Method for recovering weighting agent in shale gas drilling cuttings

Abstract

The invention provides a method for recovering a weighting agent in shale gas drilling cuttings. The method mainly comprises the following steps: (1) adding a proper amount of acidic solution into the deoiled drilling cuttings to remove impurity metal ions, filtering, washing and drying; (2) mixing the drilling cuttings subjected to impurity removal with caustic alkali; (3) dissolving and enriching silicon and aluminum components in the mixed material under a high-temperature and high-pressure hydrothermal condition; and (4) filtering to obtain a filtrate which is a water glass crude product, and washing and drying filter residues to obtain the barite weighting agent. In order to solve the problems that shale gas drilling cuttings are large in yield, high in environmental harm and difficult in barite weighting agent recovery, efficient recovery of barite in the drilling cuttings can be achieved by conducting alkali dissolution on silicon and aluminum components in the drilling cuttings. The method for recovering barite has the advantages of simple process, low cost, low energy consumption and high recovery rate, can be applied to industrial production, and also has certain recovery value as the byproduct is the crude sodium silicate product.

Description

Technical Field

[0001] The invention relates to the field of solid waste resource utilization, and in particular to a method for recovering a weighting agent from shale gas drilling cuttings. Background Art

[0002] my country is rich in shale gas resources and is estimated to be one of the countries with the largest shale gas reserves in the world. According to the Outline of the Construction Plan for the Chengdu-Chongqing Economic Circle, the Sichuan-Chongqing region will continue to play the leading role of Changning-Weiyuan (Sichuan) and Fuling National Shale Gas Demonstration Zone (Chongqing), promote the rolling development of shale gas, build a natural gas (shale gas) production capacity base of 100 billion cubic meters, and create China's "Gas Daqing". Drilling engineering is the main engineering means to obtain natural gas and shale gas, and is an operational project in oil and gas exploration and development activities. The implementation of drilling engineering for shale gas resource development will produce a large amount of drilling cuttings, especially in the drilling stage of shale gas horizontal wells, which may produce a large amount of harmful oil-based drilling cuttings, which need to be safely disposed of. The development trend is resource recycling. However, when drilling oil wells and gas wells, in order to prevent blowout accidents, barite powder is generally added to the mud to increase the mud weight, strengthen the well wall and cool the drill bit. According to statistics, 80% to 90% of the total global barite consumption is mainly used for oil and gas exploration. This also results in a large amount of barite with extremely high chemical and thermal stability in shale gas drilling cuttings, so the resource reuse of drilling cuttings requires high process conditions and high energy consumption. Therefore, recycling and utilizing barite in shale gas drilling cuttings is extremely important.

[0003] At present, relevant research has been conducted on the barite recovery technology of drilling fluid in China. Combining mineral processing technology to recover barite in drilling fluid is one of the most common methods. Patent CN106944249A discloses a method combining gravity separation, magnetic separation and flotation to carry out combined mineral processing of low-grade barite waste materials, but this method is only applicable to traditional gangue minerals, not to oil and gas cuttings, and has high cost and long cycle. Patent CN114029155B provides a mineral processing method for recovering weighting agents in drilling fluid by gravity separation. This method improves the purity of the recovered weighting agent by using a gravity separation process flow of multiple classifications and multiple roughing and selections, but this method has a complex process and a low recovery rate, and is not suitable for industrial production. Patent CN100562644C discloses a system for recovering barite in weighted drilling fluid and removing useless solid phases. The system connects the front and rear centrifuges and other related systems in series, and while recovering most of the barite, most of the rock cuttings particles are discharged, but this method has relatively high requirements for system equipment. Patent CN115340121A obtains barite concentrate and rock cuttings tailings from shale gas drilling dry residue after harmless treatment through dispersion treatment and gravity separation. The barite extracted by this method has high purity and reaches industrial grade, realizing the recycling of barite. At the same time, the remaining product is not environmentally harmful and can be used as cement admixture and raw material for firing ceramsite, which also improves the use and value of dry residue. Patent CN104609455B recovers barite with a purity of up to 90% by flotation, but the flotation cycle of this method is long and the surface hydrophobicity of the barite obtained by flotation is strong. CN116060205A combines flotation and centrifugal separation and purification to recover high-purity barite from the residual solid phase of thermal desorption of drilling oil-based rock cuttings. This method is relatively cumbersome in both flotation and centrifugal stages.

