Composition for treating well bottom zone of carbonate formation wells

FIELD: oil and gas production.

SUBSTANCE: invention relates to oil production technology involving use of hydrochloric acid-based chemicals via complex hydrochloric acid effect on well bottom zone to intensify oil production and may be specifically used to increase oil recovery of viscous oil-saturated low-permeable carbonate reservoirs. Composition contains 22-28% of 20 vol % aqueous HCl solution, 7-8% of 98% aqueous acetic acid solution, and 65-70% of solvent based on light pyrolysis tar obtained as secondary product from petroleum processing enterprises.

EFFECT: increased well bottom zone treatment efficiency due to improved quality of treatment composition, in particular stability and dipping depth into formation.

4 tbl

 

The proposal relates to the field of oil industry, in particular to the technology of oil production with the use of chemical agents on the basis of hydrochloric acid through an integrated hydrochloric acid effects on the bottomhole zone wells oil reservoir for enhanced recovery, and can be used to increase oil recovery from low-permeability carbonate reservoirs, saturated heavy oil (BBH).

Known compound for the treatment of carbonate reservoir (SCR) on the basis of hydrochloric acid [see Loginov astray freight and other Guidance on the acid treatment of wells. M.: Nedra, 1966, p.41-56].

The disadvantage is that hydrochloric acid has a high rate of reaction with the reservoir rock, resulting in the depth of its penetration into the formation is small.

In addition, often after treatment of bottom-hole zone (OPZ) hydrochloric acid permeability wells is reduced, as the hydrochloric acid solutions are characterized by a high content of iron ions due to corrosion of equipment, which in the form of hydroxide deposited on the breed. All this leads to a decrease in the efficiency of processing.

There is also known a method for treatment of the carbonate layer on the basis of concentrated acetic acid [see Amen VA and other Physico-chemical methods of increasing the productivity of wells. M.: Nedra, 1970, s]

The composition can reduce the reaction rate to the reservoir rock.

The disadvantage is the limited use due to high cost.

The closest in technical essence and the achieved result to the proposed composition for SCR carbonate reservoir is the composition [see ed. St. USSR №1170127, CL E 21 In 43/27, 1985], containing a solution of hydrochloric and acetic acids, and as an additional moderator speed of reaction with the carbonate rock - liquid products of pyrolysis from C5and above when the following ratio of components, % about:

hydrochloric acid (20%)4-20
acetic acid (98%)9-67
liquid products of pyrolysis is a mixture of condensates
hydrocarbon, C5and abovethe rest of it.

When using the composition for IPF is a decrease in the reaction rate with the reservoir rock and improving the filterability at low-permeability reservoirs with asphalt, resin and paraffin deposits (ARPD).

The disadvantage is the low efficiency of the reduction of the reaction rate with the reservoir rock and the low efficiency of removal of deposits from low-permeability porous medium due to low technology status the VA and depth of penetration into the carbonate reservoir, emulsion of an aqueous solution of hydrochloric and acetic acids in the liquid products of pyrolysis is not stable over time. In addition, the efficiency of the SCR remains low due to high water cut wells.

The disadvantage is the limited use due to the specificity of the use of the additive products of pyrolysis from C5above.

The technical result of the invention is to improve the efficiency of the SCR by improving the processability of the composition, namely the stability and depth of penetration into the carbonate reservoir, as well as expanding the range of acid compounds for SCR low-permeability carbonate reservoirs saturated with heavy oil.

The technical result is achieved in that the composition for treatment of wellbore zones of carbonate reservoir containing 20% aqueous solution of hydrochloric acid, 98% water solution of acetic acid and solvent-based secondary products of oil refineries - light pyrolysis tar FSC contains these components when following their ratio, % by vol.:

a solution of acetic acid7-8
FSC65-70
a solution of hydrochloric acid22-28

Experimental the surveys showed the proposed structure allows you to:

- to increase the filtration characteristics of the bottomhole zone due to the expansion of existing and creation of new perforating fluid channels with the dissolution of the mineral component of the reservoir;

- slow, compared with the reference solutions of acids, the rate of dissolution of carbonates to increase the radius of their influence.

It has a low value of surface tension to improve their penetrating deep into tight channels and facilitate the reverse of removal waste composition in the wellbore. The composition has a high dissolving power with respect to ASPO, low corrosion rate of metals and compatibility of the individual components with each other and with the reservoir of highly mineralized water.

The combined impact on carbonate rock reservoir and hydrocarbon deposits (ARPD) is solved by the selection of the hydrocarbon solvent - dispersant capable of using a co-solvent to dissolve in acid solutions. This co-solvent is acetic acid, which is the link between the rest and gives the phase stability of the whole system.

