RU2351628C1 - Biopolymer drilling agent - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil and gas industry, particularly to bipolymer drilling agents (BPDA) used at drilling wells, horizontal and control directional ones including, and also for well recovery by drilling second wells under conditions of abnormal low reservoir pressure. Biopolymer drilling agent contains, wt %: Saraksan-T 0.2-0.5; Polycell KMK-BUR2 1.2-1.6; neonol 0.6-0.8; calcium chloride 15-27; water - the rest.

EFFECT: increased efficiency of well drilling due to implementation of BPDA with upgraded structural-rheological properties facilitating increased retention and transporting capability of BPDA at simultaneous maintaining of its filtration properties and frost resistance, also reduction of time for BPDA preparing.

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Description

The invention relates to the oil and gas industry, in particular to biopolymer drilling fluids (BPBR) used in drilling wells, including horizontal, directional, as well as for the restoration of wells by drilling second trunks under conditions of abnormally low reservoir pressure.

Analysis of the current level of technology showed the following:

- known BPBR, the formulation of which has the following ratio of ingredients, wt.%:

Polymer Filtration Reducer 0.1-1.0 Xanthan Biopolymer 0.2-0.5 Fatty Acid Ethylene Diamides 0.05-3.0 USR or GKR 3.0-6.0 Calcium chloride 3.0-40.0 Water rest,

(see RF patent No. 2289603 dated April 13, 2005 according to class C09K 8/10, published in Bull. No. 35, 2006).

The disadvantage of this BPBR is the lack of efficiency in well drilling. This is due to the following reasons: the specified BPBR has high values of filtration properties. This facilitates the penetration of its filtrate with the water-soluble ingredients contained in it into the formation, their interaction with formation water and formation rock minerals, which leads to the colmatation of the pore space of the reservoir by reaction products and, as a result, its filtration-capacitive properties. In addition, a loose thick filter cake formed during BPBR filtration is a determining factor in the occurrence of complications associated with a decrease in bore diameter, excessive torque, puffs, and sticking of the drill string under the influence of pressure drop. The specified BPBR has insufficient structural and rheological properties to give it the necessary transporting and holding capacity (non-linearity coefficient n> 1 — calculated value for example No. 7, table 1 of the patent description). The high value of the non-linearity coefficient, due to the values of both plastic viscosity and dynamic shear stress, indicates a mismatch between the properties of BPBR and the properties inherent in pseudoplastic fluids. By rheological parameters and a value of n> 1, this BPBR refers to dilatant systems for which viscosity increases with an increase in shear rate, and therefore cannot provide effective drilling of wells. The disadvantage of this BPBR is its multicomponent nature, which complicates the method of preparation, increases the time required for preparation, as well as for additional processing of the solution during drilling to maintain the necessary parameters. At high frost resistance, due to the content in the solution of up to 40 wt.% Calcium chloride, the use of fatty acid ethylene diamides as a surfactant does not provide a solution of reduced density, since this surfactant does not impart air-drawing properties to it;

- as a prototype taken BPBR, the formulation of which has the following ratio of ingredients, wt.%:

Xanthan Biopolymer 0.2 Polyanionic cellulose 0.25 Modified Starch 2.0 Alkali metal hydroxide 0.08 Water Soluble Silicic Acid Salt 1,2 MIG SAW 0.5 Calcium chloride 30,0 Water 65.77

(see RF patent No. 2186819 of 05.23.2001, class C09K 7/02, published in Bull. No. 22, 2002).

