RU2467049C2 - Method of preparing invert-emulsion drilling mud - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to well construction, particularly to methods of preparing hydrocarbon drilling mud, which is an invert emulsion and is used for flushing when drilling oil and gas wells with a strongly crooked hole, long distance wells and horizontal wells. In the method of preparing invert-emulsion drilling mud by mixing a hydrocarbon medium, an aqueous phase, an emulsifier and a complex reagent, the hydrocarbon medium and the emulsifier are mixed first, followed by addition of the complex reagent - mixture of synthetic latex and oxal, taken in volume ratio of 1:(0.1-5). The aqueous phase is then added to said components and the mixture is dispersed, wherein components are taken in the following ratio, wt %: hydrocarbon medium 30.0-80.0; emulsifier 1.0-4.0; said complex reagent 1.5-10.0; aqueous phase 6.0-67.5. The invention is developed in subclaims.

EFFECT: high dynamic and static shearing stress, low plastic viscosity, stability of the emulsion while maintaining stability of these parameters during temperature drop at the mouth and at the bottom.

7 cl, 2 ex, 2 tbl

Description

The invention relates to the field of well construction, in particular to methods for preparing a hydrocarbon-based drilling fluid, which is an inverse emulsion and is used for flushing while drilling oil and gas wells with a very curved well, large wells and horizontal wells.

The rheological properties of invert emulsion drilling fluids (hereinafter referred to as IER), as well as other drilling fluid systems, are determined by the ultimate dynamic and static shear stress, plastic and effective viscosity. The rheological properties of the ESI depend on the viscous properties of the dispersion medium (type and viscosity of the hydrocarbon liquid), the properties of the dispersed aqueous phase (volumetric content, the nature of the distribution of globules in size, degree of mineralization, etc.), the properties of surface-active substances (hereinafter referred to as surfactants) that provide emulsification and stabilization of the system (chemical composition, solubility in phases, concentration, thickness of the interfacial protective layers created by it and their rheological properties, etc.), and properties of the solid dispersed phase (concentration, st stump dispersion, surface character and its interaction with the liquid phases and the surfactant).

The technology of using well-known invert emulsion drilling fluids in most cases is aimed at solving the narrow problem of regulating to a greater or lesser extent the specific rheological parameter of hydrocarbon-based formulations and does not allow solving the problem of regulating the rheological properties of the formulations in a comprehensive manner. IERs must have high viscosity values at low shear rates to provide the necessary holding and carrying capacity; low values of plastic viscosity and sufficiently high values of dynamic shear stress (CSN) at high shear rates to prevent an increase in the pumping pressure of the compositions; as well as the ability to maintain the stability of these parameters when changing thermobaric conditions for well construction.

Currently, one of the most common ways of regulating the rheological parameters of the IEM is to change the ratio of the hydrocarbon medium and the aqueous phase. Increased rheological indices adversely affect the conditions of well flushing, which leads to an increase in the pumping pressure of the solution up to values that make it technically impossible to perform well flushing operations. Typically, in drilling practice, a decrease in the viscosity of hydrocarbon-based solutions is achieved by diluting the solution with the dispersion medium used. However, in this case, along with a decrease in plastic viscosity and DNS, the viscosity of the solution decreases at low shear rates, the sedimentation stability of emulsions decreases, the filtrate losses increase sharply, such systems become unstable to hold the finely dispersed solid phase in suspension, which is undesirable, especially when building shallow and horizontal wells. Therefore, the task boils down to the additional introduction of invert-emulsion drilling fluids of special available structural agents - stabilizers of the rheological and filtration properties of emulsions.

