WO2016182469A1

WO2016182469A1 - Traceable proppant, method of producing a traceable proppant and method of using same

Info

Publication number: WO2016182469A1
Application number: PCT/RU2015/000294
Authority: WO
Inventors: Александра Михайловна ХУДОРОЖКОВА; Елизавета Андреевна ИНОЗЕМЦЕВА; Максим Григорьевич ИВАНОВ; Илья Андреевич СТАРКОВ; Анатолий Владимирович МЕДВЕДЕВ
Original assignee: Шлюмберже Текнолоджи Корпорейшн; Шлюмберже Канада Лимитед; Сервисес Петролиерс Шлюмберже; Шлюмберже Текнолоджи Б.В.
Priority date: 2015-05-08
Filing date: 2015-05-08
Publication date: 2016-11-17

Abstract

The invention relates to the oil and gas industry. Proposed is a traceable proppant with a bi-metal coating, said traceable proppant containing a ceramic base and a first metal layer and a second metal layer which are applied to the ceramic base, wherein the second metal layer has magnetic properties. The invention also relates to a method of producing such a traceable proppant and to a method of using same when hydraulically fracturing a subterranean formation. The invention makes it possible to produce a traceable proppant having high electrical conductivity and magnetic permeability characteristics which differ significantly from the characteristics of typical underground rock.

Description

PROPPANT-MARKER, METHOD FOR PRODUCING PROPPANT-MARKER AND METHOD FOR ITS APPLICATION AREA

The present invention relates generally to the oil and gas industry, in particular to a proppant marker, a method for producing a proppant marker, and a method for its use in hydraulic fracturing of an underground formation.

BACKGROUND OF THE INVENTION

Hydraulic fracturing (Fracturing) is the operation of creating channels with high permeability in the rock by pumping into the reservoir a carrier fluid carrying proppant particles (i.e. a proppant). The proppant particles in the fracture form a channel with high hydraulic conductivity (proppant packing), which does not allow the walls of the formed fracture to close together. The organization of hydraulic fracturing operations is aimed at optimizing proppant placement in the fracture. In particular, it is advisable that the proppant remains within the productive zone. However, a fracture can propagate beyond the productive zone. Optimization of hydraulic fracturing operation is possible with direct correction of the proppant injection schedule according to the actual placement of proppant in the fracture formed in the formation with this lithology. Thus, knowledge of the actual placement of proppant in the fracture is necessary. There are approaches to determining the fracture geometry, such as microseismic measurements or active cross-hole seismic exploration. However, there are no suitable devices and methods for direct measurement of the geometry of the proppant placed in the fracture.

One of the methods for determining the position of proppants is in underground borehole electromagnetic sounding, which includes placing a source of electromagnetic radiation and antennas placed in one well or in neighboring wells (as described in detail in US patent application · ° US 2014/0190686 A1 of 07/10/2014). This application describes the creation of a package of conductive proppant containing spherical particles with an almost uniform coating of conductive material with a thickness of at least 500 nm, and the conductive material contains a metal selected from the group consisting of aluminum, copper and nickel (see . 1 and 2 formulas). However, this application mentions a complex and expensive method of applying a conductive coating by radio frequency magnetron sputtering in a vacuum chamber or by depositing a conductive polymer such as PEDOT / aminosilane (see examples).

Proppant markers placed in a hydraulic fracture are also known, which have a ceramic base and contain long-lived radioactive isotopes in the ceramic matrix. With the help of gamma-ray detectors, it is possible to confirm the fact of the delivery of the proppant marker to a given crack. However, the drawback of such proppant markers and the method for detecting them in a fracture is the need to work with highly active radiation sources and low resolution (in particular, only the fracture height is determined from logging measurements).

Chemical metallization ("electroless plating", ie, "deposition by chemical reduction") of a ceramic surface is known and used in industry. So, for example, in US patent J4 ° US 6586047 B2 dated 07/01/2003, the process of chemical metallization of particles suspended in a solution is described, which consists in the fact that the coating solution without a reducing agent and the particles are combined in a special vessel with stirring. If necessary (the particles do not contain an activator), activating agents are added to the vessel. After the addition of a reducing agent, a process of deposition of metal on particles occurs. In particular, this patent describes methods for applying a copper coating. The example demonstrates a complex 12-stage method, but its initial stages require the use of an expensive activator made of a platinum group metal, for example, palladium. Thus, it can be noted that while there are no effective proposals for an electrically conductive proppant marker.

