RU2046932C1 - Method to kill wells - Google Patents

Abstract

FIELD: oil extraction industry. SUBSTANCE: method provides, that well is killed by squeezing liquid in amount of one volume of "НКТ" without its squeezing in formation, then they carry out lifting-lowering operations to place "НКТ" shoe on depth of production stratum, after that keeping annulus valve open blocking liquid of one volume of "НКТ" is pumped in with squeezing liquid damping in block of refilling. Then they exercise blocking and squeezing liquids further pumping in with keeping annulus valve shut. Hydrocarbon composition and/or oxygen-containing solvent is used as blocking liquid. Hydrocarbon composition is taken from hydrocarbon fractions of direct oil distillation: hexane, benzene, toluene, xylene, nephras "C 50/170; chemical oil processing; nephras A 120/200; nephras A 150/330; nephras C₅150/330; petrochemical industrial wastes; absorbents A-1 and A-2; pyrolysis light resin; butylenebenzene fraction; and oxygen-containing solvent from a number of low-molecular alcohols C₁-C₃, acids C₁-C₃ and ketones C₃-C₄. EFFECT: method provides maintaining and increase of boreholes production after repairs. 2 cl, 2 dwg, 2 tbl

Description

 The invention relates to the oil industry, in particular to methods for killing wells.

 An analysis of the results of well plugging in fields of Western Siberia characterized by high temperatures and low permeability of reservoirs (Shumilov V.A. et al. Protection and restoration of permeability of the near-wellbore zone during the development of fields in Western Siberia. M. VNIIOENG, 1980, p. 55) showed that killing wells with a known sequence of operations and traditional fluids based on calcium chloride, nitrate, etc. leads to a significant decrease in the productivity of production wells after killing.

 Known methods of killing wells using blocking fluids are not effective, in particular, because the initial blocking fluids are destroyed under high temperature conditions or are not suitable for low-permeability reservoirs by their viscosity characteristics.

A known method of killing wells with a preliminary injection of blocking fluid in front of the filling fluid (ed. St. USSR N 691556, 1979), in which liquefied gases CO ₂ , butane, propane are used as blocking fluid. The disadvantage of this method is the low efficiency at high reservoir temperatures.

 A known method of killing wells with a preliminary injection of blocking fluid in front of the filling fluid using polyglycols or VPK-4.2 as blocking fluid (ed. St. USSR N 1694868, 1988). The disadvantage of this method is the low efficiency in low permeability reservoirs.

A method is known well killing using as aqueous liquids blocking nonionic surfactants (such as OP-10, AP -12 ₉₎ and invert emulsion zero by filtration [1] A disadvantage of the method is its low efficiency for low permeable and high-temperature reservoirs.

The closest to the proposed method is well killing using as a blocking liquid micellar solution [2] However, the method is ineffective at high formation temperatures fields, since at temperatures above ⁶⁰ ° C, the bundle micellar solution to the original phase. The method is also not effective enough for low permeability hydrophilic, clayed reservoirs due to a sharp decrease in well productivity after killing.

 The aim of the invention is to preserve and increase the productivity of wells after killing in fields with high reservoir temperatures and hydrophilic clayey low-permeability reservoirs.

 The goal is achieved by pre-shutting the well with the filling fluid in the amount of 1 tubing object without pushing it into the formation and carrying out tripping operations with installing the tubing shoe at the depth of the reservoir, after which, with the annular valve open, blocking fluid is pumped in the amount of 1 tubing volume with discharge of the filling fluid into the topping unit, the subsequent injection of blocking and filling fluids is carried out with the annular valve closed, and a hydrocarbon composition is used as the blocking fluid w and / or oxygen containing solvent.

As the hydrocarbon composition, hydrocarbon fractions of a direct oil race are used: hexane, benzene, toluene, xylene, nephras C 50/170; chemical oil refining: Nefras A 120/200, Nefras A 150/220, Nefras C ₅ 150/330; petrochemical production wastes: asborbents A-1 and A-2, light pyrolysis resin, butylbenzene fraction, and oxygen-containing solvent from low molecular weight alcohols C ₁ -C ₃ , acids C ₁ -C ₃ and ketones C ₃ -C ₄ .

