RU2651687C1 - Composition with condensed solid phase for temporal insulation of productive formation - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to gas industry, in particular to compositions with condensed solid phase for temporary isolation of reservoir when killing wells with terrigenous reservoir of non-uniform permeability, including clay minerals, and reservoir temperatures up to 150°C. Composition consists of following components, mass%: carboxymethylcellulose 0.5-4.0, calcium chloride 7-12, potassium phosphate dibasic 21-25, sodium lauryl sulfate 0.5-1.2, water - balance.

EFFECT: technical result is increase in efficiency of temporary isolation of productive formation in wells, preservation of reservoir filtration-capacitive properties, possibility of using composition over wide range of reservoir temperatures, Increase of manufacturability of repair work.

1 cl, 1 tbl, 4 ex

Description

The invention relates to the gas industry, in particular to compositions with a condensable solid phase for temporary isolation of a reservoir while killing wells with a terrigenous reservoir of heterogeneous permeability, including clay minerals, and reservoir temperatures up to 150 ° C.

Analysis of the current level of technology showed the following:

- known fluid for killing gas and gas condensate wells, the formulation of which has the following ratio of components, wt. %:

Carboxymethyl cellulose 1.4-1.6 Hydroxyethyl cellulose 0.4-0.5 Potassium chloride 6.8-7.1 Chrysotilasbest 0.45-0.55 Aluminum sulphate 0.45-0.55 Potassium hydroxide 0.9-1.1 Nitrilotrimethylphosphonic acid 0.9-1.1 Calcium chloride 0.9-1.1 Potassium carbonate 0.4-0.5 Water rest

(see RF patent No. 2348672 dated 06/25/2007 according to class C09K 8/42, published on 03/10/2009).

The fluid is designed to damp productive clayey sandstones with gas saturation and the acidic nature of the residual pore water. The disadvantages of this fluid is the low efficiency of the blocking of the reservoir and insufficiently high-quality release, which negatively affects the reservoir properties of the reservoir. The insufficiently high blocking ability of the liquid is explained by the fact that its composition uses colmatant of natural origin - chrysotilasbest, which is a type of serpentine mineral - magnesium hydrosilicate of a layered structure, which, like all colmatants of natural origin, is characterized by heterogeneity of the chemical and particle size distribution, as well as the presence of impurities , significantly affecting the physico-chemical properties. As is known, the Abrams rule is applied in the oil and gas industry to select the size of colmatant, according to which the average particle size of colmatant must be equal to or slightly larger than 1/3 of the average pore size of the formation [1]. Abrams A. Mud design to minimize rock impairment due to particle invasion // JPT. - 1977 May. - P. 586-592. The variety of petrophysical properties of reservoirs significantly narrows the scope of natural colmatants due to the mismatch of their particle sizes with specific application conditions.

Impurities have a negative effect on the release. Chrysotilasbest contains calcium carbonate as impurities, which, cementing elementary crystals, increases their aggregate cohesion, which entails a decrease in fiber elasticity. Low elasticity, as a rule, makes it impossible to release the composition from the reservoir without the use of acid treatments. In acid solutions, chrysotilasbest, used as a co-colmatant, decomposes to form amorphous silica. The sand collector, like the decomposition products of chrysotile asbestos, also consists of silica. The use of acid treatments using hydrofluoric acid in sand reservoirs for which a fluid is recommended is an extremely undesirable technological operation because of the likelihood of destruction of the structure of the reservoir. As an additional blocking agent, calcium carbonate is precipitated during the preparation of the composition as a result of the reaction of aluminophosphonic liquid and potassium carbonate. The insufficient quality release is indicated in the description of the invention, indicators of the recovery coefficient of permeability, which without acid treatments is 76-82%. Permeability after acid treatments is 94-102%. The restoration of permeability of more than 100% indicates the possibility of destruction of the formation rock, which is represented mainly by silicon dioxide, soluble in hydrofluoric acid. The disadvantages include the multicomponent composition and, as a consequence, the multi-stage preparation process.

