Tight oil shale oil reservoir surface active authigenic agent and preparation method thereof

Abstract

The invention discloses a tight oil shale oil reservoir surface activity authigenic agent and a preparation method thereof. The surface activity authigenic agent is composed of a hydrogen bond complexing ligand, an auxiliary solubilizing stabilizer and an auxiliary synergist according to the mass ratio of (1.3-12): (1.5-25): (0.01-1). The surface active authigenic agent can excite an authigenic surfactant in a reservoir, and is used in fracturing fluid, so that addition of a discharge aiding agent is omitted, the cost of the fracturing fluid is reduced, and the economy of tight oil reservoir development is improved; when the hydrogen bond complex is used in fracturing fluid, the newly generated hydrogen bond complex can be rapidly enriched on an oil-water interface, interfacial tension and surface tension are remarkably reduced, and the low-tension characteristic is beneficial to reducing capillary resistance and promoting efficient flowback of gel breaking fluid from a reservoir, so that the water locking effect and stratum damage are reduced, and the yield is increased; and meanwhile, the dual goals of increasing the yield and reducing the cost are achieved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development, specifically relating to a surface-active autogenous agent for tight oil shale reservoirs and its preparation method. Background Technology

[0002] Located in the southeastern Ordos Basin, the Yanchang Oilfield presents seemingly simple geological structures, yet these structures present unique challenges for oil and gas extraction. The area features gently sloping strata with shallow dips and a lack of obvious structural traps. Oil and gas enrichment is primarily controlled by lithological variations, resulting in highly heterogeneous reservoirs and concealed oil reservoir distribution. While the main producing layer, the Chang 6 oil-bearing formation, is relatively shallow, it is a typical tight oil / shale oil reservoir with a complex microstructure, low porosity, and extremely poor permeability, creating significant resistance to fluid flow.

[0003] More importantly, through a long process of geological evolution and biodegradation and oxidation, the crude oil in this area has undergone a significant "gelling" process. This not only creates its physical characteristics of being "heavy, high-wax, and high-viscosity," but also, more often overlooked yet crucially important, results in a relatively increased content of polar heteroatoms such as O, N, and S in the crude oil, forming abundant polar components such as carboxylic acid groups and sulfonic acid groups. These components are like a double-edged sword: on the one hand, they are important reasons for the high viscosity, poor fluidity, and adsorption and retention of crude oil in reservoir pores, greatly increasing the difficulty of traditional waterflooding technology and restricting the improvement of recovery rates; on the other hand, they also provide potential chemical keys to solving extraction problems.

[0004] For a long time, conventional extraction techniques have often been ineffective for this type of reservoir. Although traditional surfactant flooding can reduce interfacial tension, exogenous chemicals are easily adsorbed by the formation during injection and are largely lost. Furthermore, they require high compatibility with specific crude oils, resulting in poor cost-effectiveness. Therefore, it is urgent to develop a new production enhancement technology that can overcome the dual barriers of reservoir tightness and high crude oil viscosity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a surface-active autogenous agent for tight oil shale oil reservoirs and its preparation method. The surface-active autogenous agent utilizes the components of crude oil itself to form structurally stable hydrogen-bonded complexes with crude oil derivatives, which not only effectively improves the fluidity of crude oil but also reduces costs.

[0006] A surface-active autogenous agent for tight oil shale oil reservoirs is composed of hydrogen-bonded complex ligands, auxiliary solubilizers and stabilizers, and auxiliary synergists in a mass ratio of (1.3-12):(1.5-25):(0.01-1).

[0007] Preferably, the hydrogen-bonded complex ligand is composed of the following raw materials in 100% by mass: 0.5-3% triethanolamine, 0.3-2% tetraethylenepentamine, 0.1-5% isopropanol, 0.3-5% ethylene glycol, 0.1-2% glycerol, and the balance being water.

[0008] Preferably, the auxiliary solubilizing stabilizer, by weight (100%), is composed of the following raw materials in the following mass percentages: 0.5-10% potassium chloride, 0.5-5% potassium sulfate, 0.5-10% sodium chloride, and the balance being water.

