A drilling fluid system for treating heavy oil invasion and its preparation method

Abstract

The present invention provides a system for treating heavy oil-invaded drilling fluid and a preparation method thereof, and belongs to the technical field of crude oil extraction process. The present invention adopts an oil-based aromatic dispersant, a water-based drilling fluid and a stabilizer to form a composite system. By selecting a petroleum fraction with an aromatic hydrocarbon content of not less than 20% as an oil-based aromatic dispersant, adding it to a solid-phase-free water-based drilling fluid, adding a stabilizer at the same time, and fully stirring and mixing to form a stable system, the system improves the dispersion state of the heavy oil in the drilling fluid, maintains the rheological properties of the drilling fluid, and ensures that the drilling process proceeds smoothly. All raw materials of the present invention are widely available, low in price, simple to prepare, and the composite system has a low cost. By using the composite system of the present invention as a drilling fluid, the heavy oil can be highly dispersed in the drilling fluid, and the heavy oil can be prevented from agglomerating or clumping. The diameter of the dispersed heavy oil particles is ≤1mm, and the drilling fluid performance can be appropriately adjusted to meet drilling requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of crude oil production process, and particularly relates to a system for treating heavy oil-invaded drilling fluid and a preparation method thereof. Background Art

[0002] Heavy oil reservoirs generally have the geological characteristics of high porosity, high permeability and developed clay minerals. These geological characteristics make it very easy to encounter the problem of heavy oil invading the drilling fluid during the drilling process. Once heavy oil invades the drilling fluid, it will affect the rheological properties of the drilling fluid, reduce its density, increase the viscosity and shear force of the drilling fluid; clog the vibrating screen cloth, causing the drilling fluid to run out, increasing drilling costs; affect the drilling fluid logging and reservoir evaluation; affect cementing construction and cementing quality; the discharge of large amounts of contaminated drilling fluid increases the cost and difficulty of drilling fluid waste treatment and causes environmental pollution. Particularly serious heavy oil invasion of drilling fluid directly leads to the inability to drill.

[0003] The patent "A solidifying plugging agent, its preparation method and plugging slurry" (CN201810913212.7) discloses a plugging agent that can seal the leakage layer in the complex geological environment of the heavy oil layer, ensure drilling safety and speed up drilling. This invention is a solidifying cross-linking agent, and its goal is to block the heavy oil from invading the drilling fluid channel.

[0004] The patent "A self-curing composition used as a plugging agent and its application" (CN201510170095.6) discloses a plugging agent, which is also used in the process of developing heavy oil to block the invasion of heavy oil into drilling fluid and block the heavy oil inlet and outlet channels. The invention is a self-curing and cross-linking polymer material.

[0005] The patent "A treatment agent for solidifying heavy oil" (CN201410108878.7) discloses a heavy oil solidifier that oxidizes or cross-links heavy oil, increasing its molecular weight and turning it into a solid or semi-solid, causing the heavy oil to lose fluidity, thereby achieving the goal of controlling heavy oil from invading drilling fluid.

[0006] The patent "A treatment agent for reducing the adhesion of heavy oil in drilling fluid" (CN201410178680.6) discloses a heavy oil viscosity reducer, which adds a macromolecular organic monomer to the drilling fluid system to perform surface cross-linking and wrapping on the heavy oil that invades the drilling fluid, causing the heavy oil that invades the drilling fluid to lose its adhesion, and then screens and removes the heavy oil on the ground to achieve heavy oil invasion control.

[0007] The paper "Handling Asphalt Invasion and Related Downhole Complexities in Well F19" reports on the use of mixed diesel drilling fluid to prevent and treat heavy oil invasion of drilling fluid based on indoor experiments. However, there are related problems such as diesel stratification in the drilling fluid, which cannot guarantee the stability of the system.

[0008] The paper "Research and Application of Asphaltene Heavy Oil Hardener for Drilling Fluid" reports that in order to solve the problem of asphaltene heavy oil contamination of drilling fluid, based on the theory of heavy oil oxidation hardening chemical reaction, heavy oil hardener LYJ-5 was selected, conditions were evaluated in the laboratory, and field tests were carried out for verification.

