Functional shunting blocking remover with controllable distribution function

Abstract

The invention discloses a functional split-flow blocking remover with a controllable distribution function, and particularly relates to the technical field of oil-gas field development, the functional split-flow blocking remover comprises a retarded acid system agent and a functional split-flow agent, the retarded acid system agent comprises the following raw materials in percentage by weight: 6-8% of hydrochloric acid, 2% of a chelating agent, 1-3% of villiaumite, 2-4% of inorganic salt hexahydrate, 1% of a corrosion inhibitor, 1% of a demulsifier, 1% of an iron ion stabilizer, 1% of a clay anti-swelling agent and 1% of a cleanup additive, and the functional shunting agent comprises the following components in percentage by weight: 2% of the functional shunting agent and the balance of water. The temporary plugging effect of the functional shunting agent and the special property of the retarded acid system agent are utilized, double transformation of a high-permeability zone and a low-permeability zone of a reservoir is achieved, and the purposes of evenly distributing acid, improving the acid etching effect and increasing the penetration distance are achieved; the wettability is changed by the nanofluid, the interfacial tension is reduced, so that the crude oil is stripped and displaced, and finally the acidification transformation and oil displacement yield increase of a heterogeneous reservoir or a low-permeability reservoir are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and more specifically, to a functional diversion plugging removal agent with a controllable distribution function. Background Art

[0002] During acidizing or acid fracturing operations, acid fluid often preferentially enters large pores or formation fractures, resulting in the concentrated consumption of acid fluid in high-permeability zones and the failure to improve the diversion capacity of low-permeability zones, greatly reducing the effective acid etching effect and penetration distance, and the diversion capacity of low-permeability zones fails to be effectively improved, thus affecting the stimulation effect.

[0003] In the prior art, in the measures for low-pressure oil wells, it is first necessary to temporarily plug the formation to ensure that well fluids do not flow into the formation and formation fluids do not flow into the well. Secondly, an efficient flowback mechanism needs to be established to ensure that after the plugging is removed, it does not remain in the formation but quickly flows back to reduce the damage to the formation. For this purpose, different types of temporary plugging systems have been developed, but they also have their own deficiencies, such as different acid systems like micellar acid, foam acid, temporary plugging acidizing, emulsified acid, etc.

[0004] ① Foam system: short stable period; complex preparation process.

[0005] ② Solid particle temporary plugging system: increases the complexity of placement; small particles and suspension systems are prone to damage the reservoir.

[0006] ③ Gel system: prone to leakage, with polymer adsorption damage.

[0007] ④ Alkyl system: prone to emulsification; not environmentally friendly.

[0008] ⑤ Gel-type system: circulating liquid, not environmentally friendly, complex operation, etc.;

[0009] To solve this problem, the diversion acidizing technology has emerged. The acid placement technology plays a very crucial role in damage removal and stimulation effect, and is also an important topic in acidizing and acid fracturing. In order to achieve the purpose of uniform acid placement, the research on diversion acidizing technology began at home and abroad in the 1990s. The so-called diversion acidizing technology is to add a diverting agent to ordinary acid. As the acid-rock reaction progresses, the diverting agent temporarily plugs the preferential channels such as large pores or high-permeability zones of the reservoir, thereby changing the injection acid flow profile, enabling the acid fluid to enter the relatively low-permeability zone for reaction, and ultimately achieving the dual transformation of the high-permeability layer and low-permeability layer of the reservoir. That is, adding a diverting agent to ordinary acid, changing the acid fluid flow profile by temporarily plugging the high-permeability zone, so that the acid fluid can enter the low-permeability zone for reaction. However, the existing diverting agents have many deficiencies, such as short stable period, easy to damage the reservoir, not environmentally friendly, etc. Summary of the Invention

[0010] To overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a functional diversion and plugging removal agent with a controllable distribution function. The technical problem to be solved by the present invention is: how to achieve the effective distribution of acid fluid through a plugging removal agent in the acidification technology of oil and gas well stimulation measures for the heterogeneity problem in the reservoir of oil and gas wells, especially for the treatment of high-permeability zones and low-permeability zones, so as to improve the acidification effect and increase the oil well production.