 Thus, the method involves performing a combined operation of killing and blocking wells without sequentially injecting non-aqueous blocking and filling fluids without squeezing the killing fluid into the reservoir and discharging it into the topping block, and the blocking fluid is injected into the reservoir practically at the depth of the reservoir. It is envisaged to use a hydrocarbon composition and / or an oxygen-containing solvent as a blocking fluid, depending on the permeability of the bottom-hole formation zone.

 The method eliminates the usual increase in injection pressure to values close to the fracture of the column, and saves and increases the productivity of the wells.

 Analysis of the essential features of a technical solution shows its compliance with the criterion of "Novelty."

ln

, где P_пл, Р_заб давления пластовое и забойной, МПа;
Q_пл суммарный приток жидкости из пласта; м³/с;
μ_пл вязкость нефти в пластовых условиях, мПа ˙ с;
R_пл, R_з, r_c соответственно радиусы контура питания, загрязненной зоны и скважины, м;
h эффективная мощность пласта, м;
К средневзвешенная по области фильтрации проницаемость пласта-коллектора при отсутствии дополнительного сопротивления в ПЗП, мкм²;
Фактически для адекватного математического описания реальных перепадов давлений требуется ввести в известное уравнение дополнительный член:
P_пл-P_заб=

ln

+ K′ln

, где K′

безразмерный коэффициент, учитывающий дополнительное сопротивление фильтрации, который разделяется на две составляющие:
первая

обусловлена присутствием водной фазы в ПЗП из-за глушения скважины жидкостями на водной основе при проведении текущих и капитальных ремонтов;
вторая (С) общим загрязнением ПЗП отложениями асфальто-смолопарафиновых веществ, образованием вязких эмульсий, твердыми частицами и др.For a single-layer formation, pressure loss with an uncontaminated bottom-hole formation zone (PZP) can be represented as
P _PL -P _Zab =

ln

where P _PL , P _Zab pressure reservoir and bottomhole, MPa;
Q _PL total fluid flow from the reservoir; m ³ / s;
μ _{PL the} viscosity of oil in reservoir conditions, MPa ˙ s;
R _pl, R _z, r _c respectively supply circuit radii contaminated zone and wells, m;
h effective reservoir thickness, m;
K weighted average permeability of the reservoir reservoir in the absence of additional resistance in the bottomhole formation zone, μm ² ;
In fact, for an adequate mathematical description of real pressure drops, an additional term is required to be introduced into the well-known equation:
P _PL -P _Zab =

ln

+ K′ln

where K ′

dimensionless coefficient taking into account the additional filtering resistance, which is divided into two components:
first

due to the presence of the aqueous phase in the PPP due to the killing of the well by water-based fluids during ongoing and major repairs;
the second (C) general pollution of the bottom-hole zone by deposits of asphalt-resin-paraffin substances, the formation of viscous emulsions, solid particles, etc.

(S_*) относительная фазовая проницаемость для нефти при предельной неподвижной водонасыщенности S_*.

(S _* ) relative phase permeability for oil at the limiting motionless saturation S _* .

A quantitative assessment is carried out in relation to the conditions of the Ust-Balykskoye field (BS ₁₀ layer).

R_пл=350 м
R_з=5 м
r_с=0,15 м
S_*=0,44
К_н (S_*)=0,279
Откуда Δ P_з/Δ P= 217; таким образом, учитывая симметричность приведенного примера, превышение энергии закачки на задавку скважины возрастает в 2,17 раза.The excess of the pressure drop with a contaminated PPP (first component) relatively uncontaminated is expressed

R _pl = 350 m
R _s = 5 m
r _s = 0.15 m
S _* = 0.44
K _n (S _* ) = 0.279
Whence Δ P _s / Δ P = 217; Thus, taking into account the symmetry of the given example, the excess of the injection energy for the well filling increases by 2.17 times.

=

Для низкопроницаемого гидрофильного коллектора Усть-Балыкского месторождения, при условии наличия только первой составляющей снижения коллекторских свойств ПЗП, увеличение притока нефти к скважине составляет порядка 2-2,5 раза в зависимости от радиуса зоны загрязнения, который определяется частотой и продолжительностью предыдущих ремонтов скважин, составом, плотностью и качеством жидкости глушения и др.Killing according to the proposed technical solution allows you to save or increase the productivity of the well. A similar assessment to the above shows that an increase in well production after killing can be expressed

=

For a low-permeability hydrophilic reservoir of the Ust-Balykskoye field, provided that there is only the first component of a decrease in the reservoir properties of the BFZ, the increase in oil flow to the well is about 2-2.5 times depending on the radius of the contamination zone, which is determined by the frequency and duration of previous well repairs, composition , the density and quality of the kill fluid, etc.

