CN102519995A - Method for rapidly evaluating effect of reducing resistance of water flow in petroleum reservoir stratum micro-channel by adopting nanoparticle adsorption method - Google Patents

Abstract

The invention relates to a rapid evaluation method for the effect of reducing the water flow resistance of oil reservoir microchannels by a nano particle adsorption method, and uses scanning electron microscopy and contact angle test results to quickly evaluate the drag reduction effect. It is to soak the core slices of the specified formation in the nanoparticle dispersion liquid for more than 24 hours, let the nanoparticles adsorb on the surface of the core slices, then take them out, rinse and dry them, and then use the contact angle tester to measure the surface of the water droplets on it. Observe the contact angle, and then scan with a scanning electron microscope to determine whether the nanoparticles have been adsorbed on the surface of the core piece, and then make a quick judgment based on the test results: when SEM detects that there is adsorption of nanoparticles and the apparent contact angle is greater than 120°, it can be considered The nanomaterial has the effect of reducing pressure and increasing injection for the core, and the follow-up core flow test evaluation is not performed. This method can shorten the indoor evaluation time (about 40%), and accelerate the research and development process of nanomaterials.

Description

A rapid evaluation method for the effect of nanoparticle adsorption on reducing water flow resistance in oil reservoir microchannels

technical field

The present invention relates to a rapid evaluation method for judging whether the nanoparticle adsorption method is effective in reducing the water flow resistance of rock microchannels in petroleum reservoirs, which is of great significance for reducing pressure and increasing injection and improving oil recovery in petroleum engineering.

Background technique

In petroleum engineering, there are two main methods to reduce the water flow (seepage) resistance in rock microchannels: one is to expand the microchannels of formation rocks and increase the drainage area through acidification and fracturing of the formation; Friction between the rock microchannel and the pore wall.

After long-term water injection, the surface of rock microchannels near the wellbore zone of the injection well has become hydrophilic, which greatly increases the water flow resistance. The interfacial tension between the surface of the rock microchannel and the water flow can be changed by injecting the surfactant, so as to reduce the water flow resistance. However, due to the weak adhesion of the surfactant on the surface of the pore wall, the effective period of this method is short.

For this reason, a new method of using hydrophobic nanoparticle adsorption method to reduce the water flow resistance of reservoir microchannels was proposed, and achieved good results. However, due to the differences between reservoirs in different oilfield blocks and the complexity of petroleum reservoirs , Different oilfield blocks require different nanomaterials. Therefore, when implementing nanoparticle adsorption depressurization and injection technology in a specific oilfield block, it is necessary to develop nanomaterials suitable for the oilfield block. This process requires a long period of trial and error and evaluation, especially the evaluation work takes a long time. In addition to the nanomaterial preparation process, the evaluation process includes:

1) Evaluation of activation degree: mainly to test the quality of nanoparticle surface modification process, that is, the overall hydrophobicity of nanomaterials. The degree of activation is directly related to the wettability reversal effect, thus affecting the effect of reducing pressure and increasing injection.

2) Adsorption effect evaluation: Scanning electron microscopy (SEM) is mainly used to test whether nanoparticles can be adsorbed on the surface of a given reservoir core slice and to observe its surface morphology. This is the basis of the nanoparticle adsorption method for depressurization and increased injection technology.

3) Evaluation of wettability reversal effect: mainly to test whether the microchannel wall can be transformed from strongly hydrophilic to strongly hydrophobic or superhydrophobic after the adsorption of nanoparticles. This is the core mechanism of whether the nanoparticle adsorption method can produce a slip effect to achieve the drag reduction effect.

4) Evaluation of drag reduction effect: Although the previous three processes have prepared conditions for drag reduction by nanoparticle adsorption method, the best way to test drag reduction effect is core flow experiment. Core flow experiments can use actual cores, formation water, and provide formation temperature, pressure and other environments, which can well simulate reservoir seepage characteristics. However, the shortcoming of the core flow experiment is that the experiment takes a long time.

Contents of the invention

The purpose of the present invention is to aim at the problems existing in the prior art, propose a kind of nano particle adsorption method to reduce the rapid evaluation method of oil reservoir microchannel flow resistance effect, reduce the time occupied by the evaluation process, and shorten the development of nanomaterials required for specific formations cycle.

In order to achieve the above object, the present invention adopts following technical scheme:

A rapid evaluation method for the effect of nanoparticle adsorption on reducing the water flow resistance of oil reservoir microchannels, using scanning electron microscopy and contact angle test results to quickly evaluate the drag reduction effect. Specific steps are as follows:

1) Soak the core slices of the specified formation in the nanoparticle dispersion for more than 24 hours, so that the nanoparticles are adsorbed on the surface of the core slices, and then the core slices are taken out, rinsed and dried;

2) Use a contact angle tester to measure the apparent contact angle of water droplets on the core slice, and then scan the core slice with a scanning electron microscope;

3) Quickly judge according to the test results, as long as the scanning results show that the nanoparticles have been adsorbed on the surface of the core piece, and the contact angle test result is greater than 120°, it can be judged that the nanomaterial has a good drag reduction effect in the corresponding formation;

The above-mentioned core slices have a diameter ranging from 5 mm to 50 mm and a thickness ranging from 1 mm to 5 mm. The nanomaterials are hydrophobic nano-SiO ₂ particles, TiO ₂ particles, ZnO particles, or other hydrophobic nanoparticles with a particle size of 5-200 nm.