[0011] To achieve the above object, the present invention provides the following technical solution: a functional diversion and plugging removal agent with a controllable distribution function, comprising a retarded acid system agent and a functional diversion agent. Among them, the retarded acid system agent is composed of hydrochloric acid, a chelating agent, a fluoride salt, a hexahydrate inorganic salt, an inhibitor, a demulsifier, an iron ion stabilizer, a clay anti-swelling agent, and a drainage aid. The retarded acid system agent includes the following in terms of weight percentage of raw materials: hydrochloric acid 6wt%-8wt%, chelating agent 2wt%, fluoride salt 1wt%-3wt%, hexahydrate inorganic salt 2wt%-4wt%, inhibitor 1wt%, demulsifier 1wt%, iron ion stabilizer 1wt%, clay anti-swelling agent 1wt%, and drainage aid 1wt%. The weight percentage of the functional diversion agent is as follows: functional diversion agent 2wt%, and the remaining amount is set as water. The functional diversion agent realizes automatic viscosity increase and thickening under the action of adjusting the acidity of the retarded acid, temporarily plugs the high-permeability zone, and changes the acid fluid flow profile.

[0012] In a preferred embodiment, the hydrochloric acid is set as a concentrated hydrochloric acid solution with a concentration of 31%; the chelating agent is set as any one of chelating agents of models AH-100, AH-101, AH-102, or EDTA; the fluoride salt is selected from one of SA701 fluoride salt or ammonium fluoride; the hexahydrate inorganic salt is selected from one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate, or magnesium chloride hexahydrate.

[0013] In a preferred embodiment, the inhibitor is set as oleic acid imidazoline of model SA1-3B; the demulsifier is set as a polyether demulsifier of model SA1-1; the iron ion stabilizer is set as citric acid; the clay anti-swelling agent is set as potassium-based polyacrylamide; the drainage aid is set as surfactant Tween-80 or a non-ionic-cationic composite surfactant; the functional diversion agent is set as a polyether-modified polysiloxane or a high molecular polymer type diversion agent of Dispex Ultra PX4585.

[0014] A functional diversion and plugging removal method with a controllable distribution function specifically includes the following steps:

[0015] Step S1: Prepare a functional diversion and plugging removal agent;

[0016] Step S2: Inject the functional diversion and plugging removal agent prepared in step S1 into the oil and gas well;

[0017] Step S3: Through the temporary plugging effect of the functional diverting agent and the special properties of the retarded acid system agent, double transformation of the high-permeability zone and low-permeability zone of the reservoir is achieved.

[0018] In a preferred embodiment, the specific steps in the step S1 include:

[0019] S1.1: Preparation of the retarded acid system agent: Prepare hydrochloric acid, chelating agent, fluoride salt, hexahydrate inorganic salt, corrosion inhibitor, demulsifier, iron ion stabilizer, clay anti-swelling agent and flowback aid in proportion, and mix them evenly to obtain the retarded acid system agent;

[0020] S1.2: Preparation of the functional diverting agent: Add the functional diverting agent to water in proportion and stir evenly to obtain the functional diverting agent. The functional diverting agent automatically becomes viscous and thickens under low pH conditions to temporarily plug the high-permeability zone and automatically reduces viscosity as the pH value increases.

[0021] In a preferred embodiment, before the step S2 is carried out, the wellbore and the near-wellbore area are pretreated. The wellbore and the near-wellbore area are cleaned with an organic cleaning agent to remove wax and colloid components to ensure the smooth progress of the subsequent acidification operation.

[0022] In a preferred embodiment, the injection method in the step S2 is to inject the functional diverting and plugging removal agent into the oil and gas well through a high-pressure pump truck;

[0023] In a preferred embodiment, the dosage formula of the functional diverting and plugging removal agent in the step S2 is:

[0024]

[0025] where, refers to the dosage volume of the plugging removal agent; h refers to the oil layer depth; refers to the porosity; R refers to the treatment radius.

