RU2719576C1 - Method of destructing a stable reverse water-oil emulsion formed after hydraulic fracturing of a formation - Google Patents

Abstract

FIELD: oil industry; technological processes.SUBSTANCE: invention relates to oil treatment, in particular, to dehydration or demulsification of hydrocarbon oils by chemical means. Invention relates to a method of destroying a stable reverse water-oil emulsion formed after hydraulic fracturing of a formation (HFF), in which a mixture of reagent-decomposer with dehydrated and degassed oil is prepared by means of pump equipment and vessel in ratio from 1:9 to 1:1 and a reagent-decomposer mixture is used in two steps, performed successively, first step – treatment of borehole zone of formation with reagent decomposer mixture at ratio of 1:9 to 1:1, determined from complete gel breakdown by result of analysis of sample, in volume of previously created crack HFF and holding for reaction for 8 hours, second step – dosing the mixture of reagent-decomposer with dehydrated and degassed oil at ratio of 1:1 through appropriate units for dispensing chemicals into oil collection and treatment system together with reagent-demulsifier, consumption of reagent-decomposer is selected experimentally by result of destruction of stable emulsion in formation after the first stage at rate of 100 to 3,000 g of reagent decomposer per one ton of hydraulic fracturing fluid, extracted from formation during well development after HFF to stable mode.EFFECT: separation of oil from water to commercial grade oil level required by regulatory document: water content in oil is not more than 0_5 % by weight.1 cl, 4 tbl, 3 ex

Description

The present invention relates to the field of oil preparation, in particular, to dehydration or demulsification of hydrocarbon oils by chemical means. The invention is applied to fields developed using hydraulic fracturing technology. In the process of bringing wells to a stable operating mode after hydraulic fracturing from the reservoir, along with the formation fluids, the remains of the undecomposed liquid of the proppant carrier gel are carried out. In the oil collection and preparation system, a stable reverse oil-water emulsion is formed, stabilized by a gel after hydraulic fracturing and other components. Widely used methods for the destruction of the inverse oil-water emulsion are introduced into the gas-liquid stream in the elements of the technological scheme for the collection and preparation of oil demulsifying agents in certain concentrations in the marketable form, or in the form of solutions in water or oil. Complete destruction of the emulsion formed after hydraulic fracturing by methods used in practice is not achieved.

A stable inverse emulsion after hydraulic fracturing in general is represented by liquid hydrocarbons - dispersion medium, surface and formation water - dispersed phase, and stabilizing components of the emulsion: residues of non-destroyed gel (viscous aqueous solution of guar gum), solid hydrocarbons such as paraffins, asphaltenes and resins , oxides, salts, solid mechanical impurities and other substances. The gel is usually based on water from surface and artesian sources, less mineralized and more alkaline in relation to the formation. When intensively dispersed during production, especially by deep-pumping equipment, water droplets (dispersed phase) are evenly distributed over the volume of oil (dispersion medium. Interfacial films are strengthened by stabilizing components, including due to the structural properties of the gel. Due to the incomplete destruction of such an inverse oil-water emulsion on An oil preparation unit accumulates a volume of substandard “trap” oil. Since the number of fields developed using hydraulic fracturing is is constantly increasing, the issue of developing a method for the destruction of such a formed stable emulsion is very relevant.

A known composition for the destruction of oil-water emulsions stabilized with a finely divided mechanical impurity (see patent RU 2549538 C1, IPC-2015.04, C10G 33/04), containing a block copolymer of ethylene and propylene oxides based on glycerol, a block copolymer of ethylene oxides and propylene based on ethylenediamine and a solvent, characterized in that it further comprises Neftenol KS, which is a condensation product of hydroxyethylated nonylphenol with varying degrees of hydroxyethylation with polyoxymethylene and carbonic diamide, and as a lock copolymer of ethylene and propylene oxides based on glycerol is used Laprol 6003-2B-18, as a block copolymer of ethylene and propylene oxides based on ethylene diamine - Diproxamine 157-65M, and as a solvent - a mixture of nephras with methanol in a ratio of 7: 3 or methanol and fresh water in a ratio of 3: 1, with the following ratio of components,% mass .:

