Clay-solubilized heavy oil viscosity-reducing and plug-removing water-based agent and application thereof

Abstract

The application provides a clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent and application thereof. The clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent comprises an organic dispersant, a first surfactant, an additive, a clay-solubilizing agent and water. The organic dispersant is tetrahydrofuran, the first surfactant is sodium dodecyl benzene sulfonate, the additive is n-pentanol, and the clay-solubilizing agent is a complex acid of hydrochloric acid and fluoroboric acid. The clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent can effectively solve the problems of sensitivity and oil sludge pollution and plug, the recovery degree of permeability is more than 66%, and the implementation of heavy oil chemical viscosity reduction mining is effectively promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil field chemistry, in particular to a clay solubilization type heavy oil water-based viscosity reduction and plug removal agent. BACKGROUND

[0002] Chinese heavy oil is generally buried deep and has high viscosity. Most of the oil reservoirs are concentrated in 1000 to 1500 m loose sandstone reservoirs. The viscosity of crude oil is generally greater than 400 mPa·s (50℃). The main method of thermal recovery is steam stimulation. The annual production is about 15 million tons. The average recovery rate is less than 20%. The formation remaining oil is abundant. However, after multiple rounds of steam stimulation, it is difficult to increase the thermal radius, the oil-gas ratio continues to decrease, the water cut continues to rise, and the thermal recovery benefit continues to deteriorate. Chemical composite flooding cold production is a potential and feasible replacement technology proposed by Sinopec. However, the existing technology follows the idea of using organic solution or acidizing to remove plugging and increase permeability. The influence of the comprehensive plugging of resin, asphaltene and mud, and fine silt migration is not fully considered. Therefore, after the transition from thermal recovery to chemical viscosity reduction in heavy oil wells, the viscosity of heavy oil increases sharply, especially in sensitive reservoirs with high mud content. Resin, asphaltene and mud are mixed and deposited near the wellbore, causing plugging near the wellbore, making it difficult for heavy oil to flow into the wellbore. This makes it difficult for the existing chemical viscosity reduction and plug removal system to meet the needs of sensitive heavy oil near the wellbore. It also cannot provide guidance for chemical plug removal systems for heavy oil injection and production wells after steam stimulation. SUMMARY

[0003] One of the present application provides a clay solubilization type heavy oil water-based viscosity reduction and plug removal agent, which comprises an organic dispersant, a first surfactant, an auxiliary agent, a clay solubilizing agent and water.

[0004] In one specific embodiment, the organic dispersant is at least one of the cyclic ether compounds.

[0005] In one specific embodiment, the organic dispersant is tetrahydrofuran and / or 2-methyltetrahydrofuran.

[0006] In one specific embodiment, the first surfactant is an anionic surfactant.

[0007] In one specific embodiment, the first surfactant is sodium dodecyl benzene sulfonate.

[0008] In one specific embodiment, the auxiliary agent is at least one of the alcohol compounds.

[0009] In one specific embodiment, the auxiliary agent is pentanol, preferably, the auxiliary agent is n-pentanol.

[0010] In one specific embodiment, the clay solubilizing agent is a composite acid solution.

[0011] In one specific embodiment, the clay solubilizing agent is a complex acid of hydrochloric acid and fluoroboric acid.

[0012] In one specific embodiment, the mass ratio of hydrogen chloride to fluoroboric acid is 1:1 to 1:1.5.

[0013] In one specific embodiment, based on the total mass of the clay solubilizing type heavy oil water-based viscosity reducing and plugging removing agent being 100%, the organic dispersant is 0.5% to 1%, the first surfactant is 0.2% to 0.4%, the content of the auxiliary agent is 0.4% to 0.6%, and the content of the clay solubilizing agent is 1% to 2%.

[0014] The second aspect of the present application provides the use of the clay solubilizing type heavy oil water-based viscosity reducing and plugging removing agent according to any one of the first aspect of the present application in viscosity reduction and plugging removal in the process of heavy oil exploitation.