Compared with the prior art, the present invention has the following outstanding advantages:

This rapid evaluation method can qualitatively judge whether the developed nanomaterials have the effect of reducing pressure and increasing injection for specific low-permeability reservoirs. Only when SEM detects nano-adsorption and the contact angle is less than 120°, the core flow test evaluation is carried out. During the research and development of nanomaterials, the number of core flow experiments can be greatly reduced, which not only reduces the consumption of actual cores and saves costs, but also shortens the indoor evaluation time (about 40%), and speeds up the research and development process of nanomaterials.

Description of drawings

Fig. 1 is the rapid evaluation flowchart of the present invention;

Fig. 2 is the scanning photo of the core slice without adsorbing nanoparticles;

Fig. 3 is the scanning photograph of the rock core sheet that has adsorbed nanoparticles;

Fig. 4 is the contact angle test result of no adsorption nanoparticle core piece surface;

Fig. 5 is the contact angle test result on the surface of the adsorbed nanoparticle core piece;

Figure 6 Water pressure gradient-flow diagrams before and after nanoparticle adsorption.

Detailed ways

The method of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a rapid evaluation method for the effect of nanoparticle adsorption on reducing the water flow resistance of microchannels in petroleum reservoirs, using scanning electron microscopy and contact angle test results to quickly evaluate the drag reduction effect. Specific steps are as follows:

1) Soak the core slices of the specified formation in the nanoparticle dispersion for more than 24 hours, so that the nanoparticles are adsorbed on the surface of the core slices, and then the core slices are taken out, rinsed and dried;

2) Use a contact angle tester to measure the apparent contact angle of water droplets on the core slice, and then scan the core slice with a scanning electron microscope;

3) Quickly judge according to the test results, as long as the scanning results show that the nanoparticles have been adsorbed on the surface of the core piece, and the contact angle test result is greater than 120°, it can be judged that the nanomaterial has a good drag reduction effect in the corresponding formation;

The above-mentioned core slices have a diameter ranging from 5 mm to 50 mm and a thickness ranging from 1 mm to 5 mm. The nanomaterials are hydrophobic nano-SiO ₂ particles, TiO ₂ particles, ZnO particles, or other hydrophobic nanoparticles with a particle size of 5-200 nm.

Example:

The characteristics of small-scale nanomaterials: The prepared hydrophobic nano-SiO ₂ material has a particle size of about 10-40nm, a specific surface area of 350-380m ² /g, and an activation degree of >99%.

Scanning results: Figure 2 is the core slice without nanoparticles, and Figure 3 is the SEM photo of the surface of the core slice with nanoparticles adsorbed. It can be seen from the figure that the nanoparticles are well adsorbed on the surface of the core slice.

Contact angle test results: OCA30 was used to test the contact angle on the surface of the core piece, and the results are shown in Figure 4 and Figure 5. Fig. 4 is the contact angle of the core slice surface without nanoparticles, and Fig. 5 is the contact angle of the core slice surface with nanoparticles adsorbed. It can be seen from the figure that before the adsorption of nanoparticles, the surface of the core piece is strongly hydrophilic. After the adsorption of nanoparticles, the contact angle of water droplets reaches 126.6°, which is greater than 120°. Injection effect.

,， 渗透率提高了42.5%，这直接验证了本快速评价方法的有效性。 In order to verify the effectiveness of this rapid evaluation method, a core flow experiment was carried out with a small test nanometer. The gas permeability of the core used is 16.337mDa, the porosity is 0.098, the length is 6.69cm, and the diameter is 2.5cm. Fig. 6 is the pressure gradient-flow diagram obtained in the experiment. According to the extended Darcy's law, we can get

, , the permeability increased by 42.5%, which directly verifies the effectiveness of this rapid evaluation method.

Claims (3)

1. A method for rapid evaluation of the effect of nanoparticle adsorption to reduce oil reservoir microchannel water flow resistance, characterized in that, utilize scanning electron microscope, contact angle test results to quickly evaluate the drag reduction effect; concrete steps are as follows: 1) Soak the core slices of the specified formation in the nanoparticle dispersion for more than 24 hours, so that the nanoparticles are adsorbed on the surface of the core slices, and then the core slices are taken out, rinsed and dried; 2) Use a contact angle tester to measure the apparent contact angle of water droplets on the core slice, and then scan the core slice with a scanning electron microscope; 3) Quickly judge according to the test results. As long as the scanning results show that the nanoparticles have been adsorbed on the surface of the core piece, and the contact angle test results are greater than 120°, it can be judged that the nanomaterials have a good drag reduction effect in the corresponding formation. 2. a kind of nanoparticle adsorption method according to claim 1 reduces the rapid evaluation method of oil reservoir microchannel flow resistance effect, it is characterized in that, described rock core piece diameter scope is 5mm～50mm, and thickness scope is 1mm～5mm . 3. a kind of nanoparticle adsorption method according to claim 1 reduces the rapid evaluation method of oil reservoir microchannel water flow resistance effect, it is characterized in that, described nanometer material is the hydrophobic nano-SiO with 5～200nm particle diameter _Particle , or TiO ₂ particles, or ZnO particles, or other hydrophobic nanoparticles.

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