EA037804B1 - Inhibiting mud for drilling high-colloidal clay deposits - Google Patents

Abstract

The invention relates to oil and gas industry, in particular to biopolymer clayless drilling muds intended to inhibit highly colloidal clay rocks during drilling. Substance of the invention: inhibiting drilling mud includes polyanionic cellulose of low viscosity, xanthan type biopolymer, Polyekol organic clay inhibitor, mineral clay inhibitor - potassium chloride, mud heaver in the form of chalk and dolomite, bactericide, pH regulator, defoamer, and water with the following ratio of components, wt.%: polyanionic cellulose of low viscosity - 0.4-0.8; xanthan type biopolymer - 0.17-0.30; Polyecol inhibitor - 1.4-2.5; potassium chloride inhibitor - 0.7-1.6; chalk - 5-14; dolomite - 5-14; bactericide - 0.04-0.09; pH regulator - 0.03-0.05; defoamer - 0.03-0.05; water - the balance. The technical result consists in improved technological parameters, minimized drilling problems, and the prevented deformational instability of wellbore when drilling rocks represented by highly colloidal clay deposits.

Description

The invention relates to the oil and gas industry (drilling oil and gas wells), namely to biopolymer clayless drilling fluids designed to inhibit highly colloidal clay rocks during drilling. This solution is ideal for drilling wells in active clay formations in various hydrogeological conditions.

Known drilling mud without a solid phase with increased inhibitory properties [1], containing a filtration reducer - carboxymethyl cellulose, an inhibiting and weighting additive sodium chloride NaCl, a structurant - a xanthan biopolymer Kem X, lubricating additives biolub LVL and glital, while as an inhibiting and weighting additive potassium carbonate K2CO3 and polyglycols - glycoil are used.

The disadvantages of this technical solution are low salt resistance due to the use of carboxymethyl cellulose; the absence of a reliable bactericide, which leads to the rapid biodegradation of the polymers contained in the drilling fluid and the violation of its technological characteristics.

Known clayless highly inhibited drilling mud [2] containing polyanine cellulose, potassium chloride, potassium methyl silicate, potassium acetate, antifoam, marble chips, xanthan biopolymer, organic inhibiting additive FK-2000 Plus M and water.

The disadvantage of this drilling fluid is that it is not resistant to mineralized waters containing alkaline earth metal ions. The presence of a water-soluble silicic acid salt in the drilling fluid will lead to precipitation in the form of alkaline earth metal silicates and imbalance of ions, which will ultimately lead to instability in the characteristics of the drilling fluid.

The closest in technological essence to the claimed invention is a biopolymer drilling mud SBK-UNI-DRILL-PRO (HARD) [3] containing polyanionic cellulose of low viscosity, polyanionic cellulose of high viscosity, xanthan type biopolymer, lubricant additive in the form of a fatty acid product triglycerides with a number of carbon atoms from 14 to 24, salts of alkali and / or alkaline earth metals KCl, NaCl, CaCl ₂ , MgCl ₂ , bischofite; inhibitor reagent glycoil, bactericide, multi-fraction weighting agent - barium sulfate, sodium hydroxide and water at the following ratio of components, wt%: low viscosity polyanionic cellulose (degree of substitution 0.9, dynamic viscosity <100 mPa-s - according to Brookfield method) - 0.21.5; polyanionic cellulose of high viscosity (degree of substitution 0.9, dynamic viscosity> 1000 mPa-s - according to the Brookfield method) - 0.2-1.5; xanthan type biopolymer - 0.1-0.6; lubricating additive - 0.07-3.5; salts of alkali and / or alkaline earth metals KCl, NaCl, CaCl ₂ , MgCl ₂ , bischofite 3.0-40.0; sodium hydroxide - 0.1-0.6; inhibitor reagent glycoil - 0.5-1.0; bactericide - 0.01-0.2; multi-fraction weighting agent - barium sulfate - up to 80; water is the rest.

However, this drilling fluid has initially high rheological characteristics (conditional viscosity, plastic viscosity, static shear stress, dynamic shear stress), which will lead to a sharp increase in rheological characteristics when drilling highly active clays.

