Delayed gel, profile control agent and application thereof

Abstract

The invention relates to the technical field of oilfield development engineering, and discloses delayed gel, a profile control agent and a preparation method of the profile control agent, and the delayed gel comprises the following components in percentage by mass: 10-40% of sulfonated tannin extract, 1.0-4.0% of urotropine, 1.0-4.0% of hydroquinone, 10-20% of silicate particles and the balance of water; the profile control agent is prepared from the following raw materials: drilling wastes, a consolidation agent and delayed gel, the drilling waste is composed of oil-based drilling cuttings and oilfield wastewater. The oilfield hazardous waste oil-based drilling cuttings are used as the main raw material of the profile control agent, so that the oilfield exploitation cost can be reduced, and harmless and resource utilization of the oil-based drilling cuttings can be realized; the filling layer is formed by utilizing the characteristics that the content of solid-phase particles in the oil-based drilling cuttings is high and the solid-phase particles with different size fractions exist, and the mixed liquid of the oil-based drilling cuttings and the oilfield wastewater stops flowing in a stratum dominant channel after the delayed gel is formed, so that plugging is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development engineering, in particular to a delayed gel, a profile control agent and applications thereof. Background Art

[0002] During water flooding, water easily enters production wells through highly permeable channels due to the uneven porosity of deep formation rocks, preventing the displacement of oil and gas from non-high permeability layers. Profile control involves injecting a profile control agent into injection wells to seal these highly permeable channels, adjust the oil-water interface during water flooding, and enhance the flooding efficiency of the injected water in low permeability layers, ultimately increasing oil and gas recovery.

[0003] At present, the profile control agent mainly uses oily sludge for physical plugging to achieve the plugging of high permeability channels. Physical plugging uses solid particles with good properties such as temperature resistance, salt resistance, shear resistance, and erosion resistance as the profile control agent. The condition for successful plugging is that the diameter of the solid particles is compatible with the pore roar of the high permeability layer of the formation. However, the high permeability layer is a porous medium with a complex structure. There is currently no unified model that can accurately describe the pore roar structure. Particles with too small a diameter cannot plug the formation pore roar, and particles with too large a diameter cannot enter the formation pore roar to achieve plugging. Even if a filling layer is formed, the strength of the filling layer is poor, and the filling layer is easily destroyed in subsequent water injection development. In addition, using oily sludge as the main raw material has poor economic efficiency and cannot effectively control the gelation time of the gel. Therefore, there is an urgent need to provide a profile control system with low cost, controllable gelation time and high filling layer strength. Summary of the Invention

[0004] In view of this, the present invention provides a delayed gelation, a profile control agent and applications thereof to solve the problems of high cost, uncontrollable gelation time of the existing profile control agent and poor filling layer strength.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In one aspect, the present invention provides a delayed gel comprising the following components in percentage by weight: 10-40% sulfonated tannin extract, 1.0-4.0% urotropine, 1.0-4.0% hydroquinone, 10-20% silicate particles, and the balance being water.

[0007] Preferably, the silicate particles have a particle size of 5-50 μm.

[0008] On the other hand, the present invention also provides a profile control agent comprising the following raw materials: drilling waste, a consolidating agent and any one of the above delayed gels, wherein the drilling waste consists of oil-based drill cuttings and oilfield wastewater.

[0009] Preferably, the mass ratio of the drilling waste to the delayed gel is 100:15-25, and the mass ratio of the drilling waste to the solidifying agent is 100:5-10.

[0010] Preferably, the water content of the drilling waste is 50-75%.

[0011] Preferably, the mass ratio of the oil-based drill cuttings to the oilfield wastewater is 1:0.5-1.0.

[0012] Preferably, the solidifying agent is a mixture of magnesium sulfate and silicate cement.

[0013] Preferably, the mass ratio of the magnesium sulfate to the Portland cement is 1:3-8.

[0014] Preferably, the particle size of the solid particles in the drilling waste is ≤125 μm.

[0015] In another aspect, the present invention further provides a use of any of the above-mentioned profile control agents in oil reservoir water plugging.