 The method is carried out by the following sequence of operations.

 Well plugging according to the standard method RD 39-0147009-6.030-86 with filling fluid taken in the amount of 1 volume of tubing, i.e. without selling it into the reservoir.

 The rise of the tubing string with a deep pump and the descent of the tubing string with the installation of the tubing shoe at a level of 1-2 m above the top of the reservoir.

 With the annular valve open, the injection of blocking fluid taken in an amount of 1 volume of tubing, with the discharge of the filling fluid into the topping unit.

, где V₂ внутренний объем НКТ;
Р₁ и Р₂ начальное и текущее пластовые давления соответственно;
ρ плотность задавочной жидкости.With a closed annular valve, the subsequent injection of blocking and filling liquids. Volume of the latter:
V ₁ =

where V _{2 is the} internal volume of the tubing;
P ₁ and P ₂ initial and current reservoir pressure, respectively;
ρ density of the filling fluid.

 In FIG. 1 presents a diagram of the implementation of the proposed method and the placement of equipment for its implementation. There is 1 layer; 2 tubing with funnel pen; 3 annular gate valve; 4 wellhead valve; 5 power unit; 6 manometer; 7 line to the topping unit; 8 block topping; 9, 10 tank trucks with filling and blocking liquids. Solid and dashed arrows show the directions of movement of the filling and blocking fluids, respectively.

 To confirm the proposed technical solution, experiments were conducted on core material from the Ust-Balyksky (BS 10), Yuzhno-Surgutsky (BS 10) and Pokamasovsky (Yu 1) deposits.

 In FIG. 2 shows a diagram of the proposed laboratory installation including: 11 constant flow sensor; 12 core holder; 13 voltage variator with a voltmeter; 14 pressure column for fluid; 15 column for chemicals; 16 differential pressure gauge; 17 capacity to determine the volume of the extracted fluid; 18 column with nitrogen; 19 cylinder with nitrogen; 20 temperature control unit; 21 contact thermometer; 22 heating tape; 23 filter; 24 racks connecting differential pressure gauges.

 In the core holder 12, a porous medium is packaged composed of core samples taken from the reservoir of the corresponding field. The displacement processes are carried out at a constant speed using a constant flow sensor 11. To maintain reservoir temperature in a porous medium, the core holder is wrapped with a heating tape 22, which is connected to the temperature control unit 20, and the unit is connected to a voltage variator.

 In the process of oil displacement using a differential pressure gauge 16 determine the pressure drop.

 The examples offered below reflect 4 possible in practice variants of the state of the bottomhole zone of the well: when the productivity of the well is reduced to zero due to the penetration of the kill fluid during repair work (examples 1-2); when the bottom-hole zone of the well is not contaminated with a kill fluid (example 3); when the productivity of the well decreases due to a breakthrough of injected water (example 4); when the productivity of the well is reduced due to the swelling of the clay material with an increase in water cut, as well as the deposition of paraffin deposits (example 5).

 The experiments in examples 1-4 were performed on the installation of fixed costs; the controlled parameter is the differential pressure. The experiments in example 5 was performed on the installation of constant pressure drops; controlled parameter is flow.

 PRI me R 1.

:

при этом перепаде давления принят за 1.To simulate well killing according to the basic version (killing with calcium chloride fluid, ρ 1.21 g / cm ³ ), the killing fluid was injected into the reservoir model BS ₁₀ , composed of cores of the Ust-Balyksky field. The permeability of the porous medium of oil 0.050 micron ² at a content of bound water is 37.9% of oil viscosity of 3.33 cps, reservoir temperature 78 ^° C pressure drop when filtering oil in said content of bound water is equal to 180 mm Hg Resistance Factor R

:

with this differential pressure is taken as 1.

Filtration of 1.0 V _{p of the} kill fluid led to an increase in the resistance factor to 3.5. Further injection of the kill fluid did not lead to an increase in the resistance factor.

The simulation of well completion after killing according to the basic version was to determine the resistance factor during oil filtration after the killing fluid. The initial resistance factor during filtration of 0.1 V _{p of} oil was 2.0. The pressure drop was stabilized by filtering 1.0 V _{p of} oil, while the residual resistance factor reached 1.2.

