Oil-containing drilling cuttings reinjection fluid, preparation method and application thereof

Abstract

The application provides an oil-containing drilling cuttings reinjection fluid and a preparation method and application thereof, which contains, based on the total weight of water in the base fluid being 100%, 0.2-0.3wt% of a suspending agent, 0.15-0.25wt% of a low-viscosity polyanionic cellulose, 0-0.25wt% of sodium carboxymethyl cellulose, 0-0.2wt% of hectorite, 0-0.2wt% of a zwitterionic polymer, 20-25wt% of oil-containing drilling cuttings and the balance of the base fluid; in the oil-containing drilling cuttings reinjection fluid, the contents of the three components of sodium carboxymethyl cellulose, hectorite and the zwitterionic polymer are not simultaneously 0, and the total content of the treating agent is less than 1wt%. The application realizes the target of reducing the total amount of the treating agent through the complementary advantages of the performance of different treating agents, and on the basis of making the rheological performance, the suspension stability and the filtration loss performance of the oil-containing drilling cuttings reinjection fluid system meet the requirements, the high-temperature resistance and the pollution resistance of the oil-containing drilling cuttings reinjection fluid system are also improved.

Description

Technical Field

[0001] This invention relates to an oil-bearing drill cuttings reinjection fluid, its preparation method, and its application, belonging to the field of oil and gas extraction technology. Background Technology

[0002] Oil-based drilling fluids possess excellent shale suppression, lubrication, and wellbore stabilization capabilities, thus finding widespread use in shale gas extraction. However, the use of oil-based drilling fluids generates a large amount of oil-bearing drill cuttings. Statistics show that a single shale gas well in southern Sichuan, China, produces 600-700 tons of oil-bearing drill cuttings, with some wells generating over 900 tons. The disposal of these large quantities of oil-bearing drill cuttings has become a major obstacle in oil and gas field development. Traditional waste disposal methods, due to their high energy consumption, secondary pollutant generation, and low efficiency, are no longer sufficient to meet the demands. Oil-bearing drill cuttings reinjection technology, by injecting oil-bearing drill cuttings underground, achieves zero emissions while processing large quantities of oil-bearing drill cuttings. Furthermore, the process consumes relatively little energy and offers good economic benefits, demonstrating promising application prospects. The performance of the oil-bearing drill cuttings reinjection fluid is crucial to the successful implementation of the reinjection process, even influencing its success or failure. However, currently, there are relatively few reports on oil-bearing drill cuttings reinjection formulations. Moreover, the existing technical solutions for reinjecting oily drill cuttings generally involve formulations with large amounts of treatment agents, high apparent viscosity, and high energy consumption.

[0003] For example, Chinese patent CN110846005A discloses a pretreatment method for reinjecting high-oil-content rock cuttings from depleted wells. This method involves grinding oil-bearing rock cuttings into fine powder with a particle size ≤300μm, then mixing it evenly with slurry water, a suspending agent, and a surfactant to prepare the reinjection slurry. While this method is simple to operate, produces a stable reinjection slurry that is not prone to settling and does not clog the reinjection channels, the formulation or preparation method of the oil-bearing drill cuttings reinjection fluid has the following problems:

[0004] (1) Large dosage of treatment agent (1wt% to 7.5wt%).

[0005] (2) The drill cuttings particle size is required to be small. The formula requires the drill cuttings particle size to be 150-180μm. Small particle size means that the cost will increase during the grinding process.

[0006] (3) The reinjection fluid has a high viscosity and a shear rate of 1022 s. -1 The apparent viscosity at that time is 30-55 mPa·s, which leads to increased pumping pressure, higher requirements for the performance of ground equipment, and greater energy consumption.

[0007] Therefore, providing a novel oil-containing drill cuttings reinjection fluid, its preparation method, and its application has become a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0008] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide an oil-containing drill cuttings reinjection fluid.

[0009] Another object of the present invention is to provide a method for preparing the oil-containing drill cuttings reinjection fluid described above.

[0010] Another object of the present invention is to provide the application of the above-described oil-containing drill cuttings reinjection fluid in drilling reinjection.

[0011] Another object of the present invention is to provide a drilling reinjection method, wherein the method includes injecting the oil-bearing drill cuttings reinjection fluid described above into an oil well.