From available sources, the patent and scientific literature is unknown to us the claimed set of distinctive features.

sledovatelno, the proposed structure meets the criteria of the invention "inventive level".

For the preparation of compounds were used the following materials:

- 20%hydrochloric acid (GOST 857-88);

is introduced into the composition in solution as a solvent breed, translating resin-paraffin deposits (ARPD) in a free state with its subsequent volumetric dispersion.

- 98%acetic acid (GOST 61-75);

is introduced into acid composition as complexing agents iron ions and as a co-solvent, which is the connecting link between the individual components, giving the phase stability of the whole system.

light pyrolysis resin (LPS) THAT 38.10285-83;

is introduced into the composition as a solvent-based secondary products of oil processing enterprises, affecting the degree of washing of sediment and allowing to increase the permeability of the rocks.

For conducting experiments used:

- produced water - density 1,113-1,156, g/cm3total mineralization 195,1-236,7, g/l;

- core material permeability by air 0,0010-0,0032 μm2,

the porosity of 6.3 and 11.6%, the content of calcite 93.32 per-98,96, dolomite 2,6-total of 5.21%;

- iron chloride (FeCl3) - THE 4147-74.

The preparation of the compounds was carried out as follows.

Concentrated hydrochloric acid was diluted with fresh water to 20%concentration by volume. The ZAT is it consistently added LPS and acetic acid, then the contents were mixed.

All the compositions are stable in time (7-9 days) and homogeneous liquids. The order of mixing of the individual components does not affect the characteristics of the composition. The compositions are compatible with water. Characteristics of the compositions are shown in table No. 1.

0,948
Table 1
No. acid composition.IngredientsVolumetric content, % vol.Density,

g/cm3
Viscosity, MPa·Varnostne tension, mn/m
123456
198% of CH3COOH34
FSC57
20% HCL90,9523,336,9
298% of CH3COOH7
FSC65
20% HCL28the 3.836,4
398% of CH3COOH10
FSC70
20% HCL200,9454,236,2
498% of CH3COOH9
FSC71
20% HCL200,9414,336,0
520% HCl10067,4
615% HCl10072,0

From table 1 it is evident that the decrease in surface tension occurs in all of the compositions as compared to hydrochloric acid, which provides a high penetration ability into the reservoir. The proposed formulations having a higher density compared to the density of the heavy oil in situ (0,874-0,908 g/cm3and smaller in comparison to the viscosity of (d is nomicheskaya viscosity BBH in situ changes from 35.6 to 81,3 MPa· C)due to the positive influence of formulations for injection into the reservoir and the displacement of oil from the reservoir.

Complexing ability of acid composition in relation to ions of iron was determined by pre-dosing at 40%ferric chloride (FeCl3). Then the composition was neutralized to pH=3, the process of precipitation of iron hydroxide was detected visually (Methodology of works by Christian M. and others Increase productivity injectivity of wells/ Lane. KN. - M.: Nedra, 1985).

Studies have shown that all compounds are iron ions complexing agents. Acetic acid in combination with other components included in the composition, stabilizes dissolved iron from re-drop it into the sediment.

The density of the compositions was measured by pycnometry, dynamic viscosity on the device Rheo-Viskometer; open porosity OST 39181-85; permeability according to OST 39161-83; surface tension was determined stalagmometer way.

The rate of dissolution of carbonate rocks was determined as follows: the core was weighed to 0.01 g, measured the area of the surface and lowered into the beaker with the test composition, after 5 minutes, removed from the composition, washed with water and dried in a drying Cabinet at t=100°C to constant weight and again weighed with the original is Inoi accuracy. The difference in weight was determined the efficiency of dissolution.

The research results are summarized in table 2.

td align="center"> 28
Table 2
The main components of the compositionComponent content, % vol.The surface area of the core, m2The duration of reaction, minThe weight of the core before treatment, gThe weight of the core after treatment, gThe dissolution rate, g/(m2·)
1234567
98% of CH3COOH34
FSC57
20% HCL90,0018219,7426,4961,42
98% of CH3COOH7
FSC65
20% HCl0,0018269,7696,4941,16
98% of CH3COOH10
FSC70
20% HCl200,0018309,7406,4901,00
98% of CH3COOH9
FSC71
20% HCl200,0018319,7436,4800,97
20% HCl1000,0013125,2650,3985,2
15% HCl1000,0013175,2900,6493,5

Table 2 shows that all the studied compounds have solubility. They all have a low rate of dissolution of carbonates compared with the hydrochloric acid that pic is of bstweet deep SCR layer.

The degree of dispersion of paraffin proposed method was determined by the method of "cold cylinder". The method consists in the following.

