A gel breaking treatment method for water-based drilling waste fluid

Abstract

The present application discloses a degelling treatment method for water-based drilling waste fluid, comprising adding chemical agents into the drilling waste fluid, wherein the chemical agents include a degelling agent, a flocculant and a coagulant aid; the degelling agent is methacryloyloxyethyl trimethylammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk; the problem that the treatment effect of the existing treatment method does not meet the standard is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste oilfield drilling fluid treatment, and in particular to a method for treating waste water-based drilling fluid suitable for adjusting well polymers, high-performance water-based drilling fluids and deep horizontal well water-based drilling fluids. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] The Songliao Basin is a typical freshwater sedimentary continental shale. Compared with the shale mainly deposited in marine or saline lake basins at home and abroad, there are obvious differences in mineral composition, which is manifested in the high clay mineral content, large thickness of single-layer mud shale, and wide distribution range. In order to meet the needs of safe drilling, polymer water-based drilling fluids, high-performance water-based drilling fluids, and deep horizontal well water-based drilling fluids that are suitable for the Upper Cretaceous strata in the northern Songliao Basin have gradually been formed. They are highly targeted, highly matched, distinctive, and technologically mature. More than 10,000 wells have been used, and the annual cumulative waste mud can reach more than 150,000 cubic meters. If it is not effectively treated, it will cause serious environmental pollution. Therefore, it is urgent to seek safe and effective methods to achieve the harmless treatment of waste water-based drilling fluids, so as to promote the development of waste water-based drilling fluid disposal in the direction of "harmlessness, resource utilization, standardization, and industrialization."

[0004] Many methods have been proposed for the treatment of waste water-based drilling fluids at home and abroad. At present, solid-liquid separation technology is mostly used. This technology is to destabilize the waste water-based drilling fluid by adding a chemical agent, and then perform solid-liquid separation, so that the separated liquid meets the standard and is discharged, and the solid phase is landfilled or reprocessed. The patent with application number CN102019110B discloses a chemical enhanced solid-liquid separation method for drilling waste fluid. The drilling waste fluid is mixed with clean water, and a destabilizing agent, an adsorbent, and a flocculant are added. The solid-liquid separation is completed by a centrifuge, and the water content of the mud is ≤70%. The patent with application number CN 109052908 A discloses a polysulfone system waste drilling mud treatment method, by adding a destabilizing agent, a pH regulator, and a coagulant, and mechanical separation is obtained to obtain separated sewage and separated sludge, and the separated sludge is sent to a sludge treatment station for centralized treatment. The separated sewage is treated by conventional treatment and purification methods to obtain qualified purified water for reinjection or discharge.

[0005] Although the treatment method mentioned in the above patent document has certain effects, due to the differences in the sedimentary environment and mineral composition of shale reservoirs, the above treatment process is not suitable for the harmless treatment of water-based drilling fluid in the Upper Cretaceous high mud formation in the Songliao Basin. Specifically, the suspended solids content (>300mg / L), COD content (>300mg / L) and chromaticity (yellow, green) of the effluent from gel breaking and flocculation are high, and the water content of the mud cake is high (>60%). The treatment effect is not up to standard and secondary treatment is still required, which increases the cost.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the invention

[0007] In view of this, the present disclosure provides a method for degelling waste water-based drilling fluid to solve the problem that the treatment effect of the existing treatment method is not up to standard.

[0008] In order to achieve the above-mentioned purpose of the invention, the degelling treatment method of water-based drilling waste fluid comprises adding a degelling agent, a flocculant and a coagulant aid to the drilling waste fluid, and is characterized in that:

[0009] The gel breaker is methacryloyloxyethyl trimethyl ammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk.

[0010] In some embodiments of the present disclosure, the flocculant is a cationic polyacrylamide with a molecular weight of 8-12 million and an ionicity of 10-20.