The task to be solved by the invention is to improve technological parameters, minimize complications and prevent deformation instability of the wellbore when drilling rocks, represented by highly colloidal clay deposits with interlayers of sandstones and siltstones by improving the inhibiting, anchorage properties of the water-based drilling mud, while reducing omentum formation.

The problem is solved due to the fact that the inhibiting drilling mud for drilling highly colloidal clay deposits, including low viscosity polyanionic cellulose, xanthan type biopolymer, organic clay inhibitor, glycol reagent, weighting agent, bactericide, pH regulator and water, according to the invention additionally contains an antifoam and mineral clay inhibitor potassium chloride, polyecol is used as a reagent of the glycol series, and chalk and dolomite are used as a weighting agent with the following ratio of components, wt%: low viscosity polyanionic cellulose - 0.4-0.8; xanthan type biopolymer -0.17-0.30; polyekol inhibitor - 1.4-2.5; potassium chloride inhibitor - 0.7-1.6; chalk - 5-14; dolomite - 5-14; bactericide 0.04-0.09; pH regulator - 0.03-0.05; antifoam agent - 0.03-0.05; water is the rest.

In addition, any xanthan-based polysaccharide can be used as the aforementioned xanthan-type biopolymer playing the role of a rheological property regulator, for example, various brands of xanthan gum obtained as a result of the action of bacteria on carbohydrates having a molecular weight of about 5,000,000 and a plastic viscosity of a 1% solution. in 1% KCl solution 1300-1600 cP, in particular gammaxan (TU 2458-010-82330939-1009 Mirrico GK), MHF80PLUS (Zibo Hailan Chemical Co., Ltd.).

In addition, potassium hydroxide can be used as the above-mentioned pH adjuster.

To prevent biodegradation of the polymers in the drilling fluid, a bactericide is used, such as Proxel TN (Code 75216).

The low viscosity polyanionic celluloses used in the above drilling fluid have an effective viscosity of no more than 40 mPa-s, for example Osnopak N-O (TU 2231-011-63121839-2010

- 1 037804

Mirriko GC), KhimPAK brand N (TU 2458-005-14023401-2011 Khimprom LLC).

Potassium chloride (TU BY 600122610.021-2011) acts as a mineral inhibitor of the swelling of shale.

Chalk (TU BY590118065.034-2017) and dolomite (GOST 14050-93) perform the functions of weighting agents and crushers in the drilling fluid.

The function of an organic clay inhibitor is performed by a glycol reagent - polyekol (TU BY 2458-021-97457491-2010).

To prevent foaming, and consequently, deterioration of technological characteristics, an antifoam agent is used, for example, Penta-461 (TU 2257-040-40245042-2002 LLC Penta-91).

In the inventive inhibiting drilling fluid, the ratio of reagents is selected, which provides optimal inhibiting properties, while maintaining the remaining technological parameters at the required level.

Achievement of the technical result is ensured by the complex effect of all components that make up the claimed inhibitory drilling mud for opening productive formations.

The invention is illustrated by graphs, where in FIG. 1 shows a graph of linear expansion of two test and control solutions in time; in fig. 2 - dynamics of capillary absorption of the studied liquids by clay samples.

The technology of preparation in laboratory conditions of the inventive inhibitory drilling mud for drilling highly colloidal clay deposits is shown in the following examples.

Example 1. To prepare 1000 ml of a solution with a density of 1.10 g / cm ³ in 500 ml of water, 0.6 g of a bactericide is added with stirring. Then, with vigorous stirring, 2.5 g of xanthan gum is introduced, the dispersion time is 20 minutes. 0.5 g of potassium hydroxide (GOST 9285-78) is added to the resulting suspension. After 5 min, low viscosity polyanionic cellulose, osnopak H-O 6 g, is introduced, the dispersion time is 15 min. A mineral clay inhibitor, potassium chloride, is introduced in an amount of 10 g. Then, 70 g of chalk and 70 g of dolomite are added, the dispersion time is 15 minutes. The inhibitor polyekol 20 is injected. The calculated amount of antifoam penta461 is introduced. 0.4 g. After the introduction of all components, the total volume is brought to 1000 ml with water, then the prepared drilling fluid is stirred for 20 minutes.