- block copolymer of ethylene and propylene oxides based on glycerol - Laprol 6003-2B-18 15.0-50.0; - block copolymer of ethylene and propylene oxides based on ethylene diamine - Diproxamine 157-65M 70.0-15.0; - condensation product of ethoxylated nonylphenol with varying degrees of hydroxyethylation with polyoxymethylene and carbonic acid diamide - Neftenol KS 1.0-10.0; - solvent - a mixture of nephras with methanol in a ratio of 7: 3 or methanol and fresh water in a ratio of 3: 1 rest.

The disadvantages of the composition and laboratory method of application are: it does not envisage the destruction of the stable emulsion formed after hydraulic fracturing, which, in addition to finely dispersed mechanical impurities, also includes the remains of the non-destroyed gel, which is a viscous aqueous solution of guar gum, and other stabilizing components of the emulsion; not given an industrial method of applying the composition.

A known method of destroying an emulsion of oil and water (see patent RU 23510413 C2, IPC-2006.01, C10G 33/04 C09K 3/00 B01D 17/05), comprising: contacting the emulsion with a demulsifying composition containing (a) an anionic surface an active substance selected from the group consisting of alkyl sulfosuccinates, alkyl phosphonic acids, their salts and combinations thereof; (b) a nonionic surfactant selected from the group consisting of copolymers of ethylene oxide and propylene oxide, ethoxylated fatty acid esters of polyethylene glycol, alcohol ethoxylates, terpene alkoxylates, modified alkanolamides and combinations thereof; and (c) a solvent base composition comprising a mixture of esters of dibasic acids, as well as combinations of this method.

The disadvantage of this method and its combinations is that it does not provide for the destruction of a stable emulsion formed after hydraulic fracturing, which, in addition to oil, water, salts, acids, asphaltenes and naphthenic acids, also contains the remains of an undegraded gel, which is a viscous aqueous solution of guar gum, paraffins and mechanical impurities.

A known method of destroying water-oil emulsions by bringing into contact with a water-oil emulsion a demulsifying composition (see patent RU 2621675 C1, IPC-2006.01, C10G 33/04 B01D 17/05) containing bottoms from the production of alcohols, nonionic surfactant nonionic surfactants and solvent characterized in that the bottoms of the production of alcohols use bottoms of the production of butyl alcohols, butyric aldehydes, 2-ethylhexanol, 2-ethylhexanoic acid, ethylene-propylene and ethylbenzene having the following chemical cue composition, wt.%: di (2-ethylhexyl) ether 4.60-4.98; 2,4-diethyl-1,3-octanediol 6.80-8.50; isobutyric aldehyde 0.17-0.58; n-butyric aldehyde 5.48-6.13; 2-ethylhexanoic acid 6.08-6.87; 2,2,4-trimethyl-1,3-pentadiol 3.31-3.72; butyl 2-ethylhexanoate 13.98-15.03; 2-ethylhexyl-2-ethylhexanoate 2.57-2.81; butyl butyrate 1.20-1.46; 2_ ethylhexyl butyrate 1.71-1.87; 2,2,4-trimethyl-1,3-pentadiol-diisobutyrate 0.45-0.53; 2-ethylhexanoic acid anhydride 1.79-1.93; 2-ethylhexanol 0.16-0.19; 2,4-dipropyl-5-ethyl-1,3-dioxane 0.28-0.56; Σ unidentified high boiling components up to 100; in this case, nonionic surfactants are used as nonionic surfactants, selected from a number of block copolymers of alkylene oxides, or from a number of modified block copolymers of alkylene oxides, or from a number of ethoxylated phenolic or phenol formaldehyde resins, and low molecular weight alcohols or aromatic hydrocarbons mixed with isopropyl alcohol in a volume ratio as a solvent (5-7): 1, respectively, in the following ratio of components, vol. %:

- specified bottoms 5-12 - specified nonionic surfactants 38-45 - solvent rest,

moreover, the total amount of the specified VAT residue and the specified nonionic surfactant is 50 vol. %; a variation of the method, characterized in that methanol or ethanol is used as low molecular weight alcohols; a variation of the method, characterized in that bottoms from the production of toluene and xylenes are used as aromatic hydrocarbons.