[0026] Technical effects and advantages of the present invention:

[0027] 1. The functional diverting and plugging removal agent provided by the present invention can achieve automatic temporary plugging of the high-permeability zone, change the acid fluid flow profile, enable the acid fluid to be evenly distributed to the low-permeability area, improve the acidification effect, and through uniform acid distribution, achieve double transformation of the high-permeability zone and low-permeability zone of the reservoir, significantly increasing the single-well production;

[0028] 2. The retarding acid system agent of the present invention and the functional diverting agent act synergistically, which can prolong the acid-rock reaction time, improve the acidizing efficiency. The functional diverting agent increases viscosity under low pH conditions and decreases viscosity under high pH conditions, and has a controllable distribution function, which can automatically adjust the viscosity according to the formation reaction conditions to avoid damage to the reservoir. The retarding acid system and the functional diverting agent act synergistically, which can prolong the acid-rock reaction time, improve the acidizing efficiency, reduce the damage of acid fluid to the reservoir at the same time, be environmentally friendly and efficient, be applicable to various types of reservoirs, and have broad application prospects. Detailed implementation mode

[0029] The following will combine the embodiments in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0030] Example 1:

[0031] The present invention provides a functional diverting and plugging removal agent with a controllable distribution function, which includes a retarding acid system agent and a functional diverting agent. Among them, the retarding acid system agent is composed of hydrochloric acid, chelating agent, fluoride salt, hexahydrate inorganic salt, corrosion inhibitor, demulsifier, iron ion stabilizer, clay anti-swelling agent and drainage aid. The retarding acid system agent includes the following in terms of weight percentage of raw materials: hydrochloric acid 6wt%-8wt%, chelating agent 2wt%, fluoride salt 1wt%-3wt%, hexahydrate inorganic salt 2wt%-4wt%, corrosion inhibitor 1wt%, demulsifier 1wt%, iron ion stabilizer 1wt%, clay anti-swelling agent 1wt% and drainage aid 1wt%. The weight percentage of the functional diverting agent is as follows: functional diverting agent 2wt%, and the remaining amount is set as water. The functional diverting agent realizes automatic viscosity increase and thickening under the acidifying adjustment of the retarding acid, temporarily plugs the high-permeability zone, and changes the acid fluid flow profile;

[0032] Specifically in this embodiment, the hydrochloric acid is set as a concentrated hydrochloric acid solution with a concentration of 31%; the chelating agent is set as any one of chelating agents of models AH-100, AH-101, AH-102 or EDTA; the fluoride salt is selected from one of SA701 fluoride salt or ammonium fluoride; the hexahydrate inorganic salt is selected from one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate or magnesium chloride hexahydrate; the corrosion inhibitor is set as oleic acid imidazoline of model SA1-3B; the demulsifier is set as a polyether demulsifier of model SA1-1; the iron ion stabilizer is set as citric acid; the clay anti-swelling agent is set as potassium-based polyacrylamide; the drainage aid is set as surfactant Tween-80 or non-ionic-cationic composite surfactant; the functional diverting agent is set as a polyether-modified polysiloxane or a polymer diverting agent such as Di spex U ltraPX4585.