A known method is the production of emulsions of hydrocarbons, water and organophilic clays and their compositions according to the PCT application: CA 2007/000646 20070418 from 04/18/2007, transferring the PCT application to the national phase on November 19, 2008. A method for controlling the viscosity of an oil / water emulsion, which comprises the step of adding an effective amount of an emulsifying agent to an oil / water emulsion containing organophilic clay (OG) in order to provide the desired emulsion viscosity, where the emulsifying agent is selected from: a) any monosaturated C ₈ -C ₁₈ fatty acid (EFA); b) a mixture of two or more different C ₈ -C ₁₈ (NLC); C) a mixture of C ₈ -C ₁₈ NLC and at least one 2-5n unsaturated fatty acid; d) a vegetable oil selected from the group comprising safflower oil, olive oil, cottonseed oil, coconut oil, peanut oil, palm oil, palm kernel oil and canola oil; e) taly oil.

The disadvantage of this method is the fact that when introduced into the emulsion of oil / water containing an emulsifying reagent and organophilic clay (OG), there is an increase in all rheological properties, both dynamic shear stress and effective and plastic viscosity. The increase in rheological properties leads to a significant increase in the hydrodynamic resistances of the flushing of the well, which, in turn, leads to the need to reduce the flow rate of flushing fluid and, as a result, this leads to a deterioration in the cleaning of the wellbore, despite the high rheological components. When implementing the known method, the introduction into the emulsion of reagents with a fluidizing effect leads not only to a decrease in rheological characteristics, but also to destabilization of the emulsion.

In addition, the disadvantage of this known method is that the resulting drilling fluid contains in its composition a high colloidal solid phase (bentonite), the presence of which in the composition of the invert emulsion drilling fluid can have a negative (irreversibly clogging) effect on the opening reservoir.

Closest to the proposed method is a method of preparing an invert emulsion drilling fluid, according to which a mixture of hydrocarbon fluid, saline water, a surfactant emulsifier and synthetic latex are produced (V.N. Glushchenko “Latex-containing inverse emulsions”, “Drilling and oil” No. 1, 2007, p. 22-23). According to the results of studies of the resulting solution, the introduction of latex affects the increase in the values of the static shear stress (SSS) of the emulsions, causing an increase in their stability. In addition, the indicated source of information indicates that the combined introduction of latex and bentonite clay into the composition of the ESI revealed a synergy of their complex action in the solution: a decrease in the filtration rate and a noticeable increase in the SNA values were noted. The observed phenomenon is explained by the authors as the effect of joint hydrophobization of bentonite clay with an emulsion emulsifier and latex, giving it an increased ability to solvate hydrocarbons due to peptization. The fact of the chemisorption relationship of latexes with bentonite clay in the literature is confirmed experimentally.

However, there is a problem in the operational reduction of the rheological parameters of invert drilling fluids, especially in the construction of sidetracks. This is due to the increased structural and rheological parameters of hydrocarbon-based solutions, and as a result, the emergence of large hydraulic resistances in the annulus with small annular gaps. In addition, significant fluctuations in the structural and rheological properties of hydrocarbon-based solutions depending on temperature create certain difficulties in the operational control of the solution properties with a large temperature difference at the bottom and on the surface. Known IER obtained by the specified known method does not possess the indicated properties.

The technical result achieved by the proposed method is to obtain an invert emulsion drilling fluid, characterized by increased values of dynamic and static shear stress, reduced plastic viscosity and stability of the emulsion while maintaining the stability of these parameters when the temperature difference at the mouth and bottom.

The specified technical result is achieved by the proposed method for the preparation of an invert emulsion drilling fluid by mixing a hydrocarbon medium, an aqueous phase, an emulsifier and a complex reagent, while it is new that a hydrocarbon medium and an emulsifier are mixed first, then a complex reagent is added - a mixture of synthetic latex and oxal taken in a volume ratio of 1: (0.1 ÷ 5), then the aqueous phase is added to these components and the mixture is dispersed, while the components are taken in the following ratio % vol.%:

hydrocarbon medium 30.0-80.0 emulsifier 1.0-4.0 specified complex reagent 1,5-10,0 water phase 6.0-67.5.