[0009] In summary, the existing technology mainly focuses on the development of heavy oil cross-linking agents (treatment agents, oxidants, curing agents), heavy oil surface treatment agents (coating agents), and gel polymer chemical plugging materials, with the purpose of hardening the heavy oil itself, losing its fluidity or making the heavy oil surface lose its adhesion and blocking the heavy oil invasion channel, so as to achieve the purpose of heavy oil invasion control. However, this type of technology has high cost and poor adaptability, and the control effect is difficult to meet the drilling needs. Based on the existing technology, the present invention provides a system for treating heavy oil invasion of drilling fluid and a preparation method thereof. The invention can improve the dispersion state of heavy oil in drilling fluid, improve the rheological properties of the system after heavy oil invades drilling fluid, and ensure that the drilling process proceeds smoothly.

[0010] Heavy oil intrusion into drilling fluids can pose significant challenges to drilling. The primary issue is that heavy oil tends to aggregate and clump in the drilling fluid, affecting the fluid's rheological properties. Furthermore, heavy oil adheres to drill tools, increasing ground torque and, in severe cases, creating the risk of drill sticking. To address this issue, it is essential to address it. Therefore, it is necessary to provide a system for treating heavy oil intrusion into drilling fluids. This technology improves the dispersion of heavy oil in the drilling fluid, improves the rheological properties of the system after heavy oil intrusion, and ensures smooth drilling operations. Summary of the Invention

[0011] The present invention addresses the problems of the prior art and provides a system for treating heavy oil-invaded drilling fluid and a preparation method thereof. An oil-based aromatic dispersant is used in combination with a water-based drilling fluid and a stabilizer to form a composite system. A petroleum fraction with an aromatic hydrocarbon content of not less than 20% is selected as the oil-based aromatic dispersant and added to a solid-free water-based drilling fluid. A stabilizer is also added and the system is thoroughly stirred and mixed to form a stable system. This system improves the dispersion of heavy oil in the drilling fluid, maintains the rheological properties of the drilling fluid, and ensures smooth drilling. All raw materials in the present invention are widely available, inexpensive, and simple to prepare, resulting in a low-cost composite system. Using the composite system as a drilling fluid, the heavy oil can be highly dispersed in the drilling fluid, preventing the heavy oil from agglomerating or clumping. The dispersed heavy oil particles have a diameter of ≤1 mm, and the drilling fluid properties can be appropriately adjusted to meet drilling requirements.

[0012] To achieve the above objectives, in a first aspect, the present invention provides a system for treating heavy oil-invaded drilling fluid, comprising a water-based drilling fluid, an oil-based aromatic dispersant, and a stabilizer.

[0013] In a preferred embodiment, the amount of the oil-based aromatic dispersant added to the drilling fluid is 2-8w%; the amount of the stabilizer added to the water-based drilling fluid is 0.1-0.8w%.

[0014] In a preferred embodiment, based on 100 parts of water, the water-based drilling fluid includes the following components: 100 parts of water, 0.1-1.0 parts of soda ash, 0.1-1.0 parts of caustic soda, 0.4-4.0 parts of fluid loss reducer, 0.1-1.0 parts of viscosity enhancer, 0.5-5.0 parts of modified starch, and 10.0-30.0 parts of sodium chloride.

[0015] In a preferred embodiment, the oil-based aromatic dispersant is selected from petroleum fractions with an aromatic hydrocarbon content of not less than 20%, and mixed petroleum fractions with two or more aromatic hydrocarbon contents of not less than 20%.

[0016] In a preferred embodiment, the distillation range of the petroleum fraction in the oil-based aromatic dispersant is 150-400°C.

[0017] In a preferred embodiment, the modified starch, viscosity enhancer and fluid loss control agent are commonly used modified starch, viscosity enhancer and fluid loss control agent in the art, and the specific types are not limited. Preferably, the modified starch is STAR-AM, the viscosity enhancer is POLY-V, and the fluid loss control agent is DEG-FLO.