[0015] The third aspect of the present application provides a method for water-based viscosity reduction and plugging removal of a heavy oil reservoir after multiple cycles (for example, 3 cycles, 4 cycles, 5 cycles or more) of steam stimulation, which comprises the following steps:

[0016] 1) forward washing a target well with a fluid to exclude the influence of metal ions;

[0017] 2) injecting the clay solubilizing type heavy oil water-based viscosity reducing and plugging removing agent according to any one of the first aspect of the present application into the target well, wherein the injected volume is 0.3 to 0.5 times the pore volume in the reservoir area with a horizontal radius of 15 to 25 m centered on the target well; wherein the length of the reservoir in the vertical direction is the thickness of the reservoir;

[0018] 3) forward displacement of 1.2 to 1.5 times the volume of the tubing of the target well with an aqueous solution of a second surfactant;

[0019] 4) soaking for 1 to 2 days and opening the well for oil production.

[0020] In one specific embodiment, in step 1), the target well is forward washed with the fluid until the incoming and outgoing fluids are consistent, while the annulus is filled.

[0021] In one specific embodiment, the fluid is clean water.

[0022] In one specific embodiment, in step 2), the injected volume calculation method is: π x radius x radius x oil layer thickness h x porosity x (0.3 to 0.5 PV) x (0.1 to 0.2).

[0023] In one specific embodiment, in step 3), the second surfactant is an anionic surfactant.

[0024] In one embodiment, the second surfactant is sodium dodecyl benzene sulfonate.

[0025] In one embodiment, the aqueous solution of the second surfactant has a mass concentration of 0.2% to 0.4%.

[0026] In one embodiment, the open well production should be consistent with the production system and measures before.

[0027] Advantages of the present application:

[0028] The clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent of the present application is based on a composite system formed by dispersion viscosity reduction, emulsification carrying and clay solubilization, and has the following advantages:

[0029] It is effective for water-sensitive and high-clay-content heavy oil wells, and can be applied to heavy oil reservoirs with a heavy oil viscosity of < 50,000 mPa·s and a clay content of < 25%, and has a complex oil sludge plug removal rate of > 66%.

[0030] The clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent of the present application has been used in some heavy oil reservoirs in Shengli Oilfield, Henan Oilfield and Jianghan Oilfield of China Petroleum Chemical Corporation after steam stimulation, and some blocks have achieved certain application effects. It can be seen that the clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent of the present application can effectively solve the problem of unsatisfactory effect of early chemical flooding, promote the near-well seepage capacity of heavy oil, improve the heavy oil viscosity reduction and production effect, has great popularization potential, and can cover about 20% (500 million tons) of the heavy oil reserves produced by steam stimulation. DETAILED DESCRIPTION

[0031] The present application will be further described below in conjunction with examples, but the examples of the present application are only exemplary descriptions, and the embodiment does not constitute a limitation on the present application in any case.

[0032] Example 1

[0033] For example, 100 g of heavy oil viscosity-reducing and plug-removing agent is prepared by mixing 1.0 g of tetrahydrofuran, 0.4 g of sodium dodecyl benzene sulfonate, 0.6 g of n-pentanol, 2.7 g of 30% hydrochloric acid aqueous solution (the effective content of hydrogen chloride is 0.8 g), 1.2 g of fluoroboric acid and the remaining water, and stirring uniformly to obtain the clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent.

[0034] Example 2

[0035] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 1.0 g of tetrahydrofuran, 0.3 g of sodium dodecyl benzene sulfonate, 0.5 g of n-pentanol, 2.5 g of 30% hydrochloric acid aqueous solution (effective content of hydrogen chloride is 0.75 g), 0.75 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a clay-solubilized thick oil water-based viscosity reducing and plug-removing agent.

[0036] Example 3

[0037] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 0.5 g of tetrahydrofuran, 0.2 g of sodium dodecyl benzene sulfonate, 0.4 g of n-pentanol, 1.7 g of 30% hydrochloric acid aqueous solution (effective content of hydrogen chloride is 0.5 g), 0.5 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a clay-solubilized thick oil water-based viscosity reducing and plug-removing agent.

[0038] Example 4

[0039] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 0.7 g of tetrahydrofuran, 0.3 g of sodium dodecyl benzene sulfonate, 0.5 g of n-pentanol, 2.7 g of 30% hydrochloric acid aqueous solution (effective content of hydrogen chloride is 0.8 g), 1.2 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a clay-solubilized thick oil water-based viscosity reducing and plug-removing agent.