[0016] Preferably, the application of the profile control agent in oil reservoir water plugging comprises the following steps:

[0017] (1) Obtaining the gelation time of the dominant channel in the formation to be blocked;

[0018] (2) determining the contents of urotropine and sulfonated tannin extract in the delayed gel according to the mass ratio of the drilling waste, the delayed gel and the solidifying agent and the gelling time, and mixing urotropine, the sulfonated tannin extract, silicate particles, hydroquinone and water to obtain the delayed gel;

[0019] (3) mixing the delayed gel, drilling waste and a consolidating agent to obtain a profile control agent;

[0020] (4) Injecting the profile control agent into the dominant channel of the formation and allowing it to stand to form a filling layer.

[0021] Preferably, the method for obtaining the gelation time of the dominant channel in the formation to be plugged is: obtaining the gelation time according to the volume of the profile control agent required for plugging the dominant channel in the formation and the displacement of the profile control agent.

[0022] Preferably, the mass ratio of the drilling waste, the delayed gel and the solidifying agent is set to 100:X:Y; the mass percentage of the sulfonated tannin extract in the delayed gel is Z1, and the mass percentage of hexamethylenetetramine is Z2; the gelling time is H;

[0023] When 30h≤H≤50h, Z1=0.03×(100+X+Y) / X×100%, Z2=(H-3.5)×(100+X+Y) / (8300×X)×100%;

[0024] When 15h≤H<30h, Z1=0.04×(100+X+Y) / X×100%, Z2=(H-2.4)×(100+X+Y) / (4300×X)×100%;

[0025] When 5h≤H<15h, Z1=0.05×(100+X+Y) / X×100%, Z2=(H-1.0)×(100+X+Y) / (3000×X)×100%.

[0026] Preferably, the standing time is 24-48 hours.

[0027] The present invention provides a delayed gel, a profile control agent and its application. Compared with the prior art, its beneficial effects are:

[0028] The delayed gel provided by the present invention can be combined with drilling waste (oil-based drill cuttings and oilfield wastewater) and a consolidating agent to prepare a profile control agent. The profile control agent can achieve harmless and resourceful utilization of oil-based drill cuttings at a low cost. Moreover, the profile control agent using oil-based drill cuttings as raw materials can be applied to the plugging of various stratum pore structures and has high plugging strength.

[0029] The present invention utilizes the characteristics of oil-based drill cuttings containing a large number of solid-phase particles of varying particle sizes. First, larger-sized solid-phase particles successfully bridge the crack channels in the pores, transforming them into pores. Then, smaller-sized solid-phase particles bridge the remaining channels to form a plugging layer. After the delayed gel forms, the viscosity of the oil-based drill cuttings and oilfield wastewater mixture increases dramatically, along with its flow resistance, stopping flow within the dominant channels of the formation. By limiting the content of sulfonated tannin extract and hexamethylenetetramine in the delayed gel, the gel system achieves pore plugging within a controllable timeframe. Simultaneously, the consolidating agent solidifies the oil-based drill cuttings in the delayed gel, increasing the strength of the plugging layer and preventing damage to the plugging layer during subsequent waterflooding. Furthermore, the present invention uses oil-based drill cuttings, a hazardous waste from oil fields, as its primary raw material, not only reducing oilfield production costs but also enabling the harmless and resourceful utilization of oil-based drill cuttings. DETAILED DESCRIPTION

[0030] The present invention will be described below by specific embodiment, and it will be appreciated by those skilled in the art that the specific embodiment below is only for illustrative purposes, and does not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise stated, the reagent and equipment used are all commercially available. If in the following examples, concrete treatment conditions and treatment process are not clearly described, then conditions and methods well known in the art can be adopted to process.

[0031] In one aspect, the present invention provides a delayed release gel comprising the following components by weight: 10-40% sulfonated tannin extract, 1.0-4.0% hexamethylenetetramine, 1.0-4.0% hydroquinone, 10-20% silicate particles, and the balance being water. The water may be oilfield wastewater, tap water, or the like.

[0032] Wherein, the delayed gel comprises sulfonated tannin extract, and the mass percentage of the sulfonated tannin extract is 10-40%, specifically 10%, 20%, 30%, 40%, etc.

[0033] The delay gel includes methenamine, and the mass percentage of methenamine is 1.0-4.0%, specifically 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, etc.