The disadvantage of this method and its combinations is that it does not provide for the destruction of a stable emulsion formed after hydraulic fracturing, which, in addition to oil, water, salts, acids, asphaltenes, resins, paraffins and naphthenic acids, also contains the remains of an undecayed gel, which is a viscous aqueous solution guar gum, and mechanical impurities.

A known method of destroying an intermediate emulsion layer (prototype) formed during oil dehydration (see patent RU 2325428 C2, IPC-2006.01, C10G 33/04 C08G 65/28 B01F 17/02) by treating it with an acid reagent containing inhibited hydrochloric acid acid and surfactant, heating and sludge, characterized in that either a water-oil-soluble surfactant selected from the group: ethoxylated monoalkylphenols based on propylene trimers with a degree of oxyethylations 6-12, glycerol-based ethylene and propylene oxide block copolymers, an ethoxylated mixture of OP-7 brand mono- and dialkylphenols, or a water-soluble surfactant selected from the group: sulfanol, quaternary ammonium salts in isopropanol, or a mixture of water-soluble and water-soluble of a surfactant consisting of ethoxylated monoalkylphenols based on propylene trimers with a degree of hydroxyethylation of 6-12 and quaternary ammonium salts, solutions are additionally introduced a body selected from the group: methanol, ethanol, propanol, isopropanol, butyl cellosolve, acetone, and water is added in the following ratio of components, mass. %:

- inhibited hydrochloric acid 6-20 - water-soluble or water-soluble surfactant or a mixture thereof as described above 0.1-7.0 - solvent 3.0-20.0 - water rest

The disadvantages of this method are: it does not provide for the destruction of a stable emulsion formed after hydraulic fracturing, which, in addition to oil, water and mechanical impurities, also includes the remains of an undegraded gel, which is a viscous aqueous solution of guar gum, paraffins, asphaltenes, naphthenic acids, salts and acids; the need to use technological equipment for the preparation of oil (tank, pump, buffer tank, furnace) by removing it from the technological scheme for the preparation of the bulk of the oil in the presence of reserves, or by preliminary reservation during construction; the duration of the implementation, subject to the proposed sequence of actions.

Thus, the known compositions and methods for breaking emulsions are generally not intended to destroy a stable emulsion formed after hydraulic fracturing.

The essence of the invention is a method of destroying a stable emulsion formed after hydraulic fracturing, consists in preparing and using the developed effective mixture of a reagent-destructor according to the appropriate technology, which together allows you to get oil separated from water. When developing an effective mixture of a reagent-destructor, it was found that the substances present in its composition exhibit general demulsifying properties, destroying the emulsion formed with the participation of natural stabilizers (paraffins, asphaltenes, resins, oxides and salts, solid solids, etc.), and the remnants of the undecomposed liquid of the proppant carrier — the gel, the artificial stabilizer after hydraulic fracturing — are destructed. The developed composition is generally a mixture of a solution of a non-ionic type surfactant with a mass fraction of at least 10% in methanol and an aromatic solvent in finished form with dehydrated and degassed oil in a ratio range from 1: 9 to 1: 1. The composition and content of the mixture of reagent-destructor are shown in table 1. The composition of the mixture of reagent-destructor prepared for use in different fields may vary depending on the ratio of the mixture of a solution of a non-ionic surfactant with a mass fraction of at least 10% in methanol and aromatic ready-made solvent with dehydrated and degassed oil, which does not change the essence of the invention.