[0012] To achieve the above objectives, in one respect, the present invention provides an oil-containing drill cuttings reinjection fluid, wherein, based on 100% of the total weight of water contained in the base fluid, it comprises:

[0013] The composition includes: 0.2-0.3 wt% suspending agent, 0.15-0.25 wt% low-viscosity polyanionic cellulose (PAC-Lv), 0-0.25 wt% sodium carboxymethyl cellulose (CMC), 0-0.2 wt% lithium saponite, 0-0.2 wt% zwitterionic polymer, 20-25 wt% oil-containing drill cuttings, and the remainder being base liquid;

[0014] In the oil-bearing drill cuttings reinjection fluid, the contents of sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymer are not all 0, and the total contents of suspending agent, low-viscosity polyanionic cellulose, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymer are less than 1 wt%.

[0015] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the content of the low-viscosity polyanionic cellulose (PAC-Lv) is 0.2 to 0.25 wt%.

[0016] In a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the content of sodium carboxymethyl cellulose is 0.1-0.25 wt%, preferably 0.2-0.25 wt%.

[0017] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the content of the lithium saponite is 0.1 to 0.2 wt%.

[0018] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the content of the zwitterionic polymer is 0.1 to 0.2 wt%.

[0019] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the base fluid includes one or a combination of several of clay-based slurry, oil and gas field waste fluid, or flowback drilling fluid.

[0020] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the suspending agent includes xanthan gum and / or water-soluble chitosan.

[0021] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0022] Xanthan gum 0.2 wt%, low viscosity polyanionic cellulose 0.15 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.2 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0023] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0024] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.1 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0025] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0026] Xanthan gum 0.15 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.15 wt%, zwitterionic polymer 0.2 wt%, lithium saponite 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0027] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0028] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.15 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0029] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0030] Xanthan gum 0.30 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.1 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0031] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0032] Xanthan gum 0.30 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.2 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0033] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the fluid comprises, based on 100% of the total weight of water contained in the clay-based slurry, the following:

[0034] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.25 wt%, sodium carboxymethyl cellulose 0.25 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

[0035] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the viscosity of the aqueous solution with a concentration of 2wt% prepared from the low-viscosity polyanionic cellulose is 150 mPa·s.

[0036] In a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer. During the hydrolysis of the dimethyl diallyl ammonium chloride-acrylamide copolymer, some of the amide groups in the polymer hydrolyze into carboxylic acid groups, that is, anionic groups are introduced into the polymer molecular chain. The polymer with anionic groups can adsorb onto the surface of the clay contained in the oil-containing drill cuttings reinjection fluid, enhancing the hydration capacity of the clay, thereby improving the rheological properties of the reinjection fluid and reducing the water loss of the reinjection fluid.

[0037] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the particle size of the oil-containing drill cuttings is 200-300 μm.

[0038] In one specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the particle size of the oil-containing drill cuttings is 230–300 μm.

[0039] This invention does not specify the oil content of the oil-bearing drill cuttings used; the content can be reasonably selected based on the actual site conditions.

[0040] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the clay-based slurry, based on a total weight of 100%, comprises 3-4 wt% clay, 0.1-0.3 wt% sodium carbonate, and the remainder water.

[0041] As a specific embodiment of the oil-containing drill cuttings reinjection fluid described above in this invention, the apparent viscosity of the oil-containing drill cuttings reinjection fluid is 18–70 mPa·s, the plastic viscosity is 18–42 mPa·s, the API water loss is 4.6–10 mL, and the density difference after standing for 24 hours is less than 0.05 g / cm³. 3 The density difference refers to the difference between the upper and lower liquid densities of the oil-bearing drill cuttings reinjection fluid.

[0042] All rheological properties parameters mentioned in this application were obtained using a six-speed viscometer, i.e., the apparent viscosity corresponds to a shear rate of 1022 s⁻¹. -1 .

[0043] In this invention, xanthan gum suspending agent, low-viscosity polyanionic cellulose, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymers are all conventional substances that can be obtained commercially. The oil-containing drill cuttings, oil and gas field waste fluids, or flowback drilling fluids used in this invention can be obtained commercially or from the oilfield site.

[0044] This invention uses oil and gas field waste fluid or flowback drilling fluid as raw materials to formulate oil-containing drill cuttings reinjection fluid, which can realize the recycling and reuse of oil and gas field waste fluid or flowback drilling fluid, reduce the waste fluid treatment cost at oil and gas field development sites, and achieve the goal of being environmentally friendly.

