Oil well water control acidification plug removal system and process for loose sandstone reservoir

Abstract

The invention discloses a water-control acidification plug removal system and process for an oil well of a loose sandstone reservoir. The water control acidification blockage removal system comprises a water control system and a blockage removal system; a preparation method of the water control system comprises the following steps: adding a surfactant with the mass fraction of 1-3% into diesel oil, mixing with clear water according to a certain proportion, stirring, and oscillating to form a water-in-oil emulsion system; the blocking removal system comprises the following components in percentage by mass: 5-15% of hydrochloric acid, 5-10% of fluoboric acid, 0.5-1% of a corrosion inhibitor, 1-2% of an iron ion stabilizer, 1-4% of an anti-swelling agent, 0.5% of a demulsifier, 0.5% of a cleanup additive and the balance of water. The water control acidification plug removal process comprises the following steps: sequentially injecting an oil-soluble cleaning agent, hydrochloric acid, a plug removal system, a spacer fluid, a water control system, a spacer fluid, a plug removal system, hydrochloric acid and a displacing fluid into a shaft, and then opening a well for production. The method is reliable in principle and easy and convenient to operate, and balanced acidification of the whole well section can be achieved while the high aquifer can be temporarily plugged.

Description

Technical Field

[0001] The invention relates to the technical field of oil production engineering acidification, and in particular to a water control acidification and plugging removal system and process for a loose sandstone reservoir oil well. Background Art

[0002] Acidizing and acid fracturing are currently one of the main measures for increasing production in oil and gas reservoirs. The oil and gas reservoirs in offshore oil fields are mainly sandstone reservoirs. Most of the main oil fields have entered the medium-to-high water content development stage. The reservoirs are thick, with many small layers and large permeability differences. Due to the strong heterogeneity and weak cementation between layers, the conventional general acid injection process has shown limitations. The main reason is that the general injection of acid fluid preferentially enters the high permeability layer, and the low permeability layer cannot be effectively unblocked, resulting in limited production increase. When the acid fluid is acidified again, it will still preferentially reach the high permeability layer, resulting in excessive acid use in the high permeability layer.

[0003] In order to solve the problem of balanced unblocking of heterogeneous reservoirs, the two main diversion technologies are mechanical diversion and chemical diversion. Offshore oil fields mostly use sand control completion. Mechanical diversion is difficult to implement, has low efficiency, and has great application limitations. Chemical diversion technology can currently be divided into diversion technologies such as chemical particles, fibers, and cross-linked polymers. Chinese invention patent CN202010191866.0 discloses a diversion acidizing method for high-permeability heterogeneous sandstone reservoirs, which relies on polymer cross-linking to achieve plugging and diversion, but there are problems such as incomplete gel breaking and formation damage during the application process, which seriously affects the normal production effect of the oil well after acidification; Chinese invention patent CN201910872298.8 discloses an in-situ self-generated micro-foam diversion acidizing fluid and acidization diversion method and application, which uses the method of self-generated foam in the formation to divert and divert, with little damage, but the production foam in the formation is unstable, and the plugging capacity is difficult to meet the needs of diversion acidizing.

[0004] Based on the above situation, it is of great significance to develop a water control and plugging removal system and process for oil well acidizing that is easy to configure, can plug high aquifers, and does not harm the reservoir. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a loose sandstone reservoir oil well water control acidification plugging system and process. The method of the present invention has reliable principle and simple operation, and can temporarily plug high water-containing layers while achieving balanced acidification of the entire well section.

[0006] In a first aspect, the present invention provides a water control and acidification plugging removal system for oil wells in loose sandstone reservoirs, which is achieved by adopting the following technical solutions.