[0009] Preferably, the auxiliary synergist is an aqueous solution of a demulsifier.

[0010] Preferably, the concentration of the demulsifier in the auxiliary synergist is 0.1-1 wt%.

[0011] Preferably, the demulsifier is a polyether-based demulsifier.

[0012] The preparation method of the surface active autogenous agent for tight oil shale oil reservoirs is as follows: the hydrogen-bonded complex ligand, auxiliary solubilizing stabilizer and auxiliary synergist are stirred and mixed.

[0013] A tight oil reservoir self-generated surfactant fracturing fluid is composed of a surface-active self-generated agent and a base fracturing fluid in a volume ratio of 1:1 to 1:99; the base fracturing fluid, by weight (100%), contains the following raw materials: guar gum 0.2-0.6%, demulsifier 0.03-0.15%, potassium chloride 0.5-2.0%, with the remainder being water; the surface-active self-generated agent is the aforementioned surface-active self-generated agent.

[0014] Preferably, the base fracturing fluid also contains a low-temperature activator, a temperature stabilizer, a pH adjuster, or a bactericide. The low-temperature activator, temperature stabilizer, and pH adjuster ensure the fracturing fluid maintains stable performance over a wide temperature range and under different pH conditions, while the bactericide prevents the liquid from spoiling and deteriorating, making the fracturing fluid suitable for various geological conditions.

[0015] Preferably, the low-temperature activator is sodium sulfite.

[0016] Preferably, the temperature stabilizer is sodium thiosulfate.

[0017] Preferably, the pH adjuster is sodium carbonate or sodium hydroxide.

[0018] Preferably, the bactericide is glutaraldehyde.

[0019] Preferably, the mass contents of the low-temperature activator, temperature stabilizer, pH adjuster, or bactericide in the basic fracturing fluid are 0.01-0.08%, 0.01-0.1%, 0.1-0.8%, and 0.1-0.6%, respectively.

[0020] More preferably, the demulsifier is a polyether-based demulsifier.

[0021] The fracturing fluid is prepared by mixing all the raw materials and stirring until homogeneous.

[0022] The surfactant self-generating agent provided by this invention is based on the discovery that tight oil / shale oil crude oil in Shaanxi and other regions commonly contains polar components such as carboxylic acid groups and sulfonic acid groups. Through specific hydrogen-bonded complex ligands, it enables molecular recognition and binding with elements such as O, N, and S in crude oil, forming structurally stable hydrogen-bonded complexes. These hydrogen-bonded complexes have the effect of reducing surface tension, which can significantly reduce the surface tension between water and crude oil, and reduce the viscosity of crude oil. Therefore, it can enhance the flow of crude oil in the pores of the oil layer and improve the recovery rate of crude oil. In other words, the components of crude oil itself are "transformed" into highly efficient surfactants, which is equivalent to the in-situ addition of surfactants contained in the tight oil and gas reservoir. This realizes a technological paradigm shift from "external addition" to "internal activation", reduces the introduction of chemical additives, reduces the potential pollution of the formation by external fluids, and conforms to the concept of green oil and gas field development. This "self-generating" mechanism reduces the amount of chemicals used, which helps to reduce carbon emissions and environmental impact.

[0023] Advantages of this invention: (1) The surface-active self-generating agent described in this invention can activate the self-generated surfactant in the reservoir, which eliminates the need for the addition of drainage aid in fracturing fluid, reduces the cost of fracturing fluid, and improves the economics of tight oil reservoir development. (2) The surface-active self-generating agent is used in fracturing fluid. The newly generated hydrogen bond complex can be rapidly enriched at the oil-water interface, significantly reducing interfacial tension and surface tension. This low tension characteristic helps to reduce capillary resistance and promotes efficient return of the rupture fluid from the reservoir, thereby reducing water lock effect and formation damage, increasing yield, and achieving the dual goals of "increasing production" and "reducing cost". Detailed Implementation