The preparation technology is complex and consists in dissolving various reagents in several containers and mixing the resulting solutions in a strictly defined sequence. As a result, the preparation of the composition requires a significant investment of time and the attraction of a large amount of equipment (tanks, pumping units).

The multicomponent and multi-stage preparation method, as well as the need for acid treatments to qualitatively restore reservoir properties of the formation, requiring additional time and reagents, significantly reduce the manufacturability of repair work;

- known composition with a condensable solid phase for temporarily blocking a water-based reservoir, the formulation of which has the following ratio of ingredients, wt. %:

Carboxymethyl cellulose 0.5-3.0 Calcium chloride 3-12 Disubstituted Ammonium Phosphate 5-15 Morpen 0.05-1.00 Potassium chloride 0.1-1.0 Zinc stearate 0.1-5.0 Water rest

(see RF patent No. 2543003 of 03/18/2014 according to class C09K 8/504, publ. 02/27/2015).

The specified composition contains a condensable solid phase. The composition has high blocking properties in reservoirs with uniform permeability and contains swelling inhibitors in the form of potassium chloride, introduced additionally during the preparation of the composition. Potassium ions have an inhibitory effect only in certain types of clay minerals, in which the interlayer space of the crystal lattice corresponds to the radius of the hydrated potassium ion.

However, in real conditions, collectors, as a rule, contain various types of clays and in various proportions. The unequal chemical composition of clay minerals of reservoir rocks or cementing material does not allow the composition to be used with equal success in different fields.

Inhibition of clay minerals due to anion exchange is unlikely, since phosphate ions (PO ₄ ^3- ), potentially capable of inhibition, are expended on the creation of a dispersed phase, which is a colmatant. This is due to the fact that the recipe provides for a close to stoichiometric ratio of the amount of ingredients.

With a stoichiometric ratio of components, the precipitated dispersed phase, which is a colmatant, has particles of the same size, which ensures high-quality blocking in collectors with uniform permeability. In reservoirs with heterogeneous permeability, the blocking effect is much lower.

In addition, the surfactant Morpine, used in the composition for structuring and creating a thixotropic structure, is problematic for use in the Far North, as it is a liquid that freezes at low temperatures. Preparation of the composition will require additional operations, which means an increase in the duration of its preparation as a whole, which will lead to a decrease in the manufacturability of the composition;

- as a prototype, a composition was selected for temporary isolation of the formation during the overhaul of wells, the formulation of which has the following ratio of ingredients, wt. %:

Carboxymethyl cellulose 0.5-2.0 Calcium chloride 7-12 Disubstituted Ammonium Phosphate 19-21 Morpen 0.05-1.00 Water rest

(see RF patent No. 2301247 of September 30, 2005, according to class C09K 8/506, published on June 20, 2007).

The disadvantages of the composition is the following. In deposits whose productive deposits are characterized by a reservoir that is heterogeneous in permeability and a significant content of clay minerals of different chemical composition and structure, this composition is not able to provide effective temporary isolation and prevent the swelling of clay minerals.

This is due to the following: the quality of the precipitated solid phase (shape and particle size) in complex dispersed systems depends not only on the concentration of sediment-forming components, but also on the qualitative and quantitative composition of the regulatory additives. This is explained by the peculiarities of chemical bonds during the formation of adsorption layers of a surfactant and a polymer on solid particles. In this composition, during the formation of the dispersed phase, the surfactant Morpen provides the formation of crystalline particles of small sizes. In wells with an inhomogeneous reservoir, this composition will ensure high-quality blocking in zones with low permeability, and in zones with high permeability, the mismatch between the size of the mud and the size of the pore space leads to deep penetration of the composition into the formation, which will significantly reduce the productivity of the wells in the after-repair period.

Prevention of the swelling of clay minerals when using the composition is carried out only due to ammonium ions NH ₄ ⁺ formed in the composition during the precipitation of the dispersed phase.

The mechanism for preventing swelling is explained by cation exchange.