[0034] The delay gel comprises hydroquinone, and the mass percentage of the hydroquinone is 1.0-4.0%, specifically 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, etc.

[0035] The delayed gel includes silicate particles, the mass percentage of the silicate particles is 10-20%, specifically 10%, 15%, 20%, etc.; the particle size of the silicate particles is 5-50 μm, specifically 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc. The main function of the silicate particles is to improve the high-temperature stability of the gel, so that the gel is suitable for the temperature of the underground formation and is not easy to break. It can also play a bridging role to a certain extent.

[0036] The present invention uses a quaternary gel system formed by sulfonated tannin extract, hexamethylenetetramine, hydroquinone, and silicate particles as a delayed gel, wherein the sulfonated tannin extract is used to improve temperature and salt resistance, the silicate particles serve as a high-temperature stabilizer, and hexamethylenetetramine and hydroquinone serve as gelling agents. By controlling the mass percentage of the sulfonated tannin extract and hexamethylenetetramine, the gelling time can be controlled, so that the profile control agent can stop flowing at a preset position after being injected into the dominant channel of the formation and form a plugging layer at the preset position.

[0037] In another aspect of the present invention, a profile control agent is provided, comprising the following raw materials: drilling waste, delayed gel and a consolidating agent.

[0038] In some embodiments of the present invention, the drilling waste consists of oil-based drill cuttings and oilfield wastewater, and the water content of the drilling waste is 50-75%, specifically 50%, 55%, 60%, 65%, 70%, 75%, etc.

[0039] The present invention can ensure moderate fluidity of the profile control agent by maintaining the water content of the drilling waste within this range. If the water content of the drilling waste is too high, the fluidity of the profile control agent will be too high and it will not be easy to form a gel. If the water content is too low, the fluidity of the profile control agent will be too low, causing the profile control agent to form a gel before reaching the position to be sealed, resulting in ineffective sealing.

[0040] As can be understood, oil-based drill cuttings are a type of hazardous waste generated during the use of oil-based drilling fluids. They consist of solids carried by the formation and drilling fluid. Oil-based drill cuttings are a complex emulsion formed by a mixture of oil, water, and solids. The oil-based drill cuttings contain a high content of solid particles (greater than 50%) and include solid particles of varying sizes (ranging from 1 μm to 1 mm). Blocking dominant formation channels is achieved through physical particle bridging. The present invention utilizes the high content of solid particles and the presence of solid particles of varying sizes in oil-based drill cuttings. First, larger-sized solid particles successfully bridge the pores, transforming fractures into pores. Then, smaller-sized solid particles bridge the remaining channels, forming a plugging layer. Delayed gelation dramatically increases the viscosity of the mixture of oil-based drill cuttings and oilfield wastewater, along with its flow resistance, stopping flow within the dominant formation channels and achieving blockage.

[0041] Furthermore, oil-based drill cuttings possess excellent resistance to heat, salt, and shear, meeting the water-blocking requirements of oilfield profile control agents. Furthermore, since they originate from strata, they exhibit excellent compatibility with the strata. This invention utilizes oil-based drill cuttings, a hazardous waste from oilfields, as the primary raw material for the profile control agent, not only reducing oilfield production costs but also enabling harmless and resourceful utilization of oil-based drill cuttings.

[0042] In some embodiments of the present invention, the mass ratio of the drilling waste to the delayed gel is 100:15-25, specifically 100:15, 100:20, 100:25, etc. By limiting the mass ratio of delayed gel to drilling waste, the gelation time and gel strength can be controlled.

[0043] In some embodiments of the present invention, the mass ratio of the drilling waste to the consolidating agent is 100:5-10, specifically 100:5, 100:7.5, 100:10, etc.

[0044] In some embodiments of the present invention, the mass ratio of the oil-based drill cuttings to the oilfield wastewater is 1:0.5-1.0, specifically 1:0.5, 1:0.75, 1:1.0, etc. It should be noted that the water content of oil-based drill cuttings is generally 10-50%. By limiting the ratio of oil-based drill cuttings to oilfield wastewater within this range, the water content of the drilling waste formed by the oil-based drill cuttings and oilfield wastewater can be ensured to be 50-75%.

