RU2348670C1 - Clay-free drilling fluid - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention concerns oil and gas industry, particularly clay-free drilling fluids (CFDF) used in drilling wells, including sloping and horizontal holes and side shafts at low formation pressure. Clay-free drilling fluid includes, wt %: Saraksan-T 0.3-0.8, Polycell KMK-BUR2 1.1-2.1, OP-10 0.5-1.2, water-repelling fluid GKZh-11N 1.0-2.9, the rest is water.

EFFECT: enhanced efficiency of well drilling at low formation pressure due to application of low-density CFDF with improved structural properties and rheological parametres ensuring enhanced containment and transportation properties while preserving filtration properties and improving environmental safety of storage.

1 tbl, 6 ex

Description

The invention relates to the oil and gas industry, in particular to non-clay drilling fluids (BBBR) used for drilling wells, including directional and horizontal, as well as sidetracks under low reservoir pressure.

Analysis of the current level of technology showed the following:

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

Bactericide LPE-11 0.2-0.25 Soda ash 0-0.35 FITO-RK starch 1,5-3,5 Biopolymer "Globe" 0.4-0.75 FHLS ferrochrome lignosulfonate 1.0-2.0 Water rest.

(see RF patent No. 2278890 of March 9, 2005, according to class C09K 8/08, published in Bull. No. 35, 2006).

The disadvantage of this BGBR is the lack of efficiency in drilling wells. This is due to the following reasons: the specified BBBR has increased values of filtration indicators, which is associated with the properties of the used FITO-RK starch, which does not completely dissolve in cold water (only 80-85%) and is characterized by high humidity (10.5%), uneven grinding and low swelling. This is due to the fact that FITO-RK is produced by an extrusion process in which partial splitting of polysaccharide units occurs. This starch is not able to form a thin, uniform crust on the filter surface. In this regard, the penetration of the BBBR filtrate with the water-soluble ingredients contained in it into the formation, their interaction with the formation fluids and minerals of the formation rock leads to the colmatation of the pore space by reaction products and, as a result, the reservoir properties of the reservoir. In addition, the loose thick filter cake formed during the filtration of the BBBR is one of the causes of complications associated with a decrease in the diameter of the barrel, excessive torque, puffs, and sticking of the drill string under pressure.

Known BBBR has low structural and mechanical properties, which is due to the insufficient strength of the gel (see Gel _10/10 in Example 12 of the test report) formed by the Globus biopolymer as a plant polysaccharide reagent, which has significant differences in the structure of macromolecules from microbial polysaccharides origin, in particular xanthan type biopolymers produced by the Xanthomonas campestris strain in a nutrient medium.

The specified BBBR has insufficient rheological properties to give it the necessary transporting and holding ability. The non-linearity coefficient of the prepared solution (n = 0.41) given in Example No. 3 of Table 2 of the patent does not correspond to its actual calculated value of 0.78, in accordance with the indices η _PL = 15 MPa · s and τ _о = 30 dPa (at rotation frequencies of 300 and 600 min ^-1 ), from which n is calculated (see Gray J.R., Darley G.S.G. Composition and properties of drilling agents (flushing fluids): transl. from English - M .: Nedra, 1985. - S.190-196.). Therefore, the BBBR with an increased n value of 0.78 does not possess the necessary properties of pseudoplasticity (n <0.5) and cannot contribute to the efficient conduct of well drilling operations. The insufficient rheological parameters are probably due to the physicochemical properties of the Globus biopolymer and FITO-RK starch, as well as to the diluting action of soda ash (Na ₂ CO ₃ ) used in the composition of BHBR to control the pH of the medium.

The disadvantage of this BBBR is the use in the composition of the chromium-containing reagent - FHLS, which does not contribute to reducing the environmental safety of the use of BBBR,

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

Xanthan Biopolymer 0.05-0.2 Modified Starch 1.15-2.0 Alkali metal hydroxide 0.045-0.16 Water Soluble Silicic Acid Salt 0.23-1.2 Surfactant MIG surfactant 0.3-1.0 Water rest,

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

The disadvantage of this BGBR is the lack of efficiency in drilling wells. This is due to the following reasons: due to the increased density of BBBR (more than 1000 kg / m ³ ) in wells with low reservoir pressures, its absorption can occur, which limits the use of this BBBR when drilling wells with different coefficients of anomalous reservoir pressure. The insufficiently low density is due to the low content of MIG surfactant, on the one hand, and the presence in its composition of silicic acid salt (Na ₂ SiO ₃ ), which reduces the effect of air entrainment, on the other hand.

