RU2445449C1 - Method for removing deposits from bore-hole pump and flow column - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves supply of solvent to bore-hole pump inlet by means of flexible wear-resistant small-diameter tube through annular space. The required amount of solvent is supplied under packer through its transient channel with non-return valve at the stopped bore-hole pump and closed damper at the outlet of flow column on the well head. After that, such solvent volume V₁ is supplied by means of bore-hole pump from the available solvent volume under the packer to flow column, which will fill in the flow column space free from deposits. Well is stopped for the period of time required for dilution of maximum possible part of deposits with volume V¹ _deposit; after that, during the second cycle the solvent with volume V₂ = V₁ + V¹ _deposit is pumped with bore-hole pump to flow column with further dilution of deposits at the stopped well. Such cyclic filling of flow column with the solvent is continued until the solvent coming out of flow column onto the well head contains inconsiderable content of deposit elements.

EFFECT: improving the cleaning quality.

2 cl, 1 dwg

Description

The present invention relates to technologies for downhole cleaning of underground equipment of producing and injection wells from deposits by injection of solvents and can be used in the oil and gas industry.

A known method of solvent delivery to the reception of a deep pump using an armored capillary hose according to the patent of the Russian Federation No. 2260677 (publ. September 20, 2005). The disadvantage of this technology is the inability to fill the deep pump and elevator pipes with a clean solvent without diluting it with well fluid. While to obtain the maximum dissolving effect from the solvent, it must be delivered to the sediment zone without dilution, i.e. in pure form.

Known coiled tubing technology [1], based on the descent into the elevator pipes and the annulus of the wells long flexible steel or reinforced pipes of small diameter for cleaning wells or risers (tubing) from tar and paraffin deposits (paraffin deposits). The method has two disadvantages. Firstly, the technology is not applicable in elevator pipes with a rod string inside as a drive to a plunger pump. When using a flexible pipe in the annulus, it is impossible to deliver the clean solvent in the required volume without loss to the elevated pipes with deposits, since a certain part of the solvent will float above the reception of the deep pump in the annulus under the action of Archimedes force. This will happen due to the difference in the density of solvents of paraffin and well products. The overwhelming majority of oils from Russian fields have a surface density of 850-950 kg / m ³ , and ASPO solvents produced by plants have a density of not more than 850 kg / m ³ . For example, the organic solvent of ZAO Neftekhim (Ufa) of the Sonpar brand - 5402 has a density of 720-820 kg / m ³ .

To increase the efficiency of cleaning the downhole pump and elevator pipes from deposits, in particular from ASPO, it is necessary to ensure the delivery of solvent to the elevator pipes through the intake of the deep pump (GN) in its pure form without mixing with the well fluid.

This goal is achieved by the fact that in the known method of cleaning the downhole pump and elevator pipes from deposits by injecting solvent into the downhole pump using a flexible wear-resistant small diameter tube, the annulus in the zone of the downhole pump is closed with a packer, and the solvent of the required volume is fed under the packer through its transition a channel with a non-return valve when the downhole pump is stopped and the shutter is closed on the exit of the elevator pipes of the well, after which from this volume of solvent the downhole pump the elevator pipes pump such a volume of solvent V ₁ that will fill the space in the column of elevator pipes that are free of deposits, the well stops for the time required to dissolve the largest possible portion of the sediments with a volume of V ¹ _ex , then the solvent volume is pumped into the elevator pipes with a second cycle to pump the volume of solvent V ₂ = V ₁ + V ¹ _ex , followed by waiting for the dissolution of part of the sediment when the well is stopped, such a cyclic filling of the elevator pipes with solvent is continued until the wellhead will not leave the solvent without a significant content of sediment elements, and if necessary, an additional volume of solvent is pumped under the packer for its subsequent injection into the lift pipes.