As is known, the inhibitory ability is significantly different in different cations. According to this criterion, cations are arranged in the following sequence: Al ³⁺ > K ⁺ > NH ₄ ⁺ > Na ⁺ > Li ⁺ , i.e. ammonium cations are less active than Al ³⁺ and K ⁺ cations. In this regard, the inhibition of swelling of rocks containing various types of clay minerals, only NH ₄ ⁺ cations is not sufficiently effective.

The disadvantage of the composition is also a limited scope, since the inhibitory effect of this composition is manifested only when used in low-temperature wells. At reservoir temperatures above 60-70 ° C, the decomposition of ammonium compounds contained in the composition with the formation of gaseous substances that are not able to participate in ion-exchange processes in clay minerals occurs.

The liquid form of an industrially produced surfactant is Morpene, the pour point of which is not higher than minus 10 ° С, when preparing the composition under conditions of negative ambient temperatures, additional equipment is required. This, in turn, increases the time costs and complicates the process of preparing the composition and reduces the overall manufacturability of the repair work.

The technical problem is to maintain the reservoir properties of the reservoir and to increase blocking of the reservoir when killing wells with a terrigenous reservoir of heterogeneous permeability, including clay minerals, and reservoir temperatures up to 150 ° C.

The technical result that can be obtained by implementing the present invention is to increase the efficiency of temporary isolation of the reservoir in wells with a terrigenous reservoir of heterogeneous permeability by using a composition with improved blocking properties, preserving the filtration-capacitive properties of the reservoir through high-quality release of increased inhibitory properties of the composition , the ability to use the composition in a wide range of reservoir temperatures at both low and and high reservoir temperatures of up to 150 ° C, increasing the processability of repairs.

The technical result is achieved using the proposed composition with a condensable solid phase for temporary isolation of the reservoir, consisting of carboxymethyl cellulose, calcium chloride, phosphoric acid salt, anionic surfactant and water, characterized in that it contains potassium phosphate disubstituted as phosphoric acid salt and as an anionic surfactant sodium lauryl sulfate in the following ratio of ingredients,% wt.:

Carboxymethyl cellulose 0.5-4.0 Calcium chloride 7-12 Potassium Disubstituted Potassium Phosphate 21-25 Sodium Lauryl Sulfate 0.5-1.2 Water Rest

The inventive composition meets the condition of "novelty."

To prepare the composition use: KMTS 85/700 carboxymethyl cellulose according to TU 2231-034-79249837-2006, calcium chloride according to TU 6-09-5077-87, disubstituted potassium phosphate according to GOST 2493-75, sodium lauryl sulfate according to TU 2481-017-71150986 2011.

The achievement of the technical result is provided by a new set of essential features.

This composition is a dispersed system in which the properties necessary to achieve a technical result are ensured by the characteristics of the physicochemical processes that occur during the interaction of the ingredients of the composition in the indicated ratios with each other and with the minerals of the rocks that make up the reservoir.

The achievement of a high blocking effect is ensured by the Kolmatant - a condensable solid phase, which is formed during the preparation of the composition by the interaction of the ingredients and contains two types of particles - crystalline and amorphous, having different shapes and sizes.

The dispersion of particles of the condensed solid phase is controlled by the ratio of the starting ingredients involved in the formation of the dispersed phase

CaCl ₂ + K ₂ HPO ₄ = CaHPO ₄ ↓ + KCl,

Ca ²⁺ + 2OH ^- = Ca (OH) ₂ ↓.

The regulatory effect of sodium lauryl sulfate during the formation of a condensed solid phase is explained by adsorption processes that regulate the growth of crystals of the solid phase, which gives the composition aggregative and sedimentation stability. The structural features of sodium lauryl sulfate molecules provide for the regulation of the size and shape of the crystalline phase of the composition. Along with the rhombic shape of the crystal lattice having smaller dimensions, crystals of a monoclinic crystal lattice are formed, that is, crystals having an elongated shape and, accordingly, large sizes. This is due to the chemical composition and structure of sodium lauryl sulfate molecules. The formation of particles having an elongated crystal shape is due to the fact that sodium lauryl sulfate molecules can not be adsorbed over the entire surface of the crystal, but only on certain faces. The above provides effective temporary isolation of the reservoir in wells with a terrigenous reservoir of heterogeneous permeability.