[0018] In a preferred embodiment, the stabilizer is selected from one or more compounds having a non-polar hydrocarbon chain of 8-16 carbon atoms at one end and a polar group at the other end, wherein the polar group is a carboxylic acid group (-COOH), a sulfonic acid group (-SO3H), a sulfinic acid group (-SOOH), an amino group (-NH2) or a hydroxyl group (-OH).

[0019] In a preferred embodiment, the stabilizer is selected from one or more of dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, octylphenol polyoxyethylene ether, and sorbitan oleate.

[0020] In a second aspect, the present invention further provides a method for preparing a drilling fluid system for treating heavy oil invasion, comprising the following steps:

[0021] Step 1): Soda ash, caustic soda, fluid loss reducer, viscosity enhancer, modified starch, and sodium chloride are uniformly mixed with water in a certain proportion to prepare a water-based drilling fluid;

[0022] Step 2): Add a certain amount of oil-based aromatic dispersant and stabilizer to the prepared water-based drilling fluid, and stir and mix thoroughly to obtain a composite system.

[0023] In a preferred embodiment, after adding the oil-based aromatic dispersant in step 2), stirring is carried out at room temperature at 1000-4000 r / min for 2-10 min, and after adding the stabilizer, stirring is carried out at 4000-6000 r / min for 5-30 min.

[0024] The present invention adjusts the ratio of water-based drilling fluid on the one hand, and adds an oil-based aromatic dispersant and a stabilizer to the water-based drilling fluid on the other hand, thereby forming a new drilling fluid composite system containing additives. The oil-based aromatic dispersant and the stabilizer are newly added components. The oil-based aromatic dispersant and the stabilizer do not interact with the drilling fluid components (one is oil-based and the other is water-based). The oil-based aromatic dispersant is highly dispersed in the water-based drilling fluid in the form of tiny droplets (the composite system appears milky white in photos) through the stabilizer. The addition of the oil-based aromatic dispersant and the stabilizer makes the drilling fluid composite system exhibit the characteristics of oil-based drilling fluid, greatly reduces the interfacial tension between the drilling fluid composite system and heavy oil, and increases the solubility of the drilling fluid composite system for heavy oil. Due to the addition of the aromatic dispersant, the peptization ability and dispersibility of the composite system for heavy components (colloidal asphaltene) in the heavy oil are also increased. In this way, the heavy oil intruded into the drilling fluid can be well dispersed in the drilling fluid, ensuring that the drilling fluid has good fluidity and stable drilling fluid performance.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention uses a water-based drilling fluid that does not contain any solids as the main body, and forms a stable composite system by adding an oil-based aromatic dispersant and a stabilizer. After adding the stabilizer, the mixed system of the oil-based aromatic dispersant and the water-based drilling fluid is stable and does not stratify within a certain period of time. The addition of the oil-based aromatic dispersant greatly enhances the aromatic solubility of the composite system, and can well disperse and even dissolve heavy oil.

[0027] 2. During the development of heavy oil reservoirs, when heavy oil invades the drilling fluid, the composite system of the present invention is used as the drilling fluid to highly disperse the heavy oil in the drilling fluid, preventing the heavy oil from agglomerating or clumping. The diameter of the dispersed heavy oil particles is ≤1 mm, and the drilling fluid properties can be appropriately adjusted to meet the requirements of continued drilling.

[0028] 3. All raw materials of the present invention are widely available, low in price, simple to prepare, and the composite system has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the system for treating heavy oil-invaded drilling fluid disclosed in Example 1.

[0030] Figure 2 This is a diagram showing the effect of heavy oil treatment in Example 1.

[0031] Figure 3This is the system for treating heavy oil-invaded drilling fluid disclosed in Example 2.

[0032] Figure 4 This is a diagram showing the effect of heavy oil treatment in Example 2.

[0033] Figure 5 This is the system for treating heavy oil-invaded drilling fluid disclosed in Example 3.