[0007] A water control and acidification plugging removal system for oil wells in loose sandstone reservoirs, comprising a water control system and a plugging removal system;

[0008] The preparation method of the water control system is as follows: adding 1-3% by mass of a surfactant to diesel, mixing it with clean water in a certain proportion, stirring and shaking to form an oil-in-water emulsion system;

[0009] The deblocking system is composed of the following components in mass percentage: 5-15% hydrochloric acid, 5-10% fluoroboric acid, 0.5-1% corrosion inhibitor, 1-2% iron ion stabilizer, 1-4% anti-swelling agent, 0.5% demulsifier, 0.5% drainage aid, and the balance is water.

[0010] Furthermore, the surfactant in the water control system is an emulsifier with a hydrophile-lipophile balance (HLB value) in the range of 3 to 8.

[0011] Furthermore, the surfactant in the water control system includes sorbitan fatty acid ester, polyoxyethylene fatty alcohol ether, and aluminum stearate.

[0012] Preferably, the surfactants in the water control system are selected from sorbitan fatty acid esters and oleic acid, and the mass ratio of sorbitan fatty acid esters to oleic acid is 1:2.

[0013] Furthermore, the ratio of diesel to clean water in the water control system of the present invention is adjusted with the water content of the oil well. The lower the water content of the oil well, the lower the oil-water ratio. Specifically, as the water content of the oil well gradually increases, the ratio of diesel to clean water in the water control system gradually increases from oil:water=1:9 to oil:water=9:1.

[0014] Furthermore, the water control system also includes nanomaterials, and the added mass fraction of the nanomaterials is 1-3%; the nanomaterials include nano silicon dioxide and nano calcium carbonate. Adding nanomaterials to the water control system can enhance the stability of the system.

[0015] Furthermore, the corrosion inhibitors in the deblocking system include imidazoline, sulfonate active agents, amines, alkyl pyridine and derivatives thereof.

[0016] Furthermore, the iron ion stabilizer in the deblocking system includes acetic acid, lactic acid, and dihydroxymaleic acid.

[0017] Furthermore, the anti-swelling agent in the plugging removal system includes potassium chloride, ammonium chloride, quaternary ammonium salt, and dodecyltrimethylammonium chloride.

[0018] Furthermore, the demulsifier in the deblocking system includes ethylene glycol butyl ether and its modified product.

[0019] Furthermore, the drainage aid in the deblocking system includes a quaternary ammonium salt type surfactant and a pyridinium salt type surfactant.

[0020] In a second aspect, the present invention provides a water control and acidification plugging removal process for oil wells in loose sandstone reservoirs, which is achieved by adopting the following technical solutions.

[0021] A process for water control and acidification plugging removal using the water control and acidification plugging removal system comprises the following steps:

[0022] S1. Inject a certain amount of oil-soluble cleaning agent into the wellbore to clean the wellbore, screen pipe and formation oil stains;

[0023] S2. Inject a certain amount of 5% to 15% hydrochloric acid into the wellbore to dissolve inorganic scale blockage in the formation;

[0024] S3. Inject a certain amount of plugging-removing system into the wellbore;

[0025] S4. Inject 5 to 15 cubic meters of isolation fluid into the wellbore to isolate the acid solution from the subsequent water control system;

[0026] S5. Inject 10 to 30 cubic meters of water control system into the wellbore, inject the water control system into the formation at a low rate, and observe the pressure change;

[0027] S6. Inject 5 to 15 cubic meters of isolation liquid to isolate the water control system from the subsequent acid system;

[0028] S7. Inject all the remaining plugging removal system into the wellbore;

[0029] S8. Inject 10 to 20 cubic meters of 5% to 15% hydrochloric acid into the wellbore to maintain the acidified environment of the formation;

[0030] S9. Inject the wellbore volume displacement fluid to inject all the acid solution into the formation to complete the acidizing operation;

[0031] S10. Open the well and resume normal production.

[0032] Furthermore, in step S1, the oil-soluble cleaning agent includes C7-9 heavy aromatic hydrocarbon derivatives.

[0033] Furthermore, in steps S1 and S2, the amount of oil-soluble cleaning agent and hydrochloric acid injected into the wellbore is the same, both V1;

[0034] V1=A×π×h×Φ

[0035] Among them, the coefficient A ranges from 0.2 to 0.6; h is the vertical thickness of the perforated layer; Φ is the average porosity of the formation.