[0045] On the other hand, the present invention also provides a method for preparing the above-mentioned oil-containing drill cuttings reinjection fluid, wherein the preparation method includes:

[0046] The oil-containing drill cuttings reinjection fluid is obtained by sequentially adding a suspending agent, low-viscosity polyanionic cellulose, oil-containing drill cuttings, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymer to the base fluid and then stirring at high speed.

[0047] As a specific embodiment of the preparation method described above in this invention, the high-speed stirring is carried out at a speed of 6000-10000 r / min for 10-15 min; preferably, it is carried out at a speed of 8000-10000 r / min for 10-15 min.

[0048] In some embodiments of the present invention, the high-speed mixing can be achieved using a high-speed mixer.

[0049] In this invention, during the preparation of the oil-containing drill cuttings reinjection fluid, a high-speed agitator is used to stir the oil-containing drill cuttings reinjection fluid system at high speed. On the one hand, this allows the treatment agent to dissolve faster, and on the other hand, it can disperse some of the crude oil on the surface of the oil-containing drill cuttings into the water phase, forming an oil-in-water mixture under the action of high-speed stirring, thereby further improving the stability of the oil-containing drill cuttings reinjection fluid.

[0050] As a specific embodiment of the preparation method described above in this invention, when the base liquid is a clay-based slurry, the preparation method of the clay-based slurry includes:

[0051] Sodium carbonate and clay were added to water, and after hydration for 24 hours, the clay-based slurry was obtained.

[0052] In another aspect, the present invention also provides the application of the above-described oil-containing drill cuttings reinjection fluid in drilling reinjection.

[0053] In another aspect, the present invention also provides a drilling reinjection method, wherein the method includes injecting the oil-bearing drill cuttings reinjection fluid described above into the target well.

[0054] In one specific embodiment of the drilling reinjection method described above in this invention, the target well is a development well, a reinjection well, or a depleted well.

[0055] In this invention, conventional methods existing in the art can be used to inject the aforementioned oil-bearing drill cuttings reinjection fluid into the target well. For example, in some embodiments of this invention, the reinjection fluid and clean water are injected alternately during the reinjection process, and the single injection cycle is guaranteed to be 12 hours. Because the single injection cycle needs to be guaranteed to be 12 hours during the reinjection process, it is necessary to ensure that the oil-bearing drill cuttings in the reinjection fluid do not settle within at least 12 hours. Furthermore, during on-site construction, the content of treatment agents (i.e., suspending agents, low-viscosity polyanionic cellulose, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymers) in the reinjection fluid formulation can be increased according to the on-site construction conditions to appropriately extend the time during which the oil-bearing drill cuttings do not settle.

[0056] Furthermore, the perforation parameters of the reinjection well section can also be adjusted according to the actual site conditions. For example, in some embodiments of the present invention, the perforation parameters of the reinjection well section may be as follows:

[0057] A 7-inch perforation gun, 12 shots per foot. To prevent blockage of the injection port due to interrupted injection during reinjection, a hole at least 50 meters long is left below the perforation as a sedimentation pool to handle any mud buildup in the well due to equipment failure or other events.

[0058] The beneficial technical effects that the oil-containing drill cuttings reinjection fluid provided by this invention can achieve are as follows:

[0059] (1) This invention uses clay-based slurry (such as clay-based slurry with a clay concentration of 4 wt%), oil and gas field waste fluid, or flowback drilling fluid as base fluids, and fully utilizes the performance and advantages of different treatment agents. Among them, suspending agents (such as xanthan gum), CMC, and lithium saponite can improve the shear force of oil-bearing drill cuttings reinjection fluid, which is beneficial for suspending oil-bearing drill cuttings; PAC-Lv and zwitterionic polymers can reduce the water loss of oil-bearing drill cuttings reinjection fluid. Although this invention uses a combination of multiple treatment agents to prepare oil-bearing drill cuttings reinjection fluid, the amount of each treatment agent is small, and the total amount of treatment agents is less than 1 wt%. Compared with the prior art, the amount of treatment agents is significantly reduced (the amount of treatment agents in the prior art is 1 to 7.5 wt%). A small amount of treatment agents can make the rheological properties, suspension stability, and filtration performance of the oil-bearing drill cuttings reinjection fluid system meet the requirements, thereby making the cost of the oil-bearing drill cuttings reinjection fluid lower. Furthermore, the oil-bearing drill cuttings reinjection fluid of this invention can suspend oil-bearing drill cuttings with larger particle sizes (200-300 μm), and using large-particle-size oil-bearing drill cuttings can reduce the grinding cost of oil-bearing rock cuttings. In addition, the clay-based slurry of this invention can also be replaced with oil and gas field waste fluids, flowback drilling fluids, etc., which can realize the recycling and reuse of oil and gas field waste fluids and flowback drilling fluids, reduce the waste fluid treatment cost at oil and gas field development sites, and achieve the goal of environmental friendliness.