[0033] A functional diversion and plugging removal method with a controllable distribution function specifically includes the following steps:

[0034] Step S1: Prepare a functional diversion and plugging removal agent;

[0035] S1.1. Preparation of a retarded acid system agent: Prepare hydrochloric acid, a chelating agent, a fluoride salt, a hexahydrate inorganic salt, a corrosion inhibitor, a demulsifier, an iron ion stabilizer, a clay swelling inhibitor, and a drainage aid in proportion, and mix them thoroughly to obtain a retarded acid system agent;

[0036] S1.2. Preparation of a functional diversion agent: Add the functional diversion agent to water in proportion and stir evenly to obtain a functional diversion agent. The functional diversion agent automatically becomes viscous and thickens under low pH conditions to temporarily block the high-permeability zone and automatically reduces viscosity as the pH value increases;

[0037] Step S2: Inject the functional diversion and plugging removal agent prepared in Step S1 into the oil and gas well through a high-pressure pump truck to pre-treat the wellbore and the near-wellbore area. Use an organic cleaning agent to clean the wellbore and the near-wellbore area to remove wax and colloid components to ensure the smooth progress of subsequent acidification operations;

[0038] Among them, the dosage formula of the functional diversion and plugging removal agent is:

[0039]

[0040] Among them, represents the dosage volume of the plugging removal agent; h represents the oil layer depth; represents the porosity; R represents the treatment radius;

[0041] Step S3: Achieve double transformation of the high-permeability zone and the low-permeability zone of the reservoir through the temporary plugging effect of the functional diversion agent and the special properties of the retarded acid system agent;

[0042] Taking the Chang 8 reservoir in the Nanliang area of a certain oilfield as an example, this reservoir belongs to a reservoir with low porosity and extra-low permeability; the following are the specific steps for acidification operations using the functional diversion and plugging removal agent provided by the present invention:

[0043] (1) Pre-treatment: Circulate until the string is unobstructed, and displace the organic cleaning and plugging removal fluid forward to clean the wellbore and the near-wellbore area;

[0044] (2) Inject the retarded acid system: Squeeze the retarded acid system agent forward to make the acid solution enter the high-permeability zone or fracture for reaction;

[0045] Principle of retarded acid plugging removal: When hydrochloric acid contacts the clay in the rock, the clay particles become acidic; subsequently, ammonium bifluoride in the solution contacts the acidic clay particles to generate HF; AlCl3 forms fluoroaluminum complexes with HF in the acid solution. Although HF is gradually consumed, the fluoroaluminum complexes in the acid solution can dissociate F step by step - and form HF for supplementation; Hydrochloric acid, HF react with some minerals and secondary plugging substances in the formation to achieve the purpose of acidizing and plugging removal:

[0046] The reaction equations are as follows:

[0047] ① NH2SO3H + NH4HF2 → NH2SO1NH4 + 2HF;

[0048] ② SiO2 (quartz) + 6HF → H2SiF3 (hexafluorosilicic acid) + 2H2O;

[0049] ③ Al2O2·4SiO2·H2O (montmorillonite) + 36HF → 4H2SiF3 + 2H3AIF6 + 12H2O;

[0050] ④ Na2O·Al2O3·6SiO2 (albite) + 50HF → 2NaF + 2H3AIF6 + 16H2O;

[0051] ⑤ Fe2O3 + 6NH2SO2H → Fe(NH4SO2)3 + 3H2O;

[0052] ⑥ CaCO3 + 2NH2SO3H → Ca(NH4SO3)2 + CO2 + H2O;

[0053] (3) Injecting functional diverting agent: Inject the functional diverting agent under positive pressure, which automatically becomes viscous and thickens, temporarily plugs the high-permeability zone, prevents the acid solution from continuing to enter, and temporarily plugs the high-permeability zone;

[0054] (4) Continuing to inject the retarded acid system: Continuing to inject the retarded acid system agent, and the mixture of fresh acid and nanofluid enters the deep zone or low-permeability zone for acidification diversion;

[0055] (5) Shut-in reaction: Shut in for a certain period of time to allow the acid-rock reaction to proceed fully. The nanofluid changes the wettability and reduces the interfacial tension, so that the crude oil is stripped and displaced, and finally the acidification transformation and oil displacement and production increase of heterogeneous reservoirs or low-permeability reservoirs are realized;

[0056] (6) Well washing: Conduct large-displacement reverse circulation well washing until the reaction residual liquid is completely returned;

[0057] Specifically, inject the functional diverting plugging removal agent into the oil and gas well through a high-pressure pump truck, and the specific construction process is as follows:

[0058] Pretreatment: Cycle until the tubing string is unobstructed, and displace 5.0 m of organic cleaning and plugging removal fluid in a positive direction. 3 , squeeze 5.0 m in a positive direction 3 of organic cleaning and plugging removal fluid at a pressure of 10 MPa and a displacement of 400 L / min. After shutting in the well for 60 min, conduct large-displacement reverse circulation well washing until the reaction residue fluid is completely returned.