[0024] Example 1 A surface-active autogenous agent for tight oil shale oil reservoirs is prepared by mixing hydrogen-bonded complex ligands, auxiliary solubilizers and stabilizers in a mass ratio of 12:25:1. The hydrogen-bonded complex ligand, by mass percentage, is composed of the following raw materials in the following mass percentages: 0.5% triethanolamine, 0.3% tetraethylenepentamine, 0.1% isopropanol, 0.3% ethylene glycol, 0.1% glycerol, and the balance being water. The auxiliary solubilizing and stabilizing agent, by weight (100%), is composed of the following raw materials in the indicated weight percentages: 0.5% potassium chloride, 0.5% potassium sulfate, 0.5% sodium chloride, and the balance being water. The auxiliary synergist is an aqueous solution of a 0.01 wt% demulsifier, which is a polyether demulsifier 330N purchased from Shandong Hongquan Chemical Technology Co., Ltd.

[0025] Example 2 A surface-active autogenous agent for tight oil shale oil reservoirs is prepared by mixing hydrogen-bonded complex ligands, auxiliary solubilizers and stabilizers in a mass ratio of 1.3:1.5:0.01. The hydrogen-bonded complex ligand, by mass percentage, is composed of the following raw materials in the following mass percentages: 3% triethanolamine, 2% tetraethylenepentamine, 5% isopropanol, 5% ethylene glycol, 2% glycerol, and the balance being water. The auxiliary solubilizing and stabilizing agent, by weight (100%), is composed of the following raw materials in the following proportions: 10% potassium chloride, 5% potassium sulfate, 10% sodium chloride, and the balance being water. The auxiliary synergist is an aqueous solution of 1 wt% demulsifier, which is polyether demulsifier 330N, purchased from Shandong Hongquan Chemical Technology Co., Ltd.

[0026] Example 3 A surface-active autogenous agent for tight oil shale oil reservoirs is prepared by mixing hydrogen-bonded complex ligands, auxiliary solubilizers and stabilizers in a mass ratio of 5:10:0.5. The hydrogen-bonded complex ligand, by mass percentage, is composed of the following raw materials in the following mass percentages: 1% triethanolamine, 1% tetraethylenepentamine, 2% isopropanol, 2% ethylene glycol, 1% glycerol, and the balance being water. The auxiliary solubilizing and stabilizing agent, by weight (100%), is composed of the following raw materials in the following mass percentages: 5% potassium chloride, 3% potassium sulfate, 5% sodium chloride, and the balance being water. The auxiliary synergist is an aqueous solution of a 0.05 wt% demulsifier, which is a polyether demulsifier 330N purchased from Shandong Hongquan Chemical Technology Co., Ltd.

[0027] Example 4 A tight oil reservoir self-generated surfactant fracturing fluid is prepared by mixing a surface-active self-generated agent with a base fracturing fluid at a volume ratio of 1:1. The base fracturing fluid, by weight (100%), is composed of the following raw materials in the indicated mass percentages: guar gum 0.2%, demulsifier 0.03%, potassium chloride 0.5%, and the remainder being water. The surface-active self-generated agent is the surface-active self-generated agent described in Example 1 above.

[0028] Example 5 A tight oil reservoir self-generated surfactant fracturing fluid is prepared by mixing a surface-active self-generated agent with a volume ratio of 1:99 and a base fracturing fluid. The base fracturing fluid, by weight (100%), is composed of the following raw materials in the indicated mass percentages: guar gum 0.6%, demulsifier 0.15%, potassium chloride 2.0%, and the remainder being water. The surface-active self-generated agent is the surface-active self-generated agent described in Example 2 above.

[0029] Example 6 A tight oil reservoir self-generated surfactant fracturing fluid is prepared by mixing a surface-active self-generated agent with a volume ratio of 1:50 and a base fracturing fluid. The base fracturing fluid, by weight (100%), is composed of the following raw materials in the indicated mass percentages: guar gum 0.4%, demulsifier 0.1%, potassium chloride 1.0%, and the remainder being water. The surface-active self-generated agent is the surface-active self-generated agent described in Example 3 above.