[0011] In some embodiments of the present disclosure, the breaker is diluted to a breaker solution with a mass concentration of 1% to 3%, and the added amount of the breaker solution is 1.0% to 5.0% of the weight of the drilling waste fluid.

[0012] In some embodiments of the present disclosure, the coagulant is diluted to a coagulant solution with a mass concentration of 1% to 1.5%, and the amount of the coagulant solution added is 0.3% to 2.5% of the weight of the drilling waste fluid.

[0013] In some embodiments of the present disclosure, the flocculant is diluted to a flocculant solution with a mass concentration of 0.01% to 0.05%, and the amount of the flocculant solution added is 0.003% to 0.007% of the weight of the drilling waste fluid.

[0014] In some embodiments of the present disclosure, the degelling agent is first added to the drilling waste fluid and mixed, then the coagulant aid is added and mixed, and finally the flocculant is added and mixed.

[0015] In some embodiments of the present disclosure, the mixing and stirring time for adding the degelling agent is 20 to 30 minutes, the mixing and stirring time for adding the coagulant aid is 20 to 30 minutes, and the mixing and stirring time for adding the flocculant is 20 to 30 minutes.

[0016] In some embodiments of the present disclosure, before adding the degumming agent, the solid particles in the drilling waste fluid are dispersed by stirring.

[0017] In some embodiments of the present disclosure, the mixed phase after the flocculant is mixed is subjected to solid-liquid separation treatment, the separated liquid is transported to a sewage treatment system, and the separated solid is landfilled or used as paving material.

[0018] In some embodiments of the present disclosure, the solid-liquid separation process uses a plate and frame filter press, the filtration pressure of the plate and frame filter press is 0.8~1.0MPa, and the filtration time is 20~30min.

[0019] The present disclosure has the following beneficial effects:

[0020] The degelling treatment method for waste water-based drilling fluid disclosed in the present invention is mainly a chemical destabilization method, specifically, a preliminary chemical treatment of the drilling waste fluid, using the method of adding chemical agents to change the properties of the colloidal particles and suspended solids in the drilling waste fluid, so that the dispersed colloidal particles and suspended solids and other pollutants are aggregated to form large particles, and then the colloidal particles and suspended solids and other pollutants are separated by solid-liquid separation. To this end, the chemical agents selected for addition in the treatment method disclosed in the present invention are degelling agents, flocculants and coagulants, wherein the degelling agent is methacryloyloxyethyl trimethylammonium chloride, which uses its positive charge to neutralize the negative charge of the colloidal particles in the drilling waste fluid, destroy the stability of the colloidal particles and condense to form large particles, and then quickly precipitate and separate, effectively reducing the turbidity and color of the drilling waste fluid.

[0021] The flocculant has a high molecular polymer bridging effect. The flocculant is an organic high molecular polymer with a very long chain structure and many free radicals, so as to firmly adsorb various suspended solids in the liquid phase and form a bridging effect between the suspended solids to achieve flocculation. When a small amount of high molecular polymer is added to the waste drilling fluid, it is quickly adsorbed on the surface of the colloidal particles; in the initial stage of flocculation, one end of the polymer molecular chain is adsorbed on the particle surface, and the other end is extended in the solution. Other particles will be adsorbed on the extended chain link. Therefore, two colloidal particles are adsorbed on one high molecular chain, located on both sides. Through the connection and bridging of the molecular chain, the colloidal particles gather together to form flocs, and settle and flocculate. At the same time, when the amount of high molecular polymer added is too high, it will cause the system to stabilize again.

[0022] The coagulant aid is a cationic electrolyte, which is used to supplement the positive charge consumed by the breaker, improve the particle structure, increase the particle density and mechanical strength, and reduce the turbidity and color of the filtrate.

[0023] In summary, after being treated by the method disclosed in the present invention, the drilling waste liquid can achieve the purpose of degumming, dealkali and decolorization. The filtrate after treatment is colorless and transparent, the COD index can be reduced from the original 8000 to below 80, the suspension and oil content indexes meet the requirements of SYT 5329 "Water Quality Index for Water Injection in Clastic Reservoirs", and the water content of the mud cake is ≤60%. DETAILED DESCRIPTION

[0024] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure.