In oil preheated to 30°dipped a cylinder, the temperature of which was maintained at a level of 15°With the addition of ice. When mixing oil for 30 min, resulting in the difference of its temperature from the temperature of the "cold" cylinder on the surface of the cylinder formed precipitate paraffin.

The cylinder with the formed precipitate was removed from the tank with oil and after complete draining him of its residues were weighed and transferred into a beaker with the test composition of a certain concentration, the temperature of which was also supported by up to 30°C. Then studied composition was gradually stirred for 3 minutes, when this occurred the separation of precipitated sludge from the surface of the "cold" cylinder. Then the cylinder was re-weighed and compared it to the weight of the initially formed precipitate was determined detergency efficiency of the investigated part of this concentration by the formula:

E=Q2/Q1·100%,

where Q1the mass of precipitate formed on the surface of the cold cylinder", g;

Q2- weight of the washed sediment was

The research results are summarized in table 3.

Table 3
The main components of the compositionComponent content, % vol.The empty weight of the cylinder, gThe weight of the cylinder with ARPD to launder, gThe mass of sediment, gThe weight of the cylinder with paraffin after washing, gThe degree of washing, % wt.
1234567
98% of CH3COOH347,4407,7200,2807,59254,2
FSC57
20% HCl9
98% of CH3COOH77,4407,6050,1757,57878,8
FSC65
20% HCl28
98% of CH3COOH107,4407,5950,155 7,56580,6
FSC70
20% HCl20
98% of CH3COOH97,4407,5950,1557,55976,7
FSC71
20% HCl20

Table 3 shows that all the studied compositions have detergent ability in relation to ARPD. The highest laundering ability to have compositions containing 65% and 70% of the IDPs.

In laboratory conditions was conducted series of experiments to determine the permeability of core material depending on the porosity of the core material and the number of washings.

The research results are summarized in table 4.

Table 4
The main components of the working solution.Component content, % vol. The porosity of the core, %Permeability μm2
SourceAfter processing/magnification of
the first pore volumeThe second pore volumethe third pore volume
1234567
98% of CH3COOH34
FSC570,00210,00360,0055
20% HCL910,60,00181,12,74,2
98% of CH3COOH7
FSC650,00380,00720,022
20% HCL2810,70,00171,93,4the 13.4
98% of CH3COOH10
FSC700,00480,0120,029
20% HCL2011,00,00192,56,515,2
98% of CH3COOH9
FSC710,00480,0120,029
20% HCL2011,00,00181,64,512,2

From table 4 it is seen that the permeability of the core increases after pumping the same volume of the proposed formulations and continues to increase significantly with increase in throughput, compounds capable of simultaneously dissolving carbonate rock and paraffin, are highly penetrating and vinyaya ability to dissolve in water of any salinity, increase the permeability of the rocks in average from 4.2 to 15.2 times.

Research phase state and the stability of the system showed that the composition is stable homogeneous liquid within seven nine days under the following ingredients,% about:

9% acetic acid 6-9
light pyrolysis resin64-71
a 20% solution of hydrochloric acidrest

With decreasing values of the FSC system is in the emulsion, which reduces the efficiency of the SCR.

The data shown in tables 1-4 show that the composition containing the following components, % by vol.:

98% solution of acetic acid (CH3COOH)7-10
light pyrolysis resin65-70
a 20% solution of hydrochloric acid (HCL)the rest,

has low values of surface tension on the border with the breed and interphase on the border of the oil composition, which contributes to a high point in his low-permeability oil-saturated part of the formation; high dissolving power with respect to the deposits that contribute to the depth of penetration and the increase in coverage across the thickness of the formation; slow dissolution rate with respect to carbonates, which also promotes deep SCR layer; maximize the permeability of the reservoir rock that field conditions will increase the injectivity of injection wells and, consequently, to increase the displacement efficiency of oil.

Research dormancy is expressed, the increase in the LPS content is above 70% leads to a decrease in the content of the hydrochloric acid phase in the solution and reduces the efficiency of the SCR. Reducing the lower limit of the content of LPS reduces the effectiveness of the SCR.

Technical and economic efficiency of the proposed formulations for SCR carbonate layer is formed by increasing the efficiency of the SCR, i.e. improve the processability of the composition, namely the stability and depth of penetration into the carbonate reservoir, as well as expanding the range of acid compounds for SCR low-permeability carbonate reservoirs saturated with heavy oil.

The composition for treatment of wellbore zones of carbonate reservoir containing 20%aqueous solution of hydrochloric acid, 98%aqueous solution of acetic acid and solvent-based secondary products of oil refineries - light pyrolysis tar LPS, characterized in that it contains the components when following their ratio,%:

A solution of acetic acid7 - 8
FSC65 - 70
A solution of hydrochloric acid22 - 28



 

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