SUMMARY OF THE ESSENCE

At the same time, the need for detecting a proppant marker in a hydraulic fracture could be the creation of a proppant marker, which would have both electrical conductivity and magnetic permeability, both at higher levels than conventional ceramic proppant or surrounding rock.

Thus, in accordance with one aspect, a bimetallic coated proppant marker is provided. This proppant marker contains a ceramic base, a first metal layer and a second metal layer. The first and second metal layers are deposited on said ceramic base. In this case, the second metal layer has magnetic properties.

In accordance with another aspect, a method for producing a bimetallic coated proppant marker is provided. The proposed method contains:

(a) preparing the surface of the ceramic proppant particles, including treating them with an acidic aqueous solution containing tin (Sn) ions;

(b) activating the surface of the ceramic proppant particles, including treating them with an aqueous solution containing silver (Ag) ions and not containing a platinum group metal; and

(c) metallization of the activated surface of proppant ceramic particles by chemical reduction to form a bimetallic coating.

The resulting bimetallic coating contains a first metal layer and a second metal layer deposited on said ceramic particles, while the second metal layer has magnetic properties.

In accordance with yet another aspect, a method for using a bimetallic coated proppant marker of the invention or a proppant marker obtained by the method of the invention is provided. This method of application includes preparing a suspension of said proppant marker in a carrier fluid and injecting said suspension into a well during hydraulic fracturing. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the following drawings: FIG. 1 illustrates a schematic representation of an experimental measuring unit with a polymer cell for preliminary testing the electrical conductivity of a proppant package;

Figure 2 is a photograph showing the initial appearance of the CarboPROP® proppant (a), silver coated proppant after washing (b) and drying (c).

Fig. 3 is a photograph showing the appearance of the obtained proppant coated with Ag: Ni-P (a) after drying (b) and annealing (c).

DETAILED DESCRIPTION

Some embodiments of the present invention will now be described in more detail.

The invention provides a bimetallic coated proppant marker containing a ceramic base, a first metal layer and a second metal layer deposited on said ceramic base, the second metal layer having magnetic properties.

The relative magnetic permeability of the proppant marker in bulk can be at least 1.5, in particular at least 2, for example, in the range from 1.5 to 100 or from 5 to 60.

The electrical conductivity of the proppant marker in bulk can be at least 100 S / m and reach 5-6 x 10 ⁷ S / cm (i.e., the specific conductivity of metallic silver and copper).

The first metal layer of the proppant marker may contain a metal or alloy selected from the group consisting of silver, copper and alloys based on silver and copper. In particular, the first metal layer may be made of copper or a copper-based alloy.

The second proppant marker metal layer may comprise a metal or alloy selected from the group consisting of nickel, cobalt and nickel or cobalt based alloys. In particular, the second metal layer may be made of nickel or an alloy based on nickel. In one embodiment, the second metal layer may be made of an alloy based on nickel doped with phosphorus. The phosphorus content in the Nickel-based alloy may be 12 wt.% Or less, in particular from 0.01 to 12 wt. more specifically, from 0.1 to 10 wt.%, for example, from 1 to 8 wt.%.

The proppant marker may further comprise a protective coating of a water-soluble polymer.

The invention also provides a method for producing a bimetallic coated proppant marker, which comprises the following steps:

(c) metallization of the activated surface of ceramic proppant particles by chemical reduction to obtain a bimetallic coating containing a first metal layer and a second metal layer deposited on said ceramic particles, the second metal layer having magnetic properties.

The production method may further include, after metallization, annealing of the proppant marker at a temperature of from 200 to 600 ° C, in particular from 250 to 500 ° C, for example, from 260 to 300 ° C. Such annealing can be carried out either in an inert atmosphere (for example, N ₂ , Ar, etc.), or in air.