Despite the fact that the specified BBBR has low values of the index of filtration properties, which is a positive quality of this solution, it is characterized by reduced structural and mechanical properties (see indicator Gel _10/10 in example No. 4 of Table 2 of the patent description). This is due to the low strength of the gel formed by the Rhodopol 23P brand biopolymer taken in insufficient quantities (0.1 wt.%), As well as the reduced strength of complex high molecular weight compounds (IUDs) formed by the interaction of the Rhodopol 23P brand biopolymer and modified starch, which have a significant effect on the strength of the gel structure.

This BGBR has insufficient rheological parameters to ensure high holding and transporting ability, which is determined by the nonlinearity coefficient n characterizing pseudoplastic properties. The non-linearity coefficient of the prepared solution (n = 0.48) given in Example No. 4, Table 2 of the patent specification does not correspond to its actual calculated value of 0.57, in accordance with the indices η _PL = 22.5 MPa · s and τ _o = 115 dPa (at rotation frequencies of 300 and 600 min ^-1 ), of which n is calculated (see Gray J.R., Darley G.S.G. Composition and properties of drilling agents (flushing fluids): transl. from English . - M .: Nedra, 1985. - S.190-196.). Therefore, BBBR with an increased n value of 0.57 does not possess the necessary properties of pseudoplasticity (n <0.5) and cannot contribute to the quality of well drilling operations. Probably, the insufficient rheological indices of BBBR are due to the low content of the Rhodopol 23P brand biopolymer in the formulation, which does not provide a manifestation of pseudoplasticity. Two of the ingredients included in the solution formulation (Na ₂ SiO ₃ and NaOH) belong to the second hazard class, 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 drilling wells with low reservoir pressure is increased due to the use of low density drilling rigs with improved structural and mechanical properties, as well as rheological indicators that provide increased holding and transporting ability when at the same time maintaining filtration properties and increasing the environmental safety of the application.

The technical result is achieved using the known BBBR, including xanthan type biopolymer, modified starch, nonionic surfactant, alkaline reagent, silicon-containing reagent and water, characterized in that it contains Saraksan-T as a xanthan type biopolymer, and - as modified starch - Polycell KMK-BUR 2, as a nonionic surfactant - OP-10, and as an alkaline and silicon-containing reagent - GKZH-11N in the following ratio of ingredients, m ac%:

Saraksan-T 0.3-0.8 Polycell KMK-BUR 2 1.1-2.1 OP-10 0.5-1.2 GKZH-11N 1.0-2.9 Water rest.

The inventive BBGR meets the condition of "novelty."

For the preparation of BBBR, Saraksan-T is used according to TU 2458-006-00480709-07, the production method is described in the patent of the Russian Federation No. 2252033 dated April 19, 2004, according to class А61К 47/36, С12Р 19/06, Polycell KMK-BUR 2 - carboxymethyl starch according to TU 2262-016-32957739-01, OP-10 according to GOST 8433-81, GKZh-11N according to TU 2229-276-05763441-99.

Saraksan-T is a free-flowing 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 the xanthan exopolysaccharide produced by the Xanthomonas campestris strain in the nutrient medium, up to 15% moisture, protein component residues, mineral background of the nutrient residue (CaCl ₂ , KH ₂ PO ₄ , MgSO ₄ , Fe ₂ (SO ₄ ) ₃ ), a protein of the formaldehyde complex.

The combined use of the ingredients used contributes to the production of BBBR, which has improved structural and mechanical properties and rheological parameters, which ensures effective drilling of wells, including horizontal and directional, as well as sidetracks under low reservoir pressures. This is due to the following processes. OP-10, which is a mixture of mono- and dialkylphenols containing an average of 9-10 carbon atoms in the alkyl chain and 10-12 groups of ethylene oxide per mole of product, is characterized by a high air-entraining effect. This, together with the ability of the protein component of Saraksan-T to air entrainment, contributes to the production of low density BBBR, which expands the range of its application when drilling wells with low reservoir pressures. Proteins (proteins) of the Saraxan-T formaldehyde complex, being surfactants, have some special properties that distinguish them from synthetic surfactants. The formation of an equilibrium adsorption layer is explained by the diffusion of globular molecules to the interphase surface and the deployment of a polypeptide chain on it, which prevents the outflow of fluid from the aerated system. Realization of the colloidal-physical properties of the used surfactant combination — nonionic OP-10 and hydrophobic GKZH-11N, which is an aqueous alkaline solution of sodium methylsiliconate, allows one to obtain BHBR including microscopic air bubbles, which, unlike foams, have a non-monomolecular shell with a hydrophilic surface, and protected by a two-layer shell surfactant with a hydrophobic surface and a layer thickened with polysaccharides (Saraksan-T and Polycell KMK-BUR 2) water.

