Solubilization and disposal of radioactive scale and sludge

Abstract

A process to transform solid, low-level, radioactive waste produced from oil and gas production into a form that may be safely disposed of, such as by re-injection into geologic formations in the Earth.

Description

PRIORITY INFORMATION [0001]This application claims priority to U.S. application Ser. No. 60 / 674,431, filed Apr. 5, 2005, the contents of which are incorporated herein by reference in their entirety.FIELD OF THE INVENTION [0002]The present invention relates to the field of oil and gas field waste treatment, and more particularly to the treatment and disposal of radioactive waste from oil and gas production. Additionally, embodiments of the present invention relate to a process of treating and disposing NORM (Naturally Occurring Radioactive Material).BACKGROUND OF THE INVENTION [0003]A large amount of formation water, brine, is co-produced when oil and gas are pumped to the surface from formations deep in the Earth. It is not unusual for 10 barrels of water to be produced for each barrel of oil. Generally, producing formations are very deep (on the order of 12,000 ft). At these depths it is very hot and the formations are under high pressure. The waters are saturated with many ingredi...

AI Technical Summary

Benefits of technology

[0022]Preferably, embodiments of the present invention are mobile, allowing the process to be performed on site.

[0023]As stated above, there are advantages to re-injection methods of disposal. Solubilizing the scales and sludges with the process described herein will allow the material to be re-injected along with the produced waters. Since there are typically no or limited solids involved, the required injection pressures will not be excessive. Thus, the methods of the present invention should be free from problems associated with plugging the rock pores. In turn, there should not be a problem with capacity. It will not be necessary to “fracture” the formations, and thus the likelihood of the material mixing with potable waters from other formations will be no greater than is the case with the brine injection wells.

[0024]Additionally, the necessary equipment for solubilizing the scales and sludges can be assembled on truck beds, which can be moved from site to site to process the material at, or near, the production sites. This will greatly reduce the need to transport these radioactive wastes over any great distances. The solubilized product can be returned to brine storage tanks already in place at the production sites for temporary storage until it can be re-injected along with the produced waters. The processing costs will be less than other common, acceptable disposal methods.

[0029]Sulfides react with water generating H2S gas, and the corresponding metal hydroxide. In aspects of the present invention, NaCl solutions are usable as solvents for re-dissolving the black ash product, with the end result being the formation of BaCl2. Removal of the sulfur from the mixture prevents any possible reformation of insoluble sulfates and therefore insures continuing stability of the re-dissolved material.

[0031]As understood when practicing the present invention, H2S is highly toxic and the re-dissolution process can be accomplished under conditions where the gas will not become a hazard. Thus, in one embodiment, the gas could be oxidized to SO2 as it is generated by burning it in air and collecting the SO2 in a water trap as sulfuric acid. The sulfuric acid, so generated, may have some commercial value to help allay the processing costs.

Problems solved by technology

At these depths it is very hot and the formations are under high pressure.

Scale formation can cause restriction or blockage of piping and may cause malfunction of equipment.

Sludge buildup in storage tanks reduces their capacities and hinders their operation.

Each year scale and sludge formation costs hydrocarbon producers millions of dollars in maintenance, treatment, and lost production time.

While brines are often disposed of by pumping into injection wells, scales and sludges that contain NORM fall under strict and expensive governmental disposal regulations.

Radium co-precipitates with alkaline earth elements of scale and sludge, rendering these radioactive.

In the past, few disposal methods have been available, and many have been based on treating the scale and sludge as low level, solid radioactive waste.

Solid radioactive waste disposal is expensive, and presents numerous liability issues for the producer.

After covering, if the level of radioactivity is below governmental action levels, the site may be considered uncontaminated.

There are obvious disadvantages to each of the disposal options outlined above.

For example, disposal at low level radioactive waste storage facilities is expensive, and it generally involves shipping the material from the site where it was produced to a distant site with the attendant transportation risks.

Disposal by land spreading has exposure dangers.

Additionally, it is unlikely that the material will remain undisturbed for any extended time period after it is deposited.

Disposal by re-injection of slurried powder in water is probably the most permanent and liability free means of disposal, but it is also the most expensive and lowest capacity means of disposal.

In addition, the required pumping pressures consume large quantities of fuel to run the pumps making the process almost prohibitively expensive.

This increases the porosity of the rock by creating cracks in the rock, which eases the re-injection process, but it comes with the risk of allowing the material to commingle with other geologic formations including potable ground waters.

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