The production method may further include, after metallization, applying a protective coating of a water-soluble polymer, such as, for example, polyvinyl alcohol (PVA), collagen (for low temperatures), polyalkylene oxide, polylactic acid, polyvinyl acetate (PVA) and PVA-PVA.

The invention also provides a method of using a bimetallic coated proppant marker proposed according to the invention or obtained by a method according to the invention, comprising preparing a suspension of said proppant marker in a carrier fluid and injecting said suspension into the well during hydraulic fracturing.

In a method of application, said suspension may be pumped into at least one fracture obtained by hydraulic fracturing, and then said at least one fracture may be closed to form a permeable proppant pack.

The method of application may also include electromagnetic well logging before and after placing the proppant marker in the well. The method of application may also include electromagnetic logging, which is carried out near the zone of placement of the proppant marker in the reservoir. The method of application may also include measuring the electrical conductivity and magnetic permeability of the rock in the formation in the proppant packing zone.

It should be noted that although the specific carrier fluids, proppants (proppants) or methods for their preparation, delivery, injection into the well, and the like, any of them may be used in the present invention are not indicated in this document.

It should also be noted that the use of the proppant marker of the invention is not limited only to hydraulic fracturing, and the present invention may find other specific applications where these properties of such proppant can be used.

The requirements that apply to conventional proppants are simple, because the proppant plays the role of a coarse-grained (particle size up to several millimeters) strong rock, which is pumped together with the carrier fluid into the crack formed during hydraulic fracturing. It is desirable that the proppant has a moderate specific gravity (2-4 g / cm ³ ), since it 2015/000294

it is transported into the well in the form of a dispersion of particles in the carrier fluid, and with a large specific gravity it will settle in the well, not getting much into hydraulic fractures. It is also desirable that the proppant be strong in order to withstand a load of the order of 30 MPa after closing the fracture wall. A round shape of the proppant particles is also desirable, which ensures high proppant packing porosity and its hydrodynamic conductivity.

The proppant marker of the invention (in other words, a detectable proppant or proppant with the properties of simple and quick detection) retains the above characteristics (strength, specific gravity, rounded shape), but also acquires new characteristics that can be easily measured by existing downhole tools .

Pumping particles of a proppant marker with an electrically conductive coating into the crack allows one to obtain a picture of the conductivity distribution in the crack already at a distance of several meters. In this case, the depth of electromagnetic (EM) sounding depends on the distance between the emitting antenna and the receiving antennas, the signal frequency and the conductivity of the proppant package from the proppant marker.

At the same time, the presence of the proppant marker according to the invention of such properties as high electrical conductivity and magnetic permeability, allows to increase the sensitivity and accuracy of the method of electromagnetic sounding proppant packaging and to expand the list of electromagnetic logging tools with which you can determine the position and orientation of the crack, filled proppant marker. In this case, it is possible to determine not only the change in the amplitude of the electromagnetic signal transmitted through such a conductive proppant marker, but also the change in the phase of the transmitted signal. Additional information on EM logging tools is available in Resistivity Behind Casing, Oilfield Review, Vol. 13, Issue 1, 2001.

The very method of constructing an interpretation of an electromagnetic signal that has passed through a package from a conductive proppant marker is not included in the description of this invention. This usually involves solving the inverse problem of electrical conductivity of the rock around the wellbore having anomalies in conductivity.

Thus, the proppant marker of the invention may have the following properties. The proppant can be spherical (or another predetermined shape), durable (not lower than that of ceramic proppant, namely 30 MPa or more), have a moderate specific gravity (such as 2-4 g / cm ³ or even less), and also have “Abnormal” properties that a proppant marker emits in comparison with a “normal” (non-conductive or non-magnetic) proppant: high electrical conductivity and high magnetic permeability, different from the magnetic permeability of the environment (formation rock).

Accordingly, the method for producing such a proppant marker can provide a number of possibilities: the proppant and its coating do not contain rare or expensive materials, which is of great importance in practical implementation, since tons of proppant are pumped into the well; The proppant production method is carried out at moderate temperatures and does not require the use of toxic materials.

Next, a proppant marker with an electrically conductive and magnetic coating will be described, as well as a method for producing it based on ceramic proppant using chemical metallization (autocatalytic metal deposition).

