RU2386656C1 - Drilling fluid for well construction in difficult conditions, mainly for drilling extended-reach wells and horizontal wells - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to drilling oil and gas wells and more specifically to drilling fluids used in difficult hydrogeological conditions, mainly for drilling extended-reach and horizontal wells, including tailing-in. The drilling fluid contains the following in wt %: drilling mud powder 1.0-4.0, stabiliser reagent - mixture of a product from modifying fatty acids with potassium alkali and nonionic surfactant containing not less than 1.5 mg-eq/l esters of organic acids in terms of dry residue, and from oxyethylated cellulose in mass ratio of 1:(1-2.0) respectively, 0.5-0.85, hydrocarbon water-repellent phase - mixture of dioxane alcohols with weight fraction of hydroxyl groups in the range of 15-36%, 2.0-5.0, potassium chloride 1-15, potassium silicate 0.5-2.0 and water - the rest. The invention is developed in subclaims.

EFFECT: optimisation of structure rheological and filtration properties of the drilling fluid with low content of the clay phase due to reduction of the pseudoplasticity index and rate of dynamic filtration, with simultaneous improvement of lubricant, anti-sticking and inhibiting properties of the drilling fluid and its resistance to effect of contaminants.

5 cl, 3 tbl, 1 ex

Description

The invention relates to the drilling of oil and gas wells, namely, drilling fluids used for drilling in difficult hydrogeological conditions, mainly for drilling shallow and horizontal wells, including when opening a reservoir.

Drilling mud for drilling wells in difficult conditions, especially when drilling the trunk through unstable deposits with large zenith angles (shallow and horizontal wells) should be characterized by the following properties:

- pseudo-plastic rheological characteristics - to provide the necessary remote and retaining ability of the drilling fluid and reduce hydraulic resistance;

- high inhibitory properties - to maintain the stability of clay rocks that form the walls of the well;

- high lubricating and water-repellent properties - to improve the working conditions of the rock cutting tool at the bottom, facilitate the passage of the drill string and prevent sticking in highly curved and horizontal sections of the wellbore;

- low dynamic filtration rate - to prevent the negative consequences of the penetration of large volumes of drilling fluid and filtrate into the near-well zone of the well;

- high resistance of physico-chemical and technological properties to the flow of chemically active impurities during drilling or when carrying out work to eliminate complications (in particular, when hydrogen sulfide, highly mineralized formation water, cement and other components of insulation compounds enter the solution after insulation work in the process drilling, etc.).

When drilling through potentially unstable clay rocks, drilling fluids are traditionally used, in order to increase their inhibitory and fixing ability, inorganic reagents (potassium chloride, calcium chloride, silicates, phosphates, etc.) are used, acting with a different mechanism of inhibiting clay hydration, in particular by changing clay exchange complex, colmatizing microcracks of layered schists.

It is also known the use of organic reagents in the composition of the drilling fluid for drilling in crumbling rocks, the mechanism of action of which is due to hydrophobization of the surface of clay particles due to the adsorption of organic compounds on it, which prevent contact and interaction of clays with water. Organic reagents such as organosilicon compounds (e.g., HCL), nonionic surfactants (e.g., ethoxylated phenols), synthetic fatty acids and alcohols, ethanolamides of fatty acids, oil-soluble polyethylene glycols and other reagents are used as such reagents of an organic nature.

BACKGROUND OF THE INVENTION A drilling fluid for drilling boreholes containing inorganic additive — sodium silicate for inhibiting rocks and an organic additive for increasing electrical resistivity — T-66 reagent (bottoms production of 4,4-dimethyldioxane-1,3) ( author certificate of the USSR No. 933696, 1982).

The disadvantages of this drilling fluid are relatively low inhibitory and fastening properties. In addition, the known solution structural and rheological indicators are provided with a sufficiently high content of clay powder (at least 5%). The known solution is also characterized by low resistance to contaminants, high dynamic filtration rates.

Also known is a drilling fluid for drilling wells in crumbling rocks, containing clay, liquid sodium glass, polyacrylamide, silicone fluid brand GKZH-94 and water (ed. Certificate of the USSR No. 899626, 1982).

The disadvantages of this solution are relatively low inhibitory and fastening properties, low resistance to contaminants, high values of the rate of dynamic filtration.

Also known are potassium chloride inhibiting clay mud stabilized by starch, condensed sulphite-alcohol stillage (KSSB), oxyl and hydroxyethyl cellulose (OEC), additionally containing barium hydroxide (RF Patent No. 2323225, class C09K 8/20, 2006), and silicate-potassium drilling fluid stabilized by KSSB and carboxymethyl cellulose (CMC) and additionally containing GKZH (RF Patent No. 1696451, CL SKK 7/02, 1989).

