Increased availability and reduced costs for viscoelastic surfactants used in hydrofracturing fluids

Abstract

The invention provides a method for employing the total product stream from hydrolysis of triglycerides comprising fatty acids, glycerin and water to address at the environmental issues associated with drilling, completion and hydrofracturing wells employed for recovery of subterranean hydrocarbon deposits in an area of shale formation.

Claims

1. A method for reducing costs of fatty acids for use in drilling and recovery operations of hydrocarbons from subterranean deposits in an area of shale formations where hydrofracking operations are employed, said method comprising: (i) erecting and operating a process plant within or in the vicinity of the area of shale formation, said process plant comprising facilities employing hydrolysis of triglycerides to produce fatty acids and a glycerin by-product, facilities for production of esters of the fatty acids, and optionally facilities for production of viscoelastic surfactants; and (ii) providing at least some of said drilling and recovery operations with at least one of the fatty acids, the viscoelastic surfactants, or the esters of fatty acids produced by the processing plant.

2. The method of claim 1, wherein said glycerin by-product is converted to a derivative for local use and/or sale for use in fluids for drilling and/or production.

3. The method claim 1, wherein said method further comprises facilities for removing water from the glycerin by-product to provide concentrated glycerin for sale and/or as a component of drilling/production fluids.

4. The method claim 1, wherein the esters of said fatty acids are produced employing low molecular weight alcohol, for use as hydrocarbon drilling/production fluid components and/or as biodiesel engine fuel.

5. The method of claim 2, wherein the derivative is polyglycerol.

6. The method of claim 1, wherein the esters of fatty acids are for use in drilling operations or derivative biodiesel.

7. The method of claim 1, wherein when appropriate to the end use, achieving savings in raw material costs by employing hydrolysis of triglycerides in said plant utilizing low cost raw materials.

Description

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(1) 1. Processes for Production of Oil and Gas Drilling and Completion Fluids and Hydrofracturing Fluids Based Upon Crude Glycerin

(2) The crude glycerin streams resulting from the processes described above—may be employed in the processes of this invention for producing oil and gas well drilling and completion fluids. Table 2 presents typical ranges of concentrations of the components in these aqueous solutions.

(3) TABLE-US-00003 TABLE 2 Glycerin- wt % ash- wt %* MONG transesterification 70-85 2-8  2-15 crude glycerin alkali neutralized 70-85 2-8 neg-2 transesterification salts crude glycerin heterogeneous cat 90+ neg. traces, depending transesterification on feed crude glycerin preparation saponification 80  5-10 2-4 crude glycerin salts hydrolysis 12-25 <1 trace-2 crude glycerin

(4) Under certain circumstances, the present invention provides recovering any of these crude glycerin streams and employing them directly in producing drilling and/or completion fluids. The salts or alkalis could have useful functions as described earlier and, depending on the characteristics of the MONG, this material could supply surface activity or lubrication. Should this not be the case, the ultrafiltration step described above could be used to remove essentially all of the MONG.

(5) In accordance with the processes disclosed herein, other materials may be added to produce a completed fluid. Among these would be; components selected from the group consisting of glycol, methyl glucoside, polyglycerine, salts, lubricants, gelling agents, methyl cellulose, corrosion inhibitors, weighting agents, water and mixtures of any of the foregoing.

(6) Regarding hydrofracturing fluids, any of the crude glycerin streams could be employed as part of the “chemicals package” employed in production of these fluids. For example, the glycerol-containing by-product stream from alkali-catalyzed transesterification contains—or can be processed to contain—a substantial portion of the components of the chemicals package included in such hydrofracturing fluids.

(7) Examples include the following; Glycerol—Glycerol can provide important functions required in hydrofracturing fluids. These include; (1) replacing ethylene glycol (a toxic material) as an agent to prevent scale formation and (2) as a friction reducer—replacing petroleum distillates that may contain carcinogens, such as benzene or other aromatic compounds. Salt—Depending on the choice of alkali as the transesterification catalyst, and the acid used to neutralize, a range of salts are possible. For employment of the glycerin by-product in hydrofracturing applications NaCl or KCl would be preferred The former would be useful as a breaker and KCl is employed to produce a “slickwater” fluid. Acid—If desired, an excess of HCl could be employed beyond that required for neutralization. Biodiesel—petroleum distillates are often used as friction reducers, but the presence of carcinogens such as benzene and other aromatics raise issues. The biodiesel product of the transesterification process is free of aromatic compounds could be employed in this service.