[0040] Comparative Example 1

[0041] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 0.2 g of sodium dodecyl benzene sulfonate, 0.4 g of n-pentanol, 1.7 g of 30% hydrochloric acid aqueous solution (effective content of hydrogen chloride is 0.5 g), 0.5 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a thick oil water-based viscosity reducing and plug-removing agent.

[0042] Comparative Example 2

[0043] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 0.5 g of tetrahydrofuran, 0.4 g of n-pentanol, 1.7 g of 30% hydrochloric acid aqueous solution (effective content of hydrogen chloride is 0.5 g), 0.5 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a thick oil water-based viscosity reducing and plug-removing agent.

[0044] Comparative Example 3

[0045] With 100 g of thick oil viscosity reducing and plug-removing agent preparation as an example, 0.5 g of tetrahydrofuran, 0.2 g of sodium dodecyl benzene sulfonate, 1.7 g of 30% hydrochloric acid aqueous solution (30% effective content), 0.5 g of fluoboric acid and the rest of water are mixed and stirred uniformly to obtain a thick oil water-based viscosity reducing and plug-removing agent.

[0046] Comparative Example 4

[0047] With 100 g thick oil viscosity breaking and plugging agent preparation as an example, 0.5 g tetrahydrofuran, 0.2 g sodium dodecyl benzene sulfonate, 0.4 g n-pentanol and 98.9 g water are mixed and stirred uniformly to obtain a thick oil water-based viscosity breaking and plugging agent.

[0048] Performance test

[0049] 1. Permeability determination

[0050] 1) Fill with 100 to 120 mesh quartz sand The sandpack tube a is used to simulate a thick oil reservoir, the dry weight of the sandpack tube filled with quartz sand is weighed, then vacuumized, saturated with clean water, the wet weight is weighed, and the porosity is calculated according to the dry weight and the wet weight.

[0051] 2) Inject clean water into the sandpack tube a at 1 mL / min, record the injection pressure when the metering is stable, and calculate the water measured permeability K1.

[0052] 3) Mix and stir 1900 g of Shengli oilfield thick oil (50℃, 41100 mPa·s) and 100 g of bentonite uniformly at 100℃ to make a sludge plug; the sandpack tube a filled with quartz sand is kept at a constant temperature of 60℃ (reservoir temperature) for 24 hours, then 10 mL of sludge plug is injected into the sandpack tube a filled with quartz sand at 1 mL / min at 100℃, and kept at a constant temperature of 60℃ (reservoir temperature) for 24 hours to simulate the near well plugging condition of the reservoir; then inject clean water into the sandpack tube a at 1 mL / min at 60℃ in the reverse direction, measure the injection pressure when stable, and calculate the water measured permeability K2 for evaluation of the plugging condition.

[0053] 4) Inject 15 mL of clay solubilized thick oil water-based viscosity breaking and plugging agent into the sandpack tube a in the forward direction at 60℃, and then keep it at a constant temperature of 60℃ for 24 hours; thereafter, inject clean water into the sandpack tube a in the reverse direction at 1 mL / min at 60℃, record the injection pressure when stable, and calculate the water measured permeability K3.

[0054] Wherein, the permeability formula is as follows:

[0055]

[0056] Wherein, K - permeability; Q - flow rate of fluid through the cross section per unit time; A - cross-sectional area; μ - viscosity of the liquid; L - length of the core; ΔP - pressure difference before and after the liquid passes through the core; all quantities are in the Darcy unit system.

[0057] The plugging rate is calculated according to the water measured permeability K1 and the core permeability K2, and the calculation formula is as follows:

[0058]

[0059] Wherein, τ - the plugging rate.

[0060] The permeability recovery degree is calculated according to the water measured permeability K1 and the water measured permeability K3, and the calculation formula is as follows:

[0061]

[0062] Wherein, n - the permeability recovery degree.

[0063] The results are shown in Table 1.

[0064] Table 1

[0065]

[0066] According to the results in Table 1, the components of the clay solubilization type heavy oil water-based viscosity reduction and plugging removal agent provided by the application have good synergistic effect, which can effectively solve the sensitive, oil sludge pollution and plugging, the permeability recovery degree is more than 66%, and effectively promotes the implementation of heavy oil chemical viscosity reduction mining.