The disadvantage of this BPBR is the lack of efficiency in well drilling. This is due to the following reasons: despite the fact that the specified BPBR with a calcium chloride content of 30 wt.% Has low values of the filtration properties and the necessary frost resistance, its formulation cannot be considered technologically feasible and cost-effective, since to ensure the stability of these indicators BPBR seven ingredients besides water. This complicates the method of preparation, increases the time required for preparation, as well as for additional processing of BPBR during drilling to maintain the necessary parameters. The disadvantage is the increased density of BPBR, which is due, in addition to the content of large amounts of salts, the properties of the applied MIG surfactant and the content of the water-soluble salt of silicic acid, which negatively affects air intake. The increased density of BPBR limits its area of application when drilling wells under conditions of abnormally low reservoir pressures. In addition, being frost-resistant, this BPBR has insufficient structural and rheological properties to provide high holding and transporting ability, which is determined by the non-linearity coefficient n characterizing the pseudoplastic properties. The nonlinearity coefficient n of the prepared solution, equal to 0.40 given in Example No. 9, Table 2 of the patent specification, does not correspond to its actual calculated value equal to 0.51 - in accordance with the indices η _pl and τ _о , from which n ( see Gray J.R., Darley G.S.G. Composition and properties of drilling agents (flushing fluids): transl. from English - M .: Nedra, 1985. - P.190-193). Therefore, the BPBR with an increased n value of 0.51 does not possess the necessary properties of pseudoplasticity (n <0.5) and cannot contribute to the quality of drilling operations. Possibly, the insufficient structural and rheological properties are due to the low content of the xanthan type biopolymer in the formulation in comparison with other polymer ingredients, which does not provide a manifestation of pseudoplasticity. Two of the ingredients included in the solution formulation belong to the second hazard class (water-soluble salt of silicic acid and alkali metal hydroxide), which complicates the task of disposing of the spent solution and does not contribute to reducing its environmental safety.

The technical result that can be obtained by implementing the present invention is as follows: the efficiency of well drilling is increased through the use of BPBR with improved structural and rheological properties, providing enhanced holding and transporting ability, while maintaining filtration properties and frost resistance, as well as simplification a way to reduce the time spent on the preparation of BPBR by reducing the initial ingredients with an increase in environmental without pasnosti their applications.

The technical result is achieved using the known BPBR, including a xanthan type biopolymer, modified starch, a surfactant, calcium chloride and water, characterized in that it contains Saraxan-T as a xanthan type biopolymer, and Policell KMK-BUR2 as a modified starch. and as a surfactant - neonol in the following ratio of ingredients, wt.%:

Saraksan-T 0.2-0.5 Polycell KMK-BUR2 1.2-1.6 Neonol 0.6-0.8 Calcium chloride 15-27 Water rest.

The inventive BPBR meets the condition of "novelty."

For the preparation of BPBR, Saraksan-T is used according to TU 2458-006-00480709-07, the production method is described in the patent of the Russian Federation No. 2252533 dated 04/19/2004, according to class. А61К 47/36, С12Р 19/06, Polycell KMK-BUR2 - carboxymethyl starch according to TU 2262-016-32957739-01, neonol according to TU 2483-077-05766801-98, calcium chloride according to GOST 450-77.

Saraksan-T is an easily loose powder of white or yellowish-cream color, belonging to hazard class 4. According to the active substance, it belongs to the xanthan type polysaccharides, it contains residues of glucose, mannose, glucuronic and pyruvic acids. Due to the introduction of a stabilizer (formalin) it is resistant to microbiological effects. In addition, Saraksan-T contains up to 75% of xanthan exopolysaccharide produced by the Xanthomonas campestris strain in the nutrient medium, up to 15% moisture, protein components, mineral background of the nutrient residue (CaCl ₃ , KH ₂ PO ₄ , MgSO ₄ , Fe ₂ ( SO ₄ ) ₃ ), a protein of the formaldehyde complex.