(8) One exemplary procedure for manufacturing a “chemicals package” for inclusion in a hydrofracturing fluid could be; Using the glycerol-containing by-product described in Table 1 above, this could be used—as is—as a component of the hydrofracturing chemicals package. Glycerol, a non-toxic, environmentally benign compound, will function as a scale inhibitor (replacing ethylene glycol—a toxic chemical) and as a friction reducer. The salt present would supply part of the salt normally added. If potassium hydroxide were employed as the catalyst, then the KCl produced in neutralization would provide that component. Further, if the neutralization employed a surplus of HCl, this would also supply part, or all, of that compound. The other necessary chemicals (detergent, biocide, etc) could be added at the point of manufacture, or at the drilling site. The finished hydrofracturing fluid would comprise principally water combined with the “chemicals package,” other necessary chemicals and proppants.

(9) Processes Involving Separation of the Crude Glycerin Stream Leaving a Remainder that is at Least Partially Employed in Producing Oil & Gas Well Drilling and/or Completion Fluids.

(10) Separation by Distillation

(11) Some processes disclosed herein may include distillation as an element of the process. As described earlier, in the case of crude glycerin from processes including transesterification, saponification and hydrolysis, it has been common practice in refining glycerin from such sources to distill—normally under a vacuum—with an emphasis on maximizing the recovery of a pure glycerin. To this end, it has been normal practice to add a processing step—such as a “foots still” or, alternatively, a wiped film evaporator—to insure maximum recovery of glycerin from the distillation bottoms stream.

(12) In the case of hydrolysis crude glycerin, the 12-25% crude glycerin by-product can be processed without a vacuum through multi-stage evaporation to a concentration of about 88% prior to being distilled under vacuum in the manner described above.

(13) As an alternative to vacuum distillation, it is also possible to avoid excessive temperatures by employing steam distillation employing techniques known to parties skilled in the art such as vapor recompression.

(14) In contrast to the stress on maximizing glycerin recovery in the distillation processes described in the manufacturers brochures, certain processes of this invention require substantial amounts of glycerin to be left in the distillation bottoms, thereby producing a functional fluid rather than a high salt content waste or low-valued animal feed component. Depending upon the requirements of the markets for the overhead and bottoms products, the amount of glycerin remaining in the bottoms product in operations under this invention will vary, typically from about 6% to about 30% or more of the glycerin contained in the distillation process feed. Employment of at least part of this functional fluid as a component of oil and gas well fluids is a novel element of this invention.

(15) If the crude glycerin being distilled comprises organic impurities (MONG), virtually all of these are higher-boiling compounds that will remain in the still bottoms. For many industrial applications of these still bottoms these impurities may not be objectionable and, in those cases, do not need to be removed prior to application. However, if a purer product is required, one option is to employ an ultrafiltration step employing a nanofiltration membrane such as MPS34 from Koch. Such as procedure may require adding water to the glycerin/salt bottoms, but addition of water will likely be required in any event for most applications of the bottoms stream. When the distillation overhead product is to be refined to a purer grade, the water removed in this process may conveniently be employed as the diluent for this procedure.

(16) In many cases, particularly where the transesterification facility and the distillation process are under common control, MONG content of the crude glycerin can be controlled by eliminating water from the triglyceride-containing feed materials and if free fatty acids are present, esterifying these with glycerin to form triglycerides. These steps minimize production of soaps during the transesterification reaction that are then converted to fatty acids during neutralization. Also, centrifuging neutralized crude glycerin following acidification/neutralization of the byproduct glycerin stream can assist in separating any fatty acids formed during neutralization.

(17) It has been typical practice, when distilling crude glycerin streams comprising water, to withdraw the essentially pure glycerin as a side-stream from the distillation column. Water, together with any alcohol and minor quantities of glycerin, will then comprise the overhead product. The relatively pure side-stream product is then further refined to meet the specification for USP glycerin or food grades such as kosher or halal. This processing step may comprise treatment with activated carbon.

