CS232646B1 - The method of chemical removal of barium sulfate - Google Patents

Abstract

The invention relates to a chemical process that allows barium sulfate to be removed from hard-to-reach locations such as, for example, a deep well. By contacting an aqueous solution of alkali metal carbonate or ammonium carbonate with barium sulfate, a double reaction occurs, accelerated by an increase in temperature, pressure and concentration of dissolved carbonate in the system: BaSCU + K2CO3 -> K2SO4 + BaCO3 . The dissolved final reaction product, i.e. ammonium sulfate or alkali metal sulfate, is washed out with water, and barium carbonate, unlike barium sulfate, can be easily dissolved in acids or complexing agents. By removing barite from oil-prospecting zones, it is possible to increase their permeability and therefore also their recovery, which is also the purpose of the invention.

Description

The invention relates to a chemical process by which barium sulphate BaSCU can be dissolved and removed mainly from harder to reach locations such as deep wells.

This problem has already been addressed in the patent literature. Rinsing fluids for drilling practice are known which are capable of forming soluble barium complexes with barium sulfate. These are alkaline aqueous solutions of phosphomethyl- and amino-substituted macrocyclic polyethers according to U.S. Pat. Lower capacity, less thermostability, especially at higher temperatures and high cost, appear to be the main drawbacks of these very complicated compounds. U.S. Pat. No. 3,396,938 as well as U.S. Pat. No. 3,308,065 it is proposed to dissolve barium sulphate by treatment with an alkali-treated aqueous solution of ethylenediaminetetraacetic acid to a basic pH. Limited thermostability at higher temperatures high sensitivity to calcium, iron, etc. as well as price, but we limit the use of these acids in exploitation practice.

The problem of chemical removal of barium sulphate is solved by the invention which is initially treated with an aqueous solution of alkali carbonic acid salts, mixtures thereof or ammonium carbonate at a given location (e.g., a barium-elongated oil well zone). By contact with said liquid, the BoSCU is subject to an exchange reaction:

BaSO 1 + X 2 CO 3 X 2 SO 4 + BaCO 2 wherein X denotes an alkali metal or NH group.

Increasing the temperature, pressure and concentration of dissolved carbonate promote the speed and yield of the process. Upon completion of the reaction (24-72 hours), the dissolved X2SO4 sulfate is removed by washing with water, similar to the excess unreacted dissolved X2CO3 carbonate. The second end product of the reaction is barium carbonate, which, unlike barium sulfate, can easily be dissolved in hydrochloric acid or other acids, and its reaction with complexing agents is faster and more complete than in the case of BaSO 3.

An advantage of the chemical process of the invention is that fasting and available chemicals can be used and the application of the method is realistic even in high temperature environments. Due to the static conditions of the experiments described in Examples 1, 2, 3 and twice the residence time of the carbonate solution on BaSCU, the barium sulfate elimination effect is comparable to that of the known flushing liquid.

Example 1

Natural oil barite with a specific gravity of 4.1 g / cm ³ containing 82% BaSOa was used for the experiment. The admixtures consisted of FezO3 and SiO2. A 0.8 cm thick 20 g naphthylic barite was treated under static conditions at 90 ° C with an aqueous solution of 200 ml and a concentration of 30% by weight of K 2 CO 3. After 48 hours, the entire mixture was filtered, washed several times with hot distilled water and made up to 1000 ml. In heated and acidified (HCl filtrate samples) sulphates were determined gravimetrically as BaSOa according to standard methodology, and the reaction changed 42% barite to BaCO3 under the above conditions.

Example 2

Under the same conditions as in Example 1, but at 150 ° C, the degree of conversion of the barite to BaCO 3 was 63%.

Example 1 and d 3

Using a 25% solution of K 2 CO 3 and Na 2 CO 4 (1.3: 1 by weight) under the same conditions as in Example 1, a 30% degree of conversion of the barite to BaCO 3 was determined.

We compare the effect of the known flushing liquid according to U.S. Pat. 4,288,333:

At a temperature of 70 ^° C in a mixture containing

1.2 ml of H2O and 0.524 g of natural barite with a concentration of 80% BaSCL and 0.37 moles of a LiOH-treated macrocyclic polyether to pH 11 managed to dissolve: 53% BaSCU.

This result was achieved by rotating the entire system (3 rpm) and after 96 hours.

The chemical process according to the invention can be applied mainly in drilling practice, since barite (BaSOi) is one of the basic loadings of drilling suspensions. Clogging of the productive zone pores with barite particles and at the same time its insolubility and chemical inertness are serious problems of exploitation. Pokie! a lot of barite was overdosed in a well for various reasons, often due to acid stimulation of the oil-bearing horizon. Even with hydrochloric or hydrofluoric acid, BaSO3 does not react and is not affected by strong hydroxides and redox agents.

By removing the curdled barite by the process of the invention, i. j. subsequent treatment with an aqueous solution of alkali carbonates, mixtures thereof, or ammonium carbonate at a concentration greater than 5% (by weight), washing the soluble salts with water, and acidic stimulation of the horizon may increase the permeability and thus the yield of the oil tank horizon. Due to its inherent properties towards clay minerals, the K2CO3 solution is particularly suitable for very deep (“hot”) wells and for locations with a real temperature not exceeding 50 ° C (NH4COCOs).

Claims (1)

A method for the chemical removal of barium sulphate in mineral mixtures, characterized in that by impregnating an aqueous solution of alkali metal carbonates, mixtures thereof or ammonium carbonate, at a concentration of more than · 5% by weight per sulphate The barium exchanges occur in a double-exchange reaction, wherein the soluble alkali metal or ammonium salts are removed by washing, water and the remaining barium carbonate is dissolved in acids or complexing agents.