RU2768340C1 - High-cation-inhibited drilling mud - Google Patents

Abstract

FIELD: drilling of soil or rocks.

SUBSTANCE: invention relates to drilling of vertical, directional and horizontal wells, in particular represented by thick deposits of high-viscosity clays, prone to swelling and softening, including with changes in wellbore integrity, especially in its horizontal part. High-cation-inhibited drilling mud for drilling wells contains, wt.%: marble chips 5–10; polyanionic cellulose 5–7; sulfonol 2–5; potassium chloride 2–5; potassium methyl siliconate 1–4; potassium acetate 1.5–4; bischofite 2–5; potassium formate 1–5; ferrochrome lignosulphonate 1–5; organosilicon liquid GKZH-11 2–5; barite 0.5–5; antifoaming agent Penta 465 0.5–1; potassium aluminate 1–5; calcium chloride 1–5; nanodispersed copper 0.5–4; magnesium chloride 1–5; liquid phase — water and wastes obtained during production of vegetable oils, in ratio 55/45–80/20 — the rest.

EFFECT: improvement of structural-rheological, inhibiting, lubricating, filtration, anti-wear, fixing and anti-seizure properties of drilling mud for construction of wells in difficult geological conditions.

1 cl, 1 tbl

Description

The invention relates to the field of drilling vertical, directional and horizontal oil and gas wells, in particular represented by thick deposits of highly viscous clays prone to swelling and softening, including with a change in the integrity of the wellbore, especially in its horizontal part, where the probability of differential sticking is quite high

Known drilling fluid, "Highly inhibited drilling fluid", patent RU No. 2303047, C1 publ. 07/20/2007, IPC С09К 8/20, consisting of bentonite clay, polyanionic cellulose, potassium chloride, ferrochromium lignosulfonate, barite, potassium methylsiliconate, potassium acetate, soda ash, bischofite, phosphatide concentrate, nitrilotrimethylphosphonic acid, graphite, defoamer, taken as analog.

The disadvantage of this solution is that, being good as an inhibitor, it does not solve the problem of holding viscous, heaving, softening clays in a stable state, especially in directional and horizontal wells, and contributes to the occurrence of differential sticking.

The solution does not solve the problem of establishing osmotic equilibrium, or creating conditions when osmosis will be directed from the reservoir to the well.

Known drilling fluid, taken as a prototype "Nanostructured, highly inhibited drilling fluid", patent RU No. 2708849 C1, publ. 12.12.2019 Bull. No. 35, MPK S09K 8/32, consisting of marble chips, polyanionic cellulose, sulfonic acid, potassium chloride, potassium methyl siliconate, potassium acetate, bischofite, ferrochrome lignosulfonate, GKZH-11, barite, defoamer, liquid phase consisting of vegetable oil and water waste in the ratio - 55/45-80/20.

The disadvantage of this solution is that, while being good as an inhibitor, it does not solve the problem of dealing with differential sticking. The objective of the invention is to develop a drilling fluid that has the highest inhibitory, crust-forming, lubricating, anti-stick properties and ensures the establishment of osmotic equilibrium, or the creation of conditions when osmosis is directed from the formation to the well, that is, to reduce differential sticking. In this case, the water loss should be close to 0 cm ³ in 30 minutes, and the friction coefficient should not exceed 0.1.

Highly cationic-inhibited drilling fluid for well drilling, including marble chips, polyanionic cellulose, potassium chloride, GKZh-11, sulphonol, potassium methyl siliconate, potassium acetate, bischofite, ferrochrome lignosulfonate, defoamer, barite, vegetable oil waste, water, potassium aluminate, nanodispersed copper, characterized in that it additionally contains potassium formate, calcium chloride and magnesium chloride in the following ratio, wt.%: marble chips - 5-10, polyanionic cellulose - 5-10, sulfonic acid - 2-5, potassium chloride - 2 -5, potassium methyl siliconate - 1-4, potassium acetate - 1.5-4, bischofite - 2-5, ferrochrome lignosulfonate - 1-5, GKZH-11 - 2-5, barite - 0, 5-5, defoamer - 0 ,5-1, potassium aluminate - 1-5, nano-dispersed copper - 0.5-4, potassium formate - 1-5, calcium chloride -1-5, magnesium chloride - 1-5, liquid phase - water and waste obtained in the manufacture of vegetable oils, in the ratio 55/45-80/20 - the rest.