[0025] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0026] Example 1

[0027] The embodiment of the present disclosure performs harmless treatment on the high-performance water-based drilling fluid discarded from Daqing Oilfield, and the specific steps are as follows:

[0028] (1) Unload the discarded high-performance water-based drilling fluid into the mud tank and continue to stir it at a low speed to prevent the solid phase particles of the drilling waste fluid from settling and agglomerating.

[0029] (2) adding a degumming agent to the drilling waste liquid, wherein the concentration of the degumming agent is 1.5%, and the amount added is 1.125% of the weight of the drilling waste liquid in step (1); stirring is performed for 20 to 30 minutes to destroy the colloidal stability of the drilling waste liquid; then adding a coagulant, wherein the concentration of the coagulant is 1.5%, and the amount added is 0.375% of the weight of the drilling waste liquid in step (1); stirring is performed for 20 to 30 minutes to enhance the degumming effect; finally, adding a flocculant, wherein the concentration of the flocculant is 0.01%, and the amount added is 0.005% of the weight of the drilling waste liquid in step (1); stirring is performed for 20 to 30 minutes to agglomerate small particles in the drilling waste liquid into large-sized particles, thereby accelerating the aggregation and sedimentation behavior of the particles.

[0030] (3) The mixed phase obtained after the gel breaking and flocculation reaction (step 2) is pumped into a plate and frame filter press for solid-liquid separation. The separated liquid is transported to a clean water tank through a pipeline and then transported to the inlet of the wastewater treatment system of the oil and gas treatment station of the oil production plant. The mud cake can be landfilled on site or used for paving the well site.

[0031] The volume ratio of the agents described in the first embodiment of the present disclosure is: coagulant aid: gel breaker: flocculant = 1:3:2.

[0032] The gel breaker is methacryloyloxyethyl trimethyl ammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk.

[0033] The flocculant is cationic polyacrylamide with a molecular weight of 8-12 million and an ionicity of 10-20; the preparation method of the flocculant solution is: adding cationic polyacrylamide particles into water and mixing them evenly by stirring, the stirring speed is 60-120r / min, and the stirring time is 120-180min.

[0034] The solid-liquid separation was carried out by plate and frame filter press with a filtration pressure of 1.0 MPa and a filtration time of 25 min.

[0035] The main indicators of the filtrate and mud cake obtained after treatment are shown in Table 1.

[0036] At the same time, the first embodiment of the present disclosure also adopts two patent methods in the background technology to respectively perform harmless treatment on the discarded high-performance water-based drilling fluid, and the treatment results are shown in Table 1.

[0037] Table 1 Indicators of discarded high-performance water-based drilling fluid before and after treatment

[0038]

[0039] Example 2

[0040] The embodiment of the present disclosure performs harmless treatment on the waste well opening polymer water-based drilling fluid of Daqing Oilfield, and the specific steps are as follows:

[0041] (1) Unload the drilling waste fluid into the mud tank and continue stirring at a low speed to prevent the solid particles of the drilling fluid from settling and agglomerating.

[0042] (2) adding a degumming agent to the drilling waste fluid, wherein the concentration of the degumming agent is 1.5%, and the amount added is 1.05% of the weight of the mud in step (1), and the mixture is stirred for 20 to 30 minutes to destroy the colloidal stability of the drilling fluid. Then, adding a coagulant, wherein the concentration of the coagulant is 1.5%, and the amount added is 0.525% of the weight of the mud in step (1), and the stirring time is 20 to 30 minutes to enhance the degumming effect. Finally, adding a flocculant, wherein the concentration of the flocculant is 0.01%, and the amount added is 0.005% of the weight of the drilling waste fluid in step (1), and the stirring time is 20 to 30 minutes to agglomerate small particles in the drilling waste fluid into large-sized particles, thereby accelerating the aggregation and sedimentation behavior of the particles.