The regulatory effect of a water-soluble polymer - carboxymethyl cellulose, lies in the fact that it provides thixotropic properties to the composition, a specific feature of which is the ability to change the rheological properties over time and restore them under mechanical action, and the necessary viscosity, which prevents the filtration of its liquid phase into a porous medium. Thixotropic properties are ensured by the fact that carboxymethyl cellulose contains a large number of hydroxyl groups, which can form hydrogen bonds with a porous medium, which ensures the maintenance of the finely dispersed phase in suspension. The preservation of the reservoir properties of the reservoir is ensured by the following. When releasing, all the ingredients of the composition, due to their multifunctionality, contribute to the preservation of the reservoir properties of the reservoir, but the mechanisms and physicochemical processes in contact with the minerals of rocks that make up the reservoir are different. The presence of carboxymethyl cellulose in the composition contributes to the release of the composition from the reservoir due to the following: its ability to form hydrogen bonds with a porous medium, which among other chemical bonds are less strong in magnitude. As a result, the particles of the condensed solid phase of the composition are easily dispersed and removed with a gas stream from the reservoir during well development without the use of acid treatments, although the clogging dispersed phase is selected from among the acid-soluble ones. Thus, high-quality release is ensured, which allows preserving the reservoir properties of the reservoir.

The flexibility of the polymer chains of carboxymethyl cellulose is due to the spatial configuration of the macromolecules. The molecular chains of carboxymethyl cellulose have greater flexibility compared to polymers having a network structure, and this is explained by the linear structure of macromolecules. The flexibility of polymer chains of linear structure is due to the possibility of rotation of chain links at constant valence angles. When creating depression during the release process, carboxymethyl cellulose macromolecules have the property of forming irregularly shaped structures, forming globules with a minimum volume. As a result of this, carboxymethyl cellulose does not form films in the pore space of the collector, and its globules are easily carried out by the gas stream together with the liquid. Productive deposits represented by sedimentary rocks, in which the cementing material is clay minerals, including, as a rule, a mixture of clay minerals - kaolinite, montmorillonite, hydromica, with different structures and properties. And the ability of clays to hydration (water addition), swelling and dispersion is determined by their mineralogical composition. The presence on the flat surface of a clay particle of a negative electric charge and a positive charge on the faces and in places where the lattice is destroyed determines the nature of the physicochemical processes in contact with process fluids used in the overhaul of wells.

In clay minerals of the kaolinite group, adsorption processes occur mainly on the lateral cleavages of the lattice, where the bulk of the exchange ions localizing the dangling valence bonds of the octahedral layers of the crystal lattice are localized. The main active surfaces of hydromica minerals capable of ion-exchange interaction with water are broken bonds of the edge parts of crystals and their external basal planes. In clay minerals of the smectite group (montmorillonite, vermiculite, bentonite, etc.), sorption of ions from a solution occurs not only on chips and basal surfaces, but also in interlayer spaces, the magnitude of which varies over a wide range (from 1 to 20 nm).

In addition, almost all varieties of natural clay minerals in the process of geological development contain various defects characterized by variability of the chemical composition, ability to layer-by-layer polymorphism between unit cells of the same structural type, and cells of various types, disorder in the displacements of the tetrahedral and octahedral networks of the structural layer or in relative displacements of adjacent layers, non-stoichiometric substitution of cations in tetrahedral positions, displacement and whether the introduction of cations in the internodes, lateral dislocations, distortion of the anionic oxygen network, etc. When using the proposed composition, the prevention of interplanar hydration, which causes swelling, as well as hydration of clay particles on chips and basal surfaces where an excess negative charge is concentrated, is provided by potassium cations K ⁺ .