The combined use of the used ingredients in the BPBR contributes to the production of the BPBR, which has improved structural and rheological properties, provides efficient drilling of wells, including horizontal, directional, and well restoration by drilling of second wells under conditions of abnormally low reservoir pressure. This is due to the following processes. Neonol, which is an ethoxylated monoalkylphenol based on polypropylene trimers, is characterized by a high air-entraining effect, which, together with the ability of the Saraxan-T protein component to air entrainment, contributes to the production of low density BPBR. Proteins (proteins) of the Saraxan-T formaldehyde complex, being surfactants, have some special properties that distinguish them from synthetic surfactants. The formation of the equilibrium adsorption layer is explained by the diffusion of globular molecules to the interfacial surface and the deployment of a polypeptide chain on it, which stabilizes the polycalcium system of the BPBR. The stabilization of the polymer-salt system of the BPBR is determined by the presence of adhesion forces between the individual molecules of the adsorption layer, as well as the mobility of these molecules, which contributes to the rapid recovery of deformations that occur at low temperatures, which ensures the frost resistance of the solution. In addition, the condensation effect of the Ca ²⁺ cation (calcium chloride) on the exopolysaccharides of Saraksan-T causes an increase in the plastic viscosity of BPBR, lowering its freezing temperature. Therefore, BPBR has increased frost resistance. Saraksan-T synthesized by Xanthomonas campestris combines the structural elements, chemical and rheological properties of the branched acid polysaccharide, which, together with the Policell KMK-BUR2 polysaccharide chain, which has the basic (alkaline) properties, determines the chemical interaction of these ingredients and neonol with the formation of a high molecular weight structure. This determines the improved structural and rheological properties of BPBR, providing its increased holding and transporting ability. The latter are characterized by a nonlinearity coefficient n. The smaller n, the more the solution exhibits pseudoplastic properties. This means that viscosity decreases with increasing relative shear rates and, conversely, viscosity increases with decreasing relative shear rates. A decrease in the constant n allows to improve the rock removal and well cleaning due to the leveling (flattening) of the fluid flow velocity profile in the annulus.

The parabolic distribution of velocities in the flow, characteristic of Newtonian fluids (n = 1), contributes to the formation of a swirling effect of suspended particles of drill cuttings and pushes them in the region with lower velocities. The result of this is the recycling of solid particles along the entire fluid stream and, as a consequence, low efficiency of well cleaning. A pseudoplastic fluid with a value of 0 <n <1 has a flatter velocity profile, which reduces the twisting effect, and hence the recirculation of the solid phase and displaces it evenly up the wellbore. Lower values of n provide a flatter velocity profile and contribute to laminar flow and stability of the well.

The n values are calculated based on any two viscometer readings for two different rotor speeds according to the formula

,

,

where R ₁ - readings of the viscometer at Ni rpm;

R ₂ - viscometer readings at N2 rpm

(see Gray J.R., Darley G.S.G. Composition and properties of drilling agents (flushing fluids): transl. from English. - M .: Nedra, 1985. - P.190-193).

The ingredients included in the formulation of BPBR in the specified amount, provide lower values of the coefficient of nonlinearity n (0.37-0.47), which, taking into account the above, indicates its increased holding and transporting ability. Preservation of the filtration properties of the claimed BPBR is ensured due to the synergistic effect of the interaction of Saraksan-T and Polycell KMK-BUR2, which have a similar empirical basis, but different structure and acid-base properties, which determine the formation of complex type compounds that significantly increase the viscosity of the liquid phase of the polymer-salt system of BPBR and contribute to the formation of thin filter cake of increased strength. This can be confirmed by comparing the BPBR filtration data given in Examples 11 and 12 of the test report, where, with other equal contents of the other ingredients of the solution (neonol and calcium chloride), the absence of one of the remaining Saraksan-T or Polycel Cell KMK-BUR2 ingredients leads to a sharp growth rate of filtration. Moreover, a less significant decrease in filtration in Example 12, due to the condensing effect of the Ca ^{2+ ion} on Polycell KMK-BUR2 and due to this increase in the density of the formed filter cake.

The preparation method is simplified and the time required to prepare the BPBR is reduced as a result of the fact that the formulation includes only four starting ingredients, except water. The time required to prepare the BPBR for drilling wells is reduced, and due to its enzymatic stability (the content of large amounts of calcium chloride and the formaldehyde treatment of Saraksan-T), the stability of the filtration properties, the number of additional treatments of the solution is reduced to maintain the necessary parameters during drilling. The inventive BPBR is environmentally safer, since it includes ingredients of hazard class 4 except for neonol belonging to class 3. In addition, due to the lack of a solid phase in the BPBR, the technical and economic performance indicators of the bits increase.

The content of Saraksan-T in BPBR is more than 0.5 wt.%, Neonol more than 0.8 wt.% Is economically and technologically impractical, since there is no significant improvement in structural and rheological properties with an increase in the number of these ingredients.

The content of Saraksan-T in BPRB is less than 0.2 wt.%, Neonol is less than 0.6 wt.%, Polycell KMK-BUR2 is less than 1.2 wt.% Leads to increased filtration, and the content of Policell KMK-BUR2 is more than 1.6 wt. .% leads to an increase in the coefficient of nonlinearity n, which indicates a deterioration of the pseudoplastic properties, a decrease in its transporting and holding ability of the BPR.