[0045] It should be noted that the oilfield wastewater mentioned in the present invention can be oily sewage and oilfield sewage, wherein the oily sewage is the associated water from the formation that accompanies the production of crude oil during the oil and gas extraction process. The associated water containing a certain amount of crude oil and impurities obtained after oil and gas separation is oily sewage; oilfield sewage includes oil production wastewater, drilling wastewater, and gas production wastewater, and its main sources are produced water, well washing water, cleaning water, etc. during the crude oil extraction process.

[0046] In some embodiments of the present invention, the particle size of the solid particles in the drilling waste is ≤125 μm. By limiting the particle size of the solid particles in the drilling waste, effective formation plugging can be achieved while ensuring the pumping capacity of the profile control agent. The formation plugging process does not require solid particles with excessively large particle sizes, and solid particles with excessively large particle sizes will affect the pumping capacity of the profile control agent.

[0047] In some embodiments of the present invention, the solidifying agent is a mixture of magnesium sulfate and Portland cement, the magnesium sulfate is anhydrous magnesium sulfate, and the mass ratio of the magnesium sulfate to the Portland cement is 1:3-8, specifically 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc. The magnesium sulfate and Portland cement are both commercially available and are not particularly limited.

[0048] The consolidating agent of the present invention can not only solidify the oil-based drill cuttings in the delayed gel and improve the strength of the plugging layer to an appropriate degree to avoid damage to the plugging layer during subsequent water injection development, but also ensure that the solidification strength is not too high to avoid difficulty in removing the plugging.

[0049] In another aspect of the present invention, the present invention further proposes a use of any of the above-mentioned profile control agents in oil reservoir water plugging.

[0050] In some embodiments of the present invention, the application of the profile control agent in oil reservoir water plugging comprises the following steps:

[0051] (1) Obtaining the gelation time of the dominant channel in the formation to be blocked;

[0052] (2) determining the contents of urotropine and sulfonated tannin extract in the delayed gel according to the mass ratio of the drilling waste, the delayed gel and the solidifying agent and the gelling time, and mixing urotropine, the sulfonated tannin extract, silicate particles, hydroquinone and water to obtain the delayed gel;

[0053] (3) mixing the delayed gel, drilling waste and a consolidating agent to obtain a profile control agent;

[0054] (4) Injecting the profile control agent into the dominant channel of the formation and allowing it to stand to form a filling layer.

[0055] In the present invention, the gelling time of the dominant channel of the formation to be blocked is firstly obtained.

[0056] In some embodiments of the present invention, the gelation time is calculated based on the volume of the profile control agent required to plug the dominant channel in the formation and the profile control agent displacement rate. The volume of the profile control agent required can be estimated based on the volume of the dominant channel in the formation to be plugged. It should be noted that the present invention does not impose any specific restrictions on the process for obtaining the gelation time; a rough estimate using existing techniques can be sufficient.

[0057] In the present invention, after obtaining the gelation time, the contents of urotropine and sulfonated tannin extract are determined according to the gelation time, and urotropine, sulfonated tannin extract, silicate particles, hydroquinone and water are mixed to obtain delayed gel.

[0058] In some embodiments of the present invention, the mass ratio of the drilling waste, the delayed gel and the solidifying agent is set to 100:X:Y; the mass percentage of the sulfonated tannin extract in the delayed gel is Z1, and the mass percentage of the hexamethylenetetramine is Z2; the gelling time is H;

[0059] When 30h≤H≤50h, Z1=0.03×(100+X+Y) / X×100%, Z2=(H-3.5)×(100+X+Y) / (8300×X)×100%;

[0060] When 15h≤H<30h, Z1=0.04×(100+X+Y) / X×100%, Z2=(H-2.4)×(100+X+Y) / (4300×X)×100%;

[0061] When 5h≤H<15h, Z1=0.05×(100+X+Y) / X×100%, Z2=(H-1.0)×(100+X+Y) / (3000×X)×100%.

