SU1716094A1 - Cross-linking agent for lignosulfonate gel used for insulation of seams and wells - Google Patents

Abstract

The invention relates to the oil industry. The goal is to reduce the time of formation of the lignosulfonate floor while reducing the consumption of the crosslinking agent. A crosslinking agent for lignosulfonate gel contains, by weight.h .: alkali metal dichromate 1-6, chromic anhydride 1-8. As the alkali metal dichromate, it is possible to use waste electroplating from, anann filling the passivation and oxidation. As chromic anhydride, galvanic production waste from etching and chrome plating baths is used. The method makes it possible to reduce the space of wells that are in overhaul, quickly eliminate the emergency situation associated with water breakthrough, depressurize the annular space by reducing the gelation time. 1 hp f-ly, 6 tab. with s

Description

The invention relates to the oil industry, in particular to the creation of gel-shaped systems for isolating formations and wells.

A crosslinking agent for gelation is known. containing chromecarboxylate complex compound and simple mineral acid.

Its disadvantage is the multicomponent and deficiency of the chromic carboxylate complex, which is obtained in special production in limited quantities.

A crosslinking agent is known for gelation in the form of an aqueous solution containing polyvalent metal cations Fe2 +, Fe3, AI3 +, Ti4 +, Zn2 +. Mn7. Cr3 +.

The disadvantage of it is a low gelation rate. In addition, these cations, including trivalent chromium, do not possess universality with respect to the polymer being crosslinked, in particular, they do not exhibit crosslinking activity to lignosulfonate solutions.

The closest in technical essence and the achieved result is a crosslinking agent to obtain a lignosulfonate gel, including alkali metal dichromate.

Os

ABOUT

Yu

J

The disadvantage of this crosslinking agent is a low crosslinking rate and a significant consumption of reagent.

The aim of the invention is to reduce the time of gel formation and reduce the amount of crosslinking agent.

This goal is achieved by the fact that the crosslinking agent for the preparation of lignosulphonate gel based on alkali metal dichromate additionally contains chromic anhydride at a mass ratio of alkali metal dichromate to chromic anhydride from 6: 1 to 1: 8.

As the proposed cross-linking agent for the preparation of lignosulfonate gel, pure pea-agents (alkali metal dichromates and chromic anhydride) manufactured by enterprises of the USSR Minchimprom can be used. In addition, in the electroplating industry of a number of enterprises, aqueous solutions of alkali metal dichromates (for example, in filling, passivation and oxidation baths) and aqueous solutions of chromic anhydride (for example, in etching and chrome plating) are used. Mixing the waste solutions of the above baths in quantities that ensure that the mixture contains hexavalent chromium compounds (alkali metal dichromate and chromic anhydride in a ratio of 6: 1 to 1: 8) allows the use of galvanic waste as a crosslinking agent to obtain lignosulfonate gel. productions.

Example. For the experimental verification of the proposed cross-linking agent for the preparation of lignosulfonate gel, the following gel-forming compositions were prepared, wt%:

Lignosulfonate10

Crosslinking agent3

Sodium Chloride15Water Else

In the prototype crosslinking agent, potassium dichromate was taken, in the proposed crosslinking agent, a mixture of potassium dichromate and chromic anhydride was taken in a mass ratio of 2: 1.

The method of preparation of the following compositions.

An aqueous solution of salt (sodium chloride) was prepared, dry lignosulfonate was dissolved in this solution and the required amount of crosslinking agent was added. The resulting gel was characterized by a viscosity, for the measurement of which the vibrational method was used.

Table 1 compares the gel preparation times with viscosity, for example, 100, 200,

300, 500 and 1000 mPa-s when used in the named composition of the cross-linking agent of the prototype and the proposed cross-linking agent.

As can be seen from table 1, the time of gel formation when using the proposed cross-linking agent is significantly less than that of the prototype cross-linking agent, which indicates the effectiveness of the proposed cross-linking agent.

EXAMPLE 2 In order to prove the reduction in the amount of crosslinking agent required to obtain a gel of a certain viscosity, the following gel-forming compositions were prepared:

The composition of the prototype

Lignosulfonate10

Crosslinking agent3

Calcium chloride15

WaterEverything

The proposed composition

Lignosulfonate10

Stitching

agent1,0; 1.5; 2.0; 2.5; 3.0

Calcium chloride15

WaterEverything

The procedure for the preparation of the formulations is given in Example 1. Potassium dichromate was used as the prototype crosslinking agent. The proposed crosslinking agent was a mixture of potassium dichromate and chromic anhydride in a 1: 1 ratio by weight.