[0036] Furthermore, in step S3, the amount of the plugging-removing system injected into the wellbore is 20 to 50% of the total amount of the plugging-removing system V2;

[0037] V2=B×π×h×Φ

[0038] Among them, the coefficient B ranges from 0.5 to 1.5; h is the vertical thickness of the perforated layer; Φ is the average porosity of the formation.

[0039] Furthermore, in steps S4 and S6, the isolation liquid is clean water or clean water with 1-4% anti-swelling agent added.

[0040] Furthermore, in step S5, the low displacement is 0.1 to 0.5 m 2 / min.

[0041] This application has the following beneficial effects.

[0042] (1) The oil-water emulsion of the water control system of the present invention increases viscosity when it encounters water and decreases viscosity when it encounters oil, and can selectively plug high water-containing strata;

[0043] (2) The oil-water emulsion system of the water control system of the present invention has a short stability time and will accelerate demulsification when encountering acid. During the construction process, it will be temporarily blocked for a short time of 2 to 3 hours and then quickly destroyed, without causing damage to the formation;

[0044] (3) Compared with conventional acidification, the process of the present invention can effectively achieve balanced distribution of acid solution and control the increase of water content after acidification;

[0045] (4) Compared with the existing diversion technology, the diversion process of the present invention has low cost, controllable construction costs, and no additional equipment is required for construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a flowchart of the oil well water control and acidification plugging removal process. DETAILED DESCRIPTION

[0047] The present patent application is further described below in conjunction with embodiments.

[0048] Unless otherwise specified, the experimental methods used in the following preparation examples and examples are all conventional methods; the materials, reagents, etc. used in the following preparation examples and examples are all commercially available unless otherwise specified.

[0049] Example 1: Indoor simulation experiment

[0050] Select 60mL diesel and 140mL clean water, add 2% dehydrated sorbitol fatty acid ester to prepare 200mL emulsion water control system. In order to verify the plugging ability of the emulsion, cores with different permeabilities are selected to verify its diversion ability. The high permeability core simulates the high water-containing layer; the low permeability core simulates the low water-containing potential layer. The emulsion system is injected into the core through a parallel experiment, and the diversion volume of the high and low permeability cores before and after the water injection test is recorded to examine the selective plugging ability of the emulsion system. Experimental steps:

[0051] (1) Select two high- and low-permeability cores with a permeability difference of >20;

[0052] (2) High and low permeability cores are saturated with crude oil, and high permeability cores are flooded with water to simulate high aquifers;

[0053] (3) Connect the parallel displacement device and inject water at 0.5 mL / min to observe the water absorption of high and low permeability cores;

[0054] (4) preparing an emulsion system, pumping the emulsion system at a low speed of 0.1 mL / min, and stopping the injection after the low-permeability core produces liquid;

[0055] (5) Resume water injection and observe the changes in water absorption of high- and low-permeability cores.

[0056] Experimental Results

[0057]

[0058] The permeability of the high permeability core fluid measured in the experiment was 1502mD, and the permeability of the low permeability core fluid was 265mD. In the first section of water injection, the water absorption of the high permeability core accounted for 89%, and the low permeability core accounted for 11%. When the emulsion system was injected into the parallel core, the injection pressure increased from 0.047MPa to 0.564MPa, and the low permeability core began to discharge liquid. After plugging, water injection was resumed, and the water absorption of the high permeability core decreased to 62%, and the water absorption of the low permeability core increased to 38%, indicating that the emulsified diesel had a plugging effect on the high permeability core. Within 5 hours after the injection of the diversion fluid, the system can maintain stable plugging performance, meeting the requirements of 3-hour offshore acidification construction; at the same time, the system can automatically degrade and demulsify within 15 hours without causing any damage to the core.

