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Method and apparatus for treating natural gas and oil well drilling waste water

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Method and apparatus for treating natural gas and oil well drilling waste water


A method of treating contaminated water effluent from a well drilling operation. The method comprises decomposing organic contaminants in the effluent by bubbling a gas containing ozone through the effluent; adding a coagulant to increase the particle size of solid particles contained in the effluent; adding a flocculant to increase the particle size of solid particles contained in the effluent, thereby forming flocs suspended in the effluent; and filtering the flocs from the effluent to produce a filtrate and flocculated solids. The method may further comprise adding the coagulant into a stream of effluent flowing within a first conduit under controlled shear conditions, and adding the flocculant into a stream of effluent containing pin flocs flowing within a second conduit under controlled shear conditions. The method may further comprise delivering the effluent containing the suspended flocs into a filter through a conduit floating in the effluent contained in the filter.
Related Terms: Drilling Waste

Browse recent Lake Country Fracwater Specialists, LLC patents - Livonia, NY, US
Inventors: Francis C. MILLER, Steven B. Addleman
USPTO Applicaton #: #20120279925 - Class: 210723 (USPTO) - 11/08/12 - Class 210 
Liquid Purification Or Separation > Processes >Making An Insoluble Substance Or Accreting Suspended Constituents >Utilizing Precipitant, Flocculant, Or Coagulant, Each With Accelerator Or With Each Other Or Plural Precipitants, Flocculants, Or Coagulants

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The Patent Description & Claims data below is from USPTO Patent Application 20120279925, Method and apparatus for treating natural gas and oil well drilling waste water.

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CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 61/481,370 filed May 2, 2011, the disclosure of which is incorporated herein by reference. This invention is also related to the inventions disclosed in U.S. patent application Ser. No. 12/914,072 filed Oct. 28, 2010, and U.S. Provisional Application for Patent No. 60/255,504, filed Oct. 28, 2009, the disclosures of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

This invention relates to the removal of contaminants from waste water discharged at a gas wellhead, and more particularly to the removal of contaminants from drilling water that is used during the process of drilling a well bore, and that is subsequently discharged from the wellhead. The waste water may contain petroleum-based drilling muds. The waste water may be treated as it is discharged from a well bore, or after it is temporarily stored in a nearby lagoon or tanks.

2. Description of Related Art

Certain subterranean geologic formations contain significant reservoirs of natural gas. For example, the Marcellus Shale subterranean formation, which extends from central and western New York southwardly through Pennsylvania, West Virginia, and eastern Ohio, contains significant natural gas deposits. Extraction of this gas has been made economically and technically feasible by the utilization of a technology referred to as hydraulic fracturing, commonly abbreviated as “hydrofracking,” or “fracking.” This technology utilizes injection of large volumes of water at high pressure to fracture the subterranean shale structures, which causes them to separate and release the pockets of methane gas contained within the shale strata.

During the drilling of the wells, drilling mud and treated water are utilized for lubrication, suspension of drilling wastes, and as weighting agents to form a plug to restrain the pressure of the natural gas within the well bore. This drilling operation produces a waste effluent stream referred to as “pit water.” This pit water is the liquid and semi-solid remnants resulting from the drilling process typically remaining after the bulk of the rock cuttings have been removed by conventional means. This pit water contains contaminants in the form of drilling mud, pulverized rock cuttings and chemicals from the subterranean structures, as well as from pretreatment of the water with certain chemicals prior to performing the drilling along with other debris. As much as one hundred thousand gallons of pit water may be generated from the drilling process for each well. Separation of the rock cuttings and drilling muds from this water is needed.

