RU2708849C1 - Nanostructured high-inhibited drilling fluid - Google Patents

Abstract

FIELD: soil or rock drilling.

SUBSTANCE: invention relates to drilling of vertical, directional and horizontal wells, in particular, represented by powerful deposits of high-viscosity clays prone to swelling and softening, including with changes of integrity of the wellbore, especially in horizontal part. Nanostructured high-inhibited drilling fluid for drilling wells contains, wt%: marble chips 5–10; polyanionic cellulose 5–10; sulphanol 2–5; potassium chloride 2–5; potassium methylsiliconate 1–4; potassium acetate 1.5–4; bischofite 2–5; ferrochrome lignosulphonate 1–5; organosilicon liquid GKZH-11 2–5; barite – 0.5–5; antifoaming agent – 0.5–1; potassium aluminate 1–5; nanodispersed copper 0.5–4; liquid phase – wastes of vegetable oil and water in ratio of 55/45–80/20 – balance.

EFFECT: improved structural-rheological, inhibiting, lubricating, filtration, fixing, anti-gripping and environmental properties of drilling fluid for construction of wells in complex geological conditions.

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Description

The invention relates to the field of drilling vertical, directional and horizontal oil and gas wells, in particular represented by powerful 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 for drilling wells (RF Patent for the invention No. 2518287, publ. 10/27/2000, IPC S09K 7/07), including the oil product SMAD, carboxymethyl cellulose, potassium chloride, water.

The disadvantages of the above solution include the fact that the solution does not have a sufficient degree of lubrication and inhibition, that is, it is not possible to achieve the formation of a high-quality polymer clay crust on the walls of the barrel.

Known drilling fluid, "Drilling fluid to prevent sticking and gland formation BUR-6." Application for invention RU 94005919 A1, publ. 04/04/2007, consisting of concrete clay, electrolyte, viscosity control agents, ATP and water loss, oil-containing additives SKBV, barite, the rest is water.

The disadvantage of this drilling fluid is that, being good as a lubricant, it does not solve the problem of keeping the wellbore upright, especially if the cut is viscous, unstable, plastic, clay deposits prone to swelling, and does not solve the problem of establishing osmotic equilibrium either creating conditions when osmosis will be directed from the reservoir to the well.

Known drilling fluid, "Highly inhibited drilling fluid", patent RU No. 2303047, C1 publ. 05/10/2006, IPC С09К 8/20, consisting of bentonite clay, polyanionic cellulose, potassium chloride, ferrochrome lignosulfonate, barite, potassium methylsiliconate, potassium acetate, soda ash, bischofite, phosphatide concentrate, nitrilotrimethylphosphonic acid.

The disadvantage of this solution is that it, being good as an inhibitory one, does not solve the problem of keeping viscous, heaving, softening clay in a steady 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 the osmosis will be directed from the reservoir into the well.

Known drilling fluid, taken as a prototype, "Drilling fluid" patent RU No. 2582197 C1, publ. 04/20/2016, bull. No. 11, IPC С09К 8/10, consisting of marble chips, polyanionic cellulose, sulfonol, potassium chloride, potassium methylsiliconate, potassium acetate, bischofite, ferrochrome lignosulfonate, GKZh-11, barite, antifoam, the liquid phase consisting of vegetable oil waste and water in ratio - 55 / 45-80 / 20.

The disadvantage of this solution is that it, being good as an inhibitory one, does not solve the problem of combating differential sticking. The objective of the invention is to develop a drilling fluid with the highest inhibitory, crust-forming, lubricating, anti-seizing properties and ensuring the establishment of osmotic equilibrium, or the creation of conditions when the osmosis is directed from the reservoir into 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.

Nanostructured, highly inhibited drilling fluid for drilling wells contains, wt.%: Marble chips 5-10; polyanionic cellulose 5-10; sulfanol 2-5; potassium chloride 2-5; potassium methylsiliconate 1-4; potassium acetate 1.5-4; bischofite 2-5; ferrochrome lignosulfonate 1-5; silicone fluid GKZH-11 2-5; barite 0.5-5; defoamer 0.5-1; potassium aluminate 1-5; nanodispersed copper 0.5-4; the liquid phase - waste vegetable oil and water in a ratio of 55 / 45-80 / 20 - the rest.

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

The novelty of the proposed composition of the drilling fluid lies in the fact that it is in such a percentage and by the name of the chemicals that the proposed solution will solve the problem of wiring oil and gas wells, that is, to fulfill its multifunctionality - to strengthen the walls of the wells, give high rates of filtration and lubricating ability, prevent differential sticking.

