RU2004781C1 - Gel-forming composition for isolation of producing formation heterogeneous in permeability - Google Patents

Abstract

FIELD OF THE INVENTION This invention relates to gelling compositions used to control water flooding of heterogeneous formations and isolate water influx in oil wells. A gelling composition based on lignosulfonate and bichromate is characterized in that. in order to increase oil recovery by increasing the strength characteristics of the gel, it additionally contains mineralized water of potassium chloride type with a salinity of 60-260 g / l in the following ratio of components. wt% - lignosulfonate brand CKB 10-20. bichromate 1.5-2, mineralized water the rest 3 tebl

Description

The invention relates to the oil and gas industry, in particular to gel-forming compositions used to isolate washed zones and highly permeable interlayers in injection wells and to isolate water influx in production wells.

Known in a viscoelastic composition containing lignosulfonate (sulphite-alcohol stillage) and potassium or sodium dichromate.

The disadvantage of this composition is the low strength properties of the resulting gel (shear strength of the gel at a shear rate of 1.5 s less than 100 Pa).

A known composition for isolating washed zones of a formation.

The disadvantage of the composition is multi-component (5 components in the composition), which excludes widespread use of the composition in commercial conditions; the constituent mineral acid (HCI) will interact with the carbonate rocks of the productive formation with the formation of a negative side effect of increasing the permeability of the formation and reducing the isolation efficiency.

The closest technical solution to the proposed one is a composition for oil production containing lignosulfonate 2-20%, dichromate 0.15-2.5% and salts of alkali and alkaline earth metals in a ratio to dichromate 1: 1-55-1. The disadvantage of the composition is the low insulation efficiency due to the insufficiently high strength characteristics of the gel.

The aim of the invention is to increase the strength of the gel.

This goal is achieved by the fact that as a lignosulfonate the composition contains a concentrate of sulphite-yeast mash of the KBP brand, and as mineral water - water of calcium chloride type with a salinity of 60-260 g / l, with a density of 1.042 - 1.183 g / cm3, with the following ratio of components , wt.%:

KBP10-20 brand sulphite-yeast mash concentrate Sodium or potassium dichromate 1.5-2.0 Mineralized calcium chloride water with a salinity of 60-260 g / l with a density of 1,042-1,183 g / cm3 Else Comparative analysis with the prototype shows that the proposed gel - the developing composition is characterized in that it contains a sulphite-yeast brew concentrate as a lignosulfonate, and calcium chloride type water with a salinity of 60-260 g / l and a density of 1.042-1.183 g / cm as mineralized water.

Thus, the claimed technical solution meets the criterion of novelty. Analysis of known compositions has shown that some features of the claimed technical solution are known, for example, the content of lignosulfonate and dichromate in the composition. However, the lignosulfonate and dichromate-based gum-forming compositions as a solvent are mainly

contain fresh non-mineralized water. The gels formed from such compositions have low strength characteristics (shear strength less than 100 Pa), as a result of which the use of these compositions is ineffective for isolating a heterogeneous permeability formation. To obtain gels with high strength, a significant increase in the content of bichromate is necessary

0 as part of known compositions. The use of saline water of calcium chloride type as a solvent is known. However, in the proposed technical solution, mineralized water is not

5 only by the solvent, but also by the active component of the structuring system, which is involved in the structuring (gel formation) reaction. As a result of this reaction, a gel is formed, which is a rigidly crosslinked spatial structure in which the binding centers of crosslinking are along with chromium ions and salt ions that are part of the mineralized water. Thus, paralyzed iodine appears in a new quality - as an additional hardening agent and its use in the composition provides a gel with high strength characteristics.

The proposed technical solution differs from the composition of the prototype in that it includes mineralized water of calcium chloride type, which is

5 salt complex based on SG ions, 80 l, HCO3, S2, Ca + 2, Mg2 +, K +, Na Fe + 2, Fe + 3. Only one salt is contained in the composition to be compared. The presence of a complex of salts in the proposed composition provides

0 high strength characteristics of the gel and high isolation efficiency. At the same time, the process of preparing the composition is greatly simplified. The composition is directly prepared in wastewater mineralized waters under commercial conditions. When using salts in the composition, it is necessary to bring water, salt into the well, to dissolve the salt in water - this greatly complicates the process of preparing the composition. In addition, at present

time, salts are a scarce chemical reagent.

As a result of the analysis, it can be concluded that the claimed technical solution meets the criterion of the invention, significant differences, since the claimed technical solution has, in addition to the known essential features, new features (the composition contains mineral water — calcium chloride water with mineralization 60 -260 g / l, as a lignosulfonate - a concentrate of sulphite-yeast mash, the ratio of components in the composition), which are associated with a new property achieved when used - the image Suitable gels have high strength properties, which provides high-performance insulation works.