[0030] Example 7 A tight oil reservoir self-generated surfactant fracturing fluid is prepared by mixing a surface-active self-generating agent with a base fracturing fluid at a volume ratio of 1:10. The base fracturing fluid, by weight (100%), is composed of the following raw materials in the indicated mass percentages: guar gum 0.3%, demulsifier 0.1%, potassium chloride 1.0%, sodium sulfite 0.03%, sodium thiosulfate 0.01%, sodium carbonate 0.2%, glutaraldehyde 0.1%, with the remainder being water. The surface-active self-generating agent is the surface-active self-generating agent described in Example 1 above.

[0031] Performance testing 1. The fracturing fluid described in Example 4 was used in a field application test in 5 wells at the Yanchang Oilfield. The reservoirs were Chang 1 to Chang 6 in the Yanchang area (Erdos Basin in northern Shaanxi). The crude oil in these 6 reservoirs was tight oil. The fracturing operations of the 5 oil wells were carried out from September to October 2023. The average flowback rate was 79.4%. The specific statistics are shown in Table 1 below. The surface tension and interfacial tension of the flowback fluid are shown in Table 2. Table 1. Statistics on the post-pressure conditions of 5 wells In terms of flowback rate, all wells had a flowback rate exceeding 50%. In terms of production, three wells were high-yield wells, accounting for 60% of the total.

[0032] Table 2 Surface tension and interfacial tension of the backflow fluid As shown in Table 2, after fracturing, the surface tension of the fracturing fluid is less than 30.0 mN / m and the interfacial tension is less than 3.0 mN / m. This invention utilizes the fact that tight oil and gas reservoirs themselves contain chemical substances (surfactants) that can reduce surface and interfacial tension. Through specific hydrogen-bonded ligands in the surfactant, it enables molecular recognition and binding with elements such as O, N, and S in crude oil, forming structurally stable hydrogen-bonded complexes. These hydrogen-bonded complexes have the effect of reducing surface and interfacial tension, significantly reducing the surface tension between water and crude oil, and lowering the viscosity of crude oil. Therefore, it can enhance the flow of crude oil in the pores of the oil reservoir, improve crude oil recovery, eliminate the need for additional flow aids, and reduce the cost of fracturing fluid.

Claims

1. A surface-active autogenous agent for tight oil shale reservoirs, characterized in that: It consists of hydrogen-bonded complex ligands, auxiliary solubilizers and auxiliary synergists in a mass ratio of (1.3-12):(1.5-25):(0.01-1).

2. The surface-active autogenous agent for tight oil shale reservoirs according to claim 1, characterized in that: The hydrogen-bonded complex ligand, by mass percentage, is composed of the following raw materials in the following mass percentages: 0.5-3% triethanolamine, 0.3-2% tetraethylenepentamine, 0.1-5% isopropanol, 0.3-5% ethylene glycol, 0.1-2% glycerol, and the balance being water.

3. The surface-active autogenous agent for tight oil shale reservoirs according to claim 1, characterized in that: The auxiliary solubilizing and stabilizing agent, by weight (100%), is composed of the following raw materials in the following mass percentages: 0.5-10% potassium chloride, 0.5-5% potassium sulfate, 0.5-10% sodium chloride, and the balance being water.

4. The surface-active autogenous agent for tight oil shale reservoirs according to claim 1, characterized in that: The auxiliary synergist is an aqueous solution of a demulsifier.

5. The surface-active autogenous agent for tight oil shale reservoirs according to claim 4, characterized in that: The concentration of the demulsifier in the auxiliary synergist is 0.1-1 wt%.

6. The surface-active autogenous agent for tight oil shale reservoirs according to claim 4, characterized in that: The demulsifier is a polyether-based demulsifier.

7. The method for preparing a surface-active autogenous agent for tight oil shale oil reservoirs according to claim 1, characterized in that: Simply mix the hydrogen-bonded complex ligand, the auxiliary solubilizer and stabilizer, and the auxiliary synergist.

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