Heterogeneous viscosity reduction composite equilibrium displacement system and injection method thereof

Abstract

The invention relates to the technical field of oilfield exploration and development, in particular to a heterogeneous viscosity reduction composite equilibrium displacement system and an injection method thereof. The system comprises a heterogeneity regulating agent, a viscosity reducer and a fluidity control agent, the heterogeneity regulating agent is composed of a dispersed gel system and / or gel particles; the viscosity reducer is an anionic / non-amphoteric surfactant solution; the mobility control agent is a polymer solution. According to the heterogeneous viscosity reduction composite equilibrium displacement system, the heterogeneous regulating agent is injected firstly, so that a dominant seepage channel can be blocked, and wave expansion of a near wellbore zone is realized; and then the viscosity reducer and the fluidity control agent are injected, so that the purposes of viscosity reduction, oil displacement and wave expansion in the deep part of the far well, integrated efficient balanced displacement and great improvement of the recovery efficiency are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploration and development, and in particular to a heterogeneous viscosity-reducing composite balanced displacement system and an injection method thereof. Background Art

[0002] Ordinary heavy oil is an important successor to unconventional resources, and the efficient development of heavy oil is of great significance to ensuring national energy security.

[0003] CN111091476B discloses a numerical simulation method for oil reservoirs with strong heterogeneity, which includes the following steps: step 1, determining the area with strong discontinuities and dividing the network; step 2, calculating the gradient intensity factor and obtaining a local analytical solution; step 3, applying the local analytical solution to calculate the equivalent permeability between grids; step 4, constructing a calculation formula for the cross-interface phase flow; step 5, solving the algebraic equation group of the variables to be determined; step 6, verifying the algorithm efficiency and grid independence. The numerical simulation method helps to gain a deep understanding of the oil displacement mechanism in the strong heterogeneity oil reservoir formation, improve the efficiency and accuracy of the numerical simulation of the oil reservoir, and guide the adjustment and optimization of the oil reservoir development method.

[0004] CN111022013B discloses a steam huff-and-puff oil production method for heterogeneous heavy oil reservoirs, the method comprising: injecting nitrogen foam plugs into the oil layer; injecting viscosity reduction plugs into the oil layer; injecting nitrogen plugs into the oil layer; injecting steam into the oil layer, and then shutting the well and recovering the oil. First, inject nitrogen foam, the Jamin effect of nitrogen foam can achieve effective plugging of high permeability and high recovery layers, and promote subsequent plugs to enter low permeability and low recovery layers with high oil saturation, so as to achieve the purpose of expanding steam sweep; the viscosity reduction plug can effectively reduce the viscosity of crude oil; the nitrogen plug is not only conducive to pushing the viscosity reduction plug into the oil layer, playing a role in expanding the radius of action of the viscosity reduction plug, but also has the effect of increasing the flowback of crude oil formations during the production process, and the synergistic effect of each plug achieves the purpose of increasing the single well cycle production and recovery rate of heterogeneous heavy oil reservoirs.

[0005] CN113153209A discloses a multi-media composite huff-and-puff development method for heavy oil reservoirs, which includes: injecting a high-temperature plugging agent into the formation; injecting a viscosity reducer, a foaming agent and a non-condensable gas, or injecting a viscosity reducer, a foaming agent and urea after the high-temperature plugging agent is condensed; and finally injecting steam into the formation. The invention realizes the purpose of increasing the utilization degree of the oil layer section, reducing the viscosity of crude oil, and replenishing the formation energy by sequentially injecting multi-media such as a high-temperature plugging agent, a viscosity reducer, a foaming agent and a non-condensable gas (or urea) into the bottom layer before injecting steam, thereby achieving the purpose of increasing the periodic oil production, the oil-gas ratio, the oil reservoir recovery rate, and increasing the economic benefits.

[0006] For the conventional water flooding of ordinary heavy oil, there is a high water-oil mobility ratio, low water flooding sweep coefficient and recovery rate. In order to improve the water flooding sweep coefficient and recovery rate of ordinary heavy oil, polymers and viscosity reducers are added to increase the viscosity of the water phase and reduce the viscosity of the oil phase. However, for strongly heterogeneous reservoirs, the traditional single chemical flooding system is prone to cross-flow in the slug, and the purpose of balanced displacement cannot be achieved. Summary of the invention

[0007] To solve the above problems, the present invention provides a heterogeneous viscosity reduction composite balanced displacement system and its injection method. The system of the present invention can achieve the purpose of far-well deep viscosity reduction, oil displacement and wave expansion, integrated high-efficiency balanced displacement and greatly improve the recovery rate.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a heterogeneous viscosity reduction composite balanced displacement system, the system comprising a heterogeneous control agent, a viscosity reducing agent and a fluidity control agent;

[0010] The heterogeneity regulator is composed of a dispersed gel system and / or gel particles; the viscosity reducer is an anionic non-amphoteric surfactant solution; and the fluidity controller is a polymer solution.