[0034] Figure 6 This is the effect diagram after heavy oil treatment in Example 3.

[0035] Figure 7 This is the system for treating heavy oil-invaded drilling fluid disclosed in Example 4.

[0036] Figure 8 This is a diagram showing the effect of heavy oil treatment in Example 4.

[0037] Figure 9 This is a diagram showing the effect of using a 1mm diameter screen to screen the drilling fluid containing heavy oil when 20% heavy oil is intruded into ordinary water-based drilling fluid in Comparative Example 1.

[0038] Figure 10 This is the system for treating heavy oil-invaded drilling fluid disclosed in Example 2.

[0039] Figure 11 This is a diagram showing the effect of heavy oil treatment in comparative example 2. DETAILED DESCRIPTION

[0040] It is worth noting that the raw materials used in the present invention are all common commercially available products, and their sources are not specifically limited.

[0041] Example 1

[0042] Preparation of drilling fluid system for treating heavy oil invasion

[0043] Step 1): Take 500mL of water and put it into the mud mixer cup. Adjust the speed to 1000r·min. -1 Stirring, add 1.25g NaOH and 1.25g Na2CO3 in sequence, stirring for 15min; adjust the speed to 8000r·min -1 While stirring, 18 g of filtrate reducer DEG-FLO was added in sequence and stirred for 10 min, 1.5 g of viscosity enhancer POLY-V was added and stirred for 10 min, 3.5 g of modified starch STAR-AM was added and stirred for 20 min, and finally 145 g of NaCl was added and stirred for 15 min to obtain a water-based drilling fluid.

[0044] Step 2): 18 g of naphthenic crude oil fraction with a distillation range of 200-350°C and an aromatic content of 32.5% was added to the prepared water-based drilling fluid, and the mixture was stirred at 2000 r / min at room temperature.-1 Stir for 3 minutes; then add 0.2% of the water-based drilling fluid mixture of dodecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate (2:1, w / w), and stir at room temperature for 5000 r·min -1 Stir for 10 minutes.

[0045] The system for treating heavy oil intrusion drilling fluid and the effect of treating heavy oil in this embodiment are as follows: Figure 1 、 Figure 2 As shown, Figure 1 For the treatment of heavy oil invasion drilling fluid system of this embodiment, Figure 2 This is the effect diagram after treatment with 10% (accounting for the composite system) heavy oil intrusion.

[0046] A 1 mm diameter screen composite system was used to process a mixture containing heavy oil. The percentage of heavy oil passing through the screen to the added heavy oil was defined as the heavy oil dispersion. In this embodiment, the heavy oil dispersion was 99.21%.

[0047] Example 2

[0048] Step 1): Take 500mL of water and put it into the mud mixer cup. Adjust the speed to 1000r·min. -1 Stirring, add 1.25g NaOH and 1.00g Na2CO3 in sequence, stirring for 20min; adjust the speed to 8000r·min -1 While stirring, 15 g of filtrate reducer DEG-FLO was added in sequence and stirred for 10 min, 2.0 g of viscosity enhancer POLY-V was added and stirred for 10 min, 3.0 g of modified starch STAR-AM was added and stirred for 20 min, and finally 125 g of NaCl was added and stirred for 15 min to obtain a water-based drilling fluid.

[0049] Step 2): Add 25g of naphthenic crude oil fraction with a distillation range of 180-400℃ and an aromatic content of 36.5% to the prepared water-based drilling fluid, and rotate at 2000r·min at room temperature. -1 Stir for 3 minutes; then add 0.25% sodium dodecyl sulfate and octylphenol polyoxyethylene ether (4:1, w / w) of water-based drilling fluid, and stir at room temperature for 5000 r·min -1 Stir for 10 minutes.

[0050] The system for treating heavy oil invasion drilling fluid and the effect of treating heavy oil in this embodiment Figure 3 、 Figure 4 As shown, Figure 3 For the treatment of heavy oil invasion drilling fluid system of this embodiment, Figure 4 This is the effect diagram after treatment of 25% (accounting for the composite system) heavy oil intrusion.