(18) This processing sequence can be employed in the embodiments herein, and the overhead product can be produced to meet USP and/or food grade specifications. However in this case the still bottoms, to be employed as an oil and/or gas well fluid, will contain 6%, or more, of the glycerin contained in the crude glycerin feed.

(19) Alternatively a single overhead stream can be produced in the distillation step. This product will contain all of the water contained in the crude glycerin as well as the glycerin not contained in the bottoms. Following any purification required to remove other material such as any alcohol and/or MONG, this product can be employed in manufacture of various products or can be sold as Technical grade glycerin. Also, in the context of this invention, such essentially pure glycerin products, that may contain water, can be employed in production of oil and gas well drilling and completion fluids.

(20) In the case of producing a chemicals package for hydrofracturing, the present invention contemplates distillation of the Table 1 compound to produce a salt-free glycerin/water overhead product and a glycerin/salt bottoms product. In this way the glycerin/salt ratio in the bottoms product can be controlled to meet the ratio desired in the hydrofracturing chemicals package. The excess acid could be added after distillation to avoid corrosive conditions in that process.

(21) Separation by Membrane Processing

(22) As noted earlier, where desired, the crude glycerin streams can be purified using ultrafiltration to reject MONG. Muraldihara shows that this procedure can also include reverse osmosis steps leading to pure glycerin as a final product. There are several intermediate points in this process where the intermediate product is a fluid comprising glycerin, salt and water. Such fluids could be usefully employed in the oil and gas fluids of this invention.

(23) The processes described above may be practiced at one site to produce a finished product or alternatively, the streams produced at the source of the glycerin-containing by-product, or at the distillation site, may be shipped—with or without added water and/or other components—to another site for finishing and/or use.—

(24) The focus of the present embodiments are methods to improve availability and costs of viscoelastic surfactants (VES) and of glycerin for the “chemical package” of hydrofracturing fluids and for use as a medium for gravel packing, as well of glycerin for multiple uses in drilling and completion fluids.

(25) In this regard, the embodiments include: 1) locating a processing plant, comprising a triglyceride hydrolysis reactor as a central feature, in an area where there is substantial oil &/or gas drilling activity—particularly an area involving production from tight shale formations requiring hydrofracking. As a rule of thumb, the processing plant could be located to serve delivery of oil-field chemicals to several drilling locations within a one-day truck delivery radius. The hydrolysis plant can have the capability of delivering the total product of the reaction as one stream comprising fatty acids, glycerin and water, or two separate products—an oil-soluble fatty acid, and a glycerin/water product. 2) locating a second processing plant, designed for esterification of fatty acids, either at the same site as the hydrolysis unit, or at a location such as a petroleum refinery within a one-day truck delivery radius. The esterified fatty acids may have a use as a friction reducing additive to the “chemical package”, as well as a use as an internal combustion engine fuel—“biodiesel”.

(26) Optional processing facilities at the site of the hydrolysis unit may include: a) Facility for preparing VES from the fatty acids produced at the site; b) Facilities for removing water from the glycerin/water hydrolysis product; c) Facility for finishing fatty acid esters for use or sale as biodiesel; and d) Facilities for conversion of glycerin to polyglycerin.

(27) The features of this arrangement are: Locating the hydrolysis plant with access to several drilling operations improves the economics of employing products such as viscoelastic surfactants as compared with the option of purchasing VES from distant locations; The fatty acid customer will have the option of choosing the form of triglyceride employed in the hydrolysis step. In several patents specific triglyceride sources are preferred (e.g. erucyl acid, or rapeseed oil, in Brown '296); Low cost sources such as waste cooking oils may be used when there is less need for specific characteristics. These may include biodiesel or VES in less critical services such as gravel placement; and The biodiesel option provides an income stream, even between drilling chemical requirements.

(28) Variations of the embodiments disclosed herein will suggest themselves to those skilled in the art in light of the above described processes. All such obvious modifications are within the full intended scope of his invention.

(29) The above referenced patents and publications are hereby incorporated by reference.