The number of solvent injection cycles into the lift pipes from its accumulated volume in the sub-packer zone is predicted when the inequality

Where:

V _otl - the estimated volume of deposits in the _downhole pump and elevator pipes;

V ₁ - the volume of solvent in the 1st cycle, necessary to fill the elevator space, free from deposits;

k is the coefficient of dissolving ability of the reagent;

n is the number of cycles of injection and waiting for the process of dissolution of deposits required for cleaning the downhole pump and elevator pipes from deposits.

We will explain in detail the essence of the parameters V _exl and _{K. The} estimated volume of deposits in the GN and elevator pipes V _{ex is} previously determined by one of the acceptable methods, for example, according to the method described in the invention according to the patent of the Russian Federation No. 2381359 (publ. 02.10.2010).

The parameter k shows the maximum solvent capacity of the solvent and is found by dividing the volume of the dissolved part of the sediment by the reacting volume of the solvent. The value of the coefficient is determined previously from laboratory or field tests. For most solvents, the parameter k is 0.1 ÷ 0.5, for example, for organic solvents ARPD produced in the Russian Federation, k = 0.10 ÷ 0.20.

Figure 1 is a diagram of the arrangement of the well for cleaning GN and elevator pipes from deposits according to the proposed method, where:

1 - a column of elevator pipes;

2 - a submersible pump of any type;

3 - packer;

4 - tube for supplying reagent;

5 - transition channel with a check valve;

6 - pumping device on the surface of the earth.

We will consider the implementation of the method by the example of an oil well, in which intense deposits of asphaltenes, resins and paraffins are constantly formed in the column of elevator pipes. The well is equipped with a rod deep plunger pump at a depth of 1000 m, lift pipes are tubing with an inner diameter of D = 62 mm, the rod string has an average d = 21 mm.

For such a well, it is necessary to do the following according to the claimed method:

1. The deep pump 2 after the next repair is lowered into the well together with the packer 5 and flexible wear-resistant pipe 4 on clean lift pipes 1 to a depth of 1000 m

2. After a certain time of operation, various diagnostic methods have established the following:

- the amount of paraffin in elevator pipes V _ex = 0.67 m ³ ;

- deposits are located in the elevator pipes evenly throughout the column from the pump to the mouth.

3. To remove deposits using organic solvent Sonpar-5402 ZAO "Neftekhim" with a density of 800 kg / m ³ . Well production is oil with a density of 880 kg / m ³ .

4. The total predicted volume of solvent V _{p is} found by dividing V _exl to

V _p = V _ex / k = 0.67 / 0.11 = 6.1 m ³ .

At the time of the first treatment, a volume of solvent should also be added to this volume of solvent to fill the flexible tube 4.

5. The operation of the downhole pump 2 is stopped, the valve at the outlet of the lift pipes at the wellhead is closed and the entire solvent of the required volume V _{p is} pumped by the pump 6 under the packer 3. Thus, at the intake of the pump 2, the pure solvent of the required volume of 6.1 m ³ is collected.

6. Organize the cyclic injection of solvent into the lift pipes using a deep pump 2. For the injection of solvent, the volume V in the lift pipes, free from deposits and boom columns, is determined by the 1st cycle:

7. Using a deep pump, 2.0 m ^{3 of} solvent is pumped into the elevator pipes and left alone for 2–4 hours, necessary for dissolving the paraffin wax. The volume of the dissolved part of the paraffin will be equal to V ¹ _ex = V ₁ · K = 2 m ³ · 0.11 = 0.22 m ³ .

8. In the second cycle of solvent injection into the elevator pipes, the required volume is equal to:

V ₂ = V ₁ + V ¹ _ex = V ₁ (1 + k) = 2.0 (1 + 0.11) = 2.22 m ³ .

9. In the third cycle, solvent of volume V ₃ should be pumped into the lift pipes:

V ₃ = V ₁ (1 + k) ² = 2.0 · 1.111 ² = 2.46 m ³ .

