RU2484238C1 - Method for preventing deposits of non-organic salts - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: in the method preventing the deposit of non-organic salts in commercial oil and gas equipment including series pumping to the bottomhole zone of formation of solution fringes, solution of inhibitor of salt deposition and hydrophilic displacement fluid; as a solvent, mutual solvent is pumped; salt deposition inhibitor is pumped in water solution of potassium chloride and as hydrophilic displacement fluid there pumped is the above water solution of potassium chloride; at that, as mutual solvent, there pumped is butyl cellosolve or mixture of solvents at the following component ratio, wt %: methanol 10, acetone 50, butyl cellosolve 35, dimethyl sulphoxide 5, salt deposition inhibitor is pumped in water solution of potassium chloride at the component ratio, wt %: salt deposition inhibitor 10, potassium chloride 1-2, fresh water is the rest; as hydrophilic displacement fluid there pumped is 1-2% of potassium chloride solution in fresh water; as salt deposition inhibitor, inhibitor of organophosphorous type is used.EFFECT: minimisation of risks of damage to the formation owing to changing phase permeabilities and swelling of clays, reduction of corrosion risks and risks due to formation of slightly soluble products of interaction of components of the composition with rocks of the formation and occasionally produced water.7 ex, 7 dwg

Description

The invention relates to the oil industry and can be used to prevent the formation of deposits of inorganic compounds of salts during oil production in wells with a working condition of casing strings and equipped with ESP.

Oil production processes are accompanied by undesirable deposits of inorganic salts in the bottom-hole zone of the formation, on underground and above-ground equipment, on the walls of wells, and in oil and gas production communications of the product collection and preparation system. To prevent salt deposits, chemical treatment of wells with scale inhibitors introduced into the formation is widely used. The processing technology consists in periodically selling an aqueous solution of an inhibitor of salt deposition in the bottomhole zone in the form of a rim with a squeezing liquid, adsorption of the inhibitor on the surface of the rock and its gradual desorption during the selection of products from the well. The removal of the inhibitor by the produced fluid (after the well was put into operation and put into operation) to the minimum required concentrations required for inhibition determines the after-effect period and the period of protection of the oilfield equipment from salt deposition and the time between the inhibitor sales.

A known method of preventing salt deposition in oilfield equipment by entering the bottom composition of the well of the following composition,% wt .:

Nitrilotrimethylphosphonic acid 4.97-13.57 Hydrochloric acid 11.24-23.74 Water rest,

and selling it into the reservoir by selling liquid at the same time produced by water (AS USSR N996721, E21B 43 / 12.1980).

A known method of preventing scaling in oilfield equipment, which is as follows. 0.5-5.0% wt. a pre-prepared inhibitor solution in produced water, acidified to a pH of less than 2.0 hydrochloric acid and containing at least 2.0 g / l of calcium ions. Before or after injection of the inhibitor solution, 0.5-2.0% wt. a solution of soda or alkali. An inert (hydrophobic) liquid is pumped as a buffer layer in order to avoid premature reaction between a solution of soda or alkali and a solution of an inhibitor. Then a hydrophobic squeezing liquid is injected gas condensate to push the mixture deep into the reservoir. The use of a hydrophobic selling fluid gives the known method a bifunctional character, aimed at the same time to treat oil-saturated reservoirs from asphalt-resin-paraffin deposits (AS USSR N1268715, E21B 37/06, 1983).

The known method (RU 2070910, C09K 3/00, 1996), in which for treatment of a well a composition is introduced containing nitrilotrimethylene phosphonic acid, hydrochloric acid, hydrofluoric acid (KFVK) and water in the following ratio of components,% wt .:

Nitrilotrimethylene Phosphonic Acid 0.2-0.5 Hydrochloric acid 8.0-13.0 Hydrofluoric Acid 1.0-3.0 Water - the rest.

However, these methods do not always provide long-term protection of the equipment of the wells from scaling, the main salvo discharge of the inhibitor occurs during the first day, during processing there is a risk of damage to the formation and changes in its phase permeability, which leads to a decrease in productivity, therefore, in some cases they are ineffective and not economically justified.

Closest to the proposed technical solution for the purpose and technical essence, taken as a prototype, is a method of preventing scaling in oilfield equipment, which is carried out as follows (RU 2320852, E21B 37/06, 2007). Successive injection of the rims of the solvent, the rims of the inhibitory solution, the rims of the alkali, and the rims of the hydrophilic displacement fluid are carried out into the well. In this case, the solvent used is: aliphatic, aromatic hydrocarbons (hexane, petroleum ether, nefras), organic solvents (benzene, toluene fraction). The composition of the inhibitory solution includes,% wt .:

Organophosphorus Compounds 1 ÷ 15 Hydrochloric acid 6 ÷ 23 Hydrofluoric acid 0,1 ÷ 5 Water 57 ÷ 92.9

The organophosphorus compounds used are: nitrilotrimethylphosphonic acid (NTP), hydroxyethylidene diphosphonic acid (HEDP), sodium salts of nitrilomethylene phosphonic acids, polyaminomethylene phosphonates, sodium hexametaphosphate, and salt melt.