A multifunctional highly cation-inhibited drilling fluid for drilling wells in difficult mining and geological conditions (rocks swell, swell, crumble, differential sticking occurs) is proposed. Areas with such a geological section are found both in the south and in the north of Russia. In field conditions, when the replacement of the solution is associated with the expenditure of a certain time, which leads to complications, the use of the proposed solution is an urgent need, and it is this composition of the solution that will successfully, without geological complications and differential sticking, construct wells for oil and gas.

The novelty of the proposed composition of the drilling fluid lies in the fact that it is in this percentage and by the name of the chemicals that the proposed solution will solve the problem of drilling oil and gas wells, that is, perform its versatility - strengthen the walls of the wells, give high rates of filtration and lubricity, prevent occurrence of differential seizures.

EFFECT: improving the structural-rheological, inhibitory, filtration, fixing, lubricating and anti-seize properties of an oil-based drilling fluid while improving the coefficient of recovery of the initial permeability of the reservoir by increasing the inhibitory and water-repellent ability of the fluid filtrate and, as a result, the absence of the formation of troughs and differential sticking in the wellbore, increasing the stability of the wellbore of directional and vertical wells.

Experimentally, in laboratory conditions, the synergistic effect of chemical reagents - cations, carriers of K ⁺ , Ca ²⁺ , Mg ²⁺ , Cu ^{2+ ions} was tested. It has been established that it is this combination of cations that makes the drilling fluid highly cation-inhibited with the highest inhibitory properties.

In order to enhance the inhibitory effect on clay deposits in the well section, K ⁺ ions (potassium chloride KCl), (potassium methyl silicate CH ₃ SiO ₂ K), (potassium acetate CH ₃ SOOK), (potassium aluminate K ₂ Al ₂ O ₄ ⋅ 3H ₂ O), (potassium formate K(HCOO). An increased content of K ⁺ ions reduces the sensitivity of clays to hydration and wetting of drilling mud filtrates.

The increased content of Ca ^{2+ ions} contributes to the calcination of clays in the well section. Calcining the clays of the well section reduces the sensitivity to hydration and to wetting by the drilling fluid filtrate. Suppliers of Ca ^{2+ ions} are marble chips - CaCO ₃ and calcium chloride CaCl ₂ . The increased content of K ⁺ and Ca ^{2+ ions} in the drilling fluid contributes to enhanced inhibition of clays that make up the well section

The increased content of Mg ^{2+ ions} due to bischofite - MgCl ₂ ⋅ 6H ₂ O and magnesium chloride - MgCl ₂ contributes to the final fixation of clays in the wellbore and enhances the synergistic effect of the polycationic, highly inhibited drilling fluid.

Mixing in one solution of several chemicals with a high content of K ⁺ , Ca ²⁺ , Mg ^{2+ ions} creates a kind of "shock" grouping that contributes to an increased degree of inhibition of the well walls, represented by clay deposits.

The use of a highly cationic, inhibited drilling fluid in the field will help reduce the time spent on complications in wells, reduce the time spent on flushing and working out the wellbore, and as a result, reduce the time to eliminate differential sticking.

Improving the inhibitory quality of the solution, possibly by increasing its fixing effect. In the mechanism of the synergistic effect, the component share of the action of each reagent was confirmed. This is achieved by introducing reagents-inhibitors of clay swelling.

Potassium chloride (KCl) - the main supplier of the K ⁺ cation plays a decisive role in the inhibitory effect of the solution. Due to the size of the ionic radius, potassium cations can enter the interlayer voids of the crystalline surface of clay minerals, firmly merging their packages, contributing to the interlayer dehydration of clays.

Bischofite (MgCl ₂ ⋅ 6H ₂ O) - due to the presence of magnesium ion Mg ⁺⁺ in the ion-exchange complex, it helps to reduce the activity of the aqueous phase of the solution and reduce the degree of moistening of clays, while maintaining their stability during drilling.

