DRILLING / COMPLETION TECHNOLOGY

Hydrogen peroxide applications for the oil industry

Interest in many unusual applications is increasing with higher oil prices

Jack H. Bayless, President, Innovated Research and Engineering Co., Houston

n May 1998, the author presented the article "Hydrogen peroxide: A new thermal stimulation technique" in World Oil. That article introduced the concept of injecting fluid with varying percentages of hydrogen peroxide (H₂O₂) downhole for the several benefits it offers in its ability to generate in situ heat. Applications in stimulation, formation damage repair and reservoir heat flooding were overviewed, and operational advantages were discussed.

This presentation updates the discussions of applications in well stimulation and reservoir flooding. The subject of drilling with superheated steam generated downhole is introduced, based on the paper "Superheated steam drilling" presented at the ASME Energy-Sources Technology Conference, Houston, Feb. 1–3, 1999. Concluding discussions herein present three other interesting applications in pressure generation, hydrate melting in subsea equipment and metal cutting for offshore structure decommissioning.

Stimulation / Flooding Economics

Since publication of the May 1998 article, more than 20 interested oil operators considered using the technique. However, in the meantime, low oil prices made heavy oil almost worthless, and interest dwindled. With oil prices in the $30 per bbl range, heavy oil is worth about $25, making stimulation with peroxide injection potentially profitable. And one operator is interested in investing in a patent describing the process.

If hydrogen peroxide use increases, economies of scale could lower the cost of the chemical to less than 10 cents/lb. Cost of the chemical raw material, hydrogen, makes up only 3% of the weight of the chemical; thus, manufacturing cost mainly determines most of the final cost. Reduced cost of large-scale operations could drop costs to less than 2 cents/lb, and hydrogen peroxide could be manufactured for about the same cost.

References in the 1998 article allude to thermal flooding – when the cost of peroxide comes down with use. For instance, peroxide of 40% is the concentration coming directly out of the manufacturing process. Peroxide of 10% concentration will generate a 400°F heat bank (steam and hot water); and the drugstore concentration of 3 to 5% will maintain that hot thermal bank as it is pushed through the reservoir. So, at 10 cents/lb for 40%, 10% would cost 2.5 cents/lb, or less than $10/bbl. If thermal flooding can be maintained with 5%, or $5/bbl, then thermal flooding with peroxide becomes feasible at higher oil prices.

Concept of drilling by melting rock with hydrogen peroxide and fuel "torch" conveyed by coiled tubing.

Drilling With Superheated Steam

The advent of coiled tubing drilling has opened the door for innovative drilling methods. One such method made possible is drilling with exotic chemicals. Superheated steam can now be generated at any pressure / temperature at the bottom of the drillstring. High-temperature / high-pressure steam is the ideal agent for melting earth materials, i.e., forming "lava," which has a melting point well within the range of temperatures that can be generated. The use of this drilling method eliminates many costs associated with drilling wells.

Generating superheated steam. The chemical of choice for generating superheated steam is hydrogen peroxide, well known for its use in rocket propellants. Hydrogen peroxide at 30–35% generates one-third of the latent heat of vaporization of water upon decomposition. In addition, the decomposition products are oxygen and water. Hydrocarbon or other fuel can then be oxidized by the oxygen, generating the remaining required heat to completely vaporize water. Downhole heat exchange then preheats the peroxide and fuel, so that the final product is superheated steam and carbon dioxide.

Lower peroxide concentrations are relatively safe to handle and can be pumped like water. To get peroxide to the bottom of the drillstring, stainless steel or titanium coiled tubing or plastic-lined tubing would be used. Another CT unit would be used to pump a liquid hydrocarbon to the downhole combustion chamber, at the bottom of a spiral grooved drill collar assembly. Various well-known catalysts can be used to start the process, or "light the torch," so to speak. Once the temperature starts up, the peroxide is decomposed by high temperature. Thus, the process is self sustaining.