The content of calcium chloride in BPBR of less than 15 wt.% Negatively affects the antifiltration parameters and reduces the frost resistance of the solution, and more than 27 wt.% Leads to an increase in its density and deterioration of pseudoplastic properties: an increase in the nonlinearity coefficient n.

Thus, according to the above, the proposed BPBR ensures the achievement of the claimed technical result.

Not identified by available sources of fame, technical solutions having features that match the distinctive features of the invention according to the claimed technical result.

The inventive BPBR meets the condition of "inventive step".

In more detail, the essence of the claimed invention is described by the following examples.

Example (fishing).

A gas well with abnormally low reservoir pressures is located in an idle reservoir (flooding). During the overhaul of this well, a violation of the production string and a narrowing of its diameter were found. To restore the well, the second well is drilled.

Initial data

Conductor 245 mm Conductor descent depth 387 m Production tower 168 mm Depth of production casing 1100 m Production casing perforation interval 986-1014 m Cement mortar lift per conductor and production casing 29 m from the mouth Reservoir pressure 1.2 MPa.

The wellhead is equipped with AFK6-100 × 210 HL fountain fittings and an OKK 1-245 × 168-210 HL column head.

The second wellbore of a gas well with a deflection angle of 83 ° is drilled with a bit with a diameter of 139.7 mm from a depth of 930 m to a length of 73 m. For drilling the second wellbore, the proposed BPBR in the volume of 23 m ³ (15 m ³ + 8 m ³ ), determined by the formula

,

,

where V _well - the volume of the well minus the volume of the metal of the drill pipe, m ³ ;

V _cs - the volume of the circulation system, m ³ ,

10 m ³ is prepared per cycle and pumped to the pump-tank unit.

For the preparation of 10 m ³ BPBR with a ratio of ingredients, wt.%:

Saraksan-T 0.2 Polycell KMK-BUR 2 1,6 Neonol 0.6 Calcium chloride fifteen Water 82.6

948 kg (15 wt.%) of calcium chloride are introduced into a water mixer filled with water in a volume of 5.22 m ³ (82.6 wt.%) and mixed until it is completely dissolved. After that, with stirring, 12.6 kg (0.2 wt.%) Of Saraxan-T is introduced into the resulting solution, stirred for 1 h and 101 kg (1.6 wt.%) Of Polycell KMK-BUR2 are introduced. The polymer solution is stirred for 1 hour, then left to swell the polymers and the ingredients to react for 2 hours, after which 56.7 l (0.6 wt.%) Of neonol with a density of 1070 kg / m ³ are added and another 0.5 hours are mixed. until a uniform composition of the BPBR is obtained.

Ready-to-use BPBRs are pumped to a pump and tank unit. Thus, the entire volume of BPBR is prepared for drilling the second wellbore.

BPBR has the following properties: a density ρ = 632 kg / m ^3, filtration F = 4.8 cm ^3/30 min, the plastic viscosity η = 16 mPa · s, the dynamic shear stress τ _o = 129 dPa, static shear stress for 1 and 10 min θ _1/10 = 34/34 dPa, nonlinearity coefficient n = 0.45, freezing temperature T _s = -12 ° C.

Drilling is carried out with a mechanical speed of about 5 m / h with a productivity of the UNB-600 mud pump equal to 12 l / s, which, given the structural and rheological parameters, the BPBR provides a laminar flow regime in the annular space of the well.

In the process of drilling, BPBR should be cleaned of cuttings. For these purposes, it is advisable to use vibrating screens, rather than hydrocyclones (sand and sludge separators), in which the structure of the IUD can be destroyed during the interaction of the biopolymer and CMC with calcium chloride, which will inevitably lead to a decrease in the pseudoplastic properties of BPBR (an increase in n), and therefore , to the deterioration of its holding and transporting abilities, as well as increased filtration. To reduce mud contamination of the drilling fluid, it is required to ensure the quality of vibrating screens by selecting grids with the appropriate mesh size, adjusting their inclination and vibration.