[0011] Furthermore, the dispersed gel system is formed by cross-linking a polymer and a phenolic resin cross-linking agent; and the gel particles include pre-cross-linked gel particles.

[0012] Furthermore, the viscosity reducer is an anionic non-amphoteric sulfonate surfactant solution, and the molecular structure is as follows:

[0013]

[0014] Among them, x, y, m, and n are all positive integers.

[0015] Furthermore, x is a positive integer ≤5, y is an integer between 2 and 7, and m and n are both integers between 2 and 4.

[0016] The preparation method of the anionic non-amphoteric sulfonate surfactant is a conventional technology and will not be described in detail here.

[0017] Furthermore, the mass concentration of the viscosity reducer is 0.3%-0.5%.

[0018] Furthermore, the fluidity control agent is a partially hydrolyzed polyacrylamide solution, the molecular weight of the partially hydrolyzed polyacrylamide is 30 million to 35 million, and the mass concentration is 0.1% to 0.3%.

[0019] The present invention also provides an injection method of the heterogeneous viscosity-reducing composite balanced displacement system, which comprises injecting the heterogeneous regulating agent, the viscosity-reducing agent and the mobility control agent in segmented plugs.

[0020] Furthermore, the heterogeneous regulating agent slug is injected first, and then the viscosity reducing agent and fluidity control agent combined slug is injected.

[0021] Furthermore, the injection amount of the heterogeneous regulating agent slug and the combined slug of the viscosity reducer and fluidity control agent is 1-5:1-5.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] By adopting the heterogeneous viscosity reduction composite balanced displacement system of the present invention, the dominant seepage channel can be blocked by first injecting a heterogeneous control agent to achieve the expansion of the near-wellbore area; and then injecting a viscosity reducer and a mobility control agent to achieve the purpose of deep viscosity reduction, oil displacement and expansion far from the wellbore, as well as integrated efficient balanced displacement and greatly improving the recovery rate. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and "including" are used in this specification, they indicate the presence of features, steps, operations and combinations thereof.

[0026] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0027] Example 1

[0028] A heterogeneous viscosity reduction composite balanced displacement system, the system comprising a heterogeneous regulator, a viscosity reducer and a fluidity control agent:

[0029] The heterogeneity regulator is a phenolic resin dispersion gel prepared by conventional cross-linking reaction of a low-concentration polymer and a cross-linking agent, wherein the polymer is partially hydrolyzed polyacrylamide with a molecular weight of 20 million and a polymer mass concentration of 0.2%. The cross-linking agent is a phenolic resin prepolymer with a cross-linking agent concentration of 0.4%.

[0030] The viscosity reducer is an anionic non-ampholytic sulfonate surfactant solution, and the molecular structure is as follows:

[0031]

[0032] Wherein, x = 2, y = 5, m = 3, n = 3. The mass concentration of the viscosity reducer is 0.3%.

[0033] The fluidity control agent is a partially hydrolyzed polyacrylamide solution with an ultra-high molecular weight. The molecular weight of the partially hydrolyzed polyacrylamide is 35 million, and the degree of hydrolysis is 20%. The mass concentration of the partially hydrolyzed polyacrylamide is 0.15%.

[0034] The injection method of the heterogeneous viscosity reduction composite balanced displacement system is to inject the heterogeneous regulating agent, viscosity reducing agent and mobility control agent in sections:

[0035] The heterogeneous control agent slug is injected first, and then the combined slug of viscosity reducer and fluidity control agent is injected; the slug injection volume is 0.4PV, and the injection volume ratio of the heterogeneous control agent slug to the combined slug of viscosity reducer and fluidity control agent is 1:1.

[0036] Example 2

[0037] A heterogeneous viscosity reduction composite balanced displacement system, the system comprising a heterogeneous regulator, a viscosity reducer and a fluidity control agent:

[0038] The heterogeneity regulating agent is pre-crosslinked gel particles, and the particle size is 500-1000 μm.

[0039] The viscosity reducer is an anionic non-ampholytic sulfonate surfactant solution, and the molecular structure is as follows:

[0040]

[0041] Wherein, x = 5, y = 2, m = 2, n = 2. The mass concentration of the viscosity reducer is 0.4%.

[0042] The fluidity control agent is a partially hydrolyzed polyacrylamide solution with an ultra-high molecular weight. The molecular weight of the partially hydrolyzed polyacrylamide is 30 million, and the degree of hydrolysis is 20%. The mass concentration of the partially hydrolyzed polyacrylamide is 0.3%.