The disadvantages of these known drilling fluids are insufficiently optimized for drilling shallow and horizontal wells structural and rheological properties, low resistance to contaminants, high values of dynamic filtration rate, as well as a high coefficient of tendency to stick (differential sticking).

The closest technical solution is a drilling mud containing clay, stabilizing agents (CMC, starch, PAC), a complex of inhibitory, fixing and hydrophobizing additives, which are used as: polyglycol - 3-5%; potassium silicate 0.5-3.0% and potassium chloride 3-15% (RF Patent No. 2163248, class C09K 7/02, 2001).

The disadvantages of this known drilling fluid using a complex of hydrophobic and inhibitory reagents are:

- high solids content - clay (at least 10%), which predetermines low rates of mechanical drilling, a tendency to groove, which is especially dangerous when drilling wells with large zenith angles;

- unsatisfactory anti-seizing and lubricating properties (coefficient of friction 0.29; coefficient of tendency to stick To _differential more than 0.15);

- insufficiently high fixing properties in relation to unstable rocks (degree of sludge erosion of more than 5%);

- low resistance to contaminants;

- high values of dynamic filtration rate.

Due to these drawbacks, the efficiency of well-known drilling fluid drilling is not high enough.

The technical result achieved by the present invention is to optimize the structural-rheological and filtration properties of the drilling fluid with a low clay phase content, by reducing the pseudo-ductility rate and dynamic filtration rate, while increasing the lubricating, anti-stick and inhibitory properties of the drilling fluid and its resistance to impact contaminants.

The specified technical result is achieved by the proposed drilling fluid for the construction of wells in difficult conditions, mainly for drilling shallow and horizontal wells containing clay powder, a stabilizing reagent, a hydrocarbon hydrophobizing phase, potassium chloride, potassium silicate and water, while according to the invention as a stabilizing reagent it contains a mixture of a product of the modification of fatty acids with potassium alkali and a nonionic surfactant containing at least 1.5 mEq / l of complex organic acids in terms of dry residue, and from ethoxylated cellulose in a mass ratio of 1: (1 ÷ 2.0), respectively, and as a hydrocarbon hydrophobizing phase, it contains a reagent, which is a mixture of dioxane alcohols with a mass fraction of hydroxyl groups within 15 -36%, in the following ratio of ingredients, wt.%:

Clay powder 1.0-4.0 The specified stabilizer reagent 0.5-0.85 Indicated hydrocarbon hydrophobizing phase 2.0-5.0 Potassium silicate 0.5-2.0 Potassium chloride 1-15 Water rest.

As a reagent, which is a mixture of dioxane alcohols with a mass fraction of hydroxyl groups in the range of 15-36%, the drilling fluid contains lubricant additives Burflyub BT or DSPB or T-80.

The drilling fluid additionally contains caustic magnesite 0.5-2.0 wt.%.

The drilling fluid additionally contains starch of 0.5-1.5 wt.%.

The drilling fluid additionally contains a mixture of derivatives of higher fatty acids obtained by processing wood or petroleum resins and tars, in the form of a reagent brands Soltex, SAF, Baratrol.

The achievement of the specified technical result is provided, apparently, due to the following. When mixing in the claimed quantitative proportions of derivatives of dioxane alcohols (hydrocarbon hydrophobic component of the claimed drilling fluid) with a mixture of derivatives of higher fatty acids and hydroxyethyl cellulose as stabilizers (aqueous phase) in the presence of a clay phase, a stable oil-in-water emulsion system forms (direct emulsion), which is characterized by increased inhibitory and hydrophobizing properties, optimized filtration and structural-rheological displays spruce, and protivoprihvatnymi improved lubricating properties. Thus, the proposed solution is an emulsion drilling fluid, characterized by the above properties.

The introduction of predominantly additional caustic magnesite, starch, a mixture of derivatives of higher fatty acids obtained from the processing of wood or petroleum resins and tars is aimed at improving a number of technological properties, such as resistance to the effects of contaminants due to the pH buffer - caustic magnesite and starch and enhanced hydrophobic properties due to a mixture of fatty acids.

For the preparation of the inventive drilling fluid in laboratory conditions, the following substances were used.

1. The product of the modification of fatty acids with potassium alkali and a nonionic surfactant containing at least 1.5 mEq / l of esters of organic acids in terms of dry residue:

- Sintal BT according to TU 2482-016-40912231-2003,

- MIG reagent according to TU 2482-014-53501222-2000.