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-BUR 2 polysaccharide chain, which has the basic (alkaline) properties, determines the chemical interaction of these ingredients with rapid formation during preparation IUDs of complex structure, modified with mono- and diethylene glycol ethers of alkyl phenols OP-10. This is due to the improved structural and mechanical properties of BBBR, determined by the strength of the gel after stirring the solution after 10 s and 10 min (Gel index _10/10 in the table of the test report).

The inventive BBGR has rheological indicators, 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 one to improve the rock removal and well cleaning due to the leveling (flattening) of the fluid 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 - viscometer readings at N ₁ rpm;

R ₂ - viscometer readings at N ₂ 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 BBBR formulation in the indicated amount provide lower values of the non-linearity coefficient n (0.30-0.40), which, taking into account the above, indicates its high holding and transporting ability. The necessary filtration properties of the claimed BHRD are provided due to the synergistic effect of the interaction of Saraksan-T and Polycell KMK-BUR 2, which have a similar empirical basis, but different structure and acid-base properties, which determine the formation of complex polysaccharide compounds of a complex type, which significantly increase the viscosity of the liquid phase of BHBR and contribute to the formation of a thin filter cake with increased strength. Confirmation of this can be seen when comparing the data on the filtration of BBBR given in Examples 10 and 11 of the test report, where, with other equal contents of the other ingredients of the solution (OP-10 and GKZH-11N), the absence of one of the remaining ingredients of Saraksan-T or Policell KMK- BUR 2 leads to a sharp increase in the filtration rate. Moreover, the decrease in filtration in Example 10 is less significant, which is due to the higher viscosity and strength of the gel of this formulation, and, consequently, to an increase in the density of the resulting filter cake due to this. In the presence of all ingredients (example No. 5), the BBBR has a filtering within acceptable values, which confirms the validity of the above conclusions.

The inventive BGBR in comparison with the prototype is environmentally safer, since it does not contain ingredients below hazard class 3. In addition, due to the lack of a solid phase in the composition of the BBBR, the technical and economic performance indicators of the bits increase.

The content of Saraksan-T in BBBR of more than 0.8 wt.% Is not economically and technologically feasible, since there is no significant improvement in the structural-mechanical and rheological properties with an increase in the amount of this ingredient.

The content of Polycell KMK-BUR 2 in BBGD is more than 2.1 wt.%, OP-10 is more than 1.2 wt.%, And GKZh-11N is more than 2.9 wt.% Leads to a deterioration of pseudoplastic properties (increases and), which holding and transporting ability of BBBR.

The content of Saraksan-T in BBBR is less than 0.3 wt.%, Polycell KMK-BUR2 is less than 1.1 wt.%, OP-10 is less than 0.5 wt.%, And GKZH 11N less than 1.0 wt.% Leads to an increase filtration, as well as the non-linearity coefficient n, which indicates the deterioration of the pseudoplastic properties of BBBR, a decrease in its transporting and holding ability. In addition, the structural and mechanical properties of BBBR are deteriorating, which together reduces the effectiveness of its use.

Thus, according to the above proposed BGDF 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 BBGR meets the condition of an inventive step.

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

Example (fishing)

The directional well of the Yamburgskoye oil and gas condensate field (Harvutinsky area) is being constructed with the aim of exploiting the Cenomanian deposits. Use the drilling rig BU 1600/100 EU with a typical drilling mud cleaning system.

Initial data

Conductor 245 mm Conductor descent depth 550 m Production tower 168 mm Depth of production casing 1530 m Cement mortar lift per conductor and production casing to the mouth Reservoir pressure 10.7 MPa.