 Modeling the jamming process according to the proposed method consisted in pumping a blocking fluid after the jamming fluid.

Nephras C 50/170 was used as a blocking fluid. At the same time, the initial resistance factor decreased from 2.0 to 1.6 compared to oil when filtering 0.1 V _p . The pressure drop was stabilized by filtering a blocking fluid of 1.0 V _p , the residual resistance factor being 0.5. That is, according to laboratory experiments, the productivity of the well should double.

PRI me R 2. Modeling a well killing according to the basic version (killing with a solution of calcium nitrate ρ 1.20 g / cm ³ ) was carried out on cores of the BS ₁₀ formation of the South Surgut field. The permeability of the porous medium of oil 0.054 micron ² at a content of bound water is 35.4% of the oil viscosity is 3.21 cp, reservoir temperature 69 ^° C pressure drop when filtering oil in said content of bound water is 225 mmHg The resistance factor at this pressure drop is taken as 1.

Filtration of 1.0 V _{p of the} kill fluid led to an increase in the resistance factor to 3.2.

When modeling well development after killing according to the basic version, which consists in pumping oil after the killing fluid, the following was established. The initial resistance factor during filtration of 0.1 V _{p of} oil was 3.1. Pressure drop stabilization was achieved by filtering 1.0 V _{p of} oil, while the residual resistance factor reached 2.1.

 Modeling of the jamming process according to the proposed method was carried out in two versions.

In the first version, the simulation consisted of filtering the blocking fluid after the kill fluid, i.e. under the same conditions as in example 1. Nefras C 50/170 was used as a blocking fluid. Filtration of 0.1 V _p blocking fluid allowed to reduce the resistance factor to 1.8. Stabilization of the pressure drop was achieved by filtering 1.0 V _p blocking fluid, the residual resistance factor in this case was 1.1. That is, the use of Nefras C 50/170 as a blocking fluid for the conditions of the South Surgut field will restore well productivity.

In the second version, the simulation consisted of filtering blocking fluid immediately after oil filtration (i.e., the bottom-hole zone of the well does not contain jamming fluid). Synthetic alcohol was used as a blocking fluid. Filtration of 0.1 V _p blocking fluid led to an increase in the initial resistance factor to 1.7. When filtering 1.0 V _p alcohol, the resistance factor was already 0.9. The stabilization of the differential pressure was achieved by injecting 3.0 V _p alcohol. The resistance factor was 0.15. Subsequent filtration of 1.0 V _p nephras C 50/170 allowed to achieve a resistance factor of 0.07. Thus, the use of alcohol as a blocking fluid will reduce the filtration resistance of the porous medium by an order of magnitude.

PRI me R 3. Modeling killing wells according to the proposed method was carried out on cores of the Pokamasovskoye field Yu ₁ formation. The oil permeability at a content of bound water of 28.9% is 0.025 μm ² . Temperature 92 ^{° C} experiment, the oil viscosity 0.9 cps.

 The pressure drop during oil filtration with a content of bound water of 28.9% is 730 mm Hg. The resistance factor at this pressure drop is taken as 1.

Blocking fluid was filtered immediately after oil. As a blocking liquid, a mixture of nephras C 50/170 and synthetic alcohol was used in a ratio of 1: 1. Filtration of 0.5 V _{p of} blocking liquid led to an initial increase in the resistance factor to 1.7. When filtering 3.0 V _p the resistance factor was 0.8. Stabilization of the differential pressure was achieved by filtering 4.0 V _p blocking fluid, the resistance factor was 0.4.

PRI me R 4. Modeling killing wells according to the proposed method on the cores of the Pokamasovskoye field Yu ₁ . The oil permeability of 0.025 μm ² with a bound water content of 28.9%. The experimental conditions are the same as in example 3.

After oil filtration, fresh water was injected into the reservoir model (ρ 1.02 g / cm ³ ) (a variant of injection water breakthrough into production wells), while there was a sharp jump in pressure drop and filter attenuation, which is associated with the swelling of clay particles. After filtering 4.0 V _{n of} water, a blocking liquid was injected. As a blocking liquid, two mixtures of Nefras A 150/330 and acetic acid were used in a ratio of 60:40 and 40:60. Filtration of 0.5 V _p blocking fluid significantly reduced the pressure drop, while the resistance factor was 1.1 and 1.4, respectively. Filtration of 1.0 V _p blocking fluid made it possible to reduce the resistance factor of 0.8 and 1.1, respectively.

