Gradient treatment process for multi-path recycling of drilling mud of oil and gas field

Abstract

The invention discloses a stepped treatment process for multi-path recycling of oil and gas field drilling mud, which comprises the following steps: oxidizing and breaking gel of the drilling mud to scatter the mud structure, and then granulating and coagulating; then, carrying out the following gradient treatment: step 1, filtering the outlet water of granulation and coagulation, and taking the filtrate as reinjection water; step 2, carrying out nucleation granulation reaction on the filtrate obtained in the step 1, using effluent for preparing drilling fluid, and carrying out solid waste treatment on solid-phase crystal seeds and solid-phase mud cakes subjected to granulation and coagulation; and step 3, carrying out ozone flotation reaction on the effluent obtained in the step 2, wherein the effluent is used for preparing the guanidine gum fracturing fluid. According to the method, resource recycling of the waste drilling mud is achieved, the usage amount of a gel breaker in a traditional gel breaking and filter pressing technology is reduced, a filter pressing plate is omitted, the treatment efficiency in the mud recycling treatment process is improved, the treatment cost of the waste water-based drilling mud is reduced, different recycling ways can be met, and the method is suitable for popularization and application. And specific operation is flexible and changeable.

Description

Technical Field The invention belongs to the technical field of harmful substance treatment, relates to harmless treatment of oil and gas field drilling mud, and particularly relates to a cascade treatment process for multi-path reuse of oil and gas field drilling mud. Background Art Abandoned drilling mud from oil and gas fields is a complex multiphase system composed of water, rock cuttings, clay, petroleum, drilling additives and metal ions. It has the characteristics of complex composition, stable performance, high pH, ​​high suspended matter content, many types of organic additives, wide pollution sources and discontinuous emissions. Therefore, its solid-liquid separation is extremely difficult. At present, the main method used for abandoned drilling mud is the "gel breaking + filter pressing" process to achieve the solid-liquid separation of mud, but this treatment method has the following main problems: 1) Incomplete gel breaking affects the separation effect: During the gel breaking process, the polymer and clay particles in the mud are not fully decomposed, resulting in the inability to completely disintegrate the colloid system, thus affecting the solid-liquid separation efficiency. Incomplete gel breaking will cause the mud viscosity to remain high, increase the burden of the filter press, lead to poor solid-liquid separation effect, make it difficult to achieve the expected dehydration target, and ultimately affect the overall efficiency of the treatment. 2) High energy consumption and severe equipment wear in the filter press process: The filter press process usually requires a high pressure to achieve solid-liquid separation of the mud, and the high concentration of solid particles in the mud will cause wear on the filter press equipment, shorten the service life of the equipment, and increase maintenance and replacement costs. In addition, the filter press equipment consumes a lot of energy under high pressure operation, especially when the mud has a high water content, the processing time is long, which further increases the operating cost and energy consumption. 3) The residual pollutants in the filtrate are high, making it difficult to meet the relevant standards for different reuse methods on site: Despite the gel breaking and filter pressing treatment, the filtrate often still contains high concentrations of organic pollutants, heavy metal ions and suspended solids. These residual pollutants make it difficult for the filtrate to meet the relevant reuse standards. Due to the complex and high cost of subsequent treatment processes, direct discharge of the filtrate will cause pollution risks to the environment, increasing the difficulty of handling waste mud and environmental pressure. Summary of the invention In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a cascade treatment process for the multi-path reuse of oil and gas field drilling mud, aiming to achieve rapid, efficient and flexible treatment of waste drilling mud to meet the water reuse needs of different reuse paths on site, and to solve the problems of low treatment efficiency, incomplete removal of pollutants, high energy consumption and high cost, and unclear resource utilization path caused by large mud production in the prior art. In order to achieve the above object, the technical solution adopted by the present invention is: A cascade treatment process for multi-path reuse of oil and gas field drilling mud comprises the following steps: Step 1, oxidizing and degelling the drilling mud to break up the mud structure, followed by granulation and coagulation; Step 2: To further enrich the reuse pathways, the following cascade treatment is performed: In the first stage, the effluent from granulation and coagulation is filtered and the filtrate is used as reinjection water; Step 2: The filtrate obtained in step 1 is subjected to a nuclear crystal granulation reaction to remove high-valent metal ions such as aluminum, magnesium, and calcium. The effluent is used to prepare drilling fluid, and the solid phase crystal seeds and the solid phase mud cake after granulation and coagulation are treated as solid waste; In the third stage, the effluent obtained in the second stage is subjected to ozone flotation reaction to remove organic pollutants, and the effluent is used to prepare guar gum fracturing fluid. In one embodiment, the method for implementing step 1, oxidizing and degelling the drilling mud is as follows: A composite calcium hypochlorite breaker is added to the drilling mud, and the breaker is subjected to hydraulic stirring to break the flocculation and break the mud structure; the composite calcium hypochlorite breaker is composed of a mixture of calcium hypochlorite and an activated breaker auxiliary agent, wherein the calcium hypochlorite content is 0.8% to 2.5% by weight, and the activated breaker auxiliary agent content is 0.8% to 1.2% by weight. This step utilizes calcium hypochlorite to couple with other degumming auxiliary agents, which significantly reduces the amount of