The technical result is an improvement in the fastening, lubricating and anti-seizing properties of a hydrocarbon-based drilling fluid while improving the recovery coefficient of the initial permeability of the reservoir by increasing the inhibitory and hydrophobizing ability of the filtrate and, as a result, the absence of gutters and differential sticking in the wellbore, increasing the stability of the wellbore directional and vertical wells.

Improving the inhibitory quality of the solution is possible by increasing its fastening effect. In the mechanism of the synergistic effect, a constituent fraction of the action of each reagent is confirmed. This is achieved through the introduction of clay swelling inhibitor reagents:

1. 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 interpackage voids of the crystalline surface of clay minerals, firmly splicing their packets, contributing to the interlayer dehydration of clays.

2. 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 to reduce the degree of hydration of clays, while maintaining their stability during drilling.

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

4. 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.

5. Ferrochromlignosulfonate (PCF) promotes a synergistic effect due to the size and structure of the reagent macromolecules adsorbed on clay particles.

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

7. Potassium aluminate (K ₂ Al ₂ O ₄ ⋅ 3Н ₂ О) supplements the fastening action of potassium in solution, reduces the magnitude of structural and adsorption deformations in the clay-liquid system.

The dependences of plastic viscosity, dynamic shear stress and solution filtration on the concentration of inhibitory reagents used in it were revealed: potassium chloride, potassium aluminate, potassium acetate, organosilicon liquid, potassium methylsiliconate, ferrochrome lignosulfonate.

The dependences of plastic viscosity, dynamic shear stress and solution filtration on the concentration of the inhibitory agents used in it were revealed: KCl, bischofite, potassium acetate, GKZh-11, potassium methylsiliconate, PCF, potassium aluminate. As vegetable oils can be used waste obtained in the manufacture of soybean, sunflower, cotton, corn, rapeseed and other oils.

Sulfonol acts as an emulsifier, which is a synthetic surfactant, anionic type in the form of a powder, readily soluble in water, forming a strong emulsion. Marble chips are a builder. Polyanionic cellulose (PAC 85/700) is a filter regulator. Penta 465 is most often used as a defoamer. Barite, as a weighting agent, is used in an amount of 0.5% to 5.0%.

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

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

Nanoparticles have their own electric charge, which they acquire in the process of friction of the drill string against the borehole wall. Under the influence of the electric field of copper nanoparticles, shells are formed around it from polarized and orderly 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 bore cover of the wellbore. This contributes to their more complete separation.

In this case, copper nanoparticles have a microabrasive effect on oxide films in solution. As a result, the thinnest surface layer activated by plastic deformations and freed from oxides becomes a catalyst for tribochemical reactions and promotes the formation of a stronger and thicker crust on the borehole walls. The thickened protective crust prevents fluid from being filtered out from the solution into the reservoir, and this helps to reduce the likelihood of differential sticking.

In laboratory conditions, it was found that the presence of nanosized particles of copper in a solution with increased lubricity increases the thickness of the crust to 1.5 mm, that is, more than three times, while it is hardened due to the chemical modification of copper in the chemical reagents of the proposed solution.

The performed electrographic studies showed that when drilling on the crust of the borehole wall, liquid crystal boundary layers are formed. 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 the action of a load and a lower shear resistance from the side of the drill string.

Thus, the introduction of a well-known drilling fluid with high lubricity to nanodispersed copper and an additional inhibitory chemical reagent potassium aluminate will help to reduce friction, stickiness, stop filtering and fluid through the crusts, increase the inhibitory component, and, as a result, a sharp decrease in differential sticking in the process well drilling.

The rheological behavior of the proposed solution is evaluated and a set of its mathematical models with improved structural-rheological, filtration and friction properties is established.

Field experience of introducing the new composition showed that the rheological parameters of the solution contribute to the improvement of the condition of the wellbore and the effective implementation of the hydraulic program for flushing the well.

A complex in properties, multicomponent, high molecular weight inhibitory solution is proposed, which has very high lubricating, filtration, and fixing properties with qualitative rheological parameters.

The proposed drilling fluid is prepared directly in the field, using existing equipment. All necessary chemicals are pre-imported to the rig. First, a solution of marble chips and water is prepared in the mixer, which is then treated with polyanionic cellulose. All other chemicals are introduced into the mixer with constant stirring. The loading order of chemicals is as follows: vegetable oil processing product, KCl, FHLS, CH ₃ COOK, CH ₃ SiO ₂ K, MgCl ₂ ⋅ 6H ₂ O, sulfonol, potassium aluminate, nanodispersed copper, GKZh-11, antifoam, barite.

