RU2490430C1 - Procedure for oilfield pipeline operation - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in compliance with the procedure qualitative and quantitative composition is defined for water produced at the well mouth or at output from a measuring group unit; concentration is calculated for mixed salts in water coming to the well from different sources considering periodicity of operation for one well or a group of wells in the collecting pipe or a measuring group unit. Calculation of the reaction termination of hard salts formation in a place of measurement, formed at mixture of different waters. A fluid flow velocity on the pipeline and place of depositions of salts is defined. The conclusion about working capacity of the equipment is made. Operation mode is changed for one well or for a group of wells in order to reach concentration of barium sulphate salts mixture at a measuring point less than 0.1 g/l according to calculation results. At that flow rate of the fluid in the pipeline is defined against an analytical expression. Shutdown of wells is considered as a varied mode of their operation. During shutdown period these wells are used for another purpose.

EFFECT: working efficiency of oilfield pipeline at active scale build-up.

1 ex, 4 tbl, 1 dwg

Description

The invention relates to the oil industry and may find application in the detection of scaling in the oil pipeline.

A known method of monitoring the technical condition of the well, which consists in pumping "labeled" fluid and measuring radioactivity before and after pumping. A precipitator of radioactive isotopes is sequentially pumped into the well, for example, an aqueous solution of sodium hydroxide and a “labeled” solvent — a 10% aqueous solution of hydrochloric acid activated by radioactive isotopes, the solvent being separated from the precipitator and process water by pillows from an organic liquid (RF Patent No. 357538 , published. 2000.01.20).

The method requires stopping the well and using special technical means. The method is complex and allows to determine violations of the casing string with a significant size.

Closest to the proposed invention in technical essence is a method of operating a producing well and oilfield pipeline, according to which the qualitative and quantitative composition of solid suspended particles and the composition of produced water at the wellhead or at the exit of a group metering unit are determined, and the concentration of mixing salts contained in waters flowing into a well from various sources, a collection pipe or in a group metering unit, calculation of completion the reaction of the formation of solid salts at the measurement site, resulting from the mixing of different waters, determining the rate of fluid flow through the pipeline, determining the location of salt deposition, making an opinion on the operability of the equipment (RF Patent No. 22325515, CL E21B 43/20, publ. 27.05,2008 - prototype).

The method allows to make a conclusion about the health of the oil field pipeline, but the method does not provide for the health of the oil field pipeline.

The proposed invention solves the problem of ensuring the operability of an oil field pipeline with active scaling.

The problem is solved in that, in the method of operating the oil field pipeline, samples are taken at flow lines of production wells, the quantitative composition of produced water at the outlet of the group metering unit is determined, and the concentration of salts formed from mixing the water entering the group metering unit from various wells is calculated the frequency of operation of one or a group of wells, calculate the end of the reaction of the formation of insoluble salts in the pipeline behind the group metering unit, determine Setting the rate of fluid flow through the pipeline, determining the location of the main salt deposition in the pipeline, change the operating mode of one or a group of wells to achieve a concentration of insoluble salts at the site of the main deposition of not more than 0.1 g / l, while the fluid flow rate through the pipeline is determined according to the formula:

Ud = Q _w / (1440 × Sgzu × t),

where Ud is the fluid flow rate through the pipeline, m / min,

Q _W - total fluid flow rate, m ³ / month.

Sgzu - sectional area of the prefabricated collector of a group metering installation, m ²

t - weighted average by the volume of produced water, the number of days of well operation per month.

SUMMARY OF THE INVENTION

When exploiting oil fields at a late stage of development, one of the main problems facing developers is the increase in salt deposition on equipment, which can lead to failure. With a large pool of wells and onshore pipelines, the question arises of early detection of scaling and deciding whether to repair or extend the overhaul period. The proposed method solves the problem of ensuring the operability of an oil field pipeline with active scaling due to early detection of scaling, i.e. at such a stage when the violation cannot yet be detected by other methods, and the appointment of measures that exclude active scaling. The problem is solved as follows.

During the operation of an oil field pipeline, the qualitative and quantitative composition of solid suspended particles and the composition of produced water at the wellhead or at the outlet of a group metering unit are determined. Barium sulfate is quantitatively determined in solid suspended particles, qualitatively - iron sulfide, calcium carbonate, gypsum, silicon oxide, etc. If necessary, quantification is possible.

