RU2777003C1 - Highly inhibition drilling fluid - Google Patents

Abstract

FIELD: oil and gas wells construction.

SUBSTANCE: invention relates to the construction of oil and gas wells, namely to water-based drilling fluids used in the construction, completion and workover of wells in conditions of unstable clay deposits. The drilling fluid has a density of 1.08-1.16 g/cm³ with the possibility of weighting up to 1.30 g/cm³ and is thermally stable up to 110°C. The drilling fluid contains, wt.%: to control the structural-rheological and filtration properties of the solution - xanthan biopolymer 0.2-0.3 and lignosulfonate 0.8-1.0; to inhibit the process of clay hydration - potassium chloride 5.5-17.2; creating an impermeable filter cake on the walls of the well and achieving the required density of the solution - ground marble 4.3-21.6; to inhibit the process of hydration of clays, hydrophobization of the walls of the well and improve the tribological properties - saponified potassium tall oil 0.8-17.7; technical water treated with caustic soda and defoamer, the rest.

EFFECT: high inhibitory ability in relation to the process of hydration of clays, minimal impact on the reservoir properties of the bottomhole formation zone, optimal structural-rheological and frictional properties.

1 cl, 1 dwg, 4 tbl, 1 ex

Description

The invention relates to the construction of oil and gas wells, namely to water-based drilling fluids used in the construction, completion and workover of wells in conditions of unstable clay deposits.

Known drilling fluid designed to stabilize clay rocks containing clay powder, tall oil and filtration reducer (patent: RU 2541666).

The composition of the drilling fluid according to patent RU 2541666, wt. %:

clay powder 4.0-8.0 tall oil 5.0-15.0 Filtration reducer 0.2-1.0 Water rest

The main disadvantage of this solution is the interaction of tall oil fatty acids with metals, which leads to acid corrosion of the contacting parts of the circulation system, casing string, drilling tool, and carbonates - with the formation of poorly soluble salts of fatty acids and the release of carbon dioxide.

Known clay-free water-based drilling fluid containing xanthan biopolymer, potassium chloride, modified starch, calcium carbonate and water (patent: USA 4098700).

The disadvantage of this solution are low: inhibitory ability, surfactant and tribological properties.

The closest to the claimed technological solution is a clay-free drilling fluid (patent RU 2318855 - prototype) containing xanthan biopolymer and modified starch as a regulator of rheological and filtration properties, potassium chloride as the main inhibitor, an organic inhibitory additive FK-2000 Plus M as an additional inhibitor and lubricant additive, marble chips as a bridging agent, and water - the rest. This drilling fluid is intended for opening productive formations of horizontal and directional wells with a vertical deviation of more than 1000 m, represented by carbonate and terrigenous reservoirs. The well-known drilling fluid, according to the patent holder, is characterized by stable structural and rheological properties to provide the necessary carrying and holding capacity to prevent the occurrence of the Boycott effect, low filtration rate into the formation, high inhibition capacity, low values of interfacial tension at the interface "drilling fluid filtrate - hydrocarbon" , good frictional properties and resistance to aggression of polyvalent metal ions.

The composition of the drilling fluid according to patent RU 2318855, wt. %:

Xanthan biopolymer 4.0-8.0 modified starch 1.0-2.5 potassium chloride 1.5-3.0 Organic inhibitory additive FK-2000 Plus M 8.0-12.0 ground marble 1.5-3.0 Water rest

The disadvantages of this drilling fluid are lower in comparison with the claimed solution inhibitory capacity and greater foam-forming activity.

Organic inhibitory additive FK-2000 Plus (TU 2458-003-494712578-07) consists of triglycerides of fatty acids of sunflower, corn, soybean, rapeseed oil with a number of carbon atoms from 14 to 24 in an amount of 50-80%, a neutralizing agent in an amount of 3 -6%, polyethylene glycol ether of monoisononylphenol with 6-12 monomer units in the radical in the amount of 5-30% and water - the rest (patent: RU 2616461). FK-2000 Plus reduces diffusion processes of surface hydration due to adsorption and chemisorption effects. FK-2000 Plus is the closest analogue of the OKTM reagent in terms of chemical composition. Similar in composition to FK-2000 Plus are organic inhibitors of CBN and CBN Plus (TU 2458-001-49472578-04).