[0060] (2) Based on controlling the filtration loss of the oil-bearing drill cuttings reinjection fluid provided by this invention to be less than 10 mL and having good suspension stability, reducing the total amount of treatment agent can also reduce the apparent viscosity of the oil-bearing drill cuttings reinjection fluid (18-70 mPa·s), thereby reducing the pumping pressure and reducing the burden and cost on ground equipment. At the same time, adding lithium saponite when preparing the oil-bearing drill cuttings reinjection fluid can ensure that the reinjection fluid still has good cuttings carrying capacity under high temperature conditions.

[0061] (3) In summary, compared with the existing reinjection fluid formulations, this invention achieves the goal of reducing the total amount of treatment agents by complementing the performance advantages of different treatment agents, and ensures that the rheological properties, suspension stability, and filtration performance of the oil-containing drill cuttings reinjection fluid system meet relevant requirements. It also improves the high-temperature resistance and anti-pollution ability of the oil-containing drill cuttings reinjection fluid. During construction, it facilitates the injection of large quantities of oil-containing drill cuttings at different layers, thereby reducing overall construction costs and energy consumption. Detailed Implementation

[0062] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, device, or composition that includes a series of steps, units, or components is not necessarily limited to those steps, units, or components that are explicitly listed, but may include other steps, units, or components that are not explicitly listed or that are inherent to these processes, methods, products, devices, or compositions.

[0063] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for specific parameters, it is also understandable that ranges of 60–110 and 80–120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5.

[0064] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this invention, and "0~5" is simply a shortened representation of these numerical combinations.

[0065] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0066] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0067] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0068] Comparative Example 1

[0069] This comparative example provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0070] The composition consists of 0.25 wt% xanthan gum, 0.25 wt% PAC-Lv, 25 wt% oil-containing drill cuttings with a particle size of 230–300 μm, and the remainder is clay-based slurry with a clay concentration of 4 wt%.

[0071] The oil-containing drill cuttings reinjection fluid provided in this comparative example was prepared by a method including the following steps:

[0072] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0073] 2) Xanthan gum, PAC-Lv and oil-containing drill cuttings are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed mixer and is stirred at a speed of 10000 r / min for 15 min.

[0074] The apparent viscosity of the oil-containing drill cuttings reinjection fluid, measured using conventional methods in the art, was 42.5 mPa·s, the plastic viscosity was 25 mPa·s, the API water loss was 12.0 mL, and the density difference after standing for 24 hours was less than 0.06 g / cm³. 3 .

[0075] Comparative Example 2

[0076] This comparative example provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0077] Xanthan gum 0.25wt%, PAC-Lv 0.25wt%, thickener hydrophobic associative polymer (HAP) 0.1wt%, oil-containing drill cuttings with a particle size of 180-230μm 25wt%, and the remainder is clay-based slurry with a clay concentration of 4wt%.

[0078] The apparent viscosity of the oil-containing drill cuttings reinjection fluid, measured using conventional methods in the art, was 55 mPa·s, the plastic viscosity was 43.5 mPa·s, the API water loss was 8.6 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. 3 .

[0079] The oil-containing drill cuttings reinjection fluid provided in this comparative example was prepared by a method including the following steps:

[0080] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0081] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings and HAP are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed mixer and is stirred at a speed of 10000 r / min for 15 min.

[0082] Compared with the oil-containing drill cuttings reinjection fluid prepared in Comparative Example 1, the oil-containing drill cuttings reinjection fluid obtained in this comparative example has a gel-like consistency due to the addition of a thickener.

