Well killing composition

FIELD: oil and gas production.

SUBSTANCE: water-based composition that can be used for killing of well during pullout of hole and well remedial work as well as for temporary abandonment of well contains, wt %: carboxymethylcellulose3.5-4.5, sodium hydroxide1.5-2.0, copper sulfate 0.3-0.4, and methanol 4.0-16.0.

EFFECT: improved rheological properties of composition and increased lifetime of formed gels.

1 tbl

 

The invention relates to the oil and gas industry and can be used in the process of killing for capital and current repairs of wells, and when the time for conservation of wells.

Known gelling composition for insulation work during the drilling and operation of oil and gas wells containing carboxymethylcellulose 1.0 to 6.0 wt.%, the chromates of 0.25-5.0 wt.%, lignosulfonates of 0.1 to 25.0 wt.%, water - the rest. The composition has high strength characteristics, stability in time [A.S. USSR №1472643, IPC E 21 In 33/138, publ. 15.04.89. Bull. No. 14].

However, the known composition does not ensure the preservation of the original formation permeability due to the presence in the composition of the lignosulfonate. In addition, the composition contains environmentally hazardous substances, namely: chromates.

Closest to the claimed technical solution of the essential features is a viscoelastic composition for completion and workover wells, which can be used as a composition for killing wells. The composition contains a reagent based on polysaccharides, such as carboxymethyl cellulose, structure-former - aluminum sulfate or copper sulfate, a hydroxide of an alkali metal, e.g. sodium hydroxide, as destructor - monoperoxyphthalate urea and water in the following aspect] the following ingredients, wt.%: reagent-based polysaccharides 1,0-3,0, amendment of 0.15-0.3, hydroxide of alkaline metal is 0.05 to 0.45, and monoperoxyphthalate urea 0.1 to 0.2 and water - the rest [p. the Russian Federation No. 2116433, IPC E 21 In 33/138, 43/26, From 09 To 7/02, publ. 27.07.98].

Known composition has a low penetrating and clogging effects on the reservoir, ensuring the preservation of permeability rocks of the productive formation by accelerating structure formation, reduction filter, increasing the viscosity.

However, the low strength of the resulting viscoelastic mass in the form of a gel and a lack of aggregate stability of known composition against time (the start time of the destruction of the resulting gel after 1-6 days) limits its use in workover, which requires killing the opened seam for a long time (up to 4 months).

The task of the invention is to improve the rheological properties of the composition and increase the longevity of the resulting gels (>40 days).

The problem is solved in that the composition for killing wells containing carboxymethylcellulose, sodium hydroxide, copper sulphate, additive and water, as an additive contains methanol in the following ratio of ingredients, wt.%:

Carboxymethylcellulose- 3.5 to 4.5
Sodium hydroxide- 1,5-2,0
The copper sulfate- 0,3-0,4
Methanol- 4,0-16,0
Water- the rest.

Methanol (methyl alcohol) is a mobile colorless transparent liquid, the smell is very reminiscent of ethyl alcohol; density - 796 kg/m3; boiling point - 64,7°With, the solidification temperature of minus 97,7°C.

The authors experimentally established that the use of methanol in the proposed composition for killing wells can significantly improve the rheological properties (viscosity-dynamic and static shear stress) and syneresis (the life expectancy of the resulting gel). The presence of the proposed composition of the methanol helps to reduce the density of the composition, which is especially important for wells with low formation pressures, and allows for killing wells at low ambient temperatures (up to 35°). Methanol is involved in the joining of carboxymethylcellulose copper sulfate in the presence of alkali, giving the resulting links additional strength and stability over time at the expense of more ties with the formation in solution of elastic and branched grid.

Thus, Samaniego component of a known composition to another (a new set of features) and the new balance of components allowed us to obtain new technical result -- improving the rheological properties of the composition for killing wells and increasing the lifetime of the resulting gels (over 40 days), which ensures the reliability and quality of ongoing killing of wells in low formation pressure for a long period of time due to the stability of viscoelastic systems, save the initial permeability of the productive formation. Low freezing point of the composition allows for killing wells regardless of the time of year and to reduce the energy intensity of technological processes in the absence of heating of the prepared composition.

Composition for well killing field is prepared as follows.

Pre prigotovleniya two initial solution - odometery solution of carboxymethyl cellulose with the addition of sodium hydroxide and odometery solution of copper sulphate. Then pump units simultaneously fetch two of the original solution into the well. By mixing these solutions in the tubing during injection, a gel is formed with the necessary rheological properties and adjustable shelf life of the gel (syneresis).

By changing the ratio of components in the inventive composition for killing wells, can be adjusted in a wide range of time degradation of the formed gel.

For confirmation is eridania quality composition for killing wells laboratory studies. When conducting laboratory experiments used the following reagents:

carboxymethylcellulose brand CMC-9, TU 6-55-221-1453-96 production of CJSC "Corporation "Esters of cellulose" Vladimir;

sodium hydroxide GOST 2263-79;

the copper sulfate GOST 19347-84;

methanol GOST 2222-95.

Example. Prepared 4%solution of CMC by dissolving 4 g of CMC in 96 ml of water. Separated 80 ml of solution in a separate glass. Dissolved 2 g of sodium hydroxide in 5 ml of water with stirring until dissolved, after which the resulting solution was slowly poured into a solution of CMC with vigorous stirring for 5-7 minutes (until complete mixing). Added 5 ml of methanol and again stirred. In a separate test tube was dissolved 0.3 g of copper sulfate in 5 ml of water, was added 5 ml of methanol, thoroughly mixed and the resulting solution was slowly poured into previously prepared odometery the CMC solution in a mixture with sodium hydroxide. Mixing was carried out at intensive stirring for 5-15 minutes until a homogeneous solution. The process of gel formation occurs rapidly, immediately as you enter into the solution of CMC staple - sulphate of copper.