The objective of the invention is to create a drilling fluid with a minimum: values of linear swelling of clay samples, dispersion and the ability to soften clay rocks, impact on the reservoir properties of the bottomhole zone of productive horizons; having rheological properties that allow the construction of horizontal wells of great length in conditions of clay deposits.

The technical result achieved by the invention is to ensure trouble-free construction of wells in conditions of clay deposits prone to scree and collapse, swelling, dispersion and softening under the action of the drilling mud filtrate, due to the high level of inhibition of the clay hydration process, achieved by the combined use of potassium chloride and an organic inhibitor of saponified potassium tall oil (hereinafter referred to as OKTM), hydrophobization of the surface of the well walls, low drilling fluid filtration through the well wall, optimal structural and rheological properties, resistance to thermal and biodegradation, good frictional properties.

The specified technical result is achieved by the fact that the highly inhibited drilling fluid includes polymers of a polysaccharide nature - xanthan biopolymer and carboxymethylated starch, potassium chloride, ground marble, an organic inhibitory additive - saponified potassium tall oil and additionally - lignosulfonate and process water treated with caustic soda and a defoamer, with the following content of components, wt.%:

Xanthan biopolymer - 0.2-0.3 Carboxymethylated starch - 1.2-1.4 Lignosulfonate - 0.8-1.0 potassium chloride - 5.5-17.2 (solution density up to 1.08-1.16 g/cm ³ ) ground marble - 4.3-21.6 (microcolmatant at solution density 1.08-1.16 g / cm ³ , weighting agent - 1.16-1.30 g / cm ³ ) Saponified potassium tall oil - 0.8-17.7 Indicated water - rest

The inventive drilling fluid has a density of 1.08-1.16 g/cm ³ , with the possibility of weighting up to 1.30 g/cm ³ , and is thermally stable up to 110°C. It is characterized by a high inhibitory ability of the clay hydration process, minimal impact on the reservoir properties of the bottomhole formation zone, optimal structural-rheological and frictional properties. In the claimed composition of the drilling fluid, potassium ions are used as the main inhibitor of the clay hydration process, the sources of which are potassium chloride (KCI) and an organic inhibitor, saponified potassium tall oil.

OKTM in laboratory conditions is obtained by mixing an aqueous solution of potassium hydroxide (KOH) with tall oil in a ratio of 1:5. To prepare the reagent, crude tall oil (TU 13-0281078-119-89) or light tall oil (TU 13-0281078-100-90) is used. The amount of potassium hydroxide used to prepare the OKTM reagent is determined based on the value of the acid number of tall oil, based on the achievement of complete neutralization of fatty acids. To control the viscosity and freezing point of the resulting reagent, it is allowed to include up to 20% of triethylene glycol, isopropyl, or butyl into the composition of OKTM alcohol.

OKTM exhibits an additional inhibitory effect due to the creation of a hydrophobic layer on the walls of the well, and in combination with a low value of the drilling fluid filtration index, it can significantly slow down the adsorption processes and the penetration of the drilling fluid filtrate into the formation.

An important factor is that ions of calcium and other polyvalent metals during ion-exchange interaction with salts of alkali metals and fatty acids form compounds that are poorly soluble in water:

The resulting compounds are able to increase the stability of the walls of wells in the intervals of occurrence of unstable deposits.

An increase in the bonding strength of the rocks that make up the walls of the wells is achieved by filling the pore and fractured space of the walls of the wells with salts of fatty acids and polyvalent metals.

OKTM has a high numerical value of the hydrophilic-lipophilic balance, due to which it is able to stabilize highly dispersed oil-in-water emulsions, and also have a strong hydrophobic effect on the well walls.

OKTM effectively reduces swelling, dispersion and softening of clays, reduces the coefficient of friction of the drilling fluid. Potassium chloride biopolymer solutions with the addition of OKTM have a low foaming ability compared to the base solution. Table 1 shows the concentrations of ingredients in the claimed and known drilling fluids.