For drilling a well under a production casing, the proposed BGRF in a volume of 100 m ³ (40 m ³ + 60 m ³ ), determined by the formula

V _BPBR = V _SLE + V _cs ,

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 BBBR with a ratio of ingredients, wt.%:

Saraksan-T 0.6 Polycell KMK-BUR 2 1,5 OP-10 0.9 GKZH-11N 1.9 Water 95.1

42 kg (0.6 wt.%) Saraksan-T are introduced into a water mixer filled with water in a volume of 6.66 m ³ (95.1 wt.%) and stirred for 1 h, after which 105 kg (1.5 wt.%) Polycell KMK-BUR 2. Stir until a homogeneous dispersion of the polymers, and then leave it to swell the polymers and the interaction of the ingredients for 2 hours, then add 59 l (0.9 wt.%) OP-10 with a density of 1070 kg / m ³ and 111 l (1.9 wt.%) GKZH-11N with a density of 1200 kg / m ³ . Stirring is carried out for another 0.5 hours until a homogeneous composition of BBBR is obtained.

Ready-to-use BBBR is pumped to the pumping and storage unit. Thus, the entire volume of BGBF is prepared for drilling a well under a production casing.

BGBR has the following properties: a density ρ = 700 kg / m ^3, filtration F = 3.2 cm ^3/30 min, the plastic viscosity η = 18 mPa · s, the dynamic shear stress τ _o = 282 dPa, the gel strength after 10 seconds and 10 min Gel _10/10 = 12/14 lb / 100 ft ² , static shear stress for 1 and 10 min θ _1/10 = 72/81 dPa, non-linearity coefficient n = 0.30.

Drilling under the production casing is carried out by the rotary-turbine method using a bit with a diameter of 215.9 mm with an average mechanical speed of 7 m / h with a productivity of the UNB-600 mud pump equal to 0.032 m ³ / s, which provides laminar flow with these structural and rheological parameters its flow regime in the annular space of the well.

In the process of drilling should be provided for the cleaning of BBBR from cuttings. For these purposes, it is advisable to use vibrating screens, rather than hydrocyclones (sand and sludge separators), in which the structure of the Navy formed during the interaction of Saraksan-T and Policell KMK-BUR 2 can be destroyed, which will inevitably lead to a decrease in the pseudoplastic properties of BBBR (increase in n), and consequently, to a 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 parameters of the BBBR are maintained at the level regulated by the introduction of additional quantities of biopolymer and KMK-BUR 2 as necessary. The density of the solution is regulated by adding OP-10 and GKZH11N.

Upon completion of drilling in the range of 550-1530 m using BHBR, the production string is lowered into the well and cementing operations are carried out.

The opening of the Cenomanian deposits is carried out by perforation using BGBR.

The use of BBBR with stable structural-mechanical, rheological, pseudoplastic and filtration properties when drilling wells at low reservoir pressures will improve the technical and economic performance of drilling.

Example No. 1 (laboratory)

To prepare 1000 g of BHBR in 971 ml (97.1 wt.%) Of water, 3 g (0.3 wt.%) Of Saraxan-T is introduced and stirred for 0.5 h, after which 11 g (1.1 wt. .%) Polycell KMK-BUR 2. Stir until a homogeneous dispersion of polymers is obtained, and then leave it to swell the polymers and react the ingredients for 2 hours, after which 4.7 ml (0.5 wt.%) Of OP-10 with a density of 1070 are added kg / m ³ and 8.3 ml (1.0 wt.%) GKZH-11N with a density of 1200 kg / m ³ . Stirring is carried out for another 0.5 hours until a homogeneous composition of BBBR is obtained.

BGBR has the following properties: ρ = 682 kg / m ^3, F = 4.0 cm ^3/30 min, η = 13 mPa · sec, τ _o = 144 dPa, Gel _10/10 = 7/8 lb / 100 ft ² , θ _1/10 = 29/34 dPa, n = 0.38.

Example No. 2

Prepare 1000 g of BBBR, g / wt.%:

All operations are carried out as in example 1.

BGBR has the following properties: ρ = 760 kg / m ^3, F = 3.2 cm ^3/30 min, η = 17 mPa · sec, τ _o = 292 dPa, Gel _10/10 = 15/18 lb / 100 ft ² , θ _1/10 = 96/101 dPa, n = 0.30.

Example No. 3

Prepare 1000 g of BBBR, g / wt.%:

All operations are carried out as in example 1.

BGBR has the following properties: ρ = 600 kg / m ³ O = 3.0 cm ^3/30 min, η = 19 mPa · sec, τ _o = 235 dPa, Gel _10/10 = 10/12 lb / 100 ft ² , θ _1/10 = 57/72 dPa, n = 0.36.