Potassium acetate (CH ₃ SOOK) - complements the fixing effect of potassium chloride by affecting the magnitude of structural-adsorption deformations in the clay-liquid system, helping to reduce the swelling fluid content in hydrated clay and stabilize the wellbore.

Organosilicon liquid (GKZH-11) - due to the hydrophobizing effect on rocks, it reduces the moisturizing ability of the solution and prevents the rapid development of hydration of water-sensitive clays.

Ferrochrome lignosulfonate (FCLS) contributes to the manifestation of a synergistic effect due to the size and structure of the macromolecules of the reagent adsorbed on clay particles.

Potassium methyl siliconate (CH ₃ SiO ₂ K) - due to the presence of K ions, it complements the fixing effect of the solution, affects the magnitude of structural-adsorption deformations in the clay-liquid system, helps to reduce the swelling fluid content in hydrated clay and stabilize the wellbore.

Potassium aluminate (K ₂ Al ₂ O ₄ ⋅ 3H ₂ O) complements the fixing effect of potassium in solution, reduces the magnitude of structural-adsorption deformations in the clay-liquid system.

Potassium formate K(HCOO) potassium salt of formic acid, white fine crystalline powder. When aqueous solutions are heated in the presence of oxygen, it gradually forms potassium carbonate. It is a corrosion inhibitor.

Calcium chloride (CaCl ₂ ) calcium salt of hydrochloric acid, non-toxic, is a food additive, density 2.15 g/cm ³ , is a supplier of Ca ^{2+ ions} .

Magnesium chloride (MgCl ₂ ) is an inorganic chemical compound, salt of hydrochloric acid and magnesium. It dissolves well in water, non-toxic, non-flammable, fire and explosion-proof, food additive, density 2.32 g/cm ³ .

Nanodispersed copper (CuSO ₄ ) is an additive to the drilling fluid that helps reduce the risk of differential sticking (the chemical is known as copper sulphate).

Marble chips (СаСО ₃ ) is a structurant and a supplier of Ca ^{2+ ions} in the drilling fluid.

In laboratory conditions, dependences of plastic viscosity, dynamic shear stress and filtration of the solution on the concentration of inhibitory reagents used in it were revealed: bischofite, potassium acetate, GKZh-11, potassium methylsiliconate, potassium formate, FHLS, potassium aluminate, calcium chloride, magnesium chloride, potassium chloride . As oils, wastes obtained during the processing of soybean, sunflower, cottonseed, corn, rapeseed and other oils can be used.

Sulfonol acts as an emulsifier, which is a synthetic surfactant, anionic type in powder form, highly soluble in water, forming a strong emulsion. Marble crumb is a structure former. Polyanionic cellulose (PAC 85/700) is a filtration regulator. Penta 465 is most often used as a defoamer. Barite, as a weighting agent, is used in an amount from 0.5% to 5.0%.

Nanodispersed copper has a particle size of 40-80 nm, a density of 5 g/cm ³ and performs the role of an antifriction antiwear additive in the drilling fluid and, together with synergistically selected chemicals in the solution, solves a joint problem - reducing differential sticking.

Copper molecules are adsorbed on the surface, plasticize the borehole walls throughout the wellbore, providing low shear resistance when nanoparticles are located between the drill string and the borehole walls. Therefore, the smaller the particle size of nanodispersed copper, the more the friction coefficient and wear intensity decrease.

Nanoparticles have their own electric charge, which they acquire in the process of friction of the drill string against the borehole walls. Under the action of an electric field, copper nanoparticles form shells of polarized and ordered molecules of the dielectric component of the lubricant (sulfonol and vegetable oil). The thickness of this shell can reach the size of the boundary layer on the friction surface of the mating bodies between the drill string and the cover of the wellbore crust. This contributes to their more complete separation.

At the same time, copper nanoparticles have a microabrasive effect on oxide films in solution. As a result, it contributes to the formation of a stronger and thicker crust on the walls of the well. It does not allow fluid to be filtered from the solution into the formation, and this helps to reduce the likelihood of differential sticking.