[0051] A 1 mm diameter screen composite system was used to process a mixture containing heavy oil. The percentage of heavy oil passing through the screen to the added heavy oil was defined as the heavy oil dispersion. In this embodiment, the heavy oil dispersion was 94.38%.

[0052] Example 3

[0053] Step 1): Take 500mL of water and put it into the mud mixer cup. Adjust the speed to 1200r·min. -1 Stirring, add NaOH 1.50g, Na2CO3 1.35g in sequence, stirring for 15min; adjust the speed to 8500r·min -1 While stirring, 20 g of filtrate reducer DEG-FLO was added in sequence and stirred for 15 min, 2.5 g of viscosity enhancer POLY-V was added in sequence and stirred for 15 min, 2.5 g of modified starch STAR-AM was added in sequence and stirred for 25 min, and finally 120 g of NaCl was added and stirred for 20 min to obtain a water-based drilling fluid.

[0054] Step 2): Add 22 g of an intermediate crude oil fraction with a distillation range of 180-325°C and an aromatic content of 35.7% to the prepared water-based drilling fluid, and rotate at 2500 r / min at room temperature. -1 Stir for 5 minutes; then add 0.22% sorbitol oleate and sodium dodecylbenzenesulfonate (1:5, w / w) of water-based drilling fluid, and stir at room temperature at 5500 r·min -1 Stir for 15 minutes.

[0055] The system for treating heavy oil invasion drilling fluid and the effect of treating heavy oil in this embodiment Figure 5 、 Figure 6 As shown, Figure 5 For the treatment of heavy oil invasion drilling fluid system of this embodiment, Figure 6 This is the effect diagram after treatment of 20% (accounting for the composite system) heavy oil intrusion.

[0056] The present invention uses a 1 mm diameter screen composite system to process a mixture containing heavy oil. The percentage of heavy oil flowing out of the screen after screening to the added heavy oil is defined as the heavy oil dispersion. In this embodiment, the heavy oil dispersion is 95.19%.

[0057] Example 4

[0058] Step 1): Take 500mL of water and put it into the mud mixer cup. Adjust the speed to 1200r·min. -1 Stirring, add NaOH 1.50g, Na2CO3 1.35g in sequence, stirring for 15min; adjust the speed to 8500r·min -1While stirring, 20 g of filtrate reducer DEG-FLO was added in sequence and stirred for 15 min, 2.5 g of viscosity enhancer POLY-V was added in sequence and stirred for 15 min, 2.5 g of modified starch STAR-AM was added in sequence and stirred for 25 min, and finally 120 g of NaCl was added and stirred for 20 min to obtain a water-based drilling fluid.

[0059] Step 2): Add 22g of intermediate crude oil fraction with a distillation range of 180-300℃ and an aromatic content of 22.5% to the prepared water-based drilling fluid, and rotate at 2500r·min at room temperature. -1 Stir for 5 minutes; then add 0.24% dodecyltrimethylammonium bromide and sorbitol oleate (2:3, w / w) of water-based drilling fluid, and stir at room temperature at 5500 r·min -1 Stir for 15 minutes.

[0060] The system for treating heavy oil invasion drilling fluid and the effect of treating heavy oil in this embodiment Figure 7 、 Figure 8 As shown, Figure 7 For the treatment of heavy oil invasion drilling fluid system of this embodiment, Figure 8 This is the effect diagram after treatment of 20% (accounting for the composite system) heavy oil intrusion.

[0061] The present invention uses a 1 mm diameter screen composite system to process a mixture containing heavy oil. The percentage of heavy oil passing through the screen to the added heavy oil is defined as the heavy oil dispersion. In this embodiment, the heavy oil dispersion is 93.55%.

[0062] Comparative Example 1

[0063] The heavy oil was treated using a common water-based drilling fluid (i.e., the water-based drilling fluid prepared in step 1 of Example 3). Figure 9 The results of 20% heavy oil intrusion in ordinary water-based drilling fluid are shown in Figure 1. A 1mm diameter screen is used to screen the drilling fluid containing heavy oil. The percentage of heavy oil flowing through the screen relative to the added heavy oil is defined as the heavy oil dispersion. The heavy oil dispersion of Comparative Example 1 is 11.32%.