[0004] The present invention utilizes an acidic solution to remove impure metal ions in the deoiled drill cuttings, then adds caustic soda to mix, and after adding water to the mixed material, dissolves it under high temperature and high pressure hydrothermal conditions to generate a crude water glass product, which can be filtered and washed to obtain a high-purity BaSO 4 .BaSO 4 It has strong thermal and chemical stability, high recovery rate, and the crude product water glass is often used in the barite flotation suppression process and other process production, and has good industrial value. The technology is simple, low cost, low energy consumption, high recovery efficiency, and easy to industrialize. Summary of the invention

[0005] The present invention provides a method for recovering weighting agent from shale gas drilling cuttings. The specific invention contents are as follows:

[0006] The method firstly acidifies and removes impurities from harmless drilling cuttings, then adds caustic soda to mix, adds water to the mixture and dissolves it under high temperature and high pressure hydrothermal conditions to generate a crude water glass product, and then filters, washes and dries to obtain BaSO 4 .

[0007] Beneficial effects of the present invention:

[0008] (1) The present invention aims to solve the problems of large shale gas drilling cuttings production, high environmental hazards, and difficulty in recovering barite weighting agents. By alkali dissolving the silicon and aluminum components in the drill cuttings, a method for chemically recovering shale gas drilling cuttings weighting agents is provided. The barite recovered by this method has a higher purity.

[0009] (2) The process of the present invention is simple to operate, low in cost, low in energy consumption, can be processed in large quantities, and has potential for engineering application.

[0010] (3) The byproduct of the present invention is a crude water glass product, which also has good industrial application value. DETAILED DESCRIPTION

[0011] Implementation Case 1:

[0012] A method for recovering shale gas drilling cuttings weighting agent, comprising: mixing the removed cuttings with sodium hydroxide according to mSiO 2 :mNaOH=0.4, according to mNaOH:mH 2 O=0.05, water is injected into the mixed material, and the mixture is sealed and dissolved at 400°C for 6 hours. After filtering, washing and drying, a barite weighting agent with a recovery rate of 85.35% can be obtained.

[0013] Implementation Case 2:

[0014] A method for recovering shale gas drilling cuttings weighting agent, comprising: mixing the removed cuttings with sodium hydroxide according to mSiO 2 :mNaOH=0.5, according to mNaOH:mH 2 O = 0.05, water is injected into the mixture, and after sealing, it is dissolved at 500 ° C for 6 hours. After filtering, washing and drying, a barite weighting agent with a recovery rate of 92.64% can be obtained. Finally, it is explained that the above preferred embodiments are only used to illustrate the technical scheme of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, it should be understood by those skilled in the art that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. The present invention discloses a method for recovering weighting agent from shale gas drilling cuttings, which mainly comprises the following steps: (1) Impurity removal: Add an appropriate amount of acidic solution to the deoiled drill cuttings to remove impure metal ions and filter, wash and dry; (2) Material mixing: mixing the drill cuttings after impurities removal with caustic soda; (3) Active silicon and aluminum enrichment: Add water to the mixed material and dissolve and enrich the active silicon and aluminum under high temperature and high pressure hydrothermal conditions; (4) Recovery of weighting agent: filtration, the filtrate is the crude product of water glass, and the filter residue is washed and dried to obtain the barite weighting agent.

2. The material mixture according to claim 1, wherein the main characteristics are as follows: mSiO2:mNaOH=0.3-0.

5.

3. The water dissolution according to claim 1, wherein the main characteristics are as follows: mNaOH:mH2O=0.04-0.

06.

4. The high-temperature and high-pressure hydrothermal equipment according to claim 1 has the following main features: the high-temperature and high-pressure hydrothermal equipment is a closed high-temperature and high-pressure reactor.

5. The high temperature and high pressure hydrothermal process according to claim 1, wherein the main characteristics are as follows: the reactor temperature is 400-500°C, the constant temperature time is 4-5h, the pressure is 5×10 5 -7×10 5 Pa.