In laboratory conditions, it was found that the presence of nanodispersed copper particles in the solution increases the thickness of the crust up to 1.0 mm, that is, more than three times, while it is strengthened due to the chemical modification of copper in the composition of the chemicals of the proposed solution.

The performed electrographic studies have shown that during drilling, liquid-crystal boundary layers are formed on the crust of the well wall. The orientation of the molecules of the boundary layer on the friction surface reproduces the orientation of the atoms or molecules of the coating on which this layer is located. The highly ordered structure of the boundary layer molecules has a high resistance to fracture under load and a lower shear resistance from the side of the drill string.

Thus, the addition of potassium formate, calcium chloride and magnesium dichloride to the well-known drilling fluid with high lubricity (patent No. 2708849) will help reduce friction, stickiness, stop fluid filtration through the crust, increase the inhibitory component, and, as a result, sharp reduction of differential sticking during well drilling.

Under laboratory conditions, the rheological behavior of the proposed solution was evaluated and a set of its mathematical models with improved structural-rheological, filtration and friction properties was established.

A multicomponent, high-molecular inhibiting solution with complex properties is proposed, which has very high lubricating, filtration, fixing properties with high-quality rheological parameters.

The proposed drilling fluid is prepared directly in the field, using existing equipment. In a mortar mixer, a solution is first prepared from marble chips and water, which is then processed with polyanionic cellulose (PAC 85/700). All other chemicals are introduced into the mortar mixer with constant stirring. The order of loading of chemicals is as follows: waste obtained in the manufacture of vegetable oil, FHLS, potassium chloride, potassium methyl siliconate, potassium acetate, sulfonol, bischofite, potassium aluminate, nanodispersed copper, GKZH-11, defoamer, potassium formate, calcium chloride, magnesium chloride, barite .

The determination of the rheological characteristics of the drilling fluid is carried out according to standard methods. The drilling fluid must be treated with recommended chemicals after 4-step cleaning. A high-pressure hydraulic disperser is used to prepare the solution.

The mechanism of inhibition is as follows: when inhibitory additives are introduced into the drilling fluid, the physicochemical effect of clay and cation occurs, which replaces free, negatively charged areas in the crystal lattice of clay particles. During cation exchange, previously passive areas of clays are activated. Adsorption of cation-inhibiting reagents on clay particles increases their resistance to moisture, reduces swelling and softening of clays.

One of the main conditions for maintaining the stability of the well walls is to ensure the lowest possible filtration rate from 1.0 to 0.5 cm ³ /30 min. This condition is met with the help of polyanionic cellulose (PAC 85/700).

It has been established that the main role in the intensification of the process of clay softening is played not by the initial moisture, but by the saturation of the drilling mud filtrate under the action of repression on the formation. Loss of drilling fluid filtrate occurs not so much under the action of pressure drop in the well-formation system, but as a result of the physicochemical impact that develops in the clay rock itself. The most optimal, from the point of view of the stability of the well walls, are the cases when osmotic equilibrium is established in the well-formation system, or osmosis is directed from the formation to the well. Despite the fact that in the case of the action of osmosis from the reservoir into the well, a change in the parameters of the drilling fluid occurs, it is much easier to manage it and maintain it within the specified limits than to deal with complications after the wellbore has been destabilized.

Therefore, the stability of clays and the reduction in the number of differential sticking will depend on the correctly selected composition of chemicals and, first of all, on the inhibitory, filtration and lubricating composition of the reagents. This is the main problem that needs to be solved.

The use of the proposed solution makes it possible to drill intervals of rocks represented by unstable, highly plastic, softening clays, and successfully construct vertical wells, as well as directional and horizontal ones.

The use of reagents with the properties of inhibitors makes it possible to carry out controlled coagulation, maintain the pH of the medium within the required limits, regulate the structural-rheological, filtration parameters and the optimal level of lyophilicity.