[0062] It can be understood that when the gelation time obtained is 35 hours and the mass ratio of drilling waste, delayed gel and solidifying agent is 100:20:10, the mass percentages of sulfonated tannin extract and urotropine in the delayed gel are 19.5% and 2.5% respectively; when the gelation time obtained is 20 hours and the mass ratio of drilling waste, delayed gel and solidifying agent is 100:20:10, the mass percentages of sulfonated tannin extract and urotropine in the delayed gel are 26% and 2.66% respectively; when the gelation time obtained is 10 hours and the mass ratio of drilling waste, delayed gel and solidifying agent is 100:20:10, the mass percentage of sulfonated tannin extract in the delayed gel is 32.5%, and the mass percentage of urotropine is 1.95%.

[0063] The present invention controls the gelation time by controlling the mass percentage of sulfonated tannin extract and hexamethylenetetramine, and matches the time for the profile control agent to reach the dominant channel of the formation through the gelation time. After the gelation is delayed, the viscosity of the drilling waste increases sharply, and the flow resistance also increases sharply. The profile control agent stops flowing in the dominant channel of the formation, forming a filling layer.

[0064] In the present invention, after the delayed gel is obtained, the delayed gel, drilling waste and a solidifying agent are mixed to obtain a profile control agent.

[0065] In some embodiments of the present invention, the drilling waste is formed by mixing oil-based drill cuttings and oilfield wastewater. The oil-based drill cuttings and oilfield wastewater are evenly mixed and then passed through a 120-mesh sieve, and the undersize is taken as the drilling waste.

[0066] In the present invention, after the profile control agent is obtained, the profile control agent is injected into the dominant channel of the formation and allowed to stand to form a filling layer.

[0067] In some embodiments of the present invention, the standing time is 24-48 hours, specifically 24 hours, 30 hours, 36 hours, 42 hours, 48 hours, etc. After standing, a filling layer is formed to block the dominant channels of the formation, thereby achieving the purpose of profile control and water blocking.

[0068] It should be noted that the operation of injecting the profile control agent into the advantageous channel of the formation can be completed by using equipment such as a piston pump. After the injection is completed, the pump is stopped and left to stand. There is no special limitation on the specific injection equipment and it can be adjusted according to actual conditions.

[0069] The following will be combined with specific embodiments to clearly and completely describe the technical solutions of the present invention. The embodiments of this application are only for example, and all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0070] Example 1

[0071] This embodiment provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0072] (1) Oil-based drill cuttings (water content 22.5%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 55%;

[0073] (2) The estimated gelling time of the profile control agent in the dominant channel of the formation to be blocked is 34 hours;

[0074] (3) Based on the gelation time and the mass ratio of drilling waste, delayed gel, and solidifying agent of 100:20:10, the contents of sulfonated tannin extract and urotropine in the delayed gel were determined to be 19.5% and 2.4%, respectively. The urotropine, sulfonated tannin extract, silicate particles, hydroquinone, and water were mixed to obtain a delayed gel; wherein the mass percentages of sulfonated tannin extract, urotropine, hydroquinone, silicate particles, and water were 19.5%, 2.4%, 2.4%, 15%, and 60.7%, respectively, and the average particle size of the silicate particles was 10 μm;

[0075] (4) mixing the drilling waste, the delayed gel and a consolidating agent to obtain a profile control agent, wherein the consolidating agent is a mixture of magnesium sulfate and silicate cement in a mass ratio of 1:5;

[0076] (5) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0077] Example 2

[0078] This embodiment provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0079] (1) Oil-based drill cuttings (water content 25.5%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 57%;

[0080] (2) The estimated gelling time of the profile control agent in the dominant channel of the formation to be blocked is 42 hours;

[0081] (3) According to the gelation time and the mass ratio of drilling waste, delayed gel and solidifying agent (100:15:8), the contents of sulfonated tannin extract and urotropine in the delayed gel were determined to be 24.6% and 3.8%, respectively. The urotropine, sulfonated tannin extract, silicate particles, hydroquinone and water were mixed to obtain the delayed gel; wherein the mass percentages of sulfonated tannin extract, urotropine, hydroquinone, silicate particles and water were 24.6%, 3.8%, 3.8%, 20% and 47.8%, respectively, and the average particle size of the silicate particles was 10 μm;

[0082] (4) mixing the drilling waste, the delayed gel and a consolidating agent to obtain a profile control agent, wherein the consolidating agent is a mixture of magnesium sulfate and silicate cement in a mass ratio of 1:5;