It is the method of chemical metallization of ceramic proppant with metals or alloys that allows you to simply and quickly create the required bimetallic coating on its non-conductive inert surface, precipitating a sufficient amount of two or three metals or their alloys. In particular, a coating of proppant ceramic particles made of an alloy containing nickel and / or cobalt gives the proppant marker not only electrically conductive, but also magnetic properties.

Chemical (non-galvanic) metallization is widely used, for example, in microelectronics in the manufacture of circuit boards. Chemical metallization is an autocatalytic method for the chemical reduction of metal ions from a solution, in which the film can be applied through oxidation chemical reagent (i.e. reducing agent) present in the solution, which creates internal currents.

In one embodiment, a proppant marker is provided comprising a ceramic base (ceramic proppant particles) coated with a first metal layer of silver, copper or alloys based on them, and then additionally coated with a second metal layer of nickel, cobalt or nickel or cobalt based alloys , in particular, a nickel-based alloy doped with phosphorus, but it is also possible to coat other metals and their alloys.

According to the invention, a method for producing a proppant marker includes the following processes: preparing and activating a proppant surface, applying a metal coating to the proppant surface using chemical metallization, then washing and drying the coated proppant, and optionally firing the coated proppant. These processes are presented in more detail in the examples below.

Upon receipt of the proppant marker with a conductive coating, an experimental setup was used, which includes a thermostat, an overhead stirrer, and a reactor in which the coating solution and the proppant were placed. The installation allows the contents of the reactor to be heated and the mixture rotated, which prevents the proppant particles from sticking together during the reaction. The pressure in the reactor can be reduced through the openings in the lid of the vessel. To obtain a uniform and high-quality metal coating on the particles, the reactor rotation speed was chosen close to 40 rpm, although other rotation speeds, such as 5-100 rpm, can be used. But this invention is not limited to the use of this particular installation, and is also not limited to the features of the mixing process and temperature increase (which depend on the specific requirements for a particular reaction).

The conductivity of the obtained particles of the proppant marker was measured by the two-electrode method in an experimental measuring setup, schematically shown in FIG. 1 and intended for preliminary testing the electrical conductivity of proppant packaging. The installation is equipped with a polymer cell 1 in the form of a cylinder, which is closed at both ends by two metal plates-electrodes 2 and 3, made, for example, of copper (Cu), which are connected to the probes (not shown) of the multimeter. The resistance of the probes was 0.7 ohms. One electrode 2 (the upper one in the figure) is connected to the piston 4, and the second electrode 3 (the lower one in the figure) is stationary. In the cell 1, the investigated proppant 5 is poured. The electrical conductivity of the poured proppant is measured according to the following procedure. First, pressure is applied to the piston and the proppant is compressed to a predetermined pressure value, and then data is collected from the multimeter.

Electrical resistance is calculated by the formula:

where R is the electrical resistance measured in ohms, 1 is the length of the proppant filled in the cell (cm), A is the cell cross-sectional area (in this case, 1.2 cm ² ), V is the proppant volume in the cell. Electrical conductivity is calculated as σ = 1 / ρ.

The process of metallization of the surface of the proppant includes three main stages:

• preliminary preparation of the particle surface;

• particle surface activation;

• deposition of metal on the surface of particles.

Before metallization, it is necessary to prepare the surface of the proppant (ceramic) to obtain a uniform coating. Proppant pretreatment steps may include the following:

• rinsing proppant in deionized water;

• degreasing of proppant with acetone;

• keeping proppant in a 20% NaOH solution;

• etching proppant with an aqueous solution of sulfuric acid with

potassium dichromate (H ₂ S0 ₄ + K ₂ Cr ₂ 0 ₇ + H ₂ 0; ratio 3/1/6); • proppant washing in a 4% HC1 solution;

• washing the proppant in deionized water and drying it at 80 ° C. Since all conventional proppant types are dielectrics, catalytic activation is necessary to initiate metal deposition. There are several approaches for creating a catalytic layer on the surface of a dielectric. The usual approach involves the use of tin and palladium chlorides (SnCl ₂ and PdCl ₂ ). The simplest models confirm that the sensitizing ion Sn ²⁺ can reduce the active metal Pd ° on the surface from a solution of the PdCl ₂ catalyst. However, due to the high catalytic activity of silver on the surface of the substrate, in this case there is no need to activate the surface; it is enough to carry out the treatment with an acidic solution of SnCl ₂ to obtain a uniform and continuous coating.