As the hydrocarbon medium, diesel fuel, or low-viscosity mineral oils, or polyalphaolefins are used.

As the aqueous phase using industrial water, or produced water, or mineralized with salts of calcium chloride and / or magnesium, sodium chloride and / or potassium, potassium formate water.

As an emulsifier use Domultal, or Olenol, or Richmole 700, or Emultal.

As synthetic latex, latex of the type BS-50, or BS-65, or SKS-50KGP, or SKS-65GP is used.

As oxal, flotation reagent-oxal of grades T-66, or T-80, or T-92, or T-94 is used.

Organobentonite is additionally introduced into the invert emulsion drilling mud in an amount of 0.5-1% by weight.

, где τ₀ - значение динамического напряжение сдвига в Па, η - значение пластической вязкости в Па*с. Буровые растворы, полученные по заявляемому способу, обладают повышенной термодинамической устойчивостью, обеспечивающей сохранение указанных свойств стабильными при перепаде температур на устье и на забое, то есть при повышении температуры реологические характеристики ИЭР, приготовленных по заявляемому способу, уменьшаются незначительно, тогда как влияние температуры на реологические свойства известных ИЭР существенно изменяет свойства последних.Thanks to the implementation of the proposed method, it became possible to obtain low-viscosity hydrocarbon-based drilling fluids with satisfactory DNS values and gel strengths, that is, fluids with a high coefficient of coagulation structure formation

, where τ ₀ is the value of the dynamic shear stress in Pa, η is the value of plastic viscosity in Pa * s. Drilling fluids obtained by the present method have increased thermodynamic stability, ensuring that these properties are stable when the temperature difference at the wellhead and bottom, that is, when the temperature rises, the rheological characteristics of the IER prepared by the claimed method are slightly reduced, while the effect of temperature on the rheological The properties of known IER substantially change the properties of the latter.

Due to a certain sequence of input components and their claimed ratio, the above technical result is achieved. It was experimentally established that the introduction of complex reagent substances separately, and not in the form of a mixture, does not provide the necessary rheological properties of the drilling fluid. So, with the introduction of latex first, and then oxal, or vice versa, the resulting ESI have low rheological characteristics, low viscosity at low shear rate (VNSS) and K _C and filtering rates that are sufficiently high for the ESI.

Using in the implementation of the proposed method, either only latex or only oxal also does not give the desired results. For example, when only oxal in the amount of 0.5-5 vol.% Is introduced into the invert emulsion drilling fluid, the emulsion is diluted, i.e. there is a decrease in rheological characteristics, and with the introduction of only latex, the specified solution thickens to a “non-fluidity” state, which makes it non-technological. Apparently, this is due to the fact that oxal (a mixture of dioxane alcohols and their esters) plays the role of a diluent and reduces the viscosity of a hydrocarbon liquid due to the dissolution of high molecular weight substances. A decrease in the viscosity of the hydrocarbon component of the solution leads to a decrease in the viscosity of the system as a whole, which leads to coalescence of the system. To increase the stability of the emulsion, oxal is pre-mixed with latex, and this complex reagent gives stability to the system and increases its coagulation stability. When latex is introduced into the drilling fluid without preliminary mixing with oxal, coagulation of latex occurs, thereby leveling its stabilizing properties.

The proposed method was implemented in laboratory conditions. For its implementation, the following substances were used:

- hydrocarbon medium:

- - diesel fuel, GOST 305-82;

- - low viscosity mineral oils (industrial oil grades I-5A, I-8A, I-12A, I-12A ₁ , I-20A, GOST 20799-88; transformer oil, TU 38-401978-98);

- - polyalphaolefins (alpha-olefins of fraction C12-C14, TU 2411-058-05766801-96; alpha-olefins of fraction C16-C18, TU 2411-067-05766801-97);

- emulsifier:

- - Domultal TU 2458-014-7146133-2004;