Calculation of the concentration of mixing salts contained in the waters entering the well from various sources, prefabricated pipeline or in a group metering installation:

- chloride content, in terms of sodium chloride, C _NaCl , g / dm ³ ;

- content of sulfate ions (SO ₄ ² -), C _SO4 , g / dm ³ ;

- the content of barium ions (Ba ²⁺ ), C _Ba , g / DM ³ .

1. The data for the calculation of the group metering unit are summarized in table 1.

Table 1 Well number The flow rate of liquid, m ³ / day Total,% Water rate, m ³ / month Water rate in fractions, ni,% Analysis results Work days Chlorides g / l Sulfates g / l Barium, g / l The total flow rate in water (D _water ): m ³ / month Sumarno flow rate of liquid (L _Yid): ³ m / month Barium mixing concentration, g / l Sulfate mixing concentration, g / l Barium sulfate concentration, g / l Mineralization by chloride, g / l

Explanations for the table

Water flow rate (m ³ / month) - is defined as the product of three values: fluid flow rate, water cut, work days.

Total water production (D _water ) - is defined as the sum of the water production of all wells per month.

The specific fraction of produced water per well (ni) is determined by the ratio of the water production rate of each well per month to the total water production rate per group metering unit per month.

The concentration (g / l) of barium mixing (C * Ba) is determined by the formula:

C * Ba = ∑ (n _i , × CBa _i ).

The concentration (g / l) of sulfate mixing (C * SO ₄ ) is determined by the formula:

C * SO ₄ = ∑ (n _i × CSO ₄ ).

The concentration (g / l) of barium sulfate is determined as follows:

if C * Ba / 137≤C * SO _4/96, the C * BaSO ₄ = C * Ba × 1,7;

if C * Ba / 137≥C * SO _4/96, the C * BaSO ₄ = C * SO ₄ × 2,43.

The concentration (g / l) of chloride (C Cl) is determined by the formula:

CNaCl = 1.65∑ (n _i × CCl _i ),

where 1.65 is the conversion factor of Cl to NaCl.

Calculate the end of the reaction of formation of solid salts at the measurement site, formed by mixing different waters.

The graphical dependences of FIG. 1 were obtained in laboratory conditions from changes in the optical characteristics of solutions obtained by mixing sulfate and barite waters with various salinity of sodium chloride.

For intermediate sodium chloride concentrations, standard interpolation formulas can be used.

According to the values of CNaCl and CBaSO ₄ * according to the graphs of figure 1 determine the end time of the reaction t _p , min.

2. Perform the determination of the fluid flow rate through the pipeline. Data for the calculation of a group metering pump installation:

- The flow rate of wells Oskskv (m ³ / day), their water cut, (%).

- Diameter (internal) of the prefabricated collector of the group metering unit, D, mm.

Sectional area of the prefabricated collector of a group metering installation, m ²

Sgzu = (tm × D ² ) / 4

- The fluid flow rate through the pipeline, m / min, is determined by the formula:

Ud = Q _w / (1440 × Sgzu × t),

where Q _W - the total fluid rate, m ³ / month, is determined by the formula:

Q _Ж = ∑ (Qжскв _i × t _i );

t - weighted average in the volume of produced water, the number of days of well operation per month, is determined by the formula:

t (day) = ∑ (n _i × t _i ).

3. Determine the location of salt deposition.

The distance from the group metering installation to the beginning of the place of formation of salt deposits, m, is determined by the formula:

N = 0.5 Ud × t _r .

The distance from the group metering unit to the end of the place of formation of salt deposits, m, is determined by the formula:

Hk = Ud × t _p ;

t _p - time limit, maximum deposits occur at 0.5 t _p .

4. Make a conclusion about the operability of the pipeline. The amount of barium sulfate released from m ³ formation water is determined by the formula:

m (r \ d) = (CBaSO -C _{4 us.)} × Dvod / t.

_{We are} determined by table 2.

table 2 No. Mineralization by chloride, g / l (by NaCl) Saturation Concentration 'BaSO ₄ , C _us , g / l one 0 to 10 (0-16.5) 0.015 2 10 to 20 (16.5-33) 0,035 3 20 to 40 (33-66) 0,048 four 40 to 60 (66-99) 0,060 5 60 to 80 (99-132) 0,068

- concentrations calculated by the product of the solubility and ionic strength of the sodium chloride solution.