This activation procedure can include two steps:

• proppant activation in a solution of this composition: SnCl ₂ 30 g / l + HC1 40 g / l;

• washing proppant in hot deionized water at pH = 9 to improve hydrolysis.

The reaction of Ag reduction from a water-ammonia silver oxide solution is carried out. The creation of the coating is based on the reaction of the silver mirror:

R-CH = 0 + 2 [Ag (NH ₃ ) ₂ ] OH - »2Ag \ + R-COONH ₄ + 3NH ₃ + H ₂ 0.

In an ammonia solution, silver oxide dissolves to form soluble complexes. The addition of glucose (i.e., anhydride) to this complex compound initiates a reduction reaction and precipitation of metallic silver.

EXAMPLES

EXAMPLE 1. Getting coated with silver proppant

Perform the following procedure: • 0.75 g of silver nitrate and 0.87 g of sodium hydroxide were placed in separate vessels and 100 ml of deionized water were added until completely dissolved;

• mixed a solution of silver nitrate and sodium hydroxide in the reactor: as a result, a black precipitate of silver oxide;

• 4 ml of ammonia and 700 ml of deionized water were added until the precipitate was completely dissolved;

• 1.44 g of glucose in 100 ml of deionized water was dissolved in a separate vessel;

· 100 g of CarboPROP® proppant from the company were added to the reactor

CARBO Ceramics® (its surface was prepared and activated in SnCl ₂ solution);

• set the temperature of the water bath at 15 ° C;

• carefully and gradually introduced the glucose solution into the reactor and ensured the rotation of the reactor at 40 rpm;

• silver is deposited on the surface of the proppant within 1-15 minutes;

• drained the liquid from the reactor and separated the proppant on a sieve;

• washed the proppant with water on a sieve;

• dried proppant in an oven at 100 ° C;

· As a result received a proppant with a silver coating.

Figure 2 shows the appearance of the original CarboPROP® proppant (a), silver coated proppant after washing (b) and drying (c).

The thickness of the silver coating is approximately 0.2 μm. The electrical conductivity of such a proppant is shown in Table 1. The reproducible and high conductivity levels of the proppant backfill indicate a high quality coating.

EXAMPLE 2. Obtaining proppant with a Nickel-phosphorus coating over a silver coating

In a second example, a chemical metallization method was carried out for obtaining a nickel-phosphorus coating on a silver-coated proppant. The theory of this type of metallization is different from the first example (silver coating).

When applying a nickel coating on a substrate, sodium hypophosphite (Na (PH ₂ 0 ₂ )) was used as a reducing agent. In this case, not a pure metal is deposited, but a layer of a nickel-phosphorus alloy. In addition, this type of coating is a strong and hard coating and highly resistant to corrosion. On the other hand, this coating is characterized by slightly reduced conductivity compared to pure nickel: σ (Νί) ~ Ts x 10 ⁶ S / m (Siemens per meter); and σ (Νϊ-Ρ) ~ 1 ^χ 10 ⁶ S / m.

The mechanism of reduction of metal ions by using hypophosphite involves two reactions: hypophosphite ions are oxidized catalytically, and nickel ions are reduced on the catalytic surface. Part of the reduced hydrogen is absorbed on the catalytic surface, and this is the anode reaction. After this, the nickel ion is reduced by absorbed active hydrogen (cathodic reaction). Part of the hydrogen reduces a small amount of hypophosphite in an aqueous solution to a hydroxyl ion and phosphorus, which is included in the coating.

When nickel ions are reduced on the proppant surface (without the use of expensive salts of platinum metals), the coating reaction is slow and unstable. To overcome this difficulty, a new metallization method was chosen, which involves applying a thin layer of silver as a catalytic layer, and then applying a second layer of metal selected from the group of nickel, cobalt, chromium and other metals used for electroplating.