[0043] The injection method of the heterogeneous viscosity reduction composite balanced displacement system is to inject the heterogeneous regulating agent, viscosity reducing agent and mobility control agent in sections:

[0044] The heterogeneous control agent slug is injected first, and then the combined slug of viscosity reducer and fluidity control agent is injected; the slug injection volume is 0.4PV, and the injection volume ratio of the heterogeneous control agent slug to the combined slug of viscosity reducer and fluidity control agent is 5:1.

[0045] Example 3

[0046] A heterogeneous viscosity reduction composite balanced displacement system, the system comprising a heterogeneous regulator, a viscosity reducer and a fluidity control agent:

[0047] The heterogeneity regulator is composed of a composite of phenolic resin dispersed gel prepared by conventional cross-linking reaction of low-concentration polymer and cross-linking agent and pre-cross-linked gel particles.

[0048] The polymer is partially hydrolyzed polyacrylamide, with a molecular weight of 20 million and a polymer mass concentration of 0.2%. The crosslinking agent is a phenolic resin prepolymer, with a crosslinking agent concentration of 0.4%.

[0049] The pre-crosslinked gel particles have a particle size of 500 to 1000 μm.

[0050] The viscosity reducer is an anionic non-ampholytic sulfonate surfactant solution, and the molecular structure is as follows:

[0051]

[0052] Wherein, x = 3, y = 7, m = 4, n = 4. The mass concentration of the viscosity reducing agent is 0.5%.

[0053] The fluidity control agent is a partially hydrolyzed polyacrylamide solution with an ultra-high molecular weight. The molecular weight of the partially hydrolyzed polyacrylamide is 35 million, and the degree of hydrolysis is 20%. The mass concentration of the partially hydrolyzed polyacrylamide is 0.1%.

[0054] The method of using the heterogeneous viscosity reduction composite balanced displacement system is to inject the heterogeneous control agent, viscosity reduction agent and mobility control agent into segmented plugs:

[0055] The heterogeneous control agent slug is injected first, and then the combined slug of viscosity reducer and fluidity control agent is injected; the slug injection volume is 0.4PV, and the injection volume ratio of the heterogeneous control agent slug to the combined slug of viscosity reducer and fluidity control agent is 1:5.

[0056] Parallel sand filling tube model The permeability difference is 3:1, and the ability of improving oil recovery by heterogeneous viscosity reduction composite balanced displacement described in each embodiment is studied.

[0057] Table 1 Different chemical systems increase oil recovery

[0058]

[0059] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A heterogeneous viscosity reduction composite balanced displacement system, characterized in that: The system includes a heterogeneity regulator, a viscosity reducer and a fluidity control agent; The heterogeneity regulator is composed of a dispersed gel system and / or gel particles; the viscosity reducer is an anionic non-amphoteric surfactant solution; and the fluidity controller is a polymer solution.

2. The heterogeneous viscosity reduction composite balanced displacement system according to claim 1, characterized in that: The dispersed gel system is formed by cross-linking a polymer and a phenolic resin cross-linking agent; and the gel particles include pre-cross-linked gel particles.

3. The heterogeneous viscosity reduction composite balanced displacement system according to claim 1, characterized in that: The viscosity reducer is an anionic non-ampholytic sulfonate surfactant solution, and the molecular structure is as follows: Among them, x, y, m, and n are all positive integers.

4. The heterogeneous viscosity reduction composite balanced displacement system according to claim 3, characterized in that: x is a positive integer ≤5, y is an integer between 2 and 7, and m and n are both integers between 2 and 4.

5. The heterogeneous viscosity reduction composite balanced displacement system according to claim 1 or 3, characterized in that: The mass concentration of the viscosity reducer is 0.3%-0.5%.

6. The heterogeneous viscosity reduction composite balanced displacement system according to claim 1, characterized in that: The fluidity control agent is a partially hydrolyzed polyacrylamide solution, the molecular weight of the partially hydrolyzed polyacrylamide is 30 million to 35 million, and the mass concentration is 0.1% to 0.3%.

7. The injection method of the heterogeneous viscosity-reducing composite balanced displacement system according to any one of claims 1 to 6, characterized in that: The heterogeneity regulator, viscosity reducer and fluidity control agent are injected in segmented plugs.

8. The method according to claim 7, characterized in that: The heterogeneous regulating agent slug is injected first, and then the viscosity reducer and fluidity control agent combined slug is injected.

9. The method according to claim 7, characterized in that: The injection amount of the heterogeneous regulating agent slug and the combined slug of the viscosity reducer and fluidity control agent is 1-5:1-5.

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