Table 1 - the Composition and content of the mixture of reagent-destructor

Name Content, mass. % polymer of ethylene and propylene oxides with ethylene glycol 1,5-7,5 dodecylbenzenesulfonic acid 1.3-6.5 ethanolamine 0.25-1.25 oil solvent 0.05-0.25 pseudocumene naphthalene kerosene 0.5-2.5 methanol 1,5-7,5 toluene 4.9-24.5 oil 50.0-90.0

The technology of using a mixture of reagent-destructor includes two stages, performed sequentially as follows. For the first stage, a reagent-destructor mixture in a certain ratio is prepared using pumping equipment and a container. The recommended ratio in the mixture is 1: 9. This ratio ensures the effectiveness of the action due to the greatest contact of the mixture with the remnants of undecomposed gel in the reservoir. They carry out processing of the borehole zone of the wellbore, where hydraulic fracturing has been carried out, both under repair and in operation (stopped directly for processing). The volume of the reagent-destructor mixture is recommended to be calculated according to the volume of the previously created hydraulic fracture. The reagent-destructor mixture is pumped in the stopped well through the pipe or annular space and then the dehydrated and degassed oil is pumped into the formation. Submersible pumping equipment may not be removed when processing a well in production. For a full response of the mixture of reagent-destructor with a stable emulsion before starting the well into operation, an exposure time of 8 hours is recommended. The well is being commissioned. For the second stage, a reagent-destructor mixture in a certain ratio is prepared using pumping equipment and a container. The recommended ratio in the mixture of reagent-destructor for the second stage is 1: 1. A solution of a non-ionic type of surfactant with a mass fraction of at least 10% in methanol and an aromatic solvent in finished form can also be used without mixing on dehydrated and degassed oil. The mixture is dosed into the collection and preparation system together with the demulsifier reagent through the corresponding chemical dosing units, for example, through the reagent unit. The consumption of the reagent-destructor is selected empirically by the result of the destruction of a stable emulsion in the reservoir after the first stage. Dosing is carried out at the rate of from 100 to 3000 g of a reagent-destructor per ton of hydraulic fracturing fluid taken from the formation during the period of well completion after hydraulic fracturing until it reaches a stable mode.

The mixture of the reagent-destructor in accordance with the invention can be used in combination with other special chemical reagents (reagents, demulsifiers, corrosion inhibitors, scaling, bactericides and others that are used in the collection and preparation of oil), which do not adversely affect performance mixtures.

Scientific, technical and patent analysis of known technical solutions showed that the set of essential features of the claimed invention is not known from the prior art, therefore, the invention meets the condition of patentability of the invention - "novelty", "industrial applicability" and "inventive step".

The essence of the invention is illustrated by the following examples, in which all parts and percentages are given by weight, unless otherwise indicated, are given to illustrate several, but not all, embodiments of this invention.

The mixture of reagent-destructor in vitro was tested as follows. We studied a sample of a stable oil-water emulsion formed after hydraulic fracturing, taken both from the well and from the entrance to the oil treatment unit. The effectiveness of the use of the reagent-destructor was evaluated by the “bottle test” method (boot test) by comparing the volumes of the separated aqueous phase and the residual (bound) water in the samples when modeling the oil preparation.

The test samples were placed in graduated 100 ml sump tanks with a conical bottom, in each of which the calculated amount of a chemical reagent (a reagent-destructor, a reagent-demulsifier, together or separately) was dosed with a syringe (dispenser). The sample was heated using a thermostat to a temperature of 40 ° C, corresponding to the preparation temperature. Shaking (mixing) was carried out for 10 min using a laboratory centrifuge. After a certain time, the amount of released water was recorded (for example, 15 minutes, 30 minutes, 1 hour, 6 hours, 12 hours). After sedimentation of the sample for a predetermined time, from 10 ml bottles from different levels (upper, middle and lower), samples were taken in centrifuge tubes in a volume of 10 ml and centrifuged. After centrifugation, the content of free water / gel was determined. Free water refers to the amount of water that can be isolated from a sample under specified conditions using a chemical reagent. Then the same tubes with emulsion were heated to 80-90 ° С, a shock dose of a demulsifying chemical reagent was introduced and centrifuged again. In this way, the amount of residual bound water / gel was determined.