The contaminants in this water render it unsuitable for reuse except in small proportions. Disposal of the water and the organically contaminated solids contained therein has become an expensive proposition for the well developers and also a difficult environmental problem. Treatment of the water with solidification additives is sometimes used. New environmental regulations, as well those proposed and likely to be implemented, may severely limit the ability to dispose of or treat this water by conventional means within the states of Pennsylvania and New York as well as Texas, and Idaho among others, and some foreign countries. There is a significant need by the well developers for technologies which will treat the water to enable its reuse to a maximum extent, and for the cost effective and environmentally satisfactory disposal of the contaminants contained in it.

The contaminants in this water include many of the following components: Sodium chloride. Calcium and magnesium (hardness) salts, typically in the bicarbonate and/or chloride form. Soluble sulfate salts. Volatile organic compounds (VOC) resulting from the degradation of the ancient sea creatures captured within the shale formation. (The VOCs may include small amounts of crude oil.) Residual organic compounds (ROC) from the water treatment chemicals introduced into the drilling water to enhance the drilling process. Pulverized rock cuttings. Bentonite clay which may be a component of the drilling mud.

The following are also possibly present, but to a lesser degree: Barium salts, typically in either the soluble chloride form or the insoluble sulfate form, which may be a component of the drilling mud or contained with the rock cuttings. Strontium salts, typically in either the soluble chloride form, or the insoluble sulfate form which may be component of the drilling mud or contained with the rock cuttings.

Common practice may provide for some reuse of the pit water in limited quantities as makeup water for hydro-fracturing water or other drilling operations, provided that the pit water is from a “water based” drilling mud operation and it is clarified through sedimentation, and the soluble contaminants levels are below predetermined limits. Alternatively, previous disposal of the pit water has been accomplished by transport to and subsequent treatment at conventional municipal waste water treatment facilities and specialized industrial treatment facilities, provided that the drilling muds utilized are “water based.” New and pending regulations may severely limit this option. “Oil based” drilling mud may not be treated in significant quantities in conventional municipal waste water treatment facilities. In fact, there are considerable limitations to the disposal of “oil based” pit waters altogether. Most of these pit waters are treated with thermal technologies, bio-remediation, deep well injection, addition of solidifiers (such as polymers, sawdust, wood chips, lime, or vermiculite) and/or evaporation of the water fraction followed by landfill disposal of the remaining contaminated solids.

The sodium chloride is not considered a significant problem relative to the reuse of the water up to some practical limit that is determined by the drilling operator. The soluble barium and strontium salts, and alternatively the soluble sulfate salts, form insoluble solids during and after the fracking process, which have been determined to be degradative to the drilling and/or hydrofracturing process when these materials exceed certain levels which depend upon the particular operator of the drilling rig. Elevated levels of these salts limit options for disposal as well. The soluble calcium salts form hardness scale in the subterranean shale structures and are similarly limited in concentration but at higher levels. Both of these conditions may result in the obstruction of portions of the fissures within the shale strata created by the fracking process when the water is reused, if the concentrations of these salts contained in it are excessive. The presence of the residual or incipient volatile organic chemicals in the return water results in further difficulties in proper reformulation of it as fracking water for reuse. The pulverized rock cuttings and residual mud present in this pit water represent suspended solids which are unacceptable in hydrofracking or drilling fluids.

The removal of certain suspended solids in the waste water from water based drilling mud is defined in various documentation and literature. The solidification of the salts may be accomplished by conventional evaporation technology, gelatinizing of the solution, or precipitation means. The current method of return water remediation is to transfer it upon its discharge from the wellhead into tanker trucks or pits, decant any clarified supernatant following settling or treatment for reuse, and then transfer the unusable remaining water and/or sludge into tankers. The tankers of sludge are then hauled substantial distances to off-site municipal or industrial water treatment plants, or to other solidification pits where further solidifiers may be added. This is expensive, and additionally, it may soon be prohibited in many jurisdictions (particularly New York, Pennsylvania and Texas) by new environmental regulations.

