RU2571786C1 - Method of cleaning spent proppant from oil - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: under method of cleaning spent proppant from oil including pulp preparation by mixing of oily proppants with water, and ultrasound treatment of the produced pulp, said proppants are mixed with water in ratio P:W 1:3.5-5.0, treatment is performed in centrifugal field created by pulp rotation upon its supply under pressure 1.5-3.0 atm at tangent to the internal cylindrical part of separating device. Invention is developed in subclaims.

EFFECT: increased treatment efficiency.

3 cl, 2 ex, 1 tbl, 1 dwg

Description

The invention relates to the field of the oil industry and can be used in the regeneration of oil-contaminated proppant after hydraulic fracturing and its subsequent use as a proppant.

In order to intensify oil production from wells, hydraulic fracturing is performed using proppant, an aluminosilicate material in the form of spherical balls with a diameter of 1.0-2.0 mm, as a proppant. After hydraulic fracturing, proppant contaminated with oil cannot be reused and, as a rule, is stored in specially designated places, representing an environmental hazard to the environment. So every year in the Khanty-Mansi Autonomous Okrug alone more than 100 thousand tons of hydraulic fracturing waste is generated, which contain a large amount of spent proppants contaminated with oil.

A known method for the disposal of oil-contaminated proppant (RF patent No. 2344006, publ. 20.01.2009) on existing equipment, including steaming proppant at a temperature of at least 100 ° C to separate it from oil products, washing in a washing solution using surface-active substances with rotational stirring until complete purification from petroleum products, drying at a temperature of 50-300 ° C. The resulting proppant refined from oil can be used as a filler in a mixture for the preparation of bricks or concrete mixtures for pouring floors in the production of cinder blocks.

The disadvantage of this method is the impossibility of further use of purified proppant as a proppant during hydraulic fracturing, since it is not achieved sufficiently complete removal of oil from the surface of the proppant.

A known method for the disposal of oil-contaminated proppant (RF patent No. 2353642, publ. 04/27/2009), including washing proppant in a washing solution using surface-active substances with rotational stirring until complete purification from oil products, drying at a temperature of 100-300 ° C, applying to proppant granules of phenol-formaldehyde resin - novolac coated proppant granules heated to a temperature of 120-180 ° C, followed by cooling, curing, fractionation and using the obtained proppant during hydraulic fracturing.

The disadvantages of this invention are the complexity of the process of regeneration of contaminated proppant and its high cost, due to the need to use expensive special production equipment and chemicals, the use of chemicals can also lead to a change in the chemical composition of the proppants.

The closest in technical essence is the "Method for the processing of oil sludge" (RF patent No. 2154515, publ. 08.20.2000), including heating the oil sludge and mixing it with a 0.05-0.5% aqueous solution of a composition containing 20-50% demulsifier and 80-50% dispersing agent, which is a mixture of surface-active substances: oxyphos and diproxamine, under ultrasonic treatment with a frequency of 15-35 kHz for 3-5 minutes, while maintaining a ratio of oil sludge to aqueous medium of 1: 3.

The use of this set of operations of the known method for cleaning proppants from oil has the following disadvantages:

- a deep degree of purification is not achieved, which does not allow reusing proppant as a proppant in hydraulic fracturing and to obtain additional petroleum products for subsequent use;

- the use of a significant amount of chemical reagents (demulsifier and dispersant) of 2-4 kilograms per ton increases the cost and complicates the process, leads to contamination of the proppant surface with these substances, which also will not allow to reuse proppant as a proppant in hydraulic fracturing.

The technical result of the claimed invention is the deep purification of proppants from oil with the aim of reusing purified proppants in hydraulic fracturing processes and obtaining additional oil products as purification products for subsequent use.

The specified result is achieved by the fact that in the method of purification of spent proppants from oil, including the preparation of pulp by mixing oil-contaminated proppants with an aqueous medium and ultrasonic treatment of the obtained pulp, according to the invention, these proppants are mixed with water in the ratio P: B 1: 3.5-5, 0, the processing is carried out in a centrifugal field formed by the rotational movement of the pulp when it is fed under a pressure of 1.5-3.0 atm tangentially to the inner cylindrical part of the separation apparatus. Moreover, the processing is carried out using emitters installed in the lower end part of the separation apparatus and the processing is carried out twice.