In just three cycles, it is necessary to feed the calculated volume of Sonpar-5402 solvent into the elevator pipes with a deep pump equal to:

, где n=3;

where n = 3;

V _p ^calculation = V ₁ + V ₂ + V ₃ = 2.0 + 2.22 + 2.46 = 6.68 m ³

It can be seen from the calculations that the calculated solvent volume V _p ^calculation slightly exceeded the forecast volume V _p (see paragraph 4), i.e. 6.68 m ³ > 6.1 m ³ per 0.58 m ³ . Therefore, in the third cycle, one should actually pump V ₃ ^f = V ₃ - (V _p ^calculation -V _p ) = 2.46-0.58 = 1.88 m ^{3 of the} solvent into the lift pipes.

Since this volume of solvent does not completely fill the internal volume of the elevator pipes, it is necessary to remove the third portion of the solvent from the elevator pipes in two stages with an intermediate time for the reaction of the solvent with ASPO so that this required reagent volume of 1.88 m ^{3 is} 2-4 hours and at the top of the elevator pipes.

If there is an excess of solvent in the oil and gas company, it is possible not to save it and pump solvent into the sub-packer space through a tube 4 in an excess volume equal to V _p ^calc = 6.68 m ³ . All these economic aspects of the claimed method are not the essence of the invention, therefore, these details are not included in the claims. One thing is clear, firstly, under the packer at the pump inlet, the solvent volume necessary for the calculations is preliminarily created, and then it is introduced portionwise into the elevator pipes using a submersible pump. In our opinion, these two combined technologies have signs of novelty and withstand examination on the criterion of “significant difference”.

It should be noted that if the required amount of solvent (V _p forecast or V _p ^calc count pumping cycles) was not sufficient for complete cleaning of tubings, it is always possible its additional volume to collect in the area below the packer and repopulate this volume tubing.

Feasibility from the use of the claimed method of cleaning the downhole pump and elevator pipes from deposits is based on improving the quality of leaching while reducing the amount of solvent per well treatment. The latter is especially true for oil wells, in the annular space of which there is a significant amount of borehole fluid. When using the previously known methods for delivering a solvent to a pump intake, a solvent inevitably mixes with this liquid, followed by a loss of initial solvent efficiency.

The source of information

1. Mini-coiled tubing as it is / Sergey Kablash, CJSC Fidmash // Time for coiled tubing. - 2009. - No. 29. - S.28-30.

Claims (2)

1. A method of cleaning the submersible pump and elevator pipes from deposits by delivering a solvent to the reception of the deep pump using a flexible, wear-resistant small diameter tube along the annulus, characterized in that the annulus in the zone of the deep pump is closed with a packer, and the solvent is supplied under the packer in the required volume through its transition channel with a non-return valve when the downhole pump is stopped and the shutter is closed at the outlet of the elevator pipes at the wellhead, after which the deep pump from the existing solvent EMA below the packer is pumped into the tubing such solvent volume V ₁ which fills the space in the column tubing, free from deposits, the well is stopped for the time required to dissolve the maximum possible part Fat volume V ¹ _exc, then a second cycle of deep pump in tubing pumped solvent volume V ₂ = V ₁ + V ¹ _ex followed expectation Fat dissolving stopped when the well is cyclically filling tubings solvent continues until op until tubing from the wellhead will not to leave the solvent without significant Fat content elements, wherein if necessary under the packer is pumped additional amount of the solvent for subsequent injection into the lift pipe. 2. The method according to claim 1, characterized in that the minimum required number of cycles of solvent injection into the lift pipes is previously determined from the conditions of the inequality:

,
where V _otl - the estimated volume of deposits in the _downhole pump and lift pipes;
V ₁ - the amount of solvent for the 1st cycle, necessary to fill the elevator space, free from deposits;
k is the coefficient of dissolving ability of the reagent;
n is the minimum number of injection cycles and waiting for the dissolution of deposits required for cleaning the pump and elevator pipes.