- - Richmole 700, TU 2458-070-18947160-2008;

- - Olenol, TU 2458-008-18947160-2001;

- - Emul TU 6-14-1035-79;

- complex reagent:

- - flotation reagent-oxal grades T-66, T-80, T-92, T-94, TU-2452-029-05766801-94;

- - synthetic latex (styrene-butadiene latex type BS-50, GOST 15080-77, TU 2294-002-00148889-2004; styrene-butadiene latex type BS-65, TU 38.103550-84; styrene-butadiene latex type SKS-50KGP , TU 38.103156-88; latex butadiene-styrene type SKS-65GP, GOST 10564-75);

- water phase:

- - industrial water with a density of 1000 kg / m ³ ;

- - produced water with a density of 1180 kg / m ³ ;

- - mineralized water: industrial water, mineralized by the addition of calcium and / or magnesium chloride, sodium and / or potassium chloride, potassium formate with a concentration of these salts up to saturation.

The essence of the invention is illustrated by the following examples. The inventive method is implemented as follows.

Example 1. 200 cm ^{3 of} hydrocarbon medium is placed in a beaker - diesel fuel, 12 cm ^{3 of} Domulsal emulsifier are poured with stirring, after 10 minutes of mixing a complex reagent is added - a pre-prepared mixture of 8 cm ^{3 of} synthetic latex BS-50 and 8 cm ^{3 of} flotation reagent- oxal T-80, the mixture is stirred for 30 minutes, and with stirring on a mixer at 13000 rpm, 172 cm of the aqueous phase is slowly introduced into it - mineralized with calcium chloride at the rate of 558 g / dm ³ . The solution is then dispersed on a mixer at 16,000 rpm for 10 minutes. After that, the obtained invert emulsion drilling fluid is ready for use. The quantitative content of the components in the prepared drilling fluid is as follows, vol.%: Diesel fuel -50; domultal - 3; complex reagent - 4; mineralized water - 43, while the complex reagent consists of a mixture of synthetic latex BS-50 and flotation reagent-oxal T-80 in their volume ratio 1: 1.

Example 2. 280 cm ^{3 of} hydrocarbon medium is placed in a beaker - transformer oil, 8 cm ^{3 of} Richmole 700 emulsifier is poured with stirring, after 10 minutes of mixing a complex reagent is added - a mixture of 4 cm ^{3 of} synthetic latex SKS-50KGP and 16 cm ^{3 of} flotation reagent-oxal T-66, the mixture is stirred for 30 minutes, and with stirring at a mixer at 13000 rpm, 92 cm ^{3 of the} aqueous phase is slowly introduced into it - mineralized with sodium chloride at the rate of 311 g / dm ³ . The solution is then dispersed on a mixer at 16,000 rpm for 10 minutes. After that, the obtained invert emulsion drilling fluid is ready for use. The quantitative content of the components in the prepared drilling fluid is as follows, vol.%: Transformer oil - 70; Richmole 700 - 2; complex reagent - 5; mineralized water - 23, while the complex reagent consists of a mixture of synthetic latex SKS-50KGP and flotoreagent-oxal T-66 in their volume ratio of 1: 4.

Invert emulsion drilling fluids with a different content of components were prepared in a similar way.

In laboratory conditions, the following properties of the invert emulsion drilling fluids prepared by the proposed method were investigated:

- density (ρ, kg / m ³ ) - measured using a pycnometer;

- rheological properties — plastic viscosity (η, MPa · s), dynamic shear stress (τ ₀ , dPa), gel strength (Gel, dPa), while η, τ ₀ and Gel were measured on an OFITE viscometer; viscosity at low shear rate (VNSS, MPa · s) was measured on a VISCO STAR plus viscometer;