[0059] Inject the retarded acid system agent: Squeeze 8 m of the retarded acid system agent in a positive direction 3 , with the pressure rising from 5 MPa to 8 MPa and a displacement of 400 L / min; then squeeze 12 m of the retarded acid system agent 3 , with the pressure rising from 10 MPa to 12 MPa and a displacement of 380 - 420 L / min;

[0060] Inject the displacement active water: Squeeze 10 m of the displacement active water 3 (over-displace 3.0 m 3 ), with the pressure rising from 15 MPa to 16 MPa and a displacement of 400 L / min;

[0061] Inject the functional diverting agent: Squeeze 8 m of the functional diverting agent in a positive direction 3 , with the pressure rising from 10 MPa to 12 MPa and a displacement of 350 L / min;

[0062] After the construction is completed, conduct an effect evaluation on the oil well; evaluate the stimulation effect by comparing indicators such as the daily liquid production, daily oil production, and water cut before and after the measures.

[0063] After the above steps, the oil well production has increased significantly, achieving the expected stimulation effect; the provided functional diverting and plugging removal agent with controllable distribution function has the advantages of environmental protection, high efficiency, wide application range, etc., and is especially suitable for the dual transformation of low-permeability reservoirs and high-permeability reservoirs; with the continuous deepening of oil and gas field development, it will have broad application prospects and huge economic benefits.

[0064] Example 2:

[0065] This example is basically the same as Example 1, except that the dosage of the retarded acid system agent and the functional diverting agent and the construction parameters are adjusted according to the specific well conditions. The specific adjustments are as follows:

[0066] Dosage of the retarded acid system agent: Adjusted to 32 m 3 ;

[0067] Dosage of the functional diverting agent: Adjusted to 10 m 3 ;

[0068] Reservoir adaptability design

[0069] Adjust the system parameters according to different reservoir types:

[0070]

[0071] Dynamically adjust injection parameters through downhole sensor data:

[0072] Pressure feedback control: When the bottom-hole pressure fluctuation coefficient (δ = σ / μ) > 0.15, automatically reduce the displacement by 10 - 15%;

[0073] Temperature compensation mechanism: When the formation temperature exceeds LCST, start the diverter pre-cooling module (cooling rate ≥ 5°C / min);

[0074] pH on-line monitoring: Use an antimony electrode sensor (measurement range 0 - 14, accuracy ±0.05) to regulate the acid mixing ratio;

[0075] Construction parameters: Appropriate adjustments have been made according to factors such as well depth and formation pressure to ensure the smooth progress of the construction;

[0076] In summary, the functional diversion and retarded acidizing technology system has achieved very good treatment effects in two oil wells in the Nanliang area, indicating that this system can effectively plug the high-permeability zone, while stimulating the low-permeability zone and increasing the single-well production; for the wax deposition situation during construction, organic cleaning has been added to thoroughly treat the near-wellbore and wellbore, cleaning out stubborn wax and gum components, which plays a key auxiliary role for the subsequent main system to enter the formation; for combined-layer acidizing, use the functional diverter to temporarily plug and shield the high-permeability intervals between or within layers, forcing the subsequent nano-retarded acid to enter the low-permeability intervals, maximizing the stimulation of the medium- and low-permeability intervals, achieving uniform acid distribution between intervals, and achieving better treatment effects; for oil wells with repeated fracturing, the usage volume of the functional diverter needs to be appropriately increased to achieve complete plugging of the high-permeability zone, so as to maximize the stimulation of the medium- and low-permeability intervals and achieve better treatment effects.