Example 2. To prepare 1000 ml of a solution with a density of 1.18 g / cm ³ in 500 ml of water, 0.6 g of a bactericide is added with stirring. Then, with vigorous stirring, 2.5 g of xanthan gum is introduced, the dispersion time is 20 minutes. 0.5 g of potassium hydroxide is added to the resulting suspension. After 5 min, low viscosity polyanionic cellulose, osnopak H-O 6 g, is introduced, the dispersion time is 15 min. A mineral clay inhibitor, potassium chloride, is introduced in an amount of 10 g. Then, 140 g of chalk and 140 g of dolomite are added, the dispersion time is 15 minutes. The inhibitor polyekol 20 is injected. The calculated amount of antifoam penta-461 is introduced, 0.4 g. After the introduction of all components, the total volume is brought to 1000 ml with water, then the prepared drilling fluid is stirred for 20 minutes.

The assessment of the main technological parameters of the studied fluids was carried out using standard instruments and techniques (Ryazanov Ya.A. Handbook of drilling fluids. M .: Nedra, 1979; API Recommended practice 13B-1 Fifth Edition / ISO 10414-1: 2017).

The following indicators of the properties of drilling fluids were analyzed under laboratory conditions: density (ρ, g / cm ³ ) was measured on an OFITE beam balance;

conditional viscosity (HC, s / 500 ml) was measured using VBR-2;

the filtration index (PF, cm ³ at a pressure drop of 0.1 MPa) was measured on an OFITE filter press;

rheological properties - plastic viscosity (PV, mPa-s), dynamic shear stress (YP, dPa) and Gel parameter after 10 s and 10 min (Gel _10/10 , lb / 100 ft ² ) were measured on an OFITE rotary 8-speed viscometer;

pH (pH) was measured on a Mettler Toledo instrument.

Table 1 shows information about the technological parameters of the two investigated solutions.

Table 1

P / p No. p, g / cm ³ uv, s / 500 ml PF, cm ³ / 30min at 0.1 MPa Gel! o / u, lb / YuOft ² PV, mPa s YP, dPa ph one 1.10 35 3.8 4/7 13 17 11.3 2 1.18 51 3.2 6/11 23 21.9 11.15

The data given in table. 1 show that the inventive solution has relatively low values of the filtration index at a pressure drop of 0.1 MPa, i.e. forms a sufficiently strong polymer crust. The drilling mud has a high pH value, which creates a favorable environment for the operation of the mud components and prevents its biological degradation. The ability of the solution at a certain shear rate to acquire the properties of a viscoelastic body provides good cleaning of the wellbore from cuttings, and low values of plastic viscosity provide

- 2 037804 provide good cleaning of drilling mud from cuttings on the surface.

The relative inhibiting ability of the proposed system of drilling mud was evaluated using a device for determining the swelling of clay in dynamic conditions - a tester of linear expansion Dynamic Linear Swellmeter OFITE. Samples of bentonite grade PBMV (moisture content 8-10%) compressed at 6000 psi were used as a clay rock model. A measure of the inhibiting properties of a solution is the change in the height of the sample over time. Research data are presented in table. 2 and in FIG. one.

table 2

Solution Change in sample height,% Control (distilled water) 81.04 Solution No. 1 34.3 Solution No. 2 39.6

The interfacial tension was also determined using an automatic tensiometer K100 KRUSS (Kruss GmbH, Germany). The filtrate of the proposed drilling mud was used as the test liquids in this technique, and fresh water and 3% solution of potassium chloride were used as control samples. PBMV bentonite was used as a material sample.

Tensiometer results are plotted in FIG. 2, where

- fresh water,

- fresh water after impregnation with 0.5 ml of 3% potassium chloride solution;

- fresh water after impregnation with 0.5 ml of the test solution filtrate;

- 3% solution of potassium chloride;

- filtrate of the test solution.

Analysis of the data obtained showed that during the impregnation, the filtrate containing potassium chloride and polyecol (test solution) penetrates into the space between the plates of the sludge sample and does not swell (Fig. 2, graph 5), thereby hydrophobizing the rock;

the water swells quickly and cannot pass through the sludge sample, i.e. makes the sample more hydrophilic (Fig. 2, graph 1);

the solution containing potassium chloride occupies an intermediate position between water and the filtrate containing polyecol (Fig. 2, graph 4), partial hydrophobization of the sample surface occurs.