To obtain a bimetallic coating on a ceramic proppant, a modified approach was used based on the catalytic properties of silver:

• sensitization of ceramic proppant in a solution of this composition: SnCl ₂ 30 g / l + HCl 40 g / l; • washing proppant in hot deionized water at pH = 9 to improve hydrolysis with the formation of tin hydroxide;

• deposition of a catalytic layer of Ag with a thickness of approximately 0.05 μm (as described in example 1, but with different concentrations);

· Applying a layer of Ni-P alloy on top of the Ag layer.

As a result, a proppant with a double metal coating was obtained: an Ag layer (0.05-0.1 μm thick) and a Ni-P alloy layer (1-10 μm thick).

The starting materials were as follows:

• proppant brand CarboPROP® 12/18 coated with silver according to example 1, 100 g;

• nickel sulfate, 25 g;

• sodium hypophosphite, 25 g;

• acetic acid, ~ 10 ml (pH -4.3);

• sodium acetate, 15 g;

Thiourea, 0.01 g;

• water, 1 l.

The process of applying a second metal layer over a silver coating was as follows:

• dissolved sodium acetate in deionized water heated to 60 ° C in the reactor;

• nickel sulfate was added and dissolved;

• added acetic acid, neutralized to a pH of -4.3-4.5;

• heated the reactor to 85 ° C and added thiourea;

• the silver metallized proppant CarboPROP®: Ag was introduced into the reactor;

• added sodium hypophosphite;

• Waited for the Ni-P mixture to deposit on the proppant surface for approximately 3 hours;

• drained the liquid from the reactor and separated the proppant on a sieve; • washed the proppant on the sieve several times with water;

• dried bimetallic coated proppant in an oven at 100

° C;

• carried out annealing of proppant with a bimetallic coating at 270 ° C for 10 hours;

• the result was a proppant with a bimetallic coating Ag: Ni-P.

In FIG. 3, the obtained proppant is shown after applying a bimetallic coating of Ag: Ni-P (a), after drying (b), and after annealing (c).

Obtained on the proppant bimetallic coating Ag: Ni-P had a total thickness of about 2.1 microns. The specific electrical conductivity of the filling of such a bimetallic proppant, measured by the two-electrode method described above, is shown in Table 1.

It was also found that the obtained proppant with a bimetallic coating had the following properties:

1. absolute magnetic permeability ~ 1.25 ^χ 10 ^"6 Gn / m (depending on various parameters, the relative magnetic permeability varied within 10-60), which allows to expand the methods for detecting simultaneously conductive and magnetic proppant in a fracture;

2. The bimetallic coating was uniform and continuous, with good adhesion to the surface of the ceramic proppant base.

In addition, such a two-layer metallization, in comparison with standard ceramic proppant particles, increases mechanical strength (which was confirmed by the tests of the obtained proppant marker for failure under load in the test cell).

EXAMPLE 3. Proppant with bimetallic silver / Nickel-phosphorus coating - magnetic properties

The proppant with a bimetallic coating (a thin layer of silver and a nickel-phosphorus coating over it) obtained in Example 2 was dried and heated to a temperature of 400-500 ° C without oxygen. When keeping phosphorus in the second, outer metal layer, proppant particles exhibit magnetic properties. Particle balls adhere upon contact.

Measurement of the relative magnetic permeability of the proppant with a thickness of the outer nickel-phosphorus layer at a level of 1-2 μm showed an increased magnetic permeability with a dense filling of particles. The relative magnetic permeability of the proppant marker with a bimetallic coating was 1.5–2.5 depending on the thickness of the second coating. The electrical conductivity of the metallized proppant is shown in table 1.

EXAMPLE 4. Obtaining proppant with a copper coating

In this example, a chemical proppant metallization procedure using a copper layer was implemented. The chemical mechanism of metal reduction from a copper salt is close to that described in the second example (for nickel).

Surface preparation and surface activation with silver was performed as in the second example. Metallization was carried out in solutions of tartaric acid, citric acid, glycerol and Trilon-B, or with other additives that prevent copper from precipitating in the solution itself. As a reducing agent, formalin or another formaldehyde solution was used. The result was a copper-coated proppant (with a small proportion of Ni to increase corrosion resistance).