[0083] Example 1

[0084] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0085] The composition consists of 0.25 wt% xanthan gum, 0.2 wt% PAC-Lv, 0.15 wt% CMC, 25 wt% oil-containing drill cuttings with a particle size of 230–300 μm, and the remainder is clay-based slurry with a clay concentration of 4 wt%.

[0086] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0087] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0088] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings and CMC are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed mixer and is stirred at a speed of 10000 r / min for 15 min.

[0089] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 28.5 mPa·s, the plastic viscosity was 24 mPa·s, the API water loss was 9.4 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0090] Compared to Comparative Example 2, in this embodiment, while ensuring the performance of the oil-bearing drill cuttings reinjection fluid meets requirements, the viscosity of the reinjection fluid is appropriately reduced to decrease the pumping pressure on the ground equipment in order to increase its ability to carry large drill cuttings. Simultaneously, the content of harmful treatment agents is reduced by replacing the thickener with CMC. Test results show that the reinjection fluid maintains good suspension performance, viscosity decreases, and water loss increases slightly but remains below 10 mL.

[0091] Example 2

[0092] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0093] Xanthan gum 0.30wt%, PAC-Lv 0.2wt%, CMC 0.1wt%, zwitterionic polymer 0.2wt%, oil-containing drill cuttings with a particle size of 230-300μm 25wt%, and the remainder is clay-based slurry with a clay concentration of 4wt%.

[0094] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0095] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0096] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0097] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0098] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 36.5 mPa·s, the plastic viscosity was 21 mPa·s, the API water loss was 8.8 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0099] Compared to Example 1, in Example 2, to control the suspension stability of the oil-containing drill cuttings reinjection fluid and reduce water loss, the amount of xanthan gum was increased and the amount of CMC was reduced. Simultaneously, to increase the apparent viscosity of the reinjection fluid and improve the seepage resistance of the liquid phase component (i.e., the liquid phase with a certain viscosity formed after the treatment agent in the oil-containing drill cuttings reinjection fluid is hydrated in an aqueous solution) in the reinjection fluid cake (the reinjection fluid cake is the solid phase component formed on the filter paper surface after the liquid phase of the reinjection fluid is filtered out during the API water loss test), a zwitterionic polymer with a mass fraction of 0.2 wt% was added to the reinjection fluid. After adding this zwitterionic polymer, the density difference of the reinjection fluid remained less than 0.05 g / cm³ after standing for 24 hours. 3 That is, its suspension stability did not change significantly, but the amount of water loss decreased.

[0100] Example 3

[0101] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0102] Xanthan gum 0.30wt%, PAC-Lv 0.2wt%, CMC 0.2wt%, zwitterionic polymer 0.2wt%, oil-containing drill cuttings with a particle size of 230-300μm 25wt%, and the remainder is clay-based slurry with a clay concentration of 4wt%.

[0103] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0104] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0105] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0106] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0107] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 40.5 mPa·s, the plastic viscosity was 25 mPa·s, the API water loss was 6.9 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0108] Although the amount of CMC used in Example 2 was reduced, the reduction in water loss of the oil-containing drill cuttings reinjection fluid was relatively limited. Therefore, in Example 3, the amount of CMC was increased to 0.2 wt%. At this time, the water loss of the oil-containing drill cuttings reinjection fluid was significantly reduced to 6.9 mL, and the other properties of the oil-containing drill cuttings reinjection fluid remained within the allowable range for engineering construction.

[0109] Example 4

[0110] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0111] Xanthan gum 0.25wt%, PAC-Lv 0.25wt%, CMC 0.25wt%, zwitterionic polymer 0.2wt%, oil-containing drill cuttings with a particle size of 230-300μm 25wt%, and the remainder is clay-based slurry with a clay concentration of 4wt%.

[0112] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0113] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0114] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0115] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0116] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 29.5 mPa·s, the plastic viscosity was 18 mPa·s, the API water loss was 7.6 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0117] Considering the relatively ideal effect of CMC in reducing water loss, the amount of CMC in the oil-bearing drill cuttings reinjection fluid was further increased in Example 4. The results showed that the water loss of the resulting oil-bearing drill cuttings reinjection fluid increased. Therefore, the optimal amount of CMC should be controlled at 0.2 wt%.