During drilling, the BPBR parameters are maintained at the level regulated by the introduction of additional quantities of Saraksan-T and Polycell KMK-BUR2 as necessary. The density of the solution is regulated by calcium chloride.

The use of BPBRs with stable structural-rheological, pseudoplastic and filtration properties when drilling wells under conditions of abnormally low reservoir pressures will increase the technical and economic performance of drilling and reduce the environmental impact.

Example 1 (laboratory).

To prepare 1000 g BPBR in 826 ml (82.6 wt.%) Water, dissolve 150 g (15 wt.%) Calcium chloride, then with stirring, 2 g (0.2 wt.%) Saraxan-T and 16 g ( 1.6%) Polycell KMK-BUR2. After stirring for 0.5 h, leave to swell for 2 h, then add 5.6 ml of neonol (ρ = 1070 kg / m ³ ), which is (0.6 wt.%), Stir another 0.5 h to obtaining a uniform composition of BPBR.

BPBR has the following properties: ρ = 632 kg / m ³ O = 4.8 cm ^3/30 min, η = 16 mPa · sec, τ _o = 129 dPa, θ _1/10 = 34/34 dPa, n = 0 , 45, T _s = -12 ° C.

Example 2

Prepare 1000 g BPBR, g / wt.%:

Saraksan-T 5 / 0.5 Polycell KMK-BUR2 12 / 1,2 Neonol 6 / 0.6 (use 5.6 ml, ρ = 1070 kg / m ³ ) Calcium chloride 200/20 Water 777 / 77.7.

All operations are carried out as in example 1.

BPBR has the following properties: ρ = 798 kg / m ^3, F = 4.5 cm ^3/30 min, η = 22 mPa · sec, τ ₀ = 254 dPa, θ _1/10 = 91/115 dPa, n = 0 , 37, T _s = -19 ° C:

Example 3

Prepare 1000 g BPBR, g / wt.%:

Saraksan-T 3 / 0.3 Polycell KMK-BUR2 15 / 1,5 Neonol 7 / 0.7 (use 6.5 ml, ρ = 1070 kg / m ³ ) Calcium chloride 160/16 Water 815 / 81.5.

All operations are carried out as in example 1.

BPBR has the following properties: ρ = 784 kg / m ^3, F = 4.7 cm ^3/30 min, η = 15 mPa · sec, τ ₀ = 134 dPa, θ _1/10 = 34/34 dPa, n = 0 , 43, T _s = -13 ° C.

Example 4

Prepare 1000 g BPBR, g / wt.%:

Saraksan-T 4 / 0.4 Polycell KMK-BUR2 15 / 1,5 Neonol 8 / 0.8 (use 7.5 ml, ρ = 1070 kg / m ³ ) Calcium chloride 230/23 Water 743 / 74.3.

All operations are carried out as in example 1.

BPBR has the following properties: ρ = 800 kg / m ^3, F = 4.0 cm ^3/30 min, η = 20 mPa · sec, τ ₀ = 163 dPa, θ _1/10 = 38/53 dPa, n = 0 , 45, T _s = -25 ° C.

Example 5

Prepare 1000 g BPBR, g / wt.%:

Saraksan-T 4 / 0.4 Polycell KMK-BUR2 14 / 1.4 Neonol 7 / 0.7 (use 6.5 ml, ρ = 1070 kg / m ³ ) Calcium chloride 270/27 Water 705 / 70.5.

All operations are carried out as in example 1.

BPBR has the following properties: ρ = 992 kg / m ^3, F = 2.0 cm ^3/30 min, η = 31 mPa · sec, τ _o = 230 dPa, θ _1/10 = 77/86 dPa, n = 0 , 47, T _s = -39 ° C.

Thus, the claimed technical solution meets the condition of novelty, inventive step, industrial applicability, that is, is patentable.

Claims (1)

A biopolymer drilling fluid comprising a xanthan type biopolymer, modified starch, a surfactant, calcium chloride and water, characterized in that it contains Saraksan-T as a xanthan type biopolymer, Polycell KMK-BUR2 as modified starch, and as surfactant - neonol in the following ratio of ingredients, wt.%:
Saraksan-T 0.2-0.5 Polycell KMK-BUR2 1.2-1.6 Neonol 0.6-0.8 Calcium chloride 15-27 Water rest