As alkali, a universal reagent for oil production (RDN-U) is used.

A hydrophilic selling liquid is an aqueous solution of alkyl sulfonate reagents or polyethylene glycol monoalkyl phenyl ether reagents.

However, the use of a similar composition of the inhibitory solution due to the presence of acid reagents in it can cause an increase in corrosion processes in wells. The presence of hydrofluoric acid in the composition can lead to the formation of sparingly soluble calcium fluoride with possible contact of the composition with formation water and formation rocks containing calcium ions. Due to the fact that the pre-spotting of the hydrocarbon solvent is used, there is a risk of introducing an inhibitory solution into the oil-saturated intervals and changes in the phase permeabilities of oil and water.

The objective of the invention is to minimize the risks of damage to the formation due to changes in phase permeability and swelling of clays, reduce corrosion risks and risks associated with the formation of sparingly soluble products of the interaction of the components of the composition with the rocks of the formation and produced water. The use of a pre-spot of a mutual solvent provides an increase in the penetrating ability of aqueous solutions of the inhibitor in low-permeability zones of the formation, which leads to an increase in the adsorption efficiency of scale inhibitors and to a longer removal of the inhibitor with produced fluid during well operation.

The problem is solved in that the proposed method for preventing the deposition of inorganic salts in oil and gas equipment, including the sequential injection of solvent rims, a solution of a scale inhibitor and a hydrophilic squeezing fluid into the bottomhole formation zone, is characterized in that a mutual solvent is injected as a solvent, and a scale inhibitor is pumped in water a solution of potassium chloride and as a hydrophilic selling fluid, the indicated aqueous solution of chloride is pumped potassium.

As a mutual solvent, butyl cellosolve or a mixture of solvents is pumped in the following ratio, wt.%:

methanol 10 acetone fifty butyl cellosolve 35 dimethyl sulfoxide 5,

scale inhibitor is pumped in an aqueous solution of potassium chloride at a ratio of components,% wt.:

scale inhibitor 10, potassium chloride 1-2, fresh water rest,

and (1-2)% solution of potassium chloride in fresh water is injected as a hydrophilic selling fluid, an organophosphorus type inhibitor is used as a scale inhibitor.

Organic solvents having a wide range of compatibility with the water and oil phases are used as a mutual solvent, for example:

option 1 - butyl cellosolve

option 2 - a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%

To reduce the risk of swelling of the clay component of reservoirs in water-injected crushed into the reservoir, it is proposed to use a potassium chloride clay swell suppressor [Ryabokon S.A. Process fluids for completion and repair of wells: Monograph. - M .: NPO "Drilling", 2006. - 230 p.] In the amount of 1-2% wt.

Due to the absence of acids in the composition, this method is not corrosive.

EFFECT: reduction of formation damage risks and minimization of corrosion processes of well equipment during formation treatments. Due to the use of a mutual solvent, the penetration of the aqueous solutions of the inhibitor into the low-permeability zones of the formation increases, which leads to an increase in the adsorption efficiency of scale inhibitors and to a longer removal of the inhibitor with the produced fluid during well operation.

The inventive method is a sequential introduction into the reservoir of the following rims:

- preliminary stage is a mutual solvent, for example:

option 1 - butyl cellosolve

option 2 - a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%

- the main stage is an aqueous solution of a scale inhibitor of the organophosphorus type, composition:

10% wt. scale inhibitor, 1-2% wt. potassium chloride, fresh water - the rest;

- Selling - a solution of 1-2% wt. potassium chloride, fresh water - the rest.

Example 1. When carrying out repairs on well 674 of the Komsomolskoye field, the following rims were crushed into the formation:

5 m ³ mutual solvent, which is a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%

25 m ^{3 of a} 10% solution of scale inhibitor of organophosphorus type Iproden S-1 (TU 2458-001-45305665-2006), in a 1% solution of potassium chloride,

45 m ³ 1% potassium chloride solution.

The dynamics of the production of water and oil before and after application of the proposed method is shown in figure 1. The arrow indicates the date of processing the well, the solid line indicates the flow rate of the well before and after the treatment, the dashed line indicates the flow rate of the well before and after the treatment, the triangles indicate the water content of the well before and after processing.

It can be seen that after applying the proposed method increased the flow rate of liquid and oil, water cut decreased.

Example 2. When carrying out repairs at well 651 of the Southern dome of the Kharampur field, the following rims were crushed into the formation:

no mutual solvent was used;

28 m ^{3 of a} 10% solution of scale inhibitor of organophosphorus type Iproden S-1 (TU 2458-001-45305665-2006) in a 1% solution of potassium chloride;

40 m ³ 1% potassium chloride solution.

The dynamics of the production of water and oil before and after the crushing in the reservoir is shown in figure 2. The arrow indicates the date of processing the well, the solid line indicates the flow rate of the well before and after the treatment, the dashed line indicates the flow rate of the well before and after the treatment, the triangles indicate the water content of the well before and after processing.