, где τ₀ - значение динамического напряжения сдвига в Па, η - значение пластической вязкости в Па*с (указанный коэффициент характеризует структурообразующую способность комплексного реагента в различных средах). С ростом К_C увеличивается транспортирующая способность потока, а также гидродинамическое давление струй бурового раствора, выходящих из насадок долота, что обеспечивает более эффективное разрушение горных пород на забое и рост механической скорости бурения. При этом высокие значения К_C желательно поддерживать за счет снижения пластической вязкости бурового раствора, а не увеличения его динамического напряжения сдвига.- To _C - the coefficient of coagulation structure formation was calculated by the formula

, where τ ₀ is the value of the dynamic shear stress in Pa, η is the value of plastic viscosity in Pa * s (this coefficient characterizes the structure-forming ability of the complex reagent in various media). With an increase in K _C , the transporting ability of the flow increases, as well as the hydrodynamic pressure of the jets of the drilling fluid leaving the bit nozzles, which ensures more efficient destruction of rocks at the bottom and an increase in the mechanical drilling speed. Moreover, it is desirable to maintain high values of K _C by reducing the plastic viscosity of the drilling fluid, rather than increasing its dynamic shear stress.

- electrical stability (ES, B) was measured on an OFITE electrical stability meter;

- filtration rate (Ф ₃₀ , cm ³ ), measured on a OFITE dynamic filter press at ΔР = 0.7 MPa;

- The temperature was measured with a mercury thermometer.

Data on the composition of the prepared by the proposed method invert emulsion drilling fluids are shown in table 1.

Data on the properties prepared by the proposed method invert emulsion drilling fluids are shown in table 2.

Laboratory test data shows the following:

- IER prepared by the proposed method (experiments 4, 5, 6, 9 and 10) are characterized by optimal properties, namely: a sufficiently high coefficient of coagulation structure formation, low filtration value, low plastic viscosity at a sufficiently high CSN value, high viscosity at low speeds shear, high stability (more than 500 V), as well as high strength values of the gel, allowing to hold drill cuttings and weighting agents;

- IER prepared by the proposed method, but with a deviation from the stated volume ratio of latex and oxal (experiment 7), have deviations in plastic viscosity and CSN, respectively, in the coefficient of coagulation structure formation, as well as in the value of VNSS and gel strength;

- IER, prepared according to the scheme, when the substances of the complex reagent are introduced separately, and not in the form of a mixture (experiments 11, 12), do not have the necessary rheological properties, so the introduction of latex and then oxal, or vice versa, leads to the fact that obtained IER have low rheological characteristics, low values of VNSS and K _C and filtration indicators high enough for IER;

- IER prepared with a deviation from the proposed method of introducing components (experiment 13) have low gel strengths, low coagulation coefficients of formation, sufficiently high filtering values for IER, low stability and low viscosity at low shear rates;

- IER prepared using only latex (experiment 2), are characterized by high values of plastic viscosity at low values of CSN, low values of K _C and low viscosity at low shear rates;

- IER prepared using only oxal (experiment 3), are characterized by complete filtration, low DNS and gel strength, low Kc and low viscosity at low shear rates;

- IER, prepared without the use of a complex reagent (experiment 1), have the following disadvantages: full filtration, low DNS and gel strength, low K _s and low viscosity at low shear rates;

- IER prepared by the proposed method, in which organobentonite is additionally introduced (experiment 8), are also characterized by high rheological characteristics, high values of gel strength, K _C , VNSS and ES, low filtration.

In the course of laboratory tests, studies were also conducted of the properties of IEM prepared by the proposed method at a temperature difference of 20 ° C to 90 ° C (such a temperature difference is possible in field conditions due to different temperatures at the wellhead and bottom hole). The results showed that the DNS score is reduced slightly, by only 4.2%; plastic viscosity decreases by 47.5%; while K _s increases by 45.3%; the filtration rate increases by 3.6% and remains acceptable for the IER; values of gel strength and electrical stability are practically unchanged.