[0043] (3) The mixed phase obtained after the gel breaking and flocculation reaction (step 2) is pumped into a plate and frame filter press for solid-liquid separation. The separated liquid is transported to a clean water tank through a pipeline and then transported to the inlet of the wastewater treatment system of the oil and gas treatment station of the oil production plant. The mud cake can be landfilled on site or used for paving the well site.

[0044] The volume ratio of the agents is: coagulant aid: degelling agent: flocculant = 7:14:10.

[0045] The gel breaker is methacryloyloxyethyl trimethyl ammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk.

[0046] The flocculant is a cationic polyacrylamide with a molecular weight of 8-12 million and an ionicity of 10-20. The preparation method of the flocculant solution is: adding cationic polyacrylamide particles into water and mixing them evenly by stirring, the stirring speed is 60-120r / min, and the stirring time is 120-180min.

[0047] The solid-liquid separation was carried out by plate and frame filter press with a filtration pressure of 0.8 MPa and a filtration time of 30 min.

[0048] The main indicators of the filtrate and mud cake obtained after treatment are shown in Table 2.

[0049] At the same time, Example 2 of the present disclosure also adopts two patented methods in the background technology to respectively perform harmless treatment on the discarded high-performance water-based drilling fluid, and the treatment results are shown in Table 2.

[0050] Table 2 Indicators of abandoned wells before and after treatment with polymer water-based drilling fluid

[0051]

[0052] Example 3

[0053] The disclosed embodiment performs harmless treatment on abandoned deep horizontal well water-based drilling fluid in Daqing Oilfield, and the specific steps are as follows:

[0054] (1) Unload the drilling waste fluid into the mud tank and continue stirring at a low speed to prevent the solid particles of the drilling waste fluid from settling and agglomerating.

[0055] (2) adding a degumming agent to the drilling waste liquid, wherein the concentration of the degumming agent is 3%, and the amount added is 4.5% of the weight of the drilling waste liquid in step (1), and the mixture is stirred for 20 to 30 minutes to destroy the colloidal stability of the drilling waste liquid. Then, adding a coagulant, wherein the concentration of the coagulant is 1.5%, and the amount added is 2.5% of the weight of the drilling waste liquid in step (1), and the stirring time is 20 to 30 minutes to enhance the degumming effect. Finally, adding a flocculant, wherein the concentration of the flocculant is 0.01%, and the amount added is 0.005% of the weight of the drilling waste liquid in step (1), and the stirring time is 20 to 30 minutes, to agglomerate small particles in the drilling waste liquid into large-sized particles, thereby accelerating the aggregation and sedimentation behavior of the particles.

[0056] (3) The mixed phase obtained after the gel breaking and flocculation reaction (step 2) is pumped into a plate and frame filter press for solid-liquid separation. The separated liquid is transported to a clean water tank through a pipeline and then transported to the inlet of the wastewater treatment system of the oil and gas treatment station of the oil production plant. The mud cake can be landfilled on site or used for paving the well site.

[0057] The volume ratio of the agents is: coagulant aid: degelling agent: flocculant = 1:5:1.

[0058] The gel breaker is methacryloyloxyethyl trimethyl ammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk.

[0059] The flocculant is a cationic polyacrylamide with a molecular weight of 8-12 million and an ionicity of 10-20. The preparation method of the flocculant solution is: adding cationic polyacrylamide particles into water and mixing them evenly by stirring, the stirring speed is 60-120r / min, and the stirring time is 120-180min.

[0060] The solid-liquid separation was carried out by plate and frame filter press with a filtration pressure of 1.0 MPa and a filtration time of 20 min.

[0061] The main indicators of the filtrate and mud cake obtained after treatment are shown in Table 3.

[0062] At the same time, Example 3 of the present disclosure also adopts two patent methods in the background technology to respectively perform harmless treatment on the discarded high-performance water-based drilling fluid, and the treatment results are shown in Table 3.