degumming agent required for normal destabilization of the mud and effectively reduces the steric hindrance between the mud particles, creating favorable conditions for subsequent process treatment. In one embodiment, the activated gel-breaking auxiliary agent is one or more of sodium hypochlorite, ferrous sulfate, and ferric chloride. In one embodiment, the step 1, granulation and coagulation is implemented as follows: Add flocculant PAC to the drilling mud after oxidation and degelling and stir quickly, then add coagulant aid PAM and stir slowly, the rapid stirring has a speed range of 500r / min to 800r / min, and the hydraulic retention time is 1min to 3min; the slow stirring has a speed range of 60r / min to 100r / min, and the hydraulic retention time is 7min to 9min. This step adopts a high-efficiency solid-liquid separation and granulation coagulation process. By adding flocculants and coagulants and assisting with hydraulic regulation, the particles are quickly flocculated and condensed to form a dense granulation body, which significantly improves the mud-water separation efficiency and achieves a high-efficiency solid-liquid separation effect. The traditional filter press operation process is avoided, and the effluent can meet the reinjection requirements by filtering with a simple filter cloth. In one embodiment, based on the weight of the drilling mud, the amount of the flocculant PAC added is 0.6% to 0.8%, and the amount of the coagulant aid PAM added is 0.05 to 0.06‰. In one embodiment, the first step uses filter cloth to remove suspended matter in the granulation and coagulation effluent to meet the water requirement for reinjection. In one embodiment, in the second step, the filtrate is sent to a nuclear crystal reaction device, and special seed crystals for hardness removal are added to induce precipitation and coagulation of metal ions. In one embodiment, the special seed crystal for hardness removal is a mixture of Na2CO3 and NaOH. Based on the weight of the filtrate used, the dosage of Na2CO3 is 2‰ to 4‰, and the dosage of NaOH is 0.8‰ to 1‰. In one embodiment, in the second stage, the solid phase seed and the solid phase mud cake after granulation and coagulation are treated as solid waste, and the implementation method is as follows: The solid phase mud cake is solidified by a solidifying agent and then landfilled or recycled, and the solid phase seed crystal is directly recycled. In one embodiment, in the step three, a coagulant PAC is further added to perform coagulation and simultaneous ozonation treatment. Based on the weight of the effluent used, the dosage of the coagulant PAC is 1.6‰ to 2‰, and the dosage of ozone is 0.12‰ to 0.15‰. Compared with the prior art, the treatment process of the present invention realizes the resource recycling of waste drilling mud, reduces the use of gel breaker in the gel breaking stage of the traditional treatment process of waste drilling mud "gel breaking + filter pressing", eliminates the filter pressing plate, improves the treatment efficiency in the mud reuse process, reduces the treatment cost of waste water-based drilling mud, and introduces deep treatment of filtrate for other reuse pathways, thereby being able to meet different reuse pathways and having flexible and varied specific operations. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a principle block diagram of the ladder processing of the present invention. Figure 2 It is a schematic diagram of water discharge of the operating effect of an embodiment of the present invention. DETAILED DESCRIPTION The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples. In order to achieve efficient treatment of abandoned drilling mud and solve the problems of low treatment efficiency, incomplete removal of pollutants, high energy consumption, high cost and unclear resource utilization path in existing treatment methods, the present invention provides a cascade treatment process for multi-path reuse of oil and gas field drilling mud, which can quickly, efficiently and flexibly treat the abandoned drilling mud generated in the process of oil and gas field exploitation to achieve multi-path cascade recycling. The process of the present invention mainly includes oxidation degelling, granulation coagulation and cascade utilization, wherein the cascade utilization is specifically divided into three stages, which are respectively achieved by filtration, nucleation granulation and ozone flotation. Figure 1The corresponding system for executing the process of the present invention is shown, which mainly includes a slurry treatment unit and a filtrate treatment unit, and may further include a solid waste treatment unit. The slurry treatment unit mainly performs oxidation degelling and granulation coagulation as well as solid-liquid separation, and the filtrate treatment unit mainly performs filtration, nucleation granulation reaction and ozone flotation reaction to achieve cascade recovery. As follows, the present invention is further described in combination with the process and the unit. Oxidative degelling reaction: Add degelling agent to the waste drilling mud to be treated, and perform degelling and flocculation through hydraulic stirring to break up the mud structure and reduce the steric hindrance between the suspended colloidal particles in the mud, thus creating favorable conditions for the subsequent efficient solid-liquid separation of the mud. Granulation and coagulation: The drilling mud after oxidation and degelling is subjected to rapid stirring and slow stirring treatments in turn, and PAC and PAM are added in two stages. The addition of PAC in the rapid stirring stage requires high-intensity hydraulic stirring to break and homogenize the flocs, so that the flocs produce a dehydration effect under the action of hydraulic shear, and then PAM is added in the slow stirring stage to make the homogenized and dehydrated flocs flocculate and condense, and finally form a dense granulation. Granulated sludge can be efficiently precipitated to obtain solid mud cake and liquid filtrate in a short time, and the filtrate can be reused for different purposes through deep treatment processes. Deep treatment of filtrate: Through filtration, crystallization granulation reaction and ozone flotation reaction treatment, the purpose of recycling the waste drilling mud in different ways can be achieved. The treatment process is flexible and changeable, and the process route can be selected according to different recycling requirements on site.