[0064] It can be seen that the heavy oil invasion drilling fluid system of Examples 1-4 of the present application can greatly improve the dispersion of heavy oil in the system and maintain the rheological properties of the drilling fluid compared with ordinary water-based drilling fluid.

[0065] Comparative Example 2

[0066] The same procedures as in Example 2 were followed except that a crude oil fraction with a distillation range of 180-400° C. and an aromatic hydrocarbon content of 15% was used.

[0067] The system for treating heavy oil invasion drilling fluid and the effect of treating heavy oil in this embodiment Figure 10 、 Figure 11As shown, Figure 10 For the treatment of heavy oil invasion drilling fluid system of this embodiment, Figure 11 This is the effect diagram after treatment of 20% (accounting for the composite system) heavy oil intrusion.

[0068] The present invention uses a 1 mm diameter screen composite system to process a mixture containing heavy oil. The percentage of heavy oil passing through the screen to flow out of the screen is defined as the heavy oil dispersion. In this embodiment, the heavy oil dispersion is 65.55%.

[0069] It can be seen that the heavy oil invasion drilling fluid system of Examples 1-4 of the present application can greatly improve the dispersion of heavy oil in the system and maintain the rheological properties of the drilling fluid compared to the crude oil fraction system drilling fluid with a distillation range of 180-400°C and an aromatic hydrocarbon content of 15%.

[0070] The present invention is not limited to the technical means disclosed above, but also includes technical solutions composed of any combination of the above technical features. The above is a specific embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A system for treating heavy oil-invaded drilling fluid, characterized in that: Including water-based drilling fluid, oil-based aromatic dispersant and stabilizer; The oil-based aromatic dispersant is selected from petroleum fractions with an aromatic hydrocarbon content of not less than 20%, and mixed petroleum fractions with two or more aromatic hydrocarbon contents of not less than 20%; The stabilizer is selected from one or more of dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, octylphenol polyoxyethylene ether, and sorbitan oleate.

2. The system for treating heavy oil-invaded drilling fluid according to claim 1, wherein: The amount of oil-based aromatic dispersant added is 2-8w% of the drilling fluid; the amount of stabilizer added is 0.1-0.8w% of the water-based drilling fluid.

3. The system for treating heavy oil-invaded drilling fluid according to claim 1, wherein: Based on 100 parts of water, the water-based drilling fluid includes the following components: 100 parts of water, 0.1-1.0 parts of soda ash, 0.1-1.0 parts of caustic soda, 0.4-4.0 parts of fluid loss reducer, 0.1-1.0 parts of viscosity enhancer, 0.5-5.0 parts of modified starch, and 10.0-30.0 parts of sodium chloride.

4. The system for treating heavy oil-invaded drilling fluid according to claim 1, wherein: In the oil-based aromatic dispersant, the distillation range of the petroleum fraction is 150-400°C.

5. The system for treating heavy oil-invaded drilling fluid according to claim 3, wherein: The modified starch is STAR-AM, the viscosity enhancer is POLY-V, and the fluid loss additive is DEG-FLO.

6. The method for preparing a system for treating heavy oil-invaded drilling fluid according to any one of claims 1 to 5, wherein: The following steps are involved: Step 1): Soda ash, caustic soda, fluid loss reducer, viscosity enhancer, modified starch, and sodium chloride are uniformly mixed with water in a certain proportion to prepare a water-based drilling fluid; Step 2): Add a certain amount of oil-based aromatic dispersant and stabilizer to the prepared water-based drilling fluid, and stir and mix thoroughly to obtain a composite system.

7. The preparation method according to claim 6, wherein In step 2), after adding the oil-based aromatic dispersant, stir at room temperature at 1000-4000 r / min for 2-10 minutes. After adding the stabilizer, stir at 4000-6000 r / min for 5-30 minutes.

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