Use of nano-wetting reversal agent SDKX-5848 for low-permeability oilfields
Technical Manual for Low Permeability Oilfield Depressurization Increased Injection Nano Wetting Reversal Agent SDKX-5848
- Overview
Wetting reversal agent is to control the wetting angle of 67℃-90℃ by reducing surface tension or interfacial tension; enable water to spread on the surface of solid materials, or penetrate into the surface to wet or make solid materials Substances that are more easily wetted by water. Usually it is the surfactant of the oil displacement system.
In oil reservoirs, the rock surface is usually lipophilic. By adding surfactant substances, the surface properties can be reversed, changing from lipophilic to hydrophilic, which can not only strip off the crude oil on the rock surface, but also improve water flooding. Oil efficiency, to achieve the effect of improving recovery. And such substances are wetting reversal agents.
The molecular structure of the surfactant as a wetting reversal agent is composed of long-chain lipophilic groups and hydrophilic ionic groups. The compound molecules of this structure can be directionally adsorbed on the two-phase interface in solution. Thereby changing the interface properties of the two phases, when the surfactant is dissolved into the solution, the amphiphilic groups will be oriented distribution in the liquid/solid interface, liquid/liquid interface and the bulk solution. When the polar groups are combined with the surface of minerals and rocks, they will destroy the crude oil boundary layer and free the crude oil bound in the boundary layer to become flowable oil. Polar water molecules or hydrophilic groups will occupy the surface of the particles, so that the surface of minerals and rocks will change from oil to water wet. At the same time, phenomena such as oil-water interfacial tension reduction, crude oil emulsification, and oil droplets coalescence will occur. The yield can be improved.
With the development of surfactants, research on the surface activity of twins has developed rapidly in recent years. Twin surfactants are called a new generation of surfactants, because they are completely different from conventional surfactants. It is like two conventional surfactants twinning. Because of its unique structure, it has unique properties, such as low cmc (Critical Micelle Concentration) value, good surface/interface activity, good water solubility and strong salt tolerance. Therefore, twin surfactants have broad application prospects.
The new and efficient wetting reversal agent is an alkanolamide long-chain fatty acid-based twin surfactant prepared by using resource-rich natural renewable oils as raw materials. The long-chain fatty acid alkanolamide made from natural raw materials has an unbranched, non-cyclic structure and good biodegradability. It is an environmentally friendly surfactant with low pollution and good safety in use. It has ultra-low interfacial tension characteristics, and because of its certain carbon number distribution, it is more compatible with alkalis and polymers than single-component products. It is an ideal surface active oil displacement agent for ternary and binary combination flooding. This type of surfactant has no cloud point and has good compatibility with other types of surfactants; it is not ionic in the solution, so it is not affected by ions in the formation and has good salt resistance; in addition, The anionic surfactant in tertiary oil recovery has a good oil displacement effect, but it has serious losses in the flow process, and its salt resistance is very poor. This fatty acid alkanolamide wetting reversal agent can just make up for these shortcomings, improve the salt resistance of the system, and further reduce the oil-water interfacial tension.
With the increasing requirements for environmental protection, countries all over the world strongly advocate the use of surfactants based on natural raw materials. In the petroleum industry, the impact of tertiary oil recovery fluid on the ecological environment has also received great attention. Using oil crops such as soybeans and rapeseeds, oil-bearing forest fruits such as rice dumplings and pistacia chinensis, aquatic plants such as engineered microalgae, or natural renewable resources such as animal fats and waste catering oil as raw materials, it can be synthesized with good environmental compatibility , Surfactant with excellent ecology and performance. The surfactant has an unbranched, non-cyclic structure with excellent biodegradability, and is called an environmentally friendly surfactant.
- Technical Principle
The production process of fatty acid alkanolamide wetting reversal agent includes fatty acid method and methyl ester method. The synthetic route is determined as a three-step process, one step: fat transesterification reaction; two steps: synthesis of fatty acid alkanolamide; three steps: synthesis of fatty acid alkanolamide sulfate. Then react with 1,3-propane sultone to obtain a series of sulfonate twin-linked wetting reversal agents with different carbon chain lengths and different linking group lengths.
3. Product indicators and performance
| name | index |
| Appearance | Yellow or light brown liquid |
| Surface tension (5000mg/L) | 29mN/m |
| Interfacial tension | 10-3 mN/m order of magnitude |
| Wetting angle | >67℃ -<90℃ |
| Salt tolerance | ≤10g/L |
| Temperature resistance | ≤ 280℃ |
| Biodegradability | ≥85% |
| Resistivity | ≤ |
The new twin type wetting reversal agent also has very good resistance to divalent salts. As the molar concentration of calcium ions increases, the interfacial tension decreases linearly.
The cmc of only C10-C2-C10 of the twin surfactants we studied is 1×10-5mol/L, and the rest are between 1～5×10-6mol/L. The cmc of twin-type wetting reversal agents is 2 to 4 orders of magnitude smaller than that of the corresponding conventional surfactants.
4. Research on core simulation of oil
displacement. The evaluation test of the oil displacement effect of the twin-type wetting reversal agent refers to SY/T 5908-1994 (Method for determining the performance of petroleum sulfonate for oil displacement), SY/T 6424-2000 ( The performance test method of oil displacement system) standard. The test conditions are as follows:
Test oil: the dehydrated and degassed crude oil from wells 98181 and 980113.
Test water: simulate formation water.
Test cores: two kinds of artificial cores.
The artificially cemented columnar core filling model is an artificially cemented columnar core model filled with loose oil sand after being washed with alcohol-benzene.
The loose core filling model is a shaped core made of quartz sand, clay minerals, etc., cemented and pressed in a certain proportion.