[0001] The preferred feature of the present invention is that the mud oxidation degumming reaction is to add a specific prepared composite calcium hypochlorite degumming agent to the collected waste drilling mud, and perform hydraulic stirring for about 10 minutes to break the mud colloidal structure, significantly reduce the mud viscosity, and improve the separation effect of subsequent treatment. Furthermore, the specific prepared composite calcium hypochlorite degumming agent used in the oxidation degumming reaction is to add other activated degumming adjuvants to the ordinary calcium hypochlorite agent, including sodium hypochlorite, ferrous sulfate, ferric chloride, etc., to improve the efficiency of the calcium hypochlorite degumming reaction. Compared with other similar common chemical degumming agents, the dosage can be reduced by about 50%, and calcium hypochlorite is cheaper and easier to obtain. The specific type and dosage vary with the type of waste drilling mud and the well depth. The dosage of calcium hypochlorite is 0.8% to 2.5%, and the dosage of activated degumming auxiliary agent is 0.8% to 1.2%. The type of agent and dosage are selected according to the specific characteristics of the waste drilling mud suspended matter concentration and organic pollutant concentration. Exceeding the above dosage range will not achieve the best degumming effect, affecting the efficient solid-liquid separation of the mud in the granulation and coagulation stage.

[0002] The preferred embodiment of the present invention is that: in the granulation and coagulation stage, the super flocculation and coagulation ability of polyaluminium chloride (PAC) and polyacrylamide (PAM) between colloidal particles is utilized, and PAC and PAM are successively added to the mud after oxidation degelling to achieve flocculation and coagulation of suspended particles in the mud, and rapid stirring with a hydraulic retention time of 1min to 3min and a stirring speed of 500r / min to 800r / min and slow stirring with a hydraulic retention time of 7min to 9min and a stirring speed of 60r / min to 100r / min are respectively performed, and granular sludge with lower water content and higher density is formed after the reaction, and efficient precipitation is directly carried out, which reduces the precipitation time and further improves the solid-liquid separation efficiency of mud and water, and can save the effect of solid-liquid separation through filter pressing operation, thereby reducing the processing time of the process system and reducing the processing cost. Because of the conditions created by the aforementioned oxidation degelling, the dosage of PAC can be further reduced to 0.6% to 0.8%, the PAM requirement is between 0.05‰ and 0.06‰, and the total hydraulic retention time required for the rapid stirring and slow stirring can be controlled within 10 minutes.

[0003] The present invention is preferably that the effluent from granulation coagulation sedimentation can be treated in the following three deep treatment ways to achieve different reuse ways, namely the three steps of the present invention. Step one, filtration is achieved by filter cloth, and the effluent is first simply intercepted and filtered by the filter cloth to remove a very small amount of suspended matter in the effluent from granulation coagulation, so as to meet the requirements of water for reinjection and realize the reuse way of reinjection. Step two, the filtered effluent can be further treated by a nuclear crystal granulation process to remove high-valent metal ions therein, so as to meet the requirements of preparing drilling fluid for reuse. Step three, the nuclear crystal effluent is subjected to a highly efficient organic matter removal process of coagulation and simultaneous ozonation, and the effluent water quality can meet the relevant standards for the preparation of guar gum fracturing fluid. Through the above-mentioned filtrate treatment methods respectively, the purpose of reusing the waste drilling mud in different ways can be achieved, the treatment process is flexible and changeable, and the process approach can be selected according to different reuse requirements on site.