The substantiation of the essential features of the claimed technical solution was carried out by studying the gelation kinetics of the composition,

cooked in various waters. A gelling composition is prepared as follows. With vigorous stirring, the lignosulfonate is dissolved in water (fresh or mineralized) for 0.5-1.0 hours. Dichromate is added to the resulting solution and dissolved with stirring for 15-20 minutes. KBP grade sulfite-yeast mash concentrates (TU 81-04-225-79) were used as lignosulfonate, potassium dichromate, grade hch (GOST 4220-75), sodium dichromate, grade ChDA (GOST 4237-76), were used as dichromate. as a solvent, fresh water (tap water) or wastewater mineralized, used to flood productive formations in oil fields. Wastewater is a potassium chloride water with a wide range of total salinity, as it is prepared by mixing Devonian potassium chloride water with fresh water. The studies took into account the total salt content in the water (total water mineralization). The gel kinetics were studied on a Reostat-2 rotational viscometer by measuring the effective viscosity at a shear rate of 0.167 s at predetermined time intervals. The research results are presented in table 1. From the table. 1 it follows that the compositions prepared on the basis of mineralized water have a significantly shorter induction period for gel formation and the resulting gels have high viscosity and strength properties. Optimal composition

gelling composition,%: lignosulfonate 10-20; bichromate 1.5-2. mineralized water with a salinity of 60-260 g / l, the rest (compositions 5 10.11,14,15,18,19,23,24,25,26,28). Such a composition has an optimal gelation period (1-5 days). For comparison, studies were carried out on the kinetics of gelation of compositions prepared on fresh (tap) water (formulations 1-7). Fresh water compositions become capable of forming gels at a concentration of lignosulfonates of more than 30% and dichromates of more than 3%.

5 Compositions prepared on mineralized water with a lignosulfonate content of less than 10% and dichromates of less than 1.5% are not capable of gelation or form gels with low viscosity and strength properties (compositions 8,9,13,17,21,22) .

Compositions prepared in saline water with a lignosulfonate content of more than 20% and dichromate more than 2%

5 form gels with high strength, however, they have an induction period of gelation of less than one day, which is obviously insufficient for their successful application in commercial conditions for isolation

0 washed zones and highly permeable formations in injection wells, where large volumes of injected composition and a long time are required (formulations 12,16,20,27). To assess the effect of mineralization of water on the strength properties of gels, studies were carried out on a Reostat-2 viscometer. Method for measuring shear strength: a gel-forming composition was poured into a cylinder measuring device of a viscometer, the composition was left to gel (for 3 days), then the shear strength of the gel was measured at a shear rate of 1.5.

The research results are presented in Table 2.

From table 2 it is seen that the composition on fresh water does not form a gel with the composition being studied. A composition on mineralized water with a mineralization of 60–260 g / l forms gels with high strength characteristics (gel strength 180–610 Pa). Reducing mineralization below 60 g / l is impractical, since the resulting gels have a low

5 strength (20-60 Pa). An increase in water mineralization of more than 260 g / l leads to complications in the process of dissolution of lignosulfonates (a large amount of foam is formed and lignosulfonates precipitate). For comparison, conducted

experiments with analog compositions: compounds 7 and 8 (US patent N 3897827), composition 9 (A.S. N 1605615), composition 16 (A.S. Nfe 630401). The measurement results show that the gel formed from analog compositions has insignificant strength characteristics (60-170 Pa). To evaluate the effectiveness of isolation, experiments were conducted on bulk models of the reservoir. The reservoir model was a metal tube (50 cm long, 6.4 cm cross-sectional area) filled with quartz sand of a certain fraction. After evacuation, the model was saturated with water, the initial water permeability was determined, then a composition in the amount of 0.5 pore volume was pumped into the model. After a holding time (3 days), the model was inverted and water permeability was determined in the opposite direction. The effect of isolation was determined by the formula

K1-K2

 1

-

Ki

 100%,

0

5

0

where "1 - permeability to water before injection of the composition;

K-2 - water permeability after injection of the composition;

In all experiments, the pressure drop between the ends of the reservoir model was 0.1 MPa. The results of the experiments are presented in table.3. The numbers of the compounds correspond to the numbers of the compounds in table 2,

The results of the experiments show that the proposed gel-forming composition has a high isolation efficiency. 100% isolation with analog compositions was not achieved.

The use of the proposed gel-forming composition for isolating a heterogeneous permeability of a productive formation will significantly increase the efficiency of repair-insulating works.

(56) U.S. Patent No. 3897827, cl. E 21 B 43/22, published. 1975.

start of gelation

Table 1

Claims (1)

The claims GEL-FORMING COMPOSITION FOR INSULATION OF INHOMOGENEOUS SOFTWARE. PRODUCTIVITY OF THE PRODUCTIVE LAYER containing lignosulfonate, potassium or sodium dichromate and mineralized water, characterized in that, in order to increase the gel's strength, it contains lignosulfonate con- Table 2 Table 3 KBP brand sulphite-yeast mash centrate, and as mineralized water - calcium chloride water with a salinity of 60 - 260 g / l, with a density of 1,042 - 1,183 g / cm3 in the following ratio of components, wt.%: KBP10-20 brand sulphite-yeast mash concentrate Sodium or potassium dichromate 1.5 - 2.0 Mineralized water of potassium chloride type with a salinity of 60 - 260 g / l and density 1,042-1,183 g / cm3 Rest