Concrete example

Operate the oil pipeline. The qualitative and quantitative composition of solid suspended particles and the composition of produced water at the wellhead or at the exit from the group metering unit are determined (table 3).

Table 3 Well number The flow rate of liquid, m ³ / day Water cut,% Water rate, m ³ / month Water rate in fractions, n _i % Analysis results Work days, t _i Chlorides, g / l Sulfates, g / l Barium, g / l 10812 73 88 1991.44 17.43% 30,636 0.0165 0.125 31 15003 31, 8 93 916,794 8.02% 144,285 0,0348 0 31 15702 92 80 2281.6 19.97% 33,601 0,0207 0.17 31 20204 75 80 1860 16.28% 39.53 0,055 0.12 31 20231 40 89 106.8 0.93% 111,673 0.9245 0 31 26839 90 91 2538.9 22.22% 45.46 0.0412 0.14 31 20209 6 fifty 93 0.81% 24,706 0,022 0.18 31 9515 164 94.9 1556.36 13.62% 27,671 0.0275 0.1 10 15749 3,5 fourteen 7.84 0.06% 16 20420 73 99 72, 27 0.63% 39.53 0,0385 0 one Summarized water rate (Water): m ³ / month 12421.8 The total fluid rate (Jed) m ³ / month 14410.8 Barium mixing concentration, g / l 0,112 Sulfate mixing concentration, g / l 0,112 Barium sulfate concentration, g / l 0.19 Mineralization by chloride, g / l 83,731

Calculation of the concentration of mixing salts contained in the waters entering the well from various sources, prefabricated pipeline or in a group metering installation.

A calculation is made of the end of the reaction of formation of solid salts at the measurement site, formed by mixing various waters.

Determined from the graphs of the drawing 1 t _p , about 27 minutes Determine the fluid flow rate through the pipeline.

D _zy = 159 mm, δ = 6.5 mm

S _gzu = (3.14 × (0.159-0.013) 2) / 4 = 0.017 m ²

Ud = Q _w / (1440 × Sgzu × t), m / min,

where t is the weighted average number of days of well operation per month in terms of the volume of water produced, is determined by the formula:

t (day) = ∑ (n _i × t _i ).

Ud = 14410.8 / (1440 × 0.017 × 28.18) = 21.22 m / min.

The places of salt deposition are determined:

N _n = 0.5 × Ud × t _p

N _n = 0.5 × 21.22 × 27 = 286 m

N _to = Ud × t _p

N _to = 21.22 × 27 = 573 m

Make a conclusion about the operability of the equipment.

In the range of 286-573 m from the group metering unit, barium sulfate deposits are formed at an average rate:

m (kg / day) = (C _BaSO4 -С _us ) × Drive / t

m = (0 / 19-0.068) × 12421.8 / 28.18 = 53.7 kg / day

of which 5.37 kg (0.1 m) are fixed on the wall, the rest is carried to the freight fleet. The time to narrow the bore of the pipeline in 2 times can be estimated using the formulas:

S * = _3/4 × S _gzu = 0.013 m2

M _BaSO4 = S * × ΔH × ρ _BaSO4 = 0.013 × 286 × 4500 = 16731 kg

T _0.5 = M _BaSO4 / m = 3116 days (about 8.5 years),

where ρ _BaSO4 = 4500 kg / m ^{3 the} density of barium sulfate.

We change the operating mode of a well with a high content of sulfate ions 20231 from 31 days of work to 3 days of work.

A calculation is made of the concentration of mixing salts contained in the waters entering the pipeline from various wells in the collection pipeline. A calculation is made of the end of the reaction of formation of solid salts at the measurement site, formed by mixing various waters. Determined from the graphs of the drawing 1 t _p , approximately 100 minutes Determine the fluid flow rate through the pipeline.