[0004] The present invention is preferably: the nuclear crystal granulation process is to put a certain amount of special crystal seeds for hardness removal into the nuclear crystal reaction device, which plays a role in inducing metal ion precipitation and condensation. Compared with the traditional double alkali method, it has the advantages of shorter hydraulic retention time and lower reagent consumption. In addition, the density of the granulation body formed by the nuclear crystal granulation process is higher than the sludge formed by the double alkali method, achieving the same or even better removal effect, without the need for sludge dehydration and sludge disposal costs, the water output is greatly increased, and resource recycling can be achieved. The granulation body after the reaction can be landfilled or recycled after harmless treatment. While the nuclear crystal granulation has a better hardness removal effect, the operating cost can be reduced by about 20% compared with the double alkali method. The Na2CO3 dosage is 2‰~4‰, the NaOH dosage is 0.8‰~1‰, and the effluent can be used for the preparation of drilling fluid.

[0005] The present invention is preferably: in the three-stage link, a coagulant PAC is also added to perform coagulation and synchronous ozonation treatment. The coagulation and synchronous ozonation process cleverly utilizes the role of PAC as an ozone catalyst to produce a large number of hydroxyl radicals with strong oxidizing properties, thereby improving the efficiency of oxidative decomposition of organic matter. At the same time, ozone and free radicals react to the flocs formed by the hydrolysis of the metal salt coagulant to improve its adsorption capacity for organic matter. Finally, under the synergistic effect of oxidation and coagulation adsorption, efficient and low-agent consumption removal of organic matter is achieved. Compared with the traditional pre-oxidation-coagulation combined process, the removal efficiency of soluble organic matter can be increased by more than 2 times, while the dosage of ozone and coagulant is significantly reduced. The dosage of PAC is 1.6‰ to 2‰, and the dosage of ozone is 0.12‰ to 0.15‰. The effluent can be used for the preparation of guar fracturing fluid.

[0006] The present invention preferably further comprises a harmless treatment stage of the solid phase mud cake and the solid phase seed crystals after the reaction, wherein the harmless treatment stage comprises landfilling or resource utilization after solidification treatment of the solid phase mud cake with a solidifying agent and resource recovery of the solid phase seed crystals.

[0007] In the following example, the multi-path cascade recovery process of waste drilling mud of the present invention is used to treat the waste drilling mud of different stages generated during the drilling process of a certain oil and gas field without landing. The well depths of the treated mud are 2560m (mid-term mud) and 5200m (late-term mud), respectively. The treatment cycle is 10 days, and the daily treatment capacity is 50m 3 . According to the process flow, combined with the above-mentioned relevant process parameters, the following specific treatments are respectively carried out: ① During the oxidation degelling process, the dosage of calcium hypochlorite in the middle mud is 1%, and the dosage of sodium hypochlorite in the middle mud is 2%, and the dosage of sodium hypochlorite in the middle mud is 0.8%, and the dosage of sodium hypochlorite in the middle mud is 1%. ② In the granulation and coagulation stage, the dosage of PAC in the middle mud is 0.6%, and PAM (Yang 80 type) is 0.05‰; the dosage of PAC in the late mud is 0.8%, and PAM (Yang 80 type) is 0.06‰. Finally, the reaction is carried out at a stirring speed of 600r / min for 2min, and then it stays at a speed of 100r / min for 8min. ③ After the granulation and coagulation effluent is filtered through the filter bag, the mid-term mud granulation and coagulation effluent is treated with nuclear crystal granulation and hardness removal at the dosage of 2‰ Na2CO3 and 0.8‰ NaOH, and the late-term mud granulation and coagulation effluent is treated accordingly at the dosage of 4‰ Na2CO3 and 1‰ NaOH; ④ The nuclear crystal granulation effluent is treated with ozone flotation and synchronous coagulation. The mid-term mud ozone dosage is 0.08‰, the PAC dosage is 1.5‰, and the late-term mud ozone dosage is 0.15‰, and the PAC dosage is 2‰, so as to reduce the effluent COD. The operation effect effluent diagram is shown in the attached figure Figure 2 The relevant effluent water quality is shown in Table 1, and the relevant recycled water quality standards are shown in Table 2.