Downhole heat exchange / torch assembly. The spiral grooved, drill collar assembly can be of such length that 25–50% of the heat in the torch can be recovered. Any heat remaining can be recovered by the drillstring itself. Thus, the only heat lost is by conduction into the earth from the borehole.

The lower part of the drill collars would be constructed into a combustion chamber much like a massive acetylene torch. The preferred metal of construction would be titanium, now readily available as oilfield tubulars.

How it works. It is postulated that the blast of high-velocity, superheated steam would atomize the rock at the bottom of the hole into small, molten globules. As the products move up the hole opposite the drill collars, these globules are the first to solidify. As further heat exchange occurs, the steam condenses, forming a slurry with these now-solid particles. This slurry would be gas lifted to some extent by carbon dioxide gas formed in the combustion process.

All requirements for drilling are met by this concept, i.e.:

• Rock removal method – a mist of molten rock in superheated steam
• Circulation method – condensed steam (water) which carries out solidified rock particles (slurry)
• Pressure control method – a hydrostatic head of a fluidized slurry (water, carbon dioxide, rock).

Advantages of the system include a drilling method that:

• Is the only known method that recovers some of the energy required to drill
• Cases the hole with solidified molten earth, i.e., glass
• Eliminates cost of drilling muds and mud disposal
• Eliminates cost of drill bits
• Drills faster as depth increases – not slower.

Further, depth capability is the same as coiled tubing drilling – now 20,000 ft. And the cost of mud motors is eliminated.

Drilling rate and costs. As seen in the accompanying table, it requires about 7.5 gal of peroxide to melt a cubic foot of rock, or about 3 ft of 7.5 to 8-in. hole. If a circulation rate of 7.5 gpm is used, then the drilling rate is 180 ft/hr. Drilling cost for the expendibles (hydrogen peroxide) is about $11/ft. In mass production, peroxide can be reduced to 15 cents/lb from 50 cents/lb – in that case, the cost of drilling would be $4/ft for peroxide.

In conclusion, this appears to be a viable drilling method. It is flexible, in that this is only a preliminary evaluation, and either lower or higher concentrations of peroxide can be used, depending on the situation.

Three Other Possible Applications

For high pressure generation, hydrogen peroxide of 40% concentration will generate over 100,000 psi as it decomposes to oxygen and water in a closed space. Thus, it could be used for metal forming and internal cladding of oilfield valves and other equipment. This application has been discussed with peroxide manufacturers, but it is not in use at present.

The ability to generate high pressure could also be used to an advantage in the fracturing of formations using a tubing string filled with peroxide to generate fracturing pressure.

Generating high pressure presents a caution for oilfield use. When injection of peroxide is done, care must be exercised not to trap any peroxide in closed spaces. All piping must include a relief valve to vent any unwanted pressure buildup.

    High temperature generation subsea. Very expensive well problems are experienced by the industry when subsea equipment freezes up due to hydrate formation. Hydrates are generally methane gas and water in a low-temperature setting, like the seafloor. With ROV technology, hydrogen peroxide can be pumped past the frozen equipment and a high temperature can be generated by peroxide decomposition. Peroxide of 40% concentration would heat up to 500°F when decomposed subsea. Thus, heating of equipment in such environments could be a practical use.

    For decommissioning offshore platforms, in addition to high temperature generation due to decomposition, oxygen is generated. When a solid or liquid fuel is mixed with the peroxide as it decomposes, much higher temperatures are generated, and a cutting torch using the chemical could be designed. With the aid of ROVs, platform legs could be cut to remove offshore structures or relocate them for artificial reef construction.

The author

Jack Bayless, President of Innovated Research and Engineering, and Hotshot Stimulation Co., Houston, holds a BS degree in chemical engineering, with honors, from Lamar University, 1956. He retired from Exxon Production Research in 1986, with 15 years’ experience in thermal oil recovery and 15 years in offshore drilling engineering. He was an instructor in blowout prevention worldwide. He has worked extensively in API and SPE. And he holds several patents, with two licenses. Mr. Bayless has authored several technical papers and articles for SPE and various trade journals.