Abstract

Studies have indicated resources of 4.6 trillion barrels of heavy oil, and some have expressed a need of novel methods to recover some of this oil. Thermal methods were the vogue twenty years ago, with only one method, steam injection, surviving to a significant extent. This paper describes economic uses of hydrogen peroxide, which is similar to steam injection but with some advantages. Hydrogen peroxide can generate 100% quality steam insitu in concentrations above 25–30%. Lesser concentrations can generate or propagate steam banks and hot water banks. Two uses of hydrogen peroxide are economic-short term stimulation in selected reservoirs, and formation damage repair. Other uses involving heat bank flooding await cost reductions that may occur due to more use and technical advances in the manufacture of hydrogen peroxide.

Introduction

Hydrogen peroxide is a relatively stable combination of hydrogen and oxygen, made by a chemical process discovered 50 years ago. Physical properties are listed in Table 1. A small amount of hydrogen is required to manufacture 50% concentration, i.e, about 3% by weight. The main uses of hydrogen peroxide are in chemical processes and paper manufacture. Hydrogen peroxide can be decomposed very rapidly over a platinum screen giving off heat, oxygen, and water. Thus if hydrogen peroxide is injected into a reservoir sand, it will decompose slowly giving off heat and oxygen, then the oxygen will react with residual oil to generate more heat and carbon dioxide. Decomposition is exponential with temperature and pH increase. This process has been reported on in a paper by Moss, et. al. Thirty per cent concentration will generate 1200 BTU/lb (100%+ quality steam) with about 1/3 of the heat coming from decomposition and 2/3 coming from reaction with oil. Thus hydrogen peroxide can be used in a variety of ways to recover oil. In addition it is well known that steam stimulation can result in formation clean-up in the vicinity of the well. Thus 50% hydrogen peroxide can generate up to 2000 F. which can repair formation damage.

Economic uses

Stimulation. Injection of hydrogen peroxide can be economic if the heat is kept near the well-bore. The heat content of a barrel of 50% peroxide can heat up to 48 barrels of oil to 100 F. above the reservoir temperature. Thus small treatments can be effective if allowing a long soak time to moderate the temperature. A study by Niko and Troost has shown that near well bore heating is effective in depletion reservoirs. Oil recovery was independent of soak time and small slugs were superior for early production. The paper by Briggs, et.al. shows that production from steam stimulation in gravity drainage reservoirs does not decline with each successive cycle as much as massive treatments do in other reservoirs. Thus small treatments will be more effective in heat utilization than massive treatments where much of the oil is forced away from the well, and much of the heat injected is lost.

Formation Damage Repair. As mentioned previously, steam stimulation can clean up a well. This may be due to wax and asphalt deposits being melted. In addition to these effects, 50% peroxide can generate up to 2000 F. a foot or so away from the well. Thus after treatment, heat conduction will treat the entire well bore vicinity to at least 1000 F. This temperature can cause clay to shrink, destroy carbonates, and vaporize emulsions. Peroxide treatment can be more effective than other treatments such as with acids and solvents, since these liquids can finger through. Peroxide decomposition causes a finger resistant foam of oxygen bubbles in hot water, and heat conduction to untreated areas gives 100% zonal coverage. Gas wells can be treated with pre-injection of a fuel oil.

Flooding with Hydrogen Peroxide

As with steam, a variety of heat floods can be achieved with hydrogen peroxide. P. 117^

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