Flare system using produced water and ozone injection

Description

This application is a continuation-in-part application of U.S. patent application Ser. No. 15/711,896, filed Sep. 21, 2017, which claims priority to U.S. Provisional Application No. 62/397,833, filed Sep. 21, 2016; this application also claims priority to and benefit of U.S. Provisional Application No. 62/784,525, filed Dec. 23, 2018. The specifications, drawings, and complete disclosures of U.S. Provisional Application Nos. 62/397,833 and 62/784,525, and U.S. patent application Ser. No. 15/711,896 are incorporated herein by specific reference for all purposes.

FIELD OF INVENTION

This invention relates to a system and apparatus for flaring gas from oilfield operations using produced water.

SUMMARY OF INVENTION

In various exemplary embodiments, the present invention comprises a system and apparatus for flaring gas from oilfield operations using produced water. The system provides an alternative treatment and disposal technique for produced water, thereby avoiding problems associated with injecting produced water back into subsurface strata, such as induced seismicity. The system is configured to be installed at or near the wellhead, thereby avoiding the problems of prior art centralized systems for handling produced water, which are substantially larger and built at a central location to store and gather large quantities of produced water. Centralized systems require the produced water to travel much greater distances and become cooler before treatment, thereby requiring more energy for heating or treatment. In several embodiments, the present invention uses produced water that is at a temperature of greater than 100 degrees F., thereby reducing the amount of energy required for heating.

In one exemplary embodiment, produced water is treated in a scrubber. Heat is applied through a flare gas field burner, which uses field gas from the oilfield operations (and thus provides a useful alternative to simply open flaring the field gas as a means of preventing the accumulation of field gas for safety reasons as well as preventing the venting of methane, a greenhouse gas, into the atmosphere). A wet scrubber unit with scrubber packing is used to clean emissions (e.g., nitrous oxides, sulfur oxides, acid gases, particulate matter, and the like). A produced water pump is used to circulate produced water, and pump produced water through spray nozzles in the scrubber unit for use as the wet scrubbing agent. The present invention thus optimizes contact and mixing between the hot air and water.

The above process also results in gradual evaporation of the produced water, which results in the accumulation of salts and other solids from the produced water. Evaporated salts and solids are continuously removed from the evaporator/scrubber unit by appropriate means, such as an auger system. The evaporated salts and solids are then treated via chemical stabilization in a mixing system with chemical reagents to prevent the residual form from being hazardous. The residual material is then stored and disposed of properly.

The present invention thus provides a more environmentally-friendly and efficient means of addressing several pollution and related concerns. First, the system eliminates open flaring by using the field gas in a field gas flare burner to heat produced water, and scrubbing the emissions using the heated produced water in a scrubbing unit. Second, the system eliminates or reduces the volume of produced water. And third, the system operates at or near the wellhead, thereby allowing use of the field gas while treating the produced water with less energy required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of a system in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In various exemplary embodiments, the present invention comprises a system and apparatus for flaring gas from oilfield operations using produced water. The system provides an alternative treatment and disposal technique for produced water, thereby avoiding problems associated with injecting produced water back into subsurface strata, such as induced seismicity.

The improved system of the present invention also is configured to be installed at or near (i.e., close proximity to) the wellhead, thereby avoiding the problems of prior art centralized systems for handling produced water, which are substantially larger and built at a central location to store and gather large quantities of produced water. Centralized systems, however, require the produced water to travel much greater distances and become cooler before treatment, thereby requiring more energy for heating or treatment. The present invention uses produced water that is at a temperature of greater than 100 degrees F., thereby reducing the amount of energy required for heating.

FIG. 1 shows an exemplary embodiment of an improved system in accordance with the present invention. Produced water is treated in the scrubber 10. Heat is applied through a flare gas field burner 12, which uses field gas from the oilfield operations (and thus provides a useful alternative to simply open flaring the field gas as a means of preventing the accumulation of field gas for safety reasons as well as preventing the venting of methane, a greenhouse gas, into the atmosphere). A wet scrubber unit with scrubber packing 14 is used to clean emissions (e.g., nitrous oxides, sulfur oxides, acid gases, particulate matter, and the like). A produced water pump 16 is used to circulate produced water, and pump produced water through spray nozzles 18 in the scrubber unit for use as the wet scrubbing agent. The present invention thus optimizes contact and mixing between the hot air and water.

In an alternative embodiment, ozone is used in the wet scrubber 10 to reduce NOx by approximately 90% or more. The ozone oxidizes insoluble NOx to a water soluble species form for removal by the scubber with little or no SO2 or CO oxidation. In several exemplary embodiments, the oxidation of NOx takes place at or below 300 degrees F. (i.e., low temperature oxidation). Ozone may be generated on-site and injected to the evaporator/scrubber unit. In several embodiments, the ozone is added to the effluent gas of the thermal oxidizer prior to entering the evaporation chamber. As a result, NOx emissions are reduced.

The above process also results in gradual evaporation of the produced water, which results in the accumulation of salts and other solids from the produced water. Evaporated salts and solids are continuously removed from the evaporator/scrubber unit by appropriate means, such as an auger system 20. The evaporated salts and solids are then treated via chemical stabilization in a mixing system (e.g., treatment mixer) 30 with chemical reagents (which are stored in a reagent silo 32) to chemically stabilize the residual and prevent the residual from being hazardous. The residual material is then stored and disposed of properly.

The present invention thus provides a more environmentally-friendly and efficient means of addressing several pollution and related concerns. First, the system eliminates open flaring by using the field gas in a field gas flare burner to heat produced water, and scrubbing the emissions using the heated produced water in a scrubbing unit. Second, the system eliminates or reduces the volume of produced water. And third, the system operates at or near the wellhead, thereby allowing use of the field gas while treating the produced water with less energy required.

Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art.