[0118] Example 5

[0119] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0120] Xanthan gum 0.15wt%, PAC-Lv 0.2wt%, CMC 0.15wt%, zwitterionic polymer 0.2wt%, lithium saponite 0.2wt%, oil-containing drill cuttings with a particle size of 230-300μm 25wt%, and the remainder is clay-based slurry with a clay concentration of 4wt%.

[0121] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0122] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0123] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0124] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC, lithium saponite and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0125] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was measured to be 60.0 mPa·s, the plastic viscosity was 30 mPa·s, the API water loss was 5.4 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. 3 .

[0126] To address the control of water loss in different formations, Example 5 further provides an oil-bearing drill cuttings reinjection fluid with lower water loss. Compared to Example 4, the amounts of xanthan gum, PAC-Lv, and CMC in this oil-bearing drill cuttings reinjection fluid are reduced, while 0.2 wt% lithium saponite is added. Test results show that the water loss of the oil-bearing drill cuttings reinjection fluid obtained in this example is further reduced to 5.4 mL.

[0127] Example 6

[0128] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0129] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.1 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings with a particle size of 230-300 μm 25 wt%, and clay-based slurry balance.

[0130] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0131] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0132] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0133] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC, lithium saponite and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0134] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 70 mPa·s, the plastic viscosity was 38 mPa·s, the API water loss was 4.9 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0135] Example 7

[0136] This embodiment provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0137] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0 wt%, lithium saponite 0.2 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings with a particle size of 230-300 μm 25 wt%, and clay-based slurry balance.

[0138] In this embodiment, the zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

[0139] The oil-containing drill cuttings reinjection fluid provided in this embodiment is prepared by a method including the following steps:

[0140] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0141] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, lithium saponite and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0142] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this embodiment was 59 mPa·s, the plastic viscosity was 35 mPa·s, the API water loss was 9.5 mL, and the density difference after standing for 24 hours was less than 0.05 g / cm³. Using conventional methods in the art, the fluid was found to be... 3 .

[0143] Comparative Example 3

[0144] This comparative example provides an oil-containing drill cuttings reinjection fluid, which, based on the water content in the clay-based slurry (i.e., the total weight of water used in preparing the clay-based slurry) as 100%, comprises:

[0145] Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.1 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings with a particle size of 230-300 μm 25 wt%, and clay-based slurry balance.

[0146] In this comparative example, the zwitterionic polymer is zwitterionic polymer filtration loss reducer HF1 produced by Sichuan Southwest Shida Jinniu Petroleum Technology Co., Ltd.

[0147] The oil-containing drill cuttings reinjection fluid provided in this comparative example was prepared by a method including the following steps:

[0148] 1) Add sodium carbonate and clay to clean water, and after hydration for 24 hours, a clay-based slurry is obtained. The clay-based slurry contains 4 wt% clay, 0.2 wt% sodium carbonate, and the remainder clean water, based on the total weight of the clay-based slurry as 100%.

[0149] 2) Xanthan gum, PAC-Lv, oil-containing drill cuttings, CMC, lithium saponite and zwitterionic polymer are added sequentially to the clay-based slurry and then stirred at high speed to obtain the oil-containing drill cuttings reinjection fluid; wherein, the high-speed stirring is achieved by a high-speed stirrer and is stirred at a speed of 10000r / min for 15min.

[0150] The apparent viscosity of the oil-containing drill cuttings reinjection fluid described in this comparative example, measured using conventional methods in the art, was 107 mPa·s, the plastic viscosity was 46 mPa·s, the API water loss was 12.5 mL, and the density difference after standing for 24 hours was less than 0.06 g / cm³. 3 .

[0151] Comparing the performance data of the oil-containing drill cuttings reinjection fluid obtained in Example 6 and Comparative Example 3, it can be seen that the hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer used in Example 6 of this invention is an amphoteric polymer. During the hydrolysis of the dimethyl diallyl ammonium chloride-acrylamide copolymer, some of the amide groups in the polymer hydrolyze into carboxylic acid groups, thus introducing anionic groups into the polymer molecular chain. Compared to the conventional amphoteric polymer used in Comparative Example 3, the polymer with anionic groups can adsorb onto the surface of the clay contained in the oil-containing drill cuttings reinjection fluid, improving the hydration capacity of the clay, thereby improving the rheological properties of the reinjection fluid and reducing the water loss of the reinjection fluid.