[0059] Example 2: Offshore field application

[0060] A production well X in Bohai Oilfield was taken as the target for acidizing and plugging removal, and the oil-water emulsion diversion system and process for oil well acidizing of the present invention were used for scheme design. The target well section has a vertical depth of 1213.5-1569.3m, an effective vertical thickness of 73m for perforation, an average porosity of 24%, an average permeability of 821mD, and a well completion by fracturing and filling. Due to the large span of the oil well section, strong reservoir heterogeneity, and large permeability differences, after the first acidizing in 2019, the water content of the oil well increased from 80% to 93%, and the daily liquid production was 75m 3 / d rise to 220m 3 / d, daily oil production 15m 3 / d rise to 17m 3 / d, the fluid increase effect is significant, but the oil increase effect is poor. Conventional acidification enters the high-permeability layer in large quantities, exacerbating the unevenness of the fluid production profile. In the subsequent production process, affected by the blockage and pollution of high-speed development reservoir particles, the fluid production of Well X gradually decreased to 99m 3 / d, oil production 17m 3 / d, with a water content of 83%. In 2022, the oil-water emulsion diversion system and process method proposed in the present invention were used for acidification design.

[0061] Before construction, use an acid tank to pre-configure pre-fluid A, unblocking system B, isolation fluid C, water control system D, post-fluid E, and displacement fluid F.

[0062] The dosage of pre-fluid A is 20 cubic meters, the dosage of unblocking system B is 100 cubic meters, the dosage of isolation liquid C is 20 cubic meters, the dosage of water control system D is 20 cubic meters, the dosage of post-fluid E is 15 cubic meters, and the dosage of displacement liquid F is 18 cubic meters.

[0063] Pre-fluid A: Add 10% hydrochloric acid + 3% anti-swelling agent + 1% corrosion inhibitor + 2% iron ion stabilizer + 2% anti-swelling agent + 0.5% demulsifier + 0.5% drainage aid into clean water.

[0064] Deblocking system B: add 13% hydrochloric acid + 8% fluoroboric acid + 1% corrosion inhibitor + 2% iron ion stabilizer + 2% anti-swelling agent + 0.5% demulsifier + 0.5% drainage aid into clean water.

[0065] Isolation liquid C: Add 3% anti-swelling agent to clean water.

[0066] Water control system D: Add 30% diesel + 3% surfactant to clean water.

[0067] Post-fluid E: Same as pre-fluid A.

[0068] Displacement fluid F: Add 3% anti-swelling agent to clean water.

[0069] The anti-swelling agent is ammonium chloride, the corrosion inhibitor is imidazoline, the iron ion stabilizer is ethylenediaminetetraacetic acid, the demulsifier is polyoxypropylene octadecyl alcohol ether, the drainage aid is oxyethyl alkyl aldehyde, and the surfactant is sorbitan fatty acid ester. The contents of each component are in mass percentage.

[0070] Specific construction steps:

[0071] (1) Stop the pump and close Well X.

[0072] (2) Reverse circulation to wash the well until the returned liquid is free of oil and gas.

[0073] (3) After the acidizing equipment is in place, check the acidizing equipment and prepare the deblocking fluid.

[0074] (4) Connect the acidizing pump outlet to the acidizing pipeline of the Christmas tree.

[0075] (5) Pump the acidification pump to the Christmas tree for a water pressure test, and after the pressure is stabilized and qualified, proceed with the squeeze injection construction.

[0076] (6) Start the forward extrusion process and inject according to the following procedure:

[0077] Pumping schedule

[0078]

[0079] (7) Stop the pump, release the pressure, and start the acid injection process.

[0080] (8) Wire operation closing sleeve.

[0081] (9) Residual acid is returned and the pump is started at 35Hz for production.

[0082] After the on-site construction, the liquid production of Well X increased from 99m 3 / d increased to 320m 3 / d, oil production from 17m 3 / d increased to 67m 3 / d, the water content dropped from 83% to 81%. Compared with conventional acidification, the oil production increased by 50m 3 / d, the water content dropped by 2%, achieving effective water control and plugging removal.