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

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

One of the main conditions for maintaining stability of the borehole walls to provide a minimum possible filter index from 0.5 to 0 cm ^3/30 min. This condition is met using polyanionic cellulose.

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

Consequently, clay stability and a decrease in the number of differential sticks will depend on the correctly selected composition of chemicals and, first of all, on the inhibitory, filtering and lubricating composition of the reagents. This is the main task that needs to be addressed.

The application of the proposed solution allows you to drill rock intervals, represented by unstable, highly plastic, softening clay, and successfully build vertical wells, as well as directional and horizontal.

The use of reagents with the properties of inhibitors allows for controlled coagulation, to maintain the pH of the medium within the required limits, to regulate structural-rheological, filtration indicators and the optimal level of lyophilism.

Laboratory studies have made it possible to establish that the use of exactly six such clay swelling inhibitors simultaneously in one solution made it possible to achieve a synergistic effect, i.e. strengthening the inhibitory component of the flushing fluid, with each reagent complementing each other enhancing the fastening properties of the drilling fluid. The reagent complex works better than each component individually. In addition, due to the selection of chemicals in this composition, sodium cations are displaced from clay deposits, sodium clay is converted to calcium, and this also enhances the inhibitory function, helping to reduce hydration and swelling, reducing bulging, fluidity, collapses and talus 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 K ⁺ ions increases to 18000 or more mg / l of ions. And this leads to an additional improvement in the quality of the solution and indicates that the osmotic process is directed from the formation to the well. The presence of potassium and magnesium ions in the solution promotes an increase in the isotonic coefficient to 4.7. Thus, there is an increase in the number of osmotic active particles in solution due to dissociation of the electrolyte.

The proposed solution has very high inhibitory properties, almost zero filtration, has improved structural and rheological, anti-seize and environmental properties and is optimal for complicated drilling conditions. The phenomenon of a synergistic effect during complex treatment of the drilling fluid with several inhibitor reagents has been experimentally confirmed.

When drilling an exploratory well on the Coastal area of the Krasnodar Territory, it was proved that the fastening properties of the solution are improved due to the synergistic effect of the proposed components.

The studies performed allowed us to draw the following conclusions:

1) the use of this solution allows you to successfully build exploration wells for oil and gas with a depth of more than 3,000 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 solution components has been experimentally confirmed - the complex of reagents works better than each component individually;

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 borehole space, reduces cavernousness;

5) it was shown that the proposed solution has improved lubricating and anti-seizing properties with significant energy-saving indicators and a sufficient level of environmental safety of all additives, while reducing the risk of differential sticking, improving the rheological velocity profile of the washing liquid in the annular space and increasing the stability of the emulsion. This contributes to the efficient implementation of a hydraulic well flushing program.

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

The proposed nanostructured drilling fluid with high anti-stick, inhibitory, filtration and lubricating properties has the following parameters: mud filtration - 0.5-0 cm ³ / in 30 minutes, the stickiness of the crust is 0.1, the coefficient of friction is less than 0.1, the thickness of the crust is less than 0 , 5 mm, the oil / water ratio in% is 80/20, the density of the solution is from 1.1 to 1.25 g / cm ³ , the conditional viscosity according to SPV-5 is 35-40 seconds, the plastic viscosity is 20-40 mPa⋅ C, SNS 1/10 minutes - 15-20 / 20-30 dPa, sand content of less than 0.5%, the content of Ca ⁺⁺ over 16,000 mg / l, Cl content of greater than 30000 mg / l, containing K ⁺ of more than 18000 mg / l.

Claims (1)

Nanostructured highly inhibited drilling fluid for drilling wells, including marble chips, polyanionic cellulose, potassium chloride, silicone fluid GKZh-11, sulfonol, potassium methylsiliconate, potassium acetate, bischofite, ferrochrome lignosulfonate, defoamer, oil, water, waste, additionally contains potassium aluminate and nanodispersed copper in the following ratio of components, wt.%: marble chips 5-10; polyanionic cellulose 5-10; sulfanol 2-5; potassium chloride 2-5; potassium methylsiliconate 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; nanodispersed copper 0.5-4; the liquid phase - waste vegetable oil and water in a ratio of 55 / 45-80 / 20 - the rest.