2. Oxyethylated cellulose of the Cellosize QP100 MN brand (by import); REOZEL B according to TU 2231-012-40912231-2003.

3. Derivatives of higher fatty acids obtained from the processing of wood or petroleum resins: reagent grade SAF according to TU 2471-037-40912231-2006, Soltex or Baratrol (for import).

4. Hydrophobic hydrophobizing phase - derivatives of dioxane alcohols with a mass fraction of hydroxyl groups in the range of 15-36%: BURFLUB-BT according to TU 2452-018-40912231-2003; Flotoreagent - Oxal T-92, 94 according to TU 2452-029-05766801-94; DSPB-BS according to TU 2452-002-52412574-00.

5. Clay powder brand PPB, GOST 25795-383.

6. Modified starch Buramil BT according to TU 9187-020-40912231-2003.

7. Caustic magnesite PMK-75, GOST 1216-87.

8. Liquid potash glass (potassium silicate) according to TU 2145-003-52257004-2003.

9. Potassium chloride according to TU 2184-072-00209527-2001.

10. Technical water.

The essence of the invention is illustrated by the following example.

Example.

To obtain the claimed drilling fluid, 8 g of industrial water was added with 20 g of PPB brand clay powder, stirred for 30 minutes on a laboratory mixer at 1000 rpm and 6 minutes on a mixer at 9000 rpm, then 8 g of stabilizing reagent was added - a mixture consisting from a product of modification of fatty acids with potassium alkali and a nonionic surfactant containing at least 1.5 mEq / l of organic acid esters in terms of dry residue (Synthal BT), and from ethoxylated cellulose (REOCEL B) in a weight ratio 1.5: 2.0 accordingly, the resulting mass was stirred for 0.5 h, then 40 g of the hydrocarbon phase (BURFLUB-BT) and 7 g of SAF were introduced into it, stirred for 0.5 h, inorganic inhibitors of 50 g of KCl and 20 g of potassium silicate were added, and for weighting, 30 g of sodium chloride, after stirring for 0.5 hours received a drilling fluid with the following ingredients, wt.%: Clay powder PPB - 2.0; stabilizer reagent - 0.8; hydrocarbon phase - 4.0; KCl - 5.0; potassium silicate - 2.0; NaCl - 3.0; derivatives of higher fatty acids SAF - 0.7; water - 82.5.

Similarly prepared other compositions of the inventive drilling fluid with a different ratio of ingredients.

In laboratory conditions, the following properties of the claimed and well-known prototype drilling fluids were investigated:

- the filtration rate (F ₃₀ , cm ³ ) and the dynamic filtration rate (V _f , cm ³ / min) were measured on a OFI dynamic filter press at ΔP = 0.7 MPa;

- rheological properties — plastic viscosity (η, MPa · s), dynamic shear stress (τ ₀ , dPa), gel strength (Gel, lb / 100 ft ² ) were measured on an OFITE viscometer; viscosity at low shear rate (VNSS, MPa · s) was measured on a Brookfield viscometer;

- indicators of pseudoplasticity "n" was calculated according to well-known formulas (Macovei N. Hydraulics of drilling. - M .: Nedra, 1986);

- Lubricating properties (K _Tr ) were studied on an OFI Extreme Pressure and Lubricity Testes Complete instrument;

- the anti-seizing properties of drilling fluids were determined on a differential stick tester at ΔР = 3.3 MPa (Fann, model 21150);

- the stickiness coefficient of the filter cake (K _l ) was determined on a CTK-2 device;

- inhibitory properties were determined by the degree of erosion of the sludge in the medium of the drilling fluid for 16 hours at a temperature of 75 ° C;

- resistance to the effects of contaminants (cement, hydrogen sulfide, polysalt mineralization) was evaluated by the change in filtration and rheological parameters after the introduction of these contaminants. The research methodology on the influence of contaminants was as follows. Initially, hydrogen sulfide water was obtained with a hydrogen sulfide content of 1.3 g / l. Since, as a rule, hydrogen sulfide enters the drilling fluid with produced water, formation water with a density of 1142 kg / m ³ and a hydrogen sulfide content of 0.29 g / l was prepared. The following were added to separate mud samples:

- 6% of produced water with a density of 1142 kg / m ³ not containing hydrogen sulfide;

- 6% of produced water with a density of 1142 kg / m ³ containing hydrogen sulfide in an amount of 0.29 g / l;

- 5% of cement (with a water-cement ratio of 0.5).

After 16 hours exposure at room temperature, the properties of the drilling fluids were measured.

Table 1 shows data on the ingredient composition of the claimed and known prototype drilling fluids.

Table 2 shows data on indicators of the properties of the claimed and well-known prototype drilling fluids.