[0063] Table 3 Indicators of abandoned deep horizontal well water-based drilling fluid before and after treatment

[0064]

[0065] Through the harmless treatment of the polymer water-based drilling fluid, high-performance water-based drilling fluid and deep horizontal well water-based drilling fluid of the Daqing Oilfield diversion well in the above embodiments, the treatment effect shows that the post-treatment indicators of the treatment method disclosed in the present invention are significantly better than the post-treatment indicators of the two patent methods described in the background technology, and fully meet the required standard values. Therefore, the treatment method disclosed in the present invention can quickly break the gel and destabilize the waste water-based drilling fluid. After using this method, the drilling fluid has a high solid-liquid separation degree, a low content of suspended matter in the separated liquid, a transparent water body, and a water content of the solid phase mud cake ≤60%.

[0066] Therefore, the method disclosed in the present invention can meet the requirements for harmless treatment of waste water-based drilling fluids from different systems, thereby eliminating the serious pollution of soil, surface and groundwater caused by waste drilling fluids, and realizing environmentally friendly drilling production and resource reuse; moreover, the chemical treatment agent used in the method disclosed in the present invention has low cost, wide source, and simple treatment process, and has the advantages of short time, easy operation, good effect, and low comprehensive treatment cost under similar processes.

[0067] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A method for degelling water-based drilling waste fluid, comprising adding a chemical agent to the drilling waste fluid, characterized in that: The chemical agents include: Gel breakers, flocculants and coagulants; The gel breaker is methacryloyloxyethyl trimethyl ammonium chloride, the flocculant is cationic polyacrylamide, and the coagulant aid is lime milk.

2. The method for degelling water-based drilling waste fluid according to claim 1, characterized in that: The flocculant is a cationic polyacrylamide with a molecular weight of 8-12 million and an ionicity of 10-20.

3. The method for degelling water-based drilling waste fluid according to claim 2, characterized in that: The breaker is diluted to a breaker solution with a mass concentration of 1% to 3%, and the added amount of the breaker solution is 1.0% to 5.0% of the weight of the drilling waste fluid.

4. The method for degelling water-based drilling waste fluid according to claim 3, characterized in that: The coagulant is diluted to form a coagulant solution with a mass concentration of 1% to 1.5%, and the amount of the coagulant solution added is 0.3% to 2.5% of the weight of the drilling waste fluid.

5. The method for degelling water-based drilling waste fluid according to claim 4, characterized in that: The flocculant is diluted to a flocculant solution with a mass concentration of 0.01% to 0.05%, and the amount of the flocculant solution added is 0.003% to 0.007% of the weight of the drilling waste fluid.

6. The method for degelling water-based drilling waste fluid according to any one of claims 1 to 5, characterized in that: The degelling agent is first added to the drilling waste fluid and mixed evenly, then the coagulant aid is added and mixed evenly, and finally the flocculant is added and mixed evenly.

7. The method for degelling water-based drilling waste fluid according to claim 6, characterized in that: The mixing and stirring time of adding the degumming agent is 20 to 30 minutes, the mixing and stirring time of adding the coagulant aid is 20 to 30 minutes, and the mixing and stirring time of adding the flocculant is 20 to 30 minutes.

8. The method for degelling water-based drilling waste fluid according to claim 7, characterized in that: Before adding the degelling agent, the solid particles in the drilling waste fluid are dispersed by stirring.

9. The method for degelling water-based drilling waste fluid according to claim 8, characterized in that: The mixed phase after mixing with the flocculant is subjected to solid-liquid separation treatment, the separated liquid is transported to a sewage treatment system, and the separated solid is landfilled or used as paving material.

10. The method for degelling water-based drilling waste fluid according to claim 9, characterized in that: The solid-liquid separation process uses a plate-frame filter press, the filtration pressure of the plate-frame filter press is 0.8-1.0 MPa, and the filtration time is 20-30 min.

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