[0008] Table 1: Water quality indicators of mud separation reuse water

[0009]

[0010] Table 2 Water quality index standards for relevant reuse pathways

[0011]

[0012] It can be seen from Table 1 and Table 2 that the waste drilling mud treated by the waste drilling mud multi-path cascade recovery process technology of the present invention can meet the relevant water quality requirements of three different reuse paths, thereby realizing the resource treatment of the waste drilling mud.

[0013] The preferred embodiments of the present invention have been described in detail herein. However, by reading the above, a person skilled in the art can easily understand and identify possible changes and extensions of each embodiment. The applicant intends to include all these possible changes and extensions within the scope of protection of the claims of the present invention.

[0014] The terms used in the present invention are only used to illustrate specific embodiments and are not intended to limit the scope of protection of the present invention. Unless clearly defined herein, all terms (including professional terms in the technical and scientific fields) should be interpreted according to the common understanding of those skilled in the art. In addition, it should be clearly pointed out that, unless otherwise clearly defined herein, terms such as those commonly seen in dictionaries should be interpreted as being consistent with their common meanings in this specification and the context of the relevant technology, and should not be overly idealized or formalized. For well-known functions or structures, in order to make the description concise and clear, they are not described in detail.

Claims

1. A cascade treatment process for multi-path reuse of drilling mud in oil and gas fields, characterized in that: The steps include: Step 1, oxidizing and degelling the drilling mud to break up the mud structure, followed by granulation and coagulation; Step 2: Perform the following cascade processing: In the first stage, the effluent from granulation and coagulation is filtered and the filtrate is used as reinjection water; Step 2: The filtrate obtained in step 1 is subjected to a nuclear crystal granulation reaction, the effluent is used to prepare drilling fluid, and the solid phase crystal seeds and the solid phase mud cake after granulation and coagulation are treated as solid waste; In the third stage, the effluent obtained in the second stage is subjected to ozone flotation reaction, and the effluent is used to prepare guar gum fracturing fluid.

2. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1 is characterized in that: The method for implementing step 1, oxidizing and degelling the drilling mud is as follows: A composite calcium hypochlorite breaker is added to the drilling mud, and the breaker is subjected to hydraulic stirring to break the flocculation and break the mud structure; the composite calcium hypochlorite breaker is composed of a mixture of calcium hypochlorite and an activated breaker auxiliary agent, wherein the calcium hypochlorite content is 0.8% to 2.5% by weight, and the activated breaker auxiliary agent content is 0.8% to 1.2% by weight.

3. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 2 is characterized in that: The activated gel-breaking auxiliary agent is one or more of sodium hypochlorite, ferrous sulfate and ferric chloride.

4. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1 is characterized in that: The implementation method of step 1, granulation and coagulation is as follows: Add flocculant PAC to the drilling mud after oxidation and degelling and stir quickly, then add coagulant aid PAM and stir slowly; The rapid stirring has a speed range of 500r / min to 800r / min, and a hydraulic retention time of 1min to 3min; the slow stirring has a speed range of 60r / min to 100r / min, and a hydraulic retention time of 7min to 9min.

5. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 4 is characterized in that: Based on the weight of the drilling mud, the added amount of the flocculant PAC is 0.6% to 0.8%, and the added amount of the coagulant aid PAM is 0.05 to 0.06‰.

6. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1, characterized in that: In the first stage, filter cloth is used to filter and remove the suspended solids in the granulation and coagulation effluent to meet the requirements of water for reinjection.

7. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1, characterized in that: In the second step, the filtrate is sent to a nuclear crystal reaction device, and special seed crystals for hardness removal are added to induce precipitation and coagulation of metal ions.

8. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 7, characterized in that: The special seed crystal for hardness removal is a mixture of Na2CO3 and NaOH. Based on the weight of the filtrate used, the dosage of Na2CO3 is 2‰ to 4‰, and the dosage of NaOH is 0.8‰ to 1‰.

9. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1, characterized in that: In the second stage, the solid phase seed and the solid phase mud cake after granulation and coagulation are treated as solid waste, and the implementation method is as follows: The solid phase mud cake is solidified by a solidifying agent and then landfilled or recycled, and the solid phase seed crystal is directly recycled.

10. The cascade treatment process for multi-path reuse of oil and gas field drilling mud according to claim 1, characterized in that: In the third stage, a coagulant PAC is also added to carry out coagulation and simultaneous ozonation treatment. Based on the weight of the effluent used, the dosage of the coagulant PAC is 1.6‰ to 2‰, and the dosage of ozone is 0.12‰ to 0.15‰.

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