D _gzu = 159 mm, δ = 6.5 mm

S _gzu = (3.14 × (0.159-0.013) 2) / 4 = 0.017 m ²

Ud = Q _w / (1440 × S _gzu × t),

where t is the weighted average number of days of well operation per month determined by the formula

t (days) = ∑ (n _i × t _i )

Ud = 13290.8 / (1440 × 0.017 × 27.7) = 19.6 m / min

Table 4 Well number The flow rate of liquid, m ³ / day Water cut,% Water rate, m ³ / month Water rate in fractions, h _i ,% Analysis results Work days, t _i Chlorides, g / l Sulfates, g / l Barium, g / l 10812 73 88 1991.44 17.43% 30,636 0.0165 0.125 31 15003 31.8 93 916,794 8.02% 144,285 0,0348 0 31 15702 92 80 2281.6 19.97% 33,601 0,0207 0.17 31 20204 75 80 1860 16.28% 39.53 0,055 0.12 31 20231 40 89 106.8 0.93% 111,673 0.9245 0 3 26839 90 91 2538.9 22.22% 45.46 0.0412 0.14 31 20209 6 fifty 93 0.81% 24,706 0,022 0.18 31 9515 164 94.9 1556.36 13.62% 27,671 0.0275 0.1 10 15749 3,5 fourteen 7.84 0.06% 16 20420 73 99 72, 27 0.63% 39.53 0,0385 0 one Summarized water rate (Water): m ³ / month 11425 The total fluid rate (Jed): m ³ / month 13,290.8 Barium mixing concentration, g / l 0.121 Sulfate mixing concentration, g / l 0,041 Barium sulfate concentration, g / l 0,099 Mineralization by chloride, g / l 74.96

Determine salt deposition sites

N _n = 0.5 × Ud × t _p

Nn = 0.5 × 19.6 × 100 = 980

N _to = Ud × t _p

N _to = 19.6 × 100 = 1960.

Make a conclusion about the operability of the equipment.

In the range of 980-1960 m from the group metering unit, barium sulfate deposits are formed at an average rate:

m (kg / day) = (C _BaSO4 -С _us ) × Drive / t

m = (0.099-0.068) × 11425 / 27.7 = 12.8 kg / day,

Of these, 1.28 kg (0.1 m) are fixed on the wall, the rest is carried to the goods park.

The time to narrow the bore of the pipeline in 2 times can be estimated using the formulas:

S * = _3/4 × S _gzu = 0.013 m ²

M _BaSO4 = S * × ΔH × ρ _BaSO4 = 0.013 × 980 × 4500 = 57330 kg

T _0.5 = M _BaSO4 / m = 44789 days (about 122 years),

where ρ _BaSO4 = 4500 kg / m ³ is the density of barium sulfate.

Thus, with a decrease in the days of operation of a well with a high content of sulfate ions, a decrease in the concentration of salt mixing to 0.1 g / l is achieved and the problem of the formation of scale deposits in the field piping system is solved.

Regarding the operation of the well for 3 days indicated in the example, it is noted that this value is a particular quantity - only for this example, which is a kind of extreme in the possible amount of salt deposited. In other cases, the duration of the work can reach 15 days.

This type of well belongs to the well stock, whose work in oil production is periodic. During shutdown periods, such wells are used as observation, research, or injection wells. The periodic well operation fund is used in cyclic water flooding when the injection and production wells operate in a "work-stop" mode, which helps to change the gradients of fluid flows in the reservoir and increase the final oil recovery of the reservoir.

The construction costs of such wells are paid off due to the fact that these wells have a small diameter. The cost of their construction is two to three times less than the cost of building conventional wells. At the same time, the volume of construction of the above observation, research or injection wells can be reduced.

Claims (1)

A method of operating an oil field pipeline, including determining the qualitative and quantitative composition of produced water at the wellhead or at the exit of a group metering unit, calculating the concentration of mixing salts contained in the waters entering the well from various sources, taking into account the frequency of operation of one or a group of wells in the team pipeline or in a group metering unit, calculation of the end of the reaction of formation of solid salts at the measurement site, formed by mixing different waters, determine the rate of fluid flow through the pipeline, determining the location of salt deposition, making an opinion on the operability of the equipment, changing the operating mode of one or a group of wells to achieve a concentration of barium sulfate salts at the measurement site according to the calculation results of not more than 0.1 g / l, while the fluid flow rate through the pipeline is determined by the formula:
Ud = Q _w / (1440 · S _GZU · t),
where Ud is the fluid flow rate through the pipeline, m / min;
Q _W - the total fluid rate, m ³ / month;
S _GZU - sectional area of the prefabricated collector of a group metering installation, m ²
t - weighted average by the volume of produced water, the number of days of well operation per month.

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