[0152] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. An oil-containing drill cuttings reinjection fluid, characterized in that, Based on the total weight of water in the base liquid as 100%, it comprises: The composition includes 0.2–0.3 wt% suspending agent, 0.15–0.25 wt% low-viscosity polyanionic cellulose, 0.1–0.25 wt% sodium carboxymethyl cellulose, 0.1–0.2 wt% lithium saponite, 0.1–0.2 wt% zwitterionic polymer, 20–25 wt% oil-containing drill cuttings, and the remainder being base liquid; and the total content of suspending agent, low-viscosity polyanionic cellulose, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymer is less than 1 wt%. The zwitterionic polymer is a hydrolyzed dimethyl diallyl ammonium chloride-acrylamide copolymer.

2. The oil-containing drill cuttings reinjection fluid according to claim 1, characterized in that, The content of sodium carboxymethyl cellulose is 0.2-0.25 wt%.

3. The oil-containing drill cuttings reinjection fluid according to claim 1, characterized in that, The base fluid includes one or a combination of several of the following: clay-based slurry, oil and gas field waste fluid, or flowback drilling fluid.

4. The oil-containing drill cuttings reinjection fluid according to claim 1, characterized in that, The suspending agent includes xanthan gum and / or water-soluble chitosan.

5. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, Based on the total weight of water in the clay-based slurry as 100%, it comprises: Xanthan gum 0.2 wt%, low viscosity polyanionic cellulose 0.15 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.2 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

6. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, Based on the total weight of water in the clay-based slurry as 100%, it comprises: Xanthan gum 0.25 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.2 wt%, lithium saponite 0.1 wt%, zwitterionic polymer 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

7. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, Based on the total weight of water in the clay-based slurry as 100%, it comprises: Xanthan gum 0.15 wt%, low viscosity polyanionic cellulose 0.2 wt%, sodium carboxymethyl cellulose 0.15 wt%, zwitterionic polymer 0.2 wt%, lithium saponite 0.2 wt%, oil-containing drill cuttings 25 wt%, and clay-based slurry balance.

8. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, The viscosity of the 2wt% aqueous solution prepared from the low-viscosity polyanionic cellulose is 150 mPa·s.

9. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, The particle size of the oil-containing drill cuttings is 200–300 μm.

10. The oil-containing drill cuttings reinjection fluid according to claim 9, characterized in that, The oil-containing drill cuttings have a particle size of 230–300 μm.

11. The oil-containing drill cuttings reinjection fluid according to claim 3, characterized in that, The clay-based slurry comprises 3-4 wt% clay, 0.1-0.3 wt% sodium carbonate, and the remainder water, based on a total weight of 100%.

12. The oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 4, characterized in that, The apparent viscosity of the oil-containing drill cuttings reinjection fluid is 18–70 mPa·s, the plastic viscosity is 18–42 mPa·s, the API water loss is 4.6–10 mL, and the density difference after standing for 24 hours is less than 0.05 g / cm³. 3 The density difference refers to the difference between the upper and lower liquid densities of the oil-bearing drill cuttings reinjection fluid.

13. The method for preparing the oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 12, characterized in that, include: The oil-containing drill cuttings reinjection fluid is obtained by sequentially adding a suspending agent, low-viscosity polyanionic cellulose, oil-containing drill cuttings, sodium carboxymethyl cellulose, lithium saponite, and zwitterionic polymer to the base fluid and then stirring at high speed.

14. The preparation method according to claim 13, characterized in that, The high-speed stirring is carried out at a speed of 6000-10000 r / min for 10-15 min.

15. The preparation method according to claim 13 or 14, characterized in that, When the base liquid is a clay-based slurry, the preparation method of the clay-based slurry includes: Sodium carbonate and clay were added to water, and after hydration for 24 hours, the clay-based slurry was obtained.

16. The application of the oil-containing drill cuttings reinjection fluid according to any one of claims 1 to 12 in drilling reinjection.

17. A drilling reinjection method, characterized in that, The method includes injecting the oil-bearing drill cuttings reinjection fluid according to any one of claims 1 to 12 into the target well.

18. The drilling reinjection method according to claim 17, characterized in that, The target well is a development well, a reinjection well, or a depleted well.