The swelling dynamics during the passage of liquids is in the same relationship:

when water passes, the swelling process occurs instantly;

the rate of passage of the filtrate of the test solution is 80 s - there is no swelling process;

the rate of passage of the potassium chloride solution is 220 s, the speed slows down significantly, there is a gradual process of clay swelling.

According to the test results, the filtrate of the proposed inhibiting drilling fluid, due to the presence of an organic inhibitor of the glycol series - polycol, changes the character of capillary wetting between clay particles in the rock, therefore, the activity of the aqueous phase decreases, forms a hydrophobic layer on the clay, and prevents osmotic swelling.

An example of a specific implementation.

The proposed inhibiting drilling mud was used while drilling the post-salt part of a number of wells in the Pripyat trough. The post-salt part of the Pripyat trough is characterized by alternation of highly colloidal clay deposits with sands, sandstones, siltstones, and limestone. Further in table. 3 shows wells, work intervals and geological characteristics of the drilled rocks.

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Table 3

P / p No. Well Work interval, m Geological characteristics of the section one 2 3 four one 114p Marmovichskaya 225-775 The section is represented by alternating clays, sandstones, siltstones and marls. 2 3 332 Rechitskaya 223 Rechitskaya 205-690 215-1455 The section is represented by alternating clays, sands and sandstones, as well as interspersed with clayey dolomite and marls. The section is represented by alternating clays, sands and sandstones interspersed with dolomite and limestone. four 219 Rechitskaya 205-655 The section is represented by alternating clays, sands and sandstones. five 4In Nekrasovskaya 290-3050 The section is represented by alternating clays, siltstones, clayey limestones interspersed with dolomite and dolomite marl.

Table 4 shows the drilling time of these intervals, as well as the acceleration of drilling compared to nearby (base) wells.

Table 4

P / p No. Well Time spent on drilling the interval, h Reduction of drilling time compared to the average drilling time of similar intervals in the nearest wells, h one 114p Marmovichskaya 114 fifteen 2 332 Rechitskaya 120 53 3 223 Rechitskaya 288 17 four 219 Rechitskaya 104 69 five 41 η Nekrasovskaya 1056 324

As can be seen from the given data table. 4, the use of an inhibiting drilling fluid for drilling highly colloidal shale deposits can reduce the time spent on drilling an interval of highly reactive clays by accelerating the drilling process itself (the effect of the inhibiting properties of the drilling fluid), as well as by reducing the time spent on auxiliary operations (cleaning the bit from oil seals, dilution of drilling mud, reaming, etc.), which as a result increases the stability of the wellbore.

Thus, when drilling rocks, represented by highly colloidal clay deposits, an improvement in the technological parameters of the drilling fluid is achieved, complications are minimized and deformation instability of the wellbore is prevented by improving the inhibiting, fastening properties of the drilling fluid.

Information sources.

1. RU 2375405, IPC E21B 21/00, publ. 2009.06.20.

2. RU 2011128219 A, IPC SO9K 8/20, publ. 2013.12.10.

3. RU 2561630 C2, IPC SO9K 8/10, publ. 2015.08.27.

Claims (3)

CLAIM 1. Inhibitory drilling mud for drilling highly colloidal clay deposits, including low viscosity polyanionic cellulose, xanthan type biopolymer, organic clay inhibitor, glycol reagent, weighting agent, bactericide, pH regulator and water, characterized in that it additionally contains an antifoam and a mineral clay inhibitor chloride potassium, polyecol is used as a reagent of the glycol series, and chalk and dolomite are used as a weighting agent with the following ratio of components, wt%: low viscosity polyanionic cellulose - 0.4-0.8, xanthan type biopolymer - 0.17-0.30, polyekol inhibitor - 1.4-2.5, potassium chloride inhibitor - 0.7-1.6, chalk - 5-14, dolomite - 5-14, bactericide - 0.04-0.09, pH regulator - 0.03-0.05, defoamer - 0.03-0.05, water - the rest. - 4 037804 2. The drilling mud according to claim 1, characterized in that any xanthan-based polysaccharide is used as the xanthan-type biopolymer. 3. Drilling mud according to claim 1, characterized in that potassium hydroxide is used as the pH regulator.