Table 1

The concentration of ingredients in the claimed and known drilling fluids

composition number Component composition, wt.% Carboxymethylated starch Xanthan biopolymer Lignosulfonate Chloride
potassium Ground
marble OKTM FC-2000
A plus CBN CBN
A plus Mineral
oil
LUKOIL
L Emulsifier
RADIA
E-24 Water Drilling fluid according to US patent 4098700 one 1.3 0.3 - 10.0 4.2 - - - - - - 84.2 Drilling fluid according to patent RU2318855 - prototype 2 ¹⁾ 1.0 0.3 - 1.5 1.5 - 8.0 - - - - 87.7 3 ¹⁾ 2.5 0.8 - 3.0 3.0 - 12.0 - - - - 78.7 Claimed drilling fluid with a density of 1.12 g/cm ^{3 3)} four 1.3 0.3 0.9 10.7 4.5 0 - - - - - 82.3 5 1.3 0.3 0.9 10.9 4.5 4.8 - - - - - 77.3 6 1.3 0.3 0.9 11.2 4.5 8.5 - - - - - 73.3 7 1.3 0.3 0.9 11.4 4.5 12.8 - - - - - 68.8 eight 1.3 0.3 0.9 11.5 4.5 17.1 - - - 64.4

Table 2 shows the parameters of drilling fluids, measured in reproduced compositions of known fluids, and the claimed drilling fluid. From the data of table 2 it can be seen that the known drilling fluids have a lower inhibitory ability in relation to the process of clay hydration compared to the claimed drilling fluid.

The combined use of potassium chloride and OKTM provides a high inhibitory ability of the drilling fluid in relation to the process of clay hydration, in addition, OKTM gives the solution good lubricating properties, hydrophobizes the surface of the borehole walls and prevents the biodegradation of polymeric reagents (due to the presence of alcohols in combination with anionic surfactants) . Low hydraulic resistance to the flow of the solution is achieved through the use of xanthan biopolymer and carboxymethylated starch, which impart pseudoplastic properties to the solution, in which the viscosity of the solution decreases with increasing shear rate, due to which the solution has a high holding and carrying capacity. The composition of the claimed solution includes chemical reagents presented in table 3.

The composition of the claimed drilling fluid is presented in table 4.

Table 4

The composition of the claimed drilling fluid

Reagent name Purpose of the reagent reagent concentration,
wt% Reagent concentration, g/l Xanthan biopolymer Rheology regulator 0.2-0.3 3.0 Carboxymethylated
Starch KMK-BUR-1N filtration reducer,
rheology regulator 1.2-1.4 15.0 Lignosulfonate KSSB-2M Filtration Regulator,
rheology regulator 0.8-1.0 10.0 Potassium chloride (KCl) inhibitor, peptizer 5.5-17.2 60.0-200.0 (solution density 1.08-1.16 g/cm ³ ) Ground marble (CaCO ₃ ) Colmatant 4.3-21.6 50.0-280.0 (microcolmatant at a solution density of 1.08-1.16 g / cm ³ , weighting agent - 1.16-1.30 g / cm ³ OKTM Inhibitor, water repellent, lubricant 0.8-17.7 10.0-190.0 (10.0-200.0 ml)* Processed process water - 40.8-87.2 585.0-940.0 *OKTM density is 0.950 g/cm ³ and can vary within 0.850-1.030 g/cm ³

The figure shows a combined chart for determining the content of potassium chloride and calcium carbonate in the claimed drilling fluid of the required density.

The use of potassium chloride in the amounts indicated in the diagram (Fig.) makes it possible to ensure the maximum inhibitory ability of the clay hydration process and the density of the drilling fluid in the range of 1.08-1.16 g/cm ³ .

The inventive drilling fluid is characterized by: high inhibitory ability in relation to the process of hydration of clays (low linear swelling of clay samples in the drilling fluid and dispersion of clays, high efficiency in maintaining the strength of clay rocks); hydrophobization of the bottom-hole formation zone of the well (reduction of the drilling fluid filtrate penetration zone); working density of 1.08-1.16 g/cm ³ , with the possibility of weighting up to 1.30 g/cm ³ by increasing the content of calcium carbonate; thermal stability up to 110°С; high emulsion stability (no phase separation in a static state); good structural and rheological properties that allow cleaning the wellbore at a low circulation rate and prevent obtaining high values of equivalent circulation density and fluid loss in conditions of low reservoir pressure; high lubricity without the use of lubricant additives; the absence of saturated hydrocarbons in the composition, which distort gas logging readings and reduce the reliability of the results of well logging; high enzymatic stability; high resistance to clay mud contamination.