Test model: The air permeability of the core model is equivalent to the permeability of the block where Well 98181 and Well 980113 are located.
Test temperature: formation temperature 45℃.
Displacement speed: Calculate the displacement speed according to L·μ·υ≥1, and 0.3mL/min is used in the experiment.
Single-tube model
Single-tube model oil displacement experiment results
| model | Columnar core 1 | Loose core 2 | Columnar core 3 | Loose core 4 |
| Permeability μm2 | 0.783 | 0.776 | 0.692 | 0.634 |
| Oil displacing agent | 0.5% | 0.5% | 1% | 1% |
| Inject slug PV | 0.3 | 0.3 | 0.3 | 0.3 |
| Original oil saturation% | 64.70 | 69.64 | 69.47 | 54.52 |
| Water drive oil displacement efficiency% | 26.34 | 25.45 | 24.67 | 23.84 |
| Total oil displacement efficiency% | 41.37 | 38.34 | 40.78 | 37.29 |
| Oil displacement efficiency of twin type wetting reversal agent% | 15.03 | 12.89 | 16.11 | 13.45 |
Load the saturated core into the holder, inject crude oil, displace water, and create irreducible water.
The simulated formation water is used to displace the crude oil in the core. When the water content at the outlet end of the core reaches 98%, the displacement is stopped, the amount of oil displaced during the water flooding process is recorded, and the water displacement efficiency is calculated.
After injecting the twin-linked wetting reversal agent solution 0.3PV into the core, close the front and rear outlets and let it stand for 12 hours.
Continue to re-displace with simulated formation water, record the amount of oil displaced, and calculate the oil displacement efficiency of the twin type wetting reversal agent. The results of the oil displacement experiment are shown in the table.
Double-tube model
Double-tube model oil displacement experiment results
| model | Columnar core 1 | Loose core 2 | Columnar core 3 | Loose core 4 |
| Permeability μm2 | 0.761 | 0.024 | 0.753 | 0.025 |
| Oil displacing agent | 0.5% | 0.5% | 1% | 1% |
| Inject slug PV | 0.3 | 0.3 | 0.3 | 0.3 |
| Original oil saturation% | 64.70 | 69.64 | 69.47 | 54.52 |
| Water drive oil displacement efficiency% | 27.34 | 5.45 | 26.67 | 5.84 |
| Total oil displacement efficiency% | 44.87 | 10.73 | 44.81 | 11.16 |
| Oil displacement efficiency of twin type wetting reversal agent% | 17.53 | 5.28 | 18.14 | 5.32 |
The core saturated with simulated formation water is loaded into the holder, and crude oil is injected to displace water and create irreducible water.
The simulated formation water is used to displace the crude oil in the core. When the water content at the outlet end of the core reaches 98%, the displacement is stopped, the amount of oil displaced during the water flooding process is recorded, and the water displacement efficiency is calculated.
After injecting the twin-linked wetting reversal agent solution 0.3PV into the core, close the front and rear outlets and let it stand for 12 hours.
Continue to re-displace with simulated formation water, record the amount of oil displaced, and calculate the oil displacement efficiency of HL-1 environmentally friendly oil displacement agent. The results of the oil displacement experiment are shown in the table.
Experimental results
From the results of the single-tube model and the double-tube model oil displacement experiment, it can be seen that
the concentration of the twin-type wetting reversal agent increases, and the oil displacement efficiency also increases; the
twin-type wetting reversal agent is in the columnar core. The oil displacement efficiency is higher than that of the loose core, that is, when the clay content in the formation increases, the oil displacement efficiency of the twin-type wetting reversal agent will be reduced; the
results of the double-tube model show that the twin-type wetting reversal
The injection concentration of twin type wetting reversal agent is not selective; the economical injection concentration of twin type wetting reversal agent is 0.5%;
single-tube physical model test shows that twin type wetting reversing agent can increase oil recovery by 12-16%, which has a high The oil displacement efficiency.
Five, use method
1. Reduce pressure and increase injection; for low-permeability water injection wells, stage injection and periodic large slug injection are carried out with high injection pressure, poor water quality and low permeability. The injection configuration concentration and slug can be referred to; permeability, water absorption index, injection requirements, and enhanced water flooding effect are determined. a; 0.05%-0.2%; b. 0.2%-0.8%; c; 1%-3 slug; 50m3-30m3;;500m3-3000m3;;3000m3-15000m3. The
injection method is simple and does not require special modification to the injection pipeline. Connect the metering pump and drip injection at the water injection station.
2. Well washing
For oil wells with waxing and scaling that require regular well washing operations, it can be formulated into a 0.3% concentration aqueous solution, and the pump truck can be used to cycle the well.
3. Viscosity reduction It is
formulated into 0.5-1% aqueous solution and mixed with crude oil in the ratio of 8:2-6:4.
4. Wax removal and paraffin prevention
Firstly use 0.3% aqueous solution to circulate the well, and then add 30-50 kg from the annulus every week according to the oil production volume.
5. Oil displacement
Determine the injected PV according to the size of the well group, prepare it into a 0.5% concentration aqueous solution, and inject it from the injection well. Slug injection can be carried out if possible.
6. Cold recovery
of heavy oil is aimed at the problem of viscosity reduction in heavy oil wells. According to the viscosity of heavy oil, a 1%-2% aqueous solution can be prepared according to the treatment radius of 2-3 meters. 8-10m3 is injected per meter of oil layer, and Inject it from the production well. Then the well was shut in for 12 hours and the well was opened for normal production.
7. Packaging and storage
This product is packaged in polyester plastic barrels for oil extraction; net weight 25kg; 50kg; 200kg;
storage room to prevent sun exposure.
8. Validity period; >18 months.