[0067] Example 5

[0068] Field test

[0069] A heavy oil well in Shengli Oilfield, the reservoir temperature is 60 DEG C, the crude oil viscosity is 11000 mPa s at 50 DEG C, the reservoir thickness is 5 m, the permeability is 1300 mD, and the porosity is 28%. After multiple rounds of huff and puff, the near wellbore plugging is obvious, and the liquid production before the treatment is only 6 m 3 / d, and the liquid volume is low. After washing the well with clean water by positive circulation, 106 m 3 (π x 20 x 20 x 5 x 0.28 x 0.4 x 0.15 = 106 m 3 ) of the clay solubilization type heavy oil water-based viscosity reduction and plugging removal agent of Example 2 is injected, 9 m 3 of the 0.3% sodium dodecyl benzene sulfonate aqueous solution is used to displace, and the well is left for 2 days before production. After the treatment, the liquid production is increased to 23 m 3 / d, the water content is the same as before the treatment, and the effect is obvious.

[0070] Although the application has been described with reference to specific embodiments, it should be understood by those skilled in the art that various changes can be made without departing from the true spirit and scope of the application. In addition, various changes can be made to the subject matter, spirit and scope of the application to adapt to specific situations, materials, material compositions and methods. All these changes are included in the scope of the claims of the application.

Claims

1. A clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent, comprising an organic dispersant, a first surfactant, an auxiliary agent, a clay-solubilizing agent, and water. The first surfactant is sodium dodecyl benzene sulfonate. The organic dispersant is tetrahydrofuran and / or 2-methyltetrahydrofuran. The clay-solubilizing agent is a complex acid of hydrochloric acid and fluoroboric acid. The content of the organic dispersant is 0.5% to 1%, the content of the first surfactant is 0.2% to 0.4%, the content of the auxiliary agent is 0.4% to 0.6%, and the content of the clay-solubilizing agent is 1% to 2%, based on the total mass of the clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent.

2. The clay solubilizing type viscous oil water-based viscosity reducing and plug-removing agent according to claim 1, characterized in that, The auxiliary agent is at least one of alcohol compounds.

3. The clay solubilizing type viscous oil water-based viscosity reducing and plug-removing agent according to claim 1, characterized in that, The auxiliary agent is pentanol.

4. The clay solubilizing type viscous oil water-based viscosity reducing and plug-removing agent according to claim 1, characterized in that, The auxiliary agent is n-pentanol.

5. The clay solubilizing type viscous oil water-based viscosity reducing and plug-removing agent according to claim 1, characterized in that, The mass ratio of hydrogen chloride to fluoroboric acid is 1:1 to 1:1.

5. 6.The clay-solubilized heavy oil water-based viscosity-reducing and plug-removing agent according to any one of claims 1 to 5, used in viscosity reduction and plug removal in a heavy oil exploitation process. 7.A method for water-based viscosity reduction and plug removal in a heavy oil reservoir after multiple rounds of steam stimulation, comprising the following steps: 1) forward washing a target well with a fluid to remove the influence of metal ions; 2) injecting into the target well the clay-solubility type heavy oil viscosity reduction and plugging removal agent of any one of claims 1 to 5, wherein, The volume of the squeeze is 0.3 to 0.5 times the pore volume in the reservoir area with a horizontal radius of 15 to 25 m centered on the target well; 3) forward displacement of 1.2 to 1.5 times the volume of the tubing of the target well with an aqueous solution of a second surfactant; the second surfactant is sodium dodecyl benzene sulfonate; 4) soak the well for 1 to 2 days and then open the well for oil production.

8. The method of claim 7, wherein, In step 1), the target well is forward washed with the fluid until the incoming and outgoing fluids are consistent, while the annulus is filled; The fluid is clean water.

9. The method of claim 7, wherein, In step 2), the calculation method of the volume of the squeeze is π × radius × radius × oil layer thickness h × porosity × (0.3 to 0.5 PV) × (0.1 to 0.2).

10. The method of claim 7, wherein, In step 3), the mass concentration of the aqueous solution of the second surfactant is 0.2% to 0.4%.

11. The method of claim 7, wherein, The well production should ensure that the production system and measures are consistent.

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