[0077] Finally: The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A functional diversion and plugging removal agent with a controllable distribution function, characterized in that: It includes a retarded acid system agent and a functional diverting agent. Among them, the retarded acid system agent is composed of hydrochloric acid, a chelating agent, a fluoride salt, a hexahydrate inorganic salt, a corrosion inhibitor, a demulsifier, an iron ion stabilizer, a clay anti-swelling agent, and a drainage aid. The retarded acid system agent includes the following raw materials by weight percentage: hydrochloric acid 6wt%-8wt%, chelating agent 2wt%, fluoride salt 1wt%-3wt%, hexahydrate inorganic salt 2wt%-4wt%, corrosion inhibitor 1wt%, demulsifier 1wt%, iron ion stabilizer 1wt%, clay anti-swelling agent 1wt%, and drainage aid 1wt%. The functional diverting agent includes the following by weight percentage: functional diverting agent 2wt%, and the remaining amount is set as water.

2. The functional diversion and plugging removal agent with controllable distribution function according to claim 1, characterized in that: The hydrochloric acid is set as a concentrated hydrochloric acid solution with a concentration of 31%; the chelating agent is set as any one of chelating agents of models AH-100, AH-101, AH-102, or EDTA; the fluoride salt is selected from one of SA701 fluoride salt or ammonium fluoride; the hexahydrate inorganic salt is selected from one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate, or magnesium chloride hexahydrate.

3. The functional diversion and plugging removal agent with controllable distribution function according to claim 1, wherein: The corrosion inhibitor is set as oleic acid imidazoline of model SA1-3B; the demulsifier is set as a polyether demulsifier of model SA1-1; the iron ion stabilizer is set as citric acid; the clay anti-swelling agent is set as potassium-based polyacrylamide; the drainage aid is set as surfactant Tween-80 or a non-ionic-cationic composite surfactant; the functional diverting agent is set as a polyether-modified polysiloxane or a polymer diverting agent of Dispex Ultra PX4585.

4. A plugging removal method using the functional flow diversion and plugging removal agent with controllable distribution function described in any one of claims 1-3, characterized in that: Specifically, it includes the following steps: Step S1: Prepare a functional diverting and plugging removal agent. Step S2: Inject the functional diverting and plugging removal agent prepared in Step S1 into the oil and gas well. Step S3: Through the temporary plugging effect of the functional diverting agent and the special properties of the retarded acid system agent, realize the dual transformation of the high-permeability zone and the low-permeability zone of the reservoir.

5. A functional shunt plugging removal method with a controllable distribution function according to claim 4, characterized in that: The specific steps in Step S1 include: S1.1: Preparation of the retarded acid system agent: Prepare hydrochloric acid, a chelating agent, a fluoride salt, a hexahydrate inorganic salt, a corrosion inhibitor, a demulsifier, an iron ion stabilizer, a clay anti-swelling agent, and a drainage aid in proportion, and mix them evenly to obtain the retarded acid system agent. S1.2: Preparation of the functional diverting agent: Add the functional diverting agent to water in proportion and stir evenly to obtain the functional diverting agent.

6. The functional diversion and plugging removal method with controllable distribution function according to claim 4, characterized in that: Before Step S2, pre-treat the wellbore and the near-wellbore area, and use an organic cleaning agent to clean the wellbore and the near-wellbore area to remove wax and gum components.

7. A functional shunt plugging removal method with a controllable distribution function according to claim 4, characterized in that: In Step S2, the injection method is to inject the functional diverting and plugging removal agent into the oil and gas well through a high-pressure pump truck.

8. A functional shunt plugging removal method with a controllable distribution function according to claim 7, characterized in that: The dosage formula of the functional diverting and plugging removal agent in Step S2 is: Wherein, represents the volume of the plugging removal agent; h represents the reservoir depth; represents the porosity; R represents the treatment radius.

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