery technologies geared to spotting and recovering accumulations will develop.

All of these technologies are closely related to oil and gas recovery. Interestingly enough, the depletion of surface and mined rare minerals could coincide with the time period when oil and gas deposits begin to shrink below economic recovery thresholds - 60-80 years out.

The pursuit of oceanic gas hydrates could be the closest to economic feasibility, especially if the global demand for energy increases substantially above current levels. Methane hydrate deposits form when rising methane is exposed to seawater and cold ocean temperatures. The solid hydrate formation widens and thickens as additional methane rises beneath and around the edges.

At least three recent developments in the technology community could begin to set in motion a method for extracting and transporting the hydrates:

  • Resource potential: A program effort to characterize the deposits of seafloor gas hydrates and the methane formations beneath them is being made undertaken by a global multi-government/industry consortium led by Stanford University's Geophysics Department. Hydrates provide a distinct seismic reflection, which can be used to characterize and measure hydrate and methane feeder volumes.

  • Hydrate equilibrium state: Extensive studies are being conducted on the chemical and thermal mechanisms that drive the various stages of hydrate formation (nucleation, agglomeration, attachment to surfaces), and how each equilibrium state can be maintained and controlled (See Drilling/ Production column).

  • Hydrate transportation: As an option to LNG transport, some gas development researchers see no reason why gas in a "slushy" hydrate state could not be moved through pipelines and in tankers. This transport method would depend on being able to maintain the hydrates in equilibrium through thermal or chemical means.

Gravitational signature reader may be used for
formation evaluation

Gravitational measurement equipment used to detect differences in underground mass and motion from airplane and satellite positions may someday be lowered into the wellbore for accurate formation evaluation.

Every mass, above ground or below, generates a gravitational field of some magnitude. The motion of molten rock inside the earth generates huge gravitational noises that tend to override the gravitational field signatures of everything else. But, not completely.

Sandia Laboratories (US Dept. of Energy) is working on an instrument that combines sensitive accelerometers set a short distance apart. The accelerometers read gravitational signatures of structures and mobile objects to determine content. Initially, the instrument will be used for defense and weapons verification purposes, but the principles involved are being examined for other uses.

The instrument's dual accelerometers are set to cancel out common noises, such as the earth's gravitational signature, and a gravity gradiometer is then able to measure variations in nearby materials. A mass or absence of mass at some short relative distance will provide a signature. Not only will the instrument detect formation variations, but also identify formation contents by signatures. The presence of casing would provide a common signature, which would be canceled, but not so the formation. The instrument can be contained in a long tool package.

Scott Field's dissolved gold
deposits worth $420 million

On April 1, the Scott Field platform, located in the UK sector of the North Sea, was scheduled to be switched from oil and gas production to gold mining. Amerada Hess' Scott reservoir is one of the deepest in the North Sea and certainly has the highest temperature, conditions conducive to high concentrations of minerals dissolved in formation water.

Production engineers estimate that Scott's gold "reservoir" will produce over one billion bbl of water over the coming years. From this volume, about 12 bbl of gold can be extracted by precipitation, along with other minerals like lead and zinc. That gold volume is valued at about $420 million.

If gold vein faulting in any direction from the production wells can be identified, then recovery could be boosted with injection wells. In any case, oil or gas will have to be brought onboard the Scott platform to power the injection units.

Since gold production may not be constant in the production water, such technologies as coupled plasma spectroscopy or hydrous inductive fourier fluorescence will be used to determine gold concentrations.

The gold mining operation has interested operators around the globe with deep high temperature fields that are at the stage where more water than oil is being produced.

Short-radius tool now available
for horizontal wells

Schlumberger Wireline and Testing has compressed the size of a well logging combination string into one 38-ft long tool in which all of the sensors share the same electronics. The tool, known as Platform Express, can successfully log short radius horizontal wells, something not easily done with conventional tool assemblies.

The tool can log wells at speeds of 3,600 ft/hour. A conventional assembly 90 ft long has been compressed in 38 ft, which includes flex joints to assist in short radius passage. Schlumberger developers say the reliability of the tool is five times that of conventional assemblies in harsh well conditions.

Listening to corrosion electrochemistry

The onset of metal corrosion creates a passive electro-chemical noise - one that can be sensed with the right equipment. Chemical reactions ionize molecules. As the molecues ionize, they create minute currents and voltages, which can then be measured.

Microvolts and picoamp differentials over time provide a noise signature or signature differential. These signatures are specific to certain chemical corrosion processes or specific to certain job site conditions.

Solartron Instruments of Houston has developed a software package that combines electrochemical noise analysis with conventional electrochemical impedance spectroscopy. A Windows-based graphical readout provides the results once every second in time or frequency domains.

The instrument can be used with lab experiments or in extended field surveys.

Copyright 1996 Offshore. All Rights Reserved.

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