The performed laboratory studies made it possible to establish that the use of just such inhibitors of clay swelling simultaneously in one solution made it possible to achieve a synergistic effect, i.e. strengthening the inhibitory component of the drilling fluid, while each reagent, complementing each other, enhances the fixing properties of the drilling fluid. The complex of reagents works better than each component separately. In addition, due to the selection of chemicals in such a composition, sodium cations are displaced from clay deposits, sodium clay turns into calcium, and this also enhances the inhibitory function, helping to reduce hydration and swelling, reducing bulging, fluidity, collapse and talus of rocks.

The advantage of the solution of the developed formulation is that as a result of its interaction with the studied clays, the concentration of ions increases to 19000 or more mg/l. And this leads to an additional improvement in the quality of the solution and indicates that the osmotic process is directed from the reservoir to the well. The presence of potassium and magnesium ions in the solution contributes to the growth of the isotonic coefficient up to 5.9. Thus, there is an increase in the number of osmotically active particles in the solution due to the dissociation of the electrolyte.

The proposed solution has very high inhibitory properties, almost zero filtration, has improved structural-rheological, anti-stick properties and is optimal for complicated drilling conditions. The phenomenon of a synergistic effect was experimentally confirmed in the complex treatment of the drilling fluid with the indicated reagents - inhibitors.

When drilling an exploratory well at drilling sites in the Rostov region, it was proved that the fixing properties of the solution improved due to the synergistic effect of the action of the proposed components.

The performed research allowed to draw the following conclusions:

1) the use of this solution makes it possible to successfully construct exploration wells for oil and gas with a depth of more than 3000 m with a horizontal end, in areas represented by unstable highly plastic clays and self-dispersing shales

2) the synergistic effect of the action of the components of the solution has been experimentally confirmed - the complex of reagents works better than each component separately;

3) the proposed composition of the new solution has the highest inhibitory ability, helps to slow down the process of hydration and swelling of clay deposits,

4) the proposed combination of reagents allows the solution to successfully prevent, suspend and suppress deformation processes in the near-wellbore space, reduces vugginess,

5) it is shown that the proposed solution has improved lubricating and anti-stick properties with significant energy-saving performance and a sufficient level of environmental safety of all additives, while reducing the risk of differential sticking, improving the rheological profile of the velocities of the flushing fluid in the annulus and increasing the stability of the emulsion. This contributes to the efficient execution of the hydraulic well flushing program.

In the claimed solution with an optimal ratio of components, a synergistic increase in the effectiveness of the inhibitory, filtration, lubricating, anti-seize and anti-wear effects of the individual components occurs, while the solution retains its properties at temperatures up to 130°C.

A multicomponent, high-molecular, highly cation-inhibited ^drilling fluid with high anti-stick, inhibitory, filtration, fixing and lubricating properties is proposed. , friction coefficient less than 0.1, crust thickness less than 1.0 mm, solution density from 1.1 to 1.25 g / cm , SNS 1/10 minutes - 15-20/20-30 dPa, sand content is less than 0.5%, the content of Ca ^{2+ ions} is more than 16000 mg/l, the content of K ⁺ ions is more than 19000 mg/l.

The performed experimental studies (Table 1) showed that the best highly cation-inhibiting drilling fluid turned out to be mud No. 8

Claims (1)

Highly cationic-inhibited drilling fluid for drilling wells, including marble chips, polyanionic cellulose, potassium chloride, organosilicon liquid GKZH-11, sulfonic acid, potassium methyl siliconate, potassium aluminate, potassium acetate, bischofite, ferrochrome lignosulfonate, nanodispersed copper, defoamer, barite, waste products obtained in the manufacture of vegetable oils, and water, characterized in that it additionally contains potassium formate, calcium chloride and magnesium chloride in the following ratio, wt.%: marble chips 5-10; polyanionic cellulose 5-7; sulfonic acid 2-5; potassium chloride 2-5; potassium methyl siliconate 1-4; potassium acetate 1.5-4; bischofite 2-5; potassium formate 1-5; ferrochrome lignosulfonate 1-5; GKZH-11 2-5; barite 0.5-5; defoamer Penta 465 0.5-1; potassium aluminate 1-5; calcium chloride 1-5; nanodispersed copper 0.5-4; magnesium chloride 1-5; liquid phase - water and waste obtained in the manufacture of vegetable oils, in a ratio of 55/45-80/20 - the rest.