Supply of prepared pulp with oil-contaminated proppants at a pressure of 1.5-3.0 atm. tangential to the inner cylindrical part of the separation apparatus provides its rotational movement and oil, not fixed on the surface of the proppants, moves to the axis of rotation and is removed with an upward flow of water. The proppants with the oil shell are concentrated in the peripheral zone near the wall of the cylindrical part of the separation apparatus, and when they move to the outlet, they undergo the operation of scrubbing part of the oil shell from the surface of the proppants due to the constrained movement of the proppants in the rotating pulp stream. Maintaining the ratio of spent proppants to water 1: 3.5-5.0 provides a more energetic course of surface reactions and a more intense scrubbing of the oil shell from the surface of the proppants. Oil removed from the surface of the proppants due to the rubbing effect also moves to the axis of rotation and is removed from the separation apparatus with an upward flow. The combined effect of a centrifugal field and ultrasonic treatment enhances the factors affecting the efficiency and speed of oil removal from the surface of proppants when they are constrained in the flow, which allows deep cleaning of the proppant surface from thin films of oil. Due to the multidirectional movement of oil and proppants in a centrifugal field, the likelihood of secondary contamination of proppants with oil previously removed from their surface is sharply reduced.

The inventive method of processing oil-contaminated proppants allows, by short-term combined exposure to a centrifugal field and ultrasonic treatment, to reduce the oil content in spent proppants to 0.1% and to preserve the shape and primary dimensions of the proppants. This allows the use of oil-free proppants for reuse in hydraulic fracturing technology.

In addition, the processing does not use chemicals and pulp heating.

Example 1

A sample of oil-contaminated proppants (P) in an amount of 10 kg with an oil content of 10% was mixed with circulating water (B) in an amount of 50 liters in a container with a stirrer (P: B = 1: 5). The resulting pulp was pumped through the upper branch pipe of the separation apparatus tangentially into its cylindrical part under a pressure of 1.5 atm. The oil removed from the surface of the proppants, due to centrifugal acceleration and the difference in the densities of water and oil products, moves to the center of rotation of the pulp and is carried upward from the apparatus through the upper central pipe. Ultrasonic processing of proppants moving in straitened conditions along a spiral trajectory near the walls of the cylindrical part of the separation apparatus from the upper nozzle of the pulp inlet to the lower outlet nozzle is carried out by ultrasonic emitters installed in the lower end part of the cylindrical separation chamber with an ultrasonic frequency of 20.0 kHz. The processing time of the pulp in the separation apparatus was 20 seconds. The proppants purified from oil, discharged through the lower nozzle mounted tangentially to the cylindrical body of the separation apparatus, were dried and analyzed for residual oil content. The oil content in the proppants purified from oil was 1.1%, the degree of purification 89%. Sufficiently deep proppant cleaning was achieved without the use of chemicals.

Example 2

For deeper oil removal, the purified proppants with an oil content of 1.1% were subjected to repeated purification by ultrasonic treatment in a centrifugal field created by the rotation of the pulp in the cylindrical part of the separation apparatus. Schematic diagram of proppant cleaning is shown in the figure. The frequency of ultrasonic exposure is 20.0 kHz. The exposure time corresponds to the residence time in a centrifugal field of a two-stage separation apparatus. The shape and size of the proppants purified by ultrasound in a centrifugal field do not change, which was confirmed by the data of particle size analysis and studies of the shape factor of the primary and purified proppants.

The content of oil products in proppants purified from oil after a double ultrasonic treatment in a centrifugal field was 0.1%, and the purification efficiency was 99%.

The results of the purification of proppants by known and proposed methods are shown in the table.

Purified proppants can again be used as an additive to a proppant in hydraulic fracturing, as well as in the construction industry, the production of building materials and as a pavement. But the latter is economically much less attractive, as proppants cost $ 1,000 per ton.

The method of purification of spent proppants from oil

Claims (3)

1. The method of purification of spent proppants from oil, including the preparation of pulp by mixing oil-contaminated proppants with an aqueous medium and ultrasonic treatment of the obtained pulp, characterized in that these proppants are mixed with water in a ratio of P: B 1: 3,5-5,0, processing carried out in a centrifugal field formed by the rotational movement of the pulp when feeding it under a pressure of 1.5-3.0 atm tangential to the inner cylindrical part of the separation apparatus. 2. The method according to p. 1, characterized in that the processing is carried out using emitters installed in the lower end part of the separation apparatus. 3. The method according to p. 1, characterized in that the said treatment is carried out twice.

Images