Prevention of clay mineral swelling in the areas of the crystal lattice with an excess positive charge arising as a result of numerous structural defects is achieved due to PO ₄ ^3– anions. The inhibitory effect of specific particles in the proposed composition is explained as follows. The prevention of clay mineral swelling is provided by potassium cations K ⁺ and PO ₄ ^3– anions, which are not introduced additionally, but are formed in the composition upon dissolution and dissociation of salts forming a condensable solid phase. Part of the potassium phosphate disubstituted K ₂ HPO ₄ (above the stoichiometric ratio) is present in the solution in the form of potassium cations K ⁺ and anions PO ₄ ^3- , which have an inhibitory effect

K ₂ HPO ₄ → 2K ⁺ + HPO ₄ ^2- ,

HPO ₄ ^2- → H ⁺ + PO ₄ ^3- ,

The inhibitory effect of potassium cations K ^{+ is} based on cation exchange, which is explained as follows. In various parts of the structure of complex clay mineral molecules, there are cations capable of being replaced by solution cations, therefore called exchange cations. Swelling is in close functional dependence on the composition of the absorbed cations. The smallest swelling and destruction is caused by salts, the cations of which due to their geometrical dimensions can enter the voids of the crystalline structure of clay particles, firmly splicing them. In the non-hydrated state, the diameter of the potassium cation K ⁺ is 2.66 A, and in the hydrated state is 7.6 A. With this ratio of the diameters of the potassium cation K ^{+, the} inhibitory effect is manifested only in certain types of clay minerals, that is, when the diameter of the K ⁺ cation corresponds to the interpacket distance clay. The mechanism of the inhibitory effect of PO ₄ ^3– anions is based on anion exchange. An important factor in anion exchange is the anion geometry with respect to the geometry of the structural cells of clay minerals. Anions of PO ₄ ^3- have almost the same size and geometry as that of a silicon-oxygen tetrahedron, and therefore can be adsorbed on the lateral surfaces of silicon-oxygen tetrahedrons, compensating for defects such as chips.

In wells with a terrigenous reservoir of heterogeneous permeability with a high content of clay minerals characterized by interlayer spaces significantly exceeding the diameter of the hydrated potassium cation K ⁺ and PO ₄ ^3- anions (for example, montmorillonite), only inhibitory ions are not present in the solution. Included in the formulation of sodium lauryl sulfate enhances the inhibitory properties of the claimed composition. Its molecules, competing with water molecules, do not allow the latter to adsorb and enter the interlayer space of clays.

The use in the recipe of the composition of these ingredients in the given quantitative ratios provides the necessary properties, including thermal stability, which in turn allows it to be used in a wide range of reservoir temperatures both at low and high formation temperatures up to 150 ° C. In field conditions, the proposed composition is prepared directly at the well using standard equipment. When preparing the composition in conditions of negative ambient temperatures using sodium lauryl sulfate in powder form, the use of additional equipment is not required, it reduces the preparation time of the composition and generally reduces the manufacturability of repair work.

The results of the studies are presented in the table.

The content of carboxymethyl cellulose in an amount of less than 0.5 wt. %, calcium chloride in an amount of less than 7 wt. %, potassium phosphate disubstituted in an amount of less than 21 wt. %, sodium lauryl sulfate in an amount of less than 0.5 wt. % is impractical, since the blocking properties of the composition are significantly deteriorated, the reservoir properties of the reservoir are worsened after release, and the inhibitory properties are reduced.

The content in the composition of carboxymethyl cellulose in an amount of more than 4.0 wt. %, calcium chloride in an amount of more than 12 wt.%, potassium phosphate disubstituted in an amount of more than 25 wt.%, sodium lauryl sulfate in an amount of more than 1.2 wt.% leads to a significant increase in viscosity, which makes it impossible to use the composition using standard processing equipment .

In more detail, the essence of the claimed invention is described by the following examples.

Example 1 (laboratory)

To prepare 1000 g of the composition in 672 ml of water (which is 66.2 wt.%), 40 g of carboxymethyl cellulose (which is 4.0 wt.%) Is dissolved. To the prepared aqueous solution of carboxymethyl cellulose add 70 g of calcium chloride (which is 7 wt.%), 210 g of potassium phosphate disubstituted (which is 21 wt.%) And 8 g of sodium lauryl sulfate (which is 0.8 wt.%), Then carry out stirring.