The materials used were as follows:

• proppant CarboPROP® 12/18 from the company CARBO Ceramics® (particle surface activated with silver according to example 1), 200 g;

• copper sulfate, 35 g;

• Nickel chloride hexahydrate NiCl ₂ -6H ₂ 0, 1.5 g;

Potassium hydroxide, 70 g;

• Trilon B, 25 g;

• Sodium carbonate, 25 g;

• formalin, 20 g;

• water, 1 liter. The coating process included the following steps:

• dissolved potassium hydroxide in water in the reactor;

• added Trilon B;

• sodium carbonate was added (pH -12.5);

· In a separate vessel dissolved copper sulfate and NiCl ₂ · 6H ₂ 0;

• the second solution was added dropwise to the first solution;

• added silver metallized proppant CarboPROP®: Ag to the reactor;

• added formalin to the reactor;

· A copper layer is deposited on the surface of the proppant within a few hours;

• drained the liquid from the reactor and separated the proppant on a sieve;

• washed proppant on a sieve with water several times;

• dried proppant at 100 ° C;

· Annealed proppant at 200 ° C for 10 hours;

• the result was a proppant coated with Ag + Cu.

The thickness of the metal layer of Ag + Cu was approximately 2 μm.

The conductivity of such a metallized proppant is shown in Table 1. The metallized proppant, in comparison with the standard ceramic proppant, had greater mechanical strength.

The method of applying a bimetallic coating on a ceramic proppant provides acceleration of the deposition of a metal layer (without a thin layer of silver, metallization is slow), uniformity of the bimetallic coating and the absence of expensive catalysts, which is desirable in large-scale production.

Table 1. Electrical conductivity of metal coated proppants.

Metallic Temperature Thickness Conductivity σ, annealing coating, ° С coating, μm S / m Ag 100 0.05 200

Ag 100 0.2 1000

Ag: Ni-P 270 2.1 2000

Ag: Ni-P 500 2.1 4000

Ag: Cu 200 1.5 6000

EXAMPLE 5. Test proppant with a protective coating

The bimetallic coated proppant of Example 3 or 4 was further coated with a protective coating of a water-soluble polymer (polyvinyl alcohol with a dissolution temperature of 70-80 ° C.) according to the technology described in US Pat. No. 7,490,667. The thickness of the protective (non-conductive) coating was 6-15 μm. Then, the particles of the resulting composite proppant were dried and tightly placed in a cylindrical cell with a slightly salted aqueous solution. It was found that the specific conductivity of such a proppant pack differs little from the conductivity of inter-pore salt solution.

When a weakly saline solution with a temperature of 80-85 ° C was pumped through the cuvette, most of the protective polymer coating was dissolved and the electrical conductivity of the proppant package increased 4-10 times.

The use of such a temporary protective polymer coating allows one to compare the distribution pattern of conductivity in the fracturing zone for conductive and non-conductive cracks with close crack geometry (the width and length of the cracks change little after polymer dissolution).

EXAMPLE 6. The use of proppant with a bimetallic coating

The proppant marker of Example 3 with a bulk density close to ceramic proppant (sand) can be delivered via a carrier fluid to a hydraulic fracture.

In one embodiment, a large part of the GPR crack is filled with a composite proppant with a bimetallic Ag: Ni-P coating.

In addition, to stabilize the dispersion and retain sand in it, various additional solid and / or liquid additives (for example, surfactants, surface-modifying agents, emulsifiers, solid particles, etc.).

The resulting technical effects

When applying a bimetallic coating to ceramic particles, proppant marker particles (according to Example 3) with electrical conductivity and magnetic permeability, significantly different from the properties of a typical underground rock, were obtained.

The contrast in these two characteristics allows using the electromagnetic and galvanic logging tools to obtain the desired crack characteristics filled with a magnetic conductive proppant.

Conducting electromagnetic logging for cases of non-conductive proppant (with a protective polymer shell) and conductive proppant (without a shell) allows you to check the correctness of the models for constructing three-dimensional (3D) distribution of conductivity in a rock with a proppant-filled crack.