 PRI me R 5. Modeling killing wells according to the proposed method was carried out using a bulk porous medium with a constant pressure drop.

 A clayed bottomhole formation zone with sedimentation deposits was simulated. The porous medium was represented by quartz sand of various fractional composition with the addition of 5 wt. bentonite clay.

For formation of pollution caused by deposits of paraffin, was passed through a column of _claim 1,0 V 5% paraffin solution in benzene. Then, the benzene was evaporated by connecting a vacuum pump to the column by heating to 80 ^° C. Upon reaching a constant column weight, bound water equal to 37.5% was created in it by passing water vapor under vacuum.

Filtering was carried out at 80 ^° C Constant differential pressure is maintained on the pressure reduction tank.

, где Q расход нефти до обработки; Q' расход нефти после обработки.As a controlled parameter, the specific consumption was selected:

where Q is the oil consumption before processing; Q 'oil consumption after processing.

As the oil, the isoviscose model (μ 1.0 SDR) of oil from the Yu ₁ formation _{of the} Pokamasovskoye field was used. The volume of the rim of the blocking fluid was taken equal to 1.0 V _p . Control measurements of expenses were carried out when stationary filtering was achieved. The results of the experiments are placed in table. 1.

 An example of a specific implementation of the method in the field.

Jamming of the well Ust-Balykskoye field N 1353
Well characteristics: production facility BS ₁₀ ; artificial slaughter 2499 m; perforation interval 2463.2-2473.2, 2488.4-2490.4; reservoir pressure 24.0 MPa; permeability (interval average) 0.011 μm ² ; the average flow rate of 12-13 m ³ / day; water cut 78%
At the first stage, the well was plugged with CaCl ₂ solutions (ρ1.30) in one cycle (according to RD-39-0147009-6.030-86) without squeezing the killing fluid into the reservoir.

 At the second stage, hoisting operations with underground equipment are performed, while the tubing string is lowered to a depth of 1-2 m above the upper holes of the perforation interval. The tubing shoe is equipped with a funnel pen.

At the third stage, blocking fluid Nefras C 50/170 is pumped in an amount equal to 1 volume of tubing (7 m ³ ) with an open annular valve. The jamming fluid is then collected in the topping unit.

At the fourth stage, killing fluid is injected in one tubing volume of 7 m ³ with the annular valve closed, while the blocking fluid is forced into the reservoir.

After development, the flow rate of the well was 23-33 m ³ / day, the water cut of 80% Over 2.5 months, an additional 250 tons of oil were produced.

 A similar technology was applied in wells 1354, 1379, 1395. The results are summarized in table. 2.

 Thus, the proposed method of killing wells is effective in fields with high temperature and low permeability reservoirs, composed of hydrophilic clay rocks. The method ensures the preservation and even increase in productivity of wells after repair work. Serial equipment is used, as well as affordable large-capacity products, intermediate products and industrial wastes.

Claims (2)

 1. WAY OF SILENCING WELLS, including sequential injection of blocking and filling fluids into the bottomhole zone, characterized in that the well is pre-muffled with filling fluid in the amount of 1 volume of tubing without putting it into the formation and they carry out tripping operations with installation of the tubing shoe at the depth of the reservoir then, when the annular valve is open, blocking fluid is pumped in an amount of 1 tubing volume with the collection of filling fluid into the topping unit and the subsequent injection of blocking and filling fluid os fected at the annular gate valve is closed, and as a blocking liquid composition using a hydrocarbon and / or oxygen containing solvent. 2. The method according to claim 1, characterized in that the hydrocarbon composition is used from among the hydrocarbon fractions of the direct race of oil: hexane, benzene, toluene, xylene, nephras C 50/170; chemical oil refining: Nefras A 120/200, Nefras A 150/330, Nefras C ₅ 150/330; petrochemical production wastes: absorbents A-1 and A-2, light pyrolysis resin, butylene benzene fraction, and oxygen-containing solvent from low molecular weight alcohols C ₁ C ₃ , acids C ₁ C ₃ and ketones C ₃ C ₄ .

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