Thus, the invert-emulsion drilling fluid prepared by the proposed method, due to its optimal properties in terms of rheological characteristics, low filtration, high coefficients of coagulation structure formation, high stability and viscosity at low shear rates, makes it possible to use it for washing in oil and gas well drilling in field conditions with a very curved trunk, wells with a large laying and horizontal wells with a large temperature difference at the mouth and on the bottom .

table 2
Data on the properties of the invert emulsion drilling fluids and prototype prepared by the proposed method No. of solution from table 1 ρ, kg / m ³ F, ^cm3 / 30 min η, MPa * s τ ₀ , dPa The strength of the gel, dPa ES, V T, ° С K _C , s ^-1 VNSS, MPa * s one 1105 complete 31 28.8 10.2 / 15.3 497 22 92.9 8509 2 1100 2.0 62 81.6 30.7 / 40.9 580 22 131.6 10341 3 1100 complete thirty 24 0 / 2,6 463 23 80.0 8454 four 1100 1,6 45 144 25.6 / 40.9 660 23 320,0 26517 5 952 1,0 73 168 51.1 / 61.3 926 23 230.1 15266 6 1083 0.4 60 182.4 61.3 / 66.4 849 22 304.0 29942 7 1001 2,8 26 28.8 5.1 / 5.1 327 22 110.8 9555 8 1050 0.2 twenty 110,4 25.6 / 30.7 701 23 552.0 48483 8a 1050 0 17 100.8 20.44 / 25.6 618 fifty 592.9 37825 9 1072 1,5 85 177.6 46.0 / 56.2 520 22 208.9 16214 10 870 1,2 25 100.8 20.4 / 25.6 533 23 403.2 28750 10a 870 0.8 twenty 96 15.33 / 15.33 502 fifty 480.0 21581 eleven 1005 4.0 35 72 10.2 / 15.3 405 22 205.7 12143 12 1042 4.4 twenty 19.2 5.1 / 10.2 187 22 96.0 8944 13 931 8.6 132 100.8 17.9 / 23.0 45 23 76,4 8238

prototype fourteen 1050 4.8 70 67.2 5.1 / 5.1 280 22 96 9524 fifteen 1048 2.2 78 100.8 20.4 / 25.6 360 22 129.2 11753 15a 1048 2.1 45 62,4 15.33 / 20.44 303 fifty 138.7 8461 16 1048 1,0 89 216 40.9 / 51.1 600 22 242.7 15835

Claims (7)

1. A method of preparing an invert emulsion drilling fluid by mixing a hydrocarbon medium, an aqueous phase, an emulsifier and latex, characterized in that the hydrocarbon medium and emulsifier are mixed first, then a complex reagent is added - a mixture of synthetic latex and oxal taken in a volume ratio of 1: (0.1 ÷ 5), then the aqueous phase is added to these components and the mixture is dispersed, while the components are taken in the following ratio, vol.%:
hydrocarbon medium 30.0-80.0 emulsifier 1.0-4.0 specified complex reagent 1.5-10.0 water phase 6.0-67.5 2. The method according to claim 1, characterized in that diesel fuel or low-viscosity mineral oils or polyalphaolefins are used as the hydrocarbon medium. 3. The method according to claim 1, characterized in that as the aqueous phase using industrial water, or produced water, or mineralized with salts of calcium and / or magnesium chloride, sodium chloride and / or potassium, potassium formate water. 4. The method according to claim 1, characterized in that as an emulsifier use Domultal, or Olenol, or Richmole 700, or Emultal. 5. The method according to claim 1, characterized in that as a synthetic latex use latex type BS-50, or BS-65, or SKS-50KGP, or SKS-65GP. 6. The method according to claim 1, characterized in that the flotation reagent-oxal grades T-66, or T-80, or T-92, or T-94 are used as oxal. 7. The method according to claim 1, characterized in that the invert-emulsion drilling fluid is additionally introduced organobentonite in an amount of 0.5-1 wt.%.