Example No. 1.

The study used a sample of water-oil emulsion from a well commissioned after hydraulic fracturing with a water cut of about 12%. Dosage: CPD demulsifiers, Flack - 40 g / t; reagent destructor - 3000 g / t. The test results are presented in tables 2 and 3.

Table 2 - Testing the reagent-destructor for 1 h

Sample / composition of the mixture The amount of released water / gel in ml per time Qty. water / gel at the upper level in 1 hour,% 15 minutes 30 minutes 45 min 1 hour freedom communication emulsion / reagent destructor 7.5 / 0.4 8.0 / 0.3 8.0 / 0.3 8.0 / 0.3 0.8 / 0.1 0.8 / 0.2 emulsion / reagent-destructor + HFA 7.0 / 0.5 7.0 / 0.4 7.5 / 0.3 8.0 / 0.3 1,0 / 0,1 1,1 / 0,1 emulsion / reagent destructor + Flack 7.0 / 0.5 7.5 / 0.3 7.5 / 0.3 7.5 / 0.3 0.8 / 0.2 1.0 / 0.2 single * 5.5 / 1.5 6.0 / 1.5 6.0 / 1.5 6.0 / 1.5 SL / 1.0 0.8 / 0.2

Note: next - footprints.

* - single - sample emulsion without the addition of chemicals.

The test results indicate that the destructor destroys the gel-like structure in the emulsion after hydraulic fracturing, and in a mixture with the demulsifier reagent provides almost complete destruction of the stable oil-water emulsion. The example shows that the minimum value of the residual (bound) water is 0.2%.

Table 3 - Testing the reagent-destructor for 12 hours

Sample / composition of the mixture The amount of released water / gel in ml for 12 hours Qty. water / gel at the upper level,% freedom communication emulsion / reagent destructor 10.5 1,0 / 0,1 1,5 / 0,1 emulsion / reagent-destructor + HFA 12.0 0,0 / 0,1 0,1 / 0,1 emulsion / reagent destructor + Flack 11.0 0.3 / 0.1 0.5 / 0.1 single * 8.5 / 2.0 2.5 / 1.0 3,5 / 1,0

Example No. 2.

An example of a dosage selection of a destructor reagent mixed with toluene, which under industrial conditions is replaced by dehydrated and degassed oil, is presented. The study used a sample of water-oil emulsion from the entrance to the oil treatment unit after hydraulic fracturing, with a water cut of about 8%. The results are presented in table 4.

Table 4 - Dosage selection of a reagent-destructor mixed with toluene

Mixture composition results emulsion (water cut - 8%) - 50 ml; toluene - 47.5 ml; ready-made reagent destructor - 2.5 ml The emulsion was divided into oil and water. The phase boundary is fuzzy. There is a visible amount of gel - 1.0%. Free water - 4.0%. The water is clean. Part of the water remained in oil - 4.0%. emulsion (water cut - 8%) - 50 ml; toluene - 45.0 ml; finished reagent-reagent - 5.0 ml The emulsion was divided into oil and water. The phase boundary is clear. There is a visible amount of gel - 0.2%. Free water - 7.0%. The water is cloudy. Part of the water remained in oil - 1.0%.

Example No. 3.