Table 3 shows the data on the performance of the claimed and well-known prototype drilling fluids after the introduction of contaminants into them.

The data shown in tables 1-3 show that the inventive drilling fluid is characterized by:

- optimal structural, rheological and filtration indices with a low clay phase content (less than 4%), namely: pseudoplasticity index 0.31-0.76; VNSS = 26256-82547; filtration rate (F _0.7 ) = 6-10; dynamic filtration rate = 0.13-0.26 cm ³ / min;

- high lubricating properties: coefficient of friction (K _Tr ) = 0.13-0.08; the stickiness coefficient of the peel (K _l ) = 3 ° -3 ° 30;

- high non-stick properties (K _diff = 0-0.1);

- high inhibitory properties in relation to clay rocks (degree of erosion of sludge 3.8-4.8%).

Studies have confirmed that the claimed drilling fluid is highly resistant to contaminants, i.e. it retains the technological properties within the regulated values when it enters the drilling fluid, for example, cement, highly saline formation water, hydrogen sulfide-containing formation water.

Thus, the proposed drilling fluid with the claimed complex of ingredients meets the requirements for drilling wells in difficult conditions, including the drilling of shallow sections of the wellbore and horizontal wells.

The technical and economic advantages of the proposed drilling fluids compared to the prototype are as follows:

- the rate of filtration and the rate of dynamic filtration of the claimed drilling fluid is less than the same indicator of the prototype, which provides less penetration of the filtrate into the near-well zone of the well and a lower rate of hydration of unstable rocks, including in the reservoir;

- the structural and rheological properties of the resulting solutions, especially at low shear rates, have higher values, and the pseudoplasticity index is lower than that of the prototype, and at the same time they meet the requirements for conducting shallow and subhorizontal sections of the wellbore.

The inventive solution is characterized by higher lubricating and anti-seizing properties, which will improve the technical and economic performance of the bits and prevent complications and accidents of the drilling tool.

The inventive solution is characterized by higher inhibitory properties, which will prevent complications when drilling unstable and highly permeable rocks.

In addition, the inventive drilling fluid is characterized by high salt resistance and resistance to ingress of contaminating components (hydrogen sulfide, cement, formation water) into the system, which will significantly reduce material and labor costs for the restoration of regulated parameters of the drilling fluid during drilling.

Table 3 The effect of contaminants on the properties of the claimed and well-known prototype drilling fluids No. of compositions from the table Drilling Fluid Properties Change in indicators after entering impurities Without additives 6% hydrogen sulfide water 6% produced water 5% cement 3 τ, dPa 218.4 202.6 210.2 220.8 F _Δ0.7 cm ³ 6.0 7.5 6.5 7.0 Gel, lb / 100ft ² 10/11 9/10 9/10 11/13 5 τ, dPa 117.6 93.6 95.5 230 F _Δ0.7 cm ³ 17.5 28.5 26.0 40,0 Gel, lb / 100ft ² 31 / 33.5 22 / 23.5 23 / 26.5 37 / 43.5

Claims (5)

1. Drilling fluid for well construction in difficult conditions, mainly for drilling shallow and horizontal wells, containing clay powder, stabilizing reagent, hydrocarbon hydrophobizing phase, potassium chloride, potassium silicate and water, characterized in that it contains a mixture of a product of the modification of fatty acids with potassium alkali and a nonionic surfactant containing at least 1.5 mEq / l of organic acid esters, calculated on the dry residue, and from hydroxyethyl cellulose in a mass ratio of 1: (1 ÷ 2.0), respectively, and as a hydrocarbon hydrophobic phase, it contains a reagent that is a mixture of dioxane alcohols with a mass fraction of hydroxyl groups in the range of 15-36%, in the following ratio of ingredients, wt. %:
Clay powder 1.0-4.0 The specified stabilizer reagent 0.5-0.85 Indicated hydrocarbon hydrophobizing phase 2.0-5.0 Potassium silicate 0.5-2.0 Potassium chloride 1-15 Water Rest 2. The drilling fluid according to claim 1, characterized in that as a reagent, which is a mixture of dioxane alcohols with a mass fraction of hydroxyl groups in the range of 15-36%, it contains a lubricant additive Burflyub BT or DSPB, or T-80. 3. The drilling fluid according to claim 1, characterized in that it further comprises caustic magnesite 0.5-2.0 wt.%. 4. The drilling fluid according to claim 1, characterized in that it further comprises starch of 0.5-1.5 wt.%. 5. The drilling fluid according to claim 1, characterized in that it further comprises a mixture of derivatives of higher fatty acids obtained from the processing of wood or oil resins and tar, in the form of a reagent brands Soltex, SAF, Baratrol.