Table 2 shows the comparative results of measuring the viscosity of the compositions with a cross-linking agent according to the prototype and with the proposed cross-linking agent after a certain time.

As can be seen from Table 2, the amount of the proposed crosslinking agent required to obtain a gel of a certain viscosity is substantially less than with the use of a prototype crosslinking agent, which indicates the effectiveness of the proposed crosslinking agent.

Example 3: To determine the ratio of the components of the proposed crosslinking agent (alkali metal dichromate to chromic anhydride), at which the goal is achieved (shortening the gel formation time and reducing the amount of crosslinking agent), a number of gelling compositions with a crosslinking agent are prepared. the prototype and with the proposed cross-linking agent, the components of which are in different mass ratios. Gelling composition was as follows, wt.%:

Lignosulfonate10

Crosslinking agent3

Sodium Chloride13

WaterEverything

Table 3 shows the results of determining the time of obtaining the gel with viscosities of 300 and 500 mPa s in systems that form a gel with both the crosslinking agent by the prototype and the proposed crosslinking agent, the components of which are of different ratios.

Table 4 shows the results of experiments showing how the ratio of the components in the proposed cross-linking agent affects the required amount of cross-linking agent for gelation. For convenience, the viscosities of the resulting gels were compared 8 hours after the formulation was prepared.

As can be seen from Tables 3 and 4, in order to achieve the goal, the proposed cross-linking agent should be more than 6 wt.h. potassium dichromate at 1 wt.h. chromic anhydride; An increase in the content of chromic anhydride in a mixture with potassium bichromate leads to an increase in the viscosity of the resulting gel and a reduction in the time of formation of the gel of the required viscosity.

The maximum permissible content of chromic anhydride in the proposed cross-linking agent was determined from the results of preserving the viscosity of the resulting lignosulfonate gels over time (Table 5).

To obtain gels, the composition was taken, wt.%:

Lignosulfonate10

A crosslinking agent3.

Calcium chloride13

WaterEverything

As can be seen from Table 5, as a result of the destruction of the gel, high values of viscosity for 30 days are maintained only at the ratio of potassium bichromate to chromic anhydride in the mixture not exceeding 1: 8. At this ratio, the gel will provide a high insulating effect in the formations and wells for at least 30 days.

Example 4. In order to prove the possibility of using electroplating waste, a number of formulations were prepared in which a prototype crosslinking agent was used, as well as the proposed crosslinking agent, composed of both chemically pure substances (alkali metal dichromate and chromic anhydride in a given ratio) and the waste of galvanic production of the Kazan machine-building plant, containing the above substances and mixed in the same ratio.

The composition was taken as follows, in wt%: Lignosulfonate 10

Crosslinking agent3

Calcium chloride15

WaterEverything

The results of measuring the gel formation time of a certain viscosity are presented in Table 6.

From table 6 it follows that the effect of a mixture of electroplating waste containing alkali metal dichromates and chromic anhydride is equivalent to the effect of a mixture of chemically pure substances despite the presence of minor impurities of other substances in the composition of the waste (traces of alkali, acids, mineral salts).

Thus, the use of the proposed crosslinking agent to obtain a lignosulfonate gel will reduce the downtime of wells undergoing major repairs by reducing the time required for the formation of gels; quickly eliminate an emergency situation with the breakthrough of water, depressurization. well space, etc. by using fast setting gels; to obtain gels of the required viscosity with less consumption of the crosslinking agent. Taking into account the scarcity of compounds based on hexavalent chromium, economy of reagents will improve economic performance by reducing the consumption of scarce reagents.

Claims (2)

1. A crosslinking agent for a lignosulfonate gel used in isolating formations and wells, including an alkali metal bichromate, characterized in that, in order to reduce the time of formation of the gel while reducing the consumption of the crosslinking agent, it additionally contains chromic anhydride in the following ratio of components, wt. .ch .: Alkali metal bichromate .1-6 Chromic anhydride1-8 2. A crosslinking agent according to claim 1, excluding the fact that, as an alkali metal dichromate, it contains electroplating production waste from the passivation and oxidation baths, and electroplating production from the baths as chromic anhydride. etching and chrome plating. Table 1 table 2 Table 3 Table.4 Table 5 Table 6