[0083] (5) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0084] Example 3

[0085] This embodiment provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0086] (1) Oil-based drill cuttings (water content 39.4%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 62%;

[0087] (2) The estimated gelling time of the profile control agent in the dominant channel of the formation to be blocked is 19 hours;

[0088] (3) Based on the gelation time and the mass ratio of drilling waste, delayed gel, and solidifying agent of 100:18:5, the contents of sulfonated tannin extract and urotropine in the delayed gel were determined to be 27.3% and 2.6%, respectively. The urotropine, sulfonated tannin extract, silicate particles, hydroquinone, and water were mixed to obtain a delayed gel; wherein the mass percentages of sulfonated tannin extract, urotropine, hydroquinone, silicate particles, and water were 27.3%, 2.6%, 2.6%, 18%, and 49.5%, respectively, and the average particle size of the silicate particles was 10 μm;

[0089] (4) mixing the drilling waste, the delayed gel and a consolidating agent to obtain a profile control agent, wherein the consolidating agent is a mixture of magnesium sulfate and silicate cement in a mass ratio of 1:5;

[0090] (5) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0091] Example 4

[0092] This embodiment provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0093] (1) Oil-based drill cuttings (water content 28.3%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 59%;

[0094] (2) The estimated gelling time of the profile control agent in the dominant channel of the formation to be blocked is 26 hours;

[0095] (3) According to the gelation time and the mass ratio of drilling waste, delayed gel and solidifying agent (100:18:8), the contents of sulfonated tannin extract and urotropine in the delayed gel are determined to be 28% and 3.8%, respectively. The urotropine, sulfonated tannin extract, silicate particles, hydroquinone and water are mixed to obtain the delayed gel; wherein the mass percentages of sulfonated tannin extract, urotropine, hydroquinone, silicate particles and water are 28%, 3.8%, 3.8%, 16% and 48.4%, respectively, and the average particle size of the silicate particles is 10 μm;

[0096] (4) mixing the drilling waste, the delayed gel and a consolidating agent to obtain a profile control agent, wherein the consolidating agent is a mixture of magnesium sulfate and silicate cement in a mass ratio of 1:5;

[0097] (5) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0098] Comparative Example 1

[0099] This comparative example provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0100] (1) Oil-based drill cuttings (water content 22.4%) and oilfield wastewater were mixed uniformly at a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 54%, which was used as a profile control agent;

[0101] (2) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0102] Comparative Example 2

[0103] This comparative example provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0104] (1) Oil-based drill cuttings (water content 32.4%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 61%;

[0105] (2) mixing urotropine, sulfonated tannin extract, silicate particles, hydroquinone, and water to obtain a delayed gel; wherein the mass percentages of sulfonated tannin extract, urotropine, hydroquinone, silicate particles, and water are 28%, 3.8%, 3.8%, 16%, and 48.4%, respectively, and the average particle size of the silicate particles is 10 μm;

[0106] (3) mixing the drilling waste and the delay gel at a mass ratio of 100:20 to obtain a profile control agent;

[0107] (4) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0108] Comparative Example 3

[0109] This comparative example provides an application of a profile control agent in oil reservoir water plugging, and the steps are as follows:

[0110] (1) Oil-based drill cuttings (water content 30.1%) and oilfield wastewater were mixed in a mass ratio of 1:1, passed through a 120-mesh vibrating screen, and the undersize was taken to obtain drilling waste with a water content of 60%;

[0111] (2) mixing drilling waste and a consolidating agent in a mass ratio of 100:10 to obtain a profile control agent, wherein the consolidating agent is a mixture of magnesium sulfate and silicate cement in a mass ratio of 1:3-8;

[0112] (3) Inject the profile control agent into the dominant channel of the formation to be blocked and let it stand for 48 hours to form a filling layer.

[0113] Comparative Example 4

[0114] This comparative example is basically the same as Example 1, except that the delayed gel is replaced with a commercially available organoboron cross-linked gel.

[0115] According to SY / T 7625-2021 "Technical Specifications for Oil Sludge Profile Control Process", the profile control agents in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0116] Table 1

[0117]

[0118] As shown in Table 1, the pH value, density, apparent viscosity and suspension stability index of the profile control agents prepared in Examples 1-4 all meet the standards and can meet the requirements of sludge profile control operations; however, due to the lack of coagulant and / or delayed gelation, the sedimentation stability of Comparative Columns 1-3 does not meet the requirements.