The term “comprising” is used here in an embracing sense, i.e. in the sense of "including" or "having in its composition." The term is not intended to be used in an exclusive sense (“consisting of” or “made of”). The preceding description has been made with reference to various embodiments of the present invention using specific devices, methods and materials. It should be understood that various modifications and changes can be made in the present invention without deviating from the essence of the invention, which is expressed by the attached claims.

Claims

CLAIM

1. The proppant marker with a bimetallic coating containing a ceramic base, a first metal layer and a second metal layer deposited on said ceramic base, while the second metal layer has magnetic properties.

2. The proppant marker according to claim 1, wherein the relative magnetic permeability of the proppant marker in bulk is at least 1.5, in particular at least 2.

3. The proppant marker according to claim 1, wherein the electrical conductivity of the proppant marker in bulk is at least 100 S / m.

4. The proppant marker according to claim 1, wherein the first metal layer comprises a metal or alloy selected from the group consisting of silver, copper and silver and copper based alloys.

5. The proppant marker according to claim 4, wherein the first metal layer is made of copper or an alloy based on copper.

6. The proppant marker according to claim 1, wherein the second metal layer contains a metal or alloy selected from the group consisting of nickel, cobalt and alloys based on nickel or cobalt.

7. The proppant marker according to claim 6, wherein the second metal layer is made of nickel or an alloy based on nickel.

8. The proppant marker according to claim 7, wherein the second metal layer is made of an alloy based on nickel doped with phosphorus.

9. The proppant marker according to claim 8, wherein the phosphorus content in the nickel-based alloy is 12 wt.% Or less.

10. The proppant marker according to claim 1, further comprising a protective coating of a water-soluble polymer.

11. A method of obtaining a proppant marker with a bimetallic coating, containing:

(a) preparing the surface of the ceramic proppant particles, including treating them with an acidic aqueous solution containing tin (Sn) ions; (b) activating the surface of the ceramic proppant particles, including treating them with an aqueous solution containing silver (Ag) ions and not containing a platinum group metal; and

12. The method according to p. 11, wherein the relative magnetic permeability of the obtained proppant marker in bulk is at least 1.5, in particular at least 2.

13. The method according to claim 11, wherein the electrical conductivity of the obtained proppant marker in bulk is at least 100 S / m.

14. The method of claim 11, wherein the first metal layer comprises a metal or alloy selected from the group consisting of silver, copper and silver and copper based alloys.

15. The method according to p. 14, wherein the first metal layer is made of copper or an alloy based on copper.

16. The method according to claim 11, wherein the second metal layer comprises a metal or alloy selected from the group consisting of nickel, cobalt and alloys based on nickel or cobalt.

17. The method according to p. 16, wherein the second metal layer is made of nickel or an alloy based on nickel.

18. The method according to p. 17, wherein the second metal layer is made of an alloy based on nickel doped with phosphorus.

19. The method according to p. 18, while the phosphorus content in the Nickel-based alloy is 12 wt.% Or less.

20. The method according to p. 1 1, wherein after (c) the proppant marker is annealed at a temperature of 200 to 600 ° C.

21. The method according to p. 20, while the annealing is carried out in an inert atmosphere or in air.

22. The method according to claim 11, wherein after (c) a protective coating is applied from a water-soluble polymer.

23. The method of application of the proppant marker with a bimetallic coating, made according to any one of paragraphs. 1-10 or obtained by the method according to any one of paragraphs. 11-22, including the preparation of a suspension of said proppant marker in a carrier fluid and pumping said suspension into a well during hydraulic fracturing.

24. The method according to p. 23, in which the suspension is pumped into at least one fracture obtained by hydraulic fracturing, and then said at least one fracture is closed to form a permeable proppant pack.

25. The method according to p. 23, in which electromagnetic well logging is performed before and after placing the proppant marker in the well.

26. The method according to p. 25, in which electromagnetic logging is carried out near the zone of placement of the proppant marker in the reservoir.

27. The method according to p. 23, in which the conductivity and magnetic permeability of the rock are measured in the formation in the proppant packing zone.