Example No. 4

Prepare 1000 g of BBBR, g / wt.%:

All operations are carried out as in example 1.

BGBR has the following properties: ρ = 700 kg / m ^3, F = 3.2 cm ^3/30 min, η = 18 mPa · sec, τ _o = 282 dPa, Gel _10/10 = 12/14 lb / 100 ft ² , θ _1/10 = 72/81 dPa, n = 0.30.

Example No. 5

Prepare 1000 g of BBBR, g / wt.%:

All operations are carried out as in example 1.

BGBR has the following properties: ρ = 784 kg / m ^3, F = 3.8 cm ^3/30 min, η = 22 mPa · sec, τ _o = 144 dPa, Gel _10/10 = 7/11 lb / 100 ft ² , θ _1/10 = 43/62 dPa, n = 0.40.

Example No. 6

Prepare 1000 g of BBBR, g / wt.%:

All operations are carried out as in example 1.

BGBR has the following properties: ρ = 842 kg / m ^3, F = 2.0 cm ^3/30 min, η = 28 mPa · sec, τ _o = 373 dPa, Gel _10/10 = 20/29 lb / 100 ft ² , θ _1/10 = 124/168 dPa, n = 0.33.

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

Table ACT laboratory tests of the claimed and well-known non-clay drilling fluids
Tested in May 2007 No. p / p The composition of clay-free drilling fluid, wt.% Clayless mud properties Biopolymer Starch Surfactant GKZH-11N Alkaline supplement Water ρ, kg / m ³ F, ^cm3 / 30 min η, MPa · s τ ₀ , dPa Gel _10/10 , lb / 100 ft ² θ _1/10 , dPa n The inventive drilling fluid one Saraksan-T 0.3 Polycell KMK-BUR 2 1.1 OP-10 0.5 1,0 - 97.1 682 4.0 13 144 7/8 29/34 0.38 2 0.8 1,2 0.6 1.4 - 96.0 760 3.2 17 292 15/18 96/101 0.30 3 0.5 2.1 1,2 2.9 - 93.3 600 3.0 19 235 10/12 57/72 0.36 four 0.6 1,5 0.9 1.9 - 95.1 700 3.2 eighteen 282 12/14 72/81 0.30 5 0.4 1.3 0.6 1.9 - 95.8 784 3.8 22 144 7/11 43/62 0.40 6 0.7 1.7 0.7 2,4 - 94.5 842 2.0 28 373 20/29 124/168 0.33 7 0.2 1,0 0.4 0.9 - 97.5 840 7.0 eleven 77 3/4 19/19 0.50 8 0.4 2.2 1.3 3.0 - 93.1 830 3.4 41 134 23/26 144/148 0.67 9 0.9 1,1 0.5 1,0 - 96.5 877 2.5 25 364 20/28 129/163 0.32 10 - 1.3 0.6 1.9 - 96.2 620 12.5 22 163 4/5 24/24 0.47 eleven 0.4 - 0.6 1.9 - 97.1 625 17.5 8 115 3/4 19/24 0.32 Analogue 12 Globe 0.6 FITO-RK 1,5 FHLS 2 Bactericide LPE-11 0.2 Na ₂ CO ₃ 0.35 95.35 920 5.5 fifteen thirty 6/7 38/53 0.78 Prototype 13 Rhodopol 23P 0.1 modified starch 2.0 PAV MIG 0,3 - NaOH 0.08 Na ₂ SiO ₃ 1.2 tech. 46.3 layer. 50.02 1098 2.0 22.5 115 5/6 7/8 0.57

Note:

1. The rheological properties of the solution were determined on a Fann-35A rheoviscimeter.

2. Filtration of the drilling fluid was determined on a Baroid filter press at ΔP = 0.1 MPa.

Claims (1)

Clay-free drilling fluid, including xanthan type biopolymer, modified starch, nonionic surfactant, alkaline reagent, silicon-containing reagent and water, characterized in that it contains Saraksan-T as a xanthan type biopolymer, and Polytsell KMK-BUR as modified starch 2, as a nonionic surfactant - OP-10, and as an alkaline and silicon-containing reagent - GKZH-11N in the following ratio of ingredients, wt.%:
Saraksan-T 0.3-0.8 Polycell KMK-BUR 2 1.1-2.1 OP-10 0.5-1.2 GKZH-11N 1.0-2.9 Water rest