Comparison of the treatment results given in examples 1 and 2 show that when using a mutual solvent, negative changes in the production of liquid and oil did not occur, while without a mutual solvent, a decrease in oil production rate and an increase in water cut in well production are observed. The explanation for this is as follows. Since the mutual solvent is pumped in the very first rim, when the well is put into operation it is the last to leave the formation and restores the phase permeability of water and oil, which significantly reduces the risk of disturbing the permeability of the formation in oil.

Example 3. Comparison of the removal of scale inhibitor of the organophosphorus type Iproden S-1 (TU 2458-001-45305665-2006) from the core model using a mutual solvent, which is a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%

according to the proposed method and without its use (figure 3) in the laboratory.

As you can see, the addition of a mutual solvent allows you to reduce the initial salvo removal of the inhibitor and, accordingly, to ensure a longer removal of the inhibitor in time to a minimum working concentration.

Example 4. When carrying out repairs on well 6389 of the Priobskoye field, the following rims were crushed into the formation:

4.2 m ³ mutual solvent WAW85202, which is butyl cellosolve,

50 m ^{3 of a} 10% solution of a scale inhibitor of organophosphorus type SCW82697 in a 1% solution of potassium chloride,

150 m ³ 1% potassium chloride solution.

A comparison of the mean time between failures before and after processing is shown in FIG. The shaded column on the left indicates the mean time between failures of the well equipment before processing the well, and the column on the right indicates the mean time between failures of the well after processing. The numbers indicate the MTBF, expressed in days. As you can see, after processing the proposed method, the mean time between failures of the equipment of the well has increased.

Example 5. When carrying out repairs at well 939 of the Prirazlomnoye field, the following rims were crushed into the formation:

3 m ³ mutual solvent, which is a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%;

28 m ^{3 of a} 10% solution of a scale inhibitor of organophosphorus type SCW82697 in a 1% solution of potassium chloride;

70 m ³ 1% potassium chloride solution.

A comparison of the mean time between failures before and after processing is shown in FIG. The shaded column on the left indicates the mean time between failures of the well equipment before processing the well, and the column on the right indicates the mean time between failures of the well after processing. The numbers indicate the MTBF, expressed in days. As can be seen, after processing the proposed method, the mean time between failures of the equipment of the well increased.

Example 6. When carrying out repairs at well 8760 of the Priobskoye field, the following rims were crushed into the formation:

6 m ³ mutual solvent, which is a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%;

85 m ^{3 of a} 10% solution of a scale inhibitor of organophosphorus type Iproden S-1 (TU 2458-001-45305665-2006) in a 1% solution of potassium chloride;

210 m3 of 1% potassium chloride solution.

A comparison of the mean time between failures before and after processing is shown in FIG. 6. The shaded column on the left indicates the mean time between failures of the well equipment before processing the well, and the column on the right indicates the mean time between failures of the well after processing. The numbers indicate the MTBF, expressed in days. As you can see, after processing the proposed method, the mean time between failures of the equipment of the well has increased.

Example 7. When carrying out repairs on well 12376 of the Komsomolskoye field, the following rims were crushed into the formation:

5 m ³ mutual solvent, which is a mixture of organic solvents of the following composition:

methanol 10% acetone fifty% butyl cellosolve 35% dimethyl sulfoxide 5%;

20 m ^{3 of a} 10% solution of a scale inhibitor of organophosphorus type Iproden S-1 (TU 2458-001-45305665-2006) in a 2% solution of potassium chloride;

45 m ^{3 of a} 2% potassium chloride solution.

Comparison of MTBF before and after processing is shown in Fig.7. The shaded column on the left indicates the mean time between failures of the well equipment before processing the well, and the column on the right indicates the mean time between failures of the well after processing. The numbers indicate the MTBF, expressed in days. As you can see, after the treatment, the MTBF has increased.

Thus, the method minimizes the risks of formation damage due to changes in phase permeability and clay swelling, reduces the corrosion risks and risks associated with the formation of poorly soluble products of the interaction of the components of the composition with the rocks of the formation and produced water. The pre-spot of the mutual solvent provides an increase in the penetrating ability of the aqueous solutions of the inhibitor in the low-permeability zones of the formation, which leads to an increase in the efficiency of adsorption of scale inhibitors and a longer removal of the inhibitor with the produced fluid during well operation.

Claims (1)

A method for preventing the inorganic salt deposition in oil and gas equipment, including the sequential injection of solvent rims, a solution of a scale inhibitor and a hydrophilic squeezing fluid into the bottomhole formation zone, characterized in that a mutual solvent is pumped as a solvent, a scale inhibitor is pumped in an aqueous solution of potassium chloride and as a hydrophilic said aqueous solution of potassium chloride is pumped with a squeezing liquid, moreover, as a mutual solvent butyl cellosolve or a mixture of solvents is pumped in the following ratio of components, wt.%:
Methanol 10 Acetone fifty Butyl cellosolve 35 Dimethyl sulfoxide 5,
scale inhibitor is pumped in an aqueous solution of potassium chloride at a ratio of components, wt.%:
Scale Inhibitor 10 Potassium chloride 1-2 Fresh water Rest,
and as a hydrophilic selling fluid, a 1-2% solution of potassium chloride in fresh water is pumped in, an organophosphorus type inhibitor is used as a scale inhibitor.

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