[0083] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A water control and acidification system for unconsolidated sandstone reservoir oil wells, characterized by: Including water control system and plugging relief system; The preparation method of the water control system is as follows: adding 1-3% by mass of a surfactant to diesel, mixing it with clean water in a certain proportion, stirring and shaking to form an oil-in-water emulsion system; The deblocking system is composed of the following components in mass percentage: 5-15% hydrochloric acid, 5-10% fluoroboric acid, 0.5-1% corrosion inhibitor, 1-2% iron ion stabilizer, 1-4% anti-swelling agent, 0.5% demulsifier, 0.5% drainage aid, and the balance is water.

2. The water control and acidification plugging removal system for loose sandstone reservoir oil wells according to claim 1, characterized in that: The surfactant in the water control system is an emulsifier with a hydrophile-lipophile balance value within the range of 3 to 8.

3. The water control and acidification plugging removal system for loose sandstone reservoir oil wells according to claim 2, characterized in that: The surfactants in the water control system include sorbitan fatty acid ester, polyoxyethylene fatty alcohol ether and aluminum stearate.

4. The water control and acidification plugging removal system for loose sandstone reservoir oil wells according to claim 1, characterized in that: As the water content of the oil well gradually increases, the ratio of diesel to clean water in the water control system gradually increases from oil:water=1:9 to oil:water=9:

1.

5. The water control and acidification plugging removal system for loose sandstone reservoir oil wells according to claim 1, characterized in that: The water control system also includes nanometer materials, and the added mass fraction of the nanometer materials is 1-3%; the nanometer materials include nanometer silicon dioxide and nanometer calcium carbonate.

6. A process for water-controlling acidification and plugging removal using the water-controlling acidification and plugging removal system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Inject a certain amount of oil-soluble cleaning agent into the wellbore to clean the wellbore, screen pipe and formation oil stains; S2. Inject a certain amount of 5% to 15% hydrochloric acid into the wellbore to dissolve inorganic scale blockage in the formation; S3. Inject a certain amount of plugging-removing system into the wellbore; S4. Inject 5 to 15 cubic meters of isolation fluid into the wellbore to isolate the acid solution from the subsequent water control system; S5. Inject 10 to 30 cubic meters of water control system into the wellbore, inject the water control system into the formation at a low rate, and observe the pressure change; S6. Inject 5 to 15 cubic meters of isolation liquid to isolate the water control system from the subsequent acid system; S7. Inject all the remaining deblocking system into the wellbore; S8. Inject 10 to 20 cubic meters of 5% to 15% hydrochloric acid into the wellbore to maintain the acidified environment of the formation; S9. Inject the wellbore volume displacement fluid to inject all the acid solution into the formation to complete the acidizing operation; S10. Open the well and resume normal production.

7. The process for water-controlled acidification and plugging removal according to claim 6, characterized in that: In steps S1 and S2, the amount of oil-soluble cleaning agent and hydrochloric acid injected into the wellbore is the same, both V1; V1=A×π×h×Φ Among them, the coefficient A ranges from 0.2 to 0.6; h is the vertical thickness of the perforated layer; Φ is the average porosity of the formation.

8. The process for water-controlling acidification and plugging removal according to claim 6, characterized in that: In step S3, the amount of the plugging-removing system injected into the wellbore is 20-50% of the total amount of the plugging-removing system V2; V2=B×π×h×Φ Among them, the coefficient B ranges from 0.5 to 1.5; h is the vertical thickness of the perforated layer; Φ is the average porosity of the formation.

9. The process for water-controlled acidification and plugging removal according to claim 6, characterized in that: In step S5, the low displacement is 0.1 to 0.5 m 2 / min.

10. The process for water-controlling acidification and plugging removal according to claim 6, characterized in that: In steps S4 and S6, the isolation liquid is clean water or clean water with 1-4% anti-swelling agent added.

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