The study of the blocking properties of the composition and their influence on the change in the natural permeability of the rock is carried out on the installation UIPK-1M. The following indicators are determined:

- blocking ability - pressure drop, MPa;

- permeability recovery coefficient - ratio of core permeability values after release and before blocking,%.

Studies are carried out on artificial cores simulating the reservoirs of the North Stavropol field, with permeability up to 1 Darcy.

The permeability of the sample before and after exposure to the composition is calculated by the formula

where μ is the dynamic viscosity of air, Pa⋅s;

P _atm - atmospheric pressure, Pa;

q - flow rate of pumped air, m ³ / s;

l is the length of the sample, m;

F is the cross-sectional area of the sample, m ² ;

P ₁ and P ₂ - pressure at the inlet and outlet of the test sample, Pa.

The study of clay swelling is carried out on a device for determining the swelling of soils. As clay minerals, rocks of the North Stavropol area were used, represented by a melodic marl, characterized by a clay fraction content of up to 70%.

The maximum swelling N (cm ³ / g) is calculated by the formula

where h is the height of the swelling, determined by the indicator, cm;

S is the surface area of the clay sample, cm ² ;

F - weight of clay, g.

The composition has the following indicators: blocking ability of 27.9 MPa.

At a temperature of 25 ° C: permeability recovery coefficient of 99.4%, N = 0.35 cm ³ / g.

At a temperature of 150 ° C: permeability recovery coefficient of 99.5%, N = 0.35 cm ³ / g.

Example 2. Prepare 1000 g of the composition, g / wt. %:

Carboxymethyl cellulose 5 / 0.5 Calcium chloride 120/12 Potassium Disubstituted Potassium Phosphate 250/25 Sodium Lauryl Sulfate 12 / 1,2 Water 613 / 61.3

Perform all operations, as in example 1.

The composition has the following indicators: blocking ability of 28.7 MPa.

At a temperature of 25 ° C: permeability recovery coefficient of 99.7%, N = 0.30 cm ³ / g.

At a temperature of 150 ° C: permeability recovery coefficient of 99.7%, N = 0.31 cm ³ / g.

Example 3. Prepare 1000 g of the composition, g / wt. %:

Carboxymethyl cellulose 25 / 2.5 Calcium chloride 90/9 Potassium Disubstituted Potassium Phosphate 230/23 Sodium Lauryl Sulfate 8 / 0.8 Water 647 / 64.7

Perform all operations, as in example 1.

The composition has the following indicators: blocking ability of 29.5 MPa,

At a temperature of 25 ° C: permeability recovery coefficient of 99.8%, N = 0.24 cm ³ / g.

At a temperature of 150 ° C: permeability recovery coefficient of 99.8%, N = 0.24 cm ³ / g.

Example 4. Prepare 1000 g of the composition, g / wt. %:

Carboxymethyl cellulose 40/4 Calcium chloride 70/7 Potassium Disubstituted Potassium Phosphate 250/25 Sodium Lauryl Sulfate 5 / 0.5 Water 635 / 63.5

Perform all operations, as in example 1.

The composition has the following indicators: blocking ability of 28.1 MPa.

At a temperature of 25 ° C: permeability recovery coefficient of 99.0%, N = 0.27 cm ³ / g.

At a temperature of 150 ° C: permeability recovery coefficient of 99.2%, N = 0.27 cm ³ / g.

Thus, according to the above, a composition with a condensable solid phase for temporary isolation of the reservoir ensures the achievement of the claimed technical result.

Claims (2)

Composition with a condensable solid phase for temporary isolation of the reservoir, consisting of carboxymethyl cellulose, calcium chloride, phosphoric acid salt, anionic surfactant and water, characterized in that it contains potassium phosphate disubstituted as phosphoric acid salt and surfactant as anionic surfactant -active substance - sodium lauryl sulfate in the following ratio of ingredients, wt. %: Carboxymethyl cellulose 0.5-4.0 Calcium chloride 7-12 Potassium Disubstituted Potassium Phosphate 21-25 Sodium Lauryl Sulfate 0.5-1.2 Water Rest