The proposed mixture of reagent-destructor in a production environment was used as follows. We chose the well on which the hydraulic fracturing was performed, then the conclusion to the mode and operation, and on which, according to the field data, contamination with residues of undecomposed gel was revealed. A sample of the produced fluid from this well was a stable oil-water emulsion formed after hydraulic fracturing. For processing, we used the CA-320 aggregate, a stationary buffer tank with a volume of 50 m ³ for preparation, a tanker truck for transporting dehydrated oil, and strapping elements. Prepared a mixture of reagent-destructor in accordance with the data of table 1 by mixing the reagent-destructor in finished form and dehydrated and degassed oil in a ratio of 1: 9. We processed the near-wellbore zone of the formation with a prepared reagent-destructor mixture in the volume of the hydraulic fracture - 50 m ³ . The well was launched and put into operation. The effectiveness of the use of the reagent-destructor was evaluated by the result of the analysis of the sample of produced well fluid from the wellhead after this treatment. In the aqueous part of the sample, the decomposition products of the gel are visually present in the form of a turbid-white precipitate. Then, using the Flac demulsifier reagent in the calculated dosage of 40 g / t after 12 hours of settling at room temperature, the emulsion is completely divided into oil and water. To obtain a complex effect, a 1: 1 reagent-destructor mixture was dosed per day at the rate of 500 g of destructive reagent per ton of hydraulic fracturing fluid taken from the reservoir during the period of well completion in the settling tanks at the oil treatment unit. Dosing was carried out in conjunction with the use of a flak demulsifier reagent, 40 g / t. As a result, the means of controlling water cut of the products revealed that the oil was dehydrated to the required level of 0.5%.

Thus, a method for destroying a stable reverse oil-water emulsion formed after hydraulic fracturing, which allows to obtain a technical result - the separation of oil from water to the desired level for marketable oil: the water content in oil is not more than 0.5% by weight. Due to the complete destruction of the reverse water-oil stable emulsion formed after hydraulic fracturing, the volume of substandard “trap” oil does not accumulate in the oil treatment unit. The proposed new method when comparing with known methods of destruction of stable reverse water-oil emulsions has the following differences:

- the method involves the destruction of a stable emulsion formed after hydraulic fracturing, represented by liquid hydrocarbons - dispersion medium, surface and formation water - dispersed phase, and stabilizing components of the emulsion: residues of non-destroyed gel (viscous aqueous solution of guar gum), solid hydrocarbons such as paraffins, asphaltenes and resins, oxides and salts, solid mechanical impurities and other substances;

- the composition and content of the mixture of the reagent-destructor differs from those characteristic for the used reagents-demulsifiers;

- the application technology includes two effective stages, carried out sequentially, providing a comprehensive effect;

- the first technological stage of the developed method involves the destruction of undecomposed gel in the near-wellbore zone of the formation, even before the stage of maximum dispersion in the downhole pumping equipment, thereby preventing an increase in the stability of the emulsion;

- there is no need to use technological equipment for oil treatment (tank, pump, buffer tank, furnace) to destroy substandard "trap" oil by removing it from the existing technological scheme.

Although the invention has been described with specific embodiments and examples, it should be understood that such embodiments are provided only to illustrate the principles and application of this invention. Additional embodiments may be apparent to those skilled in the art after reading and understanding the present invention. It is intended that all such embodiments be included within the scope of this invention. Therefore, it should be understood that numerous modifications of the embodiments may be made, and that other variations may be developed without departing from the spirit and scope of the invention, as defined in the claims.

Claims (3)

The method of destroying a stable reverse oil-water emulsion formed after hydraulic fracturing (hydraulic fracturing), which consists in preparing using a pumping equipment and a tank a mixture of a reagent-destructor with dehydrated and degassed oil in ratios from 1: 9 to 1: 1:

and the reagent-destructor mixture is used in two stages, performed sequentially, the first stage is the treatment of the borehole zone of the formation with the reagent-destructor mixture in a ratio of 1: 9 to 1: 1, determined by the complete disintegration of the gel according to the result of the analysis of the sample, in the volume of the previously created crack Hydraulic fracturing and reaction time for 8 hours, the second stage - dosing the mixture of the reagent-destructor with dehydrated and degassed oil in a ratio of 1: 1 through the appropriate metering units of chemical reagents in the oil collection and treatment system together with the demulsifier reagent, the flow rate of the breakdown reagent is selected empirically based on the result of the destruction of the stable emulsion in the formation after the first stage, based on the calculation of 100 to 3000 g of breakdown reagent per ton of hydraulic fracturing fluid taken from the reservoir during the time of well completion after Hydraulic fracturing before reaching stable mode.