Thus, the obtained composition with the following ratio of ingredients, wt.%: CMC - 4,0; sodium hydroxide - 2,0; copper sulfate and 0.3, methanol - 4.0 and water - other (experiment 4).

Similarly prepared other compounds with the ranks of the ratio of ingredients (experiments 3, 5-7), as well as the composition of the prototype (experiment 1) and the composition of methanol (experiment 2).

In laboratory studies determined the rheological properties of the obtained gels: dynamic viscosity (PA· (C) static shear stress SNA (PA), which was determined on the viscometer "Polymer RPE-1M". The rheological properties of the resulting gel was determined after 1 hour after preparation of the gel, then after 10, 20 and 30 days. The lifetime of the formed gel was determined visually by observing its destruction, according to the time degradation of the gel.

The results of laboratory experiments are presented in the table.

As can be seen from the table, known composition (experiment 1) has a low rheological properties and lack of syneresis (the beginning of the destruction of the formed gel after 2 days).

On the basis of the conducted researches it is established that in the absence of methanol gel-forming composition based on CMC, custom made copper sulfate in the presence of alkali, has a high rheological properties, but after a time the rheological properties are reduced, and after aging for 20 days formed a gel begins to delaminate (experiment 2).

Introduction of methanol in the composition for killing wells preserves the properties of the gel-like viscoelastic plastic mass in a long time (over 40 days) and allow yet use it when it is repaired, and getprofileid wells. In addition, the reduced density of the proposed structure (less than 1.0 g/cm3) allows to reduce the repression on the layer, which is especially important for wells with low formation pressures, and to prevent the penetration of the composition into the formation.

It is established that the optimum content of methanol in the inventive composition is 4,0-16,0 wt.% (lessons 4-6). When the methanol content of less than 4.0 wt.% (experiment 3) the composition has a sufficiently high rheological performance, but the lack of stability in time (less than 40 days). The content in the inventive composition of methanol over to 16.0 wt.% it is not economically feasible (experiment 7).

The optimum content of carboxymethyl cellulose is 3.5 to 4.5 wt.%, of sodium hydroxide and 1.5-2.0 wt.% and copper sulfate - 0.3 to 0.4 wt.%.

The lower contents of these components below the recommended limits leads to a decrease in the rheological properties of the composition, which leads to the formation of malolactic fragile gel, as well as lower long-term blocking effect. The increase in the content of these components in the proposed structure above the recommended limits leads to the fact that the composition sagaseta to strikingly high values of viscosity and SNA and may not be used for killing wells.

The main advantages of the proposed structure for glushen what I wells are:

- high and adjustable value of viscosity and static shear stress that the application of other compositions for killing wells (clayey muds, brines, emulsions, hydrogels, foam) are not attained;

- decrease the depth of penetration of the composition into a layer that allows you to save and restore the permeability of the reservoir after repair;

is quite high and adjustable term life viscoelastic composition that is necessary for different times of repair works;

- the possibility of destruction and removal composition of hydrochloric acid, i.e. a conventional hydrochloric acid treatment during the development of the well.

Thus, the use of the composition for plugging wells with low formation pressure ensures reliable locking of high-permeability intervals productive reservoir for varying periods of major repairs, including on long-term (up to 4 months).

Table
no experienceIngredients gelMass fraction of ingredients, %Mass fraction of methanol. %Rheological properties of MAS through:The beginning of destruction (destruction) of the gel, the dayPL is tnost gel, g/cm3
1 hour10 days20 days30 days
Dyn. viscosity, PA·SNA, PADyn. viscosity, PA·SNA, PADyn. viscosity, PA·SNA, PADyn. viscosity, PA·SNA, PA
1234567891011121314
1CMC

Caustic soda

Copper sulphate

Monoperoxyphthalate urea

Water
2,5

0,45

0,3



0,2

rest


-


0,15


39,00


-


-


-


-


-


-


2


1,02
2CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3


-


1,85


234,20


1,14


153,00


0,78


54,00


-


-


22


1,02
3CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3

rest


2,5


1,91


257,50


2,20


402,30


2,00


268,80


1,01


131,30


33


1,02
The continuation of the s table
1234567891011121314
4CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3

rest


4,0


2,00


268,80


2,72


365,57


2,55


342,72


1,55


208,32


60


1,00
5CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3

rest


8,0


1,82


228,70


2,15


356,08


1,55


287,00


1,21


202,00


60/td>


0,98
6CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3

rest


16,0


1,79


256,30


2,20


402,30


1,69


311,00


1,39


260,00


120


0,97
7CMC

Caustic soda

Copper sulphate

Water
4,0

2,0

0,3

rest


24,0


1,71


213,44


1,98


383,00


1,62


303,00


1,11


140,00


35


0,95

Composition for killing wells containing carboxymethylcellulose, sodium hydroxide, copper sulphate, additive and water, wherein it as a Supplement contains methanol in the following ratio of ingredients, m is S.%:

Carboxymethylcellulose- 3.5 to 4.5
Sodium hydroxide- 1,5-2,0
The copper sulfate- 0,3-0,4
Methanol- 4,0-16,0
Water- the rest.



 

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