The aforementioned U.S. patent application Ser. Nos. 12/914,072 and 60/255,504 of Miller provide for a modular, portable and cost effective method and apparatus for treating the frack water for the removal of the barium, calcium and strontium salts onsite at the wellhead. However, there remains a need for a modular, portable, and cost effective method and apparatus for treating waste water produced from the utilization of oil-based drilling mud. The separation of the settleable and finely dispersed suspended solids from the aqueous phase must be accomplished in a manner such that the solids may be disposed of separately, and the water may be reused. It is desirable that the process and apparatus also accommodate the presence of any residual or volatile organic chemicals, typically including finely dispersed or emulsified diesel oil or other “oil” components of the drilling mud formulation, or natural crude oil component brought up from the wellhead; and residual soluble precipitate-forming salts as well.

SUMMARY

The Applicants have developed a method and apparatus to meet this need. The method and apparatus separate and remove the settleable and finely dispersed suspended solids from the waste water from oil based drilling mud operations. The method and apparatus also removes residual soluble precipitate forming salts where applicable. The suspended solids are coagulated and flocculated and then dewatered, which renders the resulting solids mass suitable for conventional landfill or on site disposal. Any problematic levels of barium, strontium, calcium and magnesium salts may be selectively precipitated into their inert forms for removal and disposal as recited in the aforementioned patent application Ser. Nos. 12/914,072 and 60/255,504 of Miller. The soluble sulfate salts are precipitated in the inert barite and celestite forms which are similarly coagulated and flocculated, and then dewatered for disposal.

The product water from the instant process is a sodium chloride (brine) solution, which is suitable for reuse as a portion of the makeup water in drilling operations or hydrofracturing operations. The instant process may include an ozone treatment process for removal of organic contamination prior to treatment to improve chemical efficiency and performance. In addition, ozone treatment, or alternately carbon absorptions, may be utilized following filtration to remove any residual organic materials.

More specifically, in accordance with the invention, there is provided a method of treating contaminated water effluent from a well drilling operation. The method comprises decomposing organic contaminants in the effluent by bubbling a gas containing ozone through the effluent; adding a coagulant to increase the particle size of solid particles contained in the effluent; adding a flocculant to increase the particle size of solid particles contained in the effluent, thereby forming flocs suspended in the effluent; and filtering the flocs from the effluent to produce a filtrate and flocculated solids.

The ozone concentration in the gas is preferably at least one percent by weight. The size of the gas bubbles is preferably less than 500 microns in diameter. The pH of the effluent during ozonation (gas bubbling) is preferably between 3 and 10. For most pit water effluent mixtures, the ozone treatment will operate in the range of 10 ppm ozone to 50 ppm ozone concentration with a pit water effluent average residence time in the apparatus 18 of between approximately 10 and 30 minutes. The method may further comprise causing pin flocs to form in the effluent by adding the coagulant. The method may further comprise adding the coagulant into a stream of effluent flowing within a first conduit under controlled shear conditions, and adding the flocculant into a stream of effluent containing pin flocs flowing within a second conduit under controlled shear conditions. The method may further comprise delivering the effluent containing the suspended flocs into a filter through a conduit floating in a portion of the effluent contained in the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be provided with reference to the following drawings, in which like numerals refer to like elements, and in which:

FIG. 1 is a schematic diagram of one exemplary embodiment of the instant process and apparatus for treating waste water from oil based drilling mud;

FIG. 2 is a flowchart of the instant process for treating pit water;

FIG. 3A is a schematic cross-sectional illustration of a “box” type filter that may be used as a part of the instant apparatus, shown during delivery of liquid containing flocculated solids; and

FIG. 3B is a schematic cross-sectional illustration of the filter of FIG. 3A, shown during dewatering of sludge contained therein.

DETAILED DESCRIPTION



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stats Patent Info
Application #
US 20120279925 A1
Publish Date
11/08/2012
Document #
13461871
File Date
05/02/2012
USPTO Class
210723
Other USPTO Classes
International Class
02F1/52
Drawings
5


Drilling Waste


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