[0119] The gel storage modulus and rock compressive strength test methods were used to test the gel storage modulus and rock compressive strength of the core packing layers formed in Examples 1-4 and Comparative Examples 1-4. The results are shown in Table 2.

[0120] Table 2

[0121]

[0122] As can be seen from Table 2, the storage modulus of the gel formed after plugging the dominant channel of the formation using the profile control agent prepared in Examples 1-4 reached more than 6.0 Pa, and the compressive strength of the core filling layer reached more than 3.9 MPa, which can provide sufficient strength; however, the profile control agent of Comparative Example 1 did not solidify and gel in the dominant channel of the formation because no consolidating agent and delayed gel were added, so the storage modulus and the compressive strength of the filling layer could not be measured; the profile control agent of Comparative Example 2 had significantly reduced compressive strength because no consolidating agent was added; the profile control agent of Comparative Example 3 could not gel because no delayed gel was added, so the storage modulus was zero; Comparative Example 4 used other delayed gels, but the gelation time was difficult to control, and the compressive strength of the formed filling layer was low.

[0123] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A delayed gel, characterized in that The invention comprises the following components in percentage by mass: 10-40% of sulfonated tannin extract, 1.0-4.0% of urotropine, 1.0-4.0% of hydroquinone, 10-20% of silicate particles, and the balance being water.

2. The delayed gel according to claim 1, characterized in that The particle size of the silicate particles is 5-50 μm 。 3. A profile control agent, characterized in that The invention comprises the following raw materials: drilling waste, a solidifying agent and the delayed gel according to any one of claims 1 to 2, wherein the drilling waste consists of oil-based drill cuttings and oilfield wastewater.

4. The profile control agent according to claim 3, characterized in that The mass ratio of the drilling waste to the delayed gel is 100:15-25, and the mass ratio of the drilling waste to the solidifying agent is 100:5-10.

5. The profile control agent according to claim 3, characterized in that The water content of the drilling waste is 50-75%; The particle size of the solid particles in the drilling waste is ≤125 μm.

6. The profile control agent according to any one of claims 3 to 5, characterized in that The solidifying agent is formed by mixing magnesium sulfate and silicate cement; The mass ratio of the magnesium sulfate to the silicate cement is 1:3-8.

7. Use of the profile control agent according to any one of claims 3 to 6 in oil reservoir water plugging.

8. The use of the profile control agent in oil reservoir water plugging according to claim 7, characterized in that: The following steps are involved: (1) Obtaining the gelation time of the dominant channel in the formation to be blocked; (2) determining the contents of urotropine and sulfonated tannin extract in the delayed gel according to the mass ratio of the drilling waste, the delayed gel and the solidifying agent and the gelling time, and mixing urotropine, the sulfonated tannin extract, silicate particles, hydroquinone and water to obtain the delayed gel; (3) mixing the delayed gel, drilling waste and a consolidating agent to obtain a profile control agent; (4) Injecting the profile control agent into the dominant channel of the formation and allowing it to stand to form a filling layer.

9. The use of the profile control agent in oil reservoir water plugging according to claim 8, characterized in that: The mass ratio of the drilling waste, the delayed gel and the solidifying agent is set to 100:X:Y; the mass percentage of the sulfonated tannin extract in the delayed gel is Z1, and the mass percentage of the hexamethylenetetramine is Z2; and the gelling time is H; When 30h≤H≤50h, Z1=0.03×(100+X+Y) / X×100%, Z2=(H-3.5)×(100+X+Y) / (8300×X)×100%; When 15h≤H<30h, Z1=0.04×(100+X+Y) / X×100%, Z2=(H-2.4)×(100+X+Y) / (4300×X)×100%; When 5h≤H<15h, Z1=0.05×(100+X+Y) / X×100%, Z2=(H-1.0)×(100+X+Y) / (3000×X)×100%.

10. Use of the profile control agent in oil reservoir water plugging according to claim 8 or 9, characterized in that: The standing time in step (4) is 24-48h.

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