Low values of linear swelling, dispersion and softening of clay rocks in the inventive drilling fluid make it possible to ensure high efficiency of the drilling fluid reuse technology.

An example of the preparation of the proposed drilling fluid in a container with a volume of 40 m ³ :

1. Collect 30,000 liters of technical water in a container.

2. Treat process water in the tank through the loading hatch with 25 kg of caustic soda and 60 liters of MEX-DEFOAM antifoam.

3. Introduce 600 kg of carboxymethylated starch KMK-BUR-1N through the ejector hydrofunnel. The reagent should be injected at a rate of not more than 30 kg in 5 minutes. At the end of the introduction of carboxymethylated starch, mix the resulting solution with an ejector hydrofunnel for at least 30 minutes.

4. Introduce 120 kg xanthan biopolymer DUO-VIS NS into the solution through an ejector funnel. Enter the reagent to produce at a rate of not more than 25 kg per 10 minutes. Upon completion of the introduction of the xanthan biopolymer, mix the resulting solution with an ejector hydrofunnel for at least 60 minutes.

5. Introduce 400 kg of KSSB-2M lignosulfonate through the ejector hydrofunnel. The reagent should be injected at a rate of no more than 25 kg in 5 minutes. At the end of the reagent addition, stir the solution for at least 30 minutes.

6. Introduce 5000 kg of potassium chloride into the solution through an ejector hydrofunnel.

7. Introduce 1000 kg of ground marble MK-10 and MK-60 into the solution through an ejector hydrofunnel.

8. Introduce 2000 liters of organic OKTM inhibitor into the solution, and pour technical water into the container up to the top level. Mix the resulting solution with an ejector hydrofunnel for at least 180 minutes. In the future, long-term operation of the ejector hydraulic funnel on working tanks should be prevented in order to avoid mechanical airing (aeration) of the drilling fluid.

9. After mixing, turn off the ejector hydrofunnel and leave the prepared solution to stabilize for 6-8 hours.

10. After stabilization, make a complete measurement of the technological parameters of the prepared solution.

When drilling from under the conductor of the wells, it is supposed to use the inventive drilling fluid with a content of 2-5% by volume of OKTM and, before opening the problem interval, to increase the content of the organic inhibitor in the solution to 10-20% by volume.

The priority objects for the experimental application of the proposed drilling fluid, characterized by the presence of intervals of unstable clay-argillite deposits, are horizontal wells 3 and 4-column construction of the Kochevsky, Mishaevsky, Imilorsky, Tevlin-sko-Russkinskoye fields on target formations of the Yu group, as well as horizontal wells Khalmerpayutinskoye and Pyakyakhinskoye fields on the BU _6-9 and PK _18-20 layers.

Sources of information:

1. RU 2541666, October 18, 2013, C09K 8/18, publ. 20.02.2015 Bull. No. 5;

2. USA 4098700, 09/25/1975, C09K 8/08, publ. 07/04/1978;

3. RU 2318855, April 17, 2006, C09K 8/08, publ. 10.03.2008 Bull. No. 7;

4. RU 2616461, March 16, 2015, C09K 8/035, publ. 04/17/2017 Bull. #11

Claims (2)

Highly inhibited drilling fluid, including polymers of a polysaccharide nature - xanthan biopolymer and carboxymethyl starch, potassium chloride, ground marble, an organic inhibitory additive, characterized in that it contains saponified potassium tall oil as an organic inhibitory additive and additionally - lignosulfonate and process water treated with caustic soda and defoamer, with the following content of components, wt.%: Xanthan biopolymer 0.2-0.3 Carboxymethylated starch 1.2-1.4 Lignosulfonate 0.8-1.0 potassium chloride 5.5-17.2 ground marble 4.3-21.6 Saponified potassium tall oil 0.8-17.7 Indicated water rest

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