A prediction method for coke formation during the cracking conversion of heavy oil based on a four-component model

Abstract

The present invention relates to a method for predicting coke formation during the cracking transformation of heavy oil based on a four-component model, belonging to the technical field of oil and gas exploitation. The method includes: S1. The heavy oil is divided into four components: saturates, aromatics, resins, and asphaltenes, and the coke formation rates of each component under different conditions are measured; S2. Based on the coke formation rates of each component, a four-component coke formation model for heavy oil is established; S3. Based on the characteristics of each component of the heavy oil to be predicted and the four-component coke formation model, the coke formation rate of the cracking transformation of the heavy oil under the corresponding reaction conditions is predicted. The coke formation rate of each component refers to the mass ratio of the solid residue formed after the cracking of each component, which is soaked and washed with toluene, to the mass of the part of each component participating in coke formation. The cracking is thermal cracking or oxidative cracking. The principle of the present invention is reliable and the operation is simple. It can obtain the coke formation rate of any heavy oil under different conditions simply, quickly, and accurately, and has the advantages of high efficiency and low cost compared with traditional testing methods.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas production, and in particular relates to a method for predicting coke generation by cracking and conversion of heavy oil based on a four-component model. Background Art

[0002] Heavy oil is an important unconventional oil and gas resource in the world. The cracking process of heavy oil generally includes thermal cracking and oxidative cracking. Steam-assisted gravity drainage (SAGD) is one of the most commercialized technologies for heavy oil extraction. In the in-situ solvent-assisted SAGD technology, the generation of solvent relies on the pyrolysis of crude oil in the oil layer near the wellbore by a downhole electric heating device. However, the pyrolysis of heavy oil is often accompanied by the generation of coke. Taking the Fengcheng Oilfield in Xinjiang as an example, when the formation temperature rises above 300℃, a large amount of coke will be produced in the formation near the wellbore. The blocking effect of these cokes will hinder the flow of crude oil into the wellbore, thereby affecting the cumulative oil production and causing a decrease in recovery. In the air injection-assisted SAGD technology, when the oil layer temperature is between 200 and 300℃, the oxygen injected in the air will react with the heavy oil at a low temperature, and the reaction will also generate a large amount of coke, which will be deposited at the edge of the steam cavity, affecting the development of the steam cavity. Therefore, it is of great significance to clarify the coke generation rate of different heavy oils under different conditions for the research of the above-mentioned related thermal recovery technologies.

[0003] At present, the coking rate of heavy oil cracking conversion is generally predicted by physical experiments, combined with the chemical mechanism of the reaction, and the establishment of a reaction kinetic model. This method predicts the results more accurately, but the prediction process is more complicated, time-consuming and labor-intensive. "A method for evaluating the coking rate of heavy oil contact cracking" (CN110823750A) can quickly obtain the coking rate through simple physical experiments, but this method is only a method for measuring the coking rate through physical experiments and cannot predict the coke production.

[0004] Heavy oil is generally divided into four components: saturates, aromatics, colloids and asphaltene. A large number of heavy oil cracking experiments have shown that the coking rate of the same component of different heavy oils cracked in the same way is basically the same. Therefore, combining the coking rates of different heavy oil components, the coking rate of heavy oil cracking can be predicted based on the weighted average of the component content.

[0005] Based on this, the present invention proposes a method for simply, quickly and accurately predicting the coking rate of heavy oil cracking. Summary of the invention

[0006] The purpose of the present invention is to provide a method for predicting coking by cracking and conversion of heavy oil based on a four-component model. The method has reliable principle and is easy to operate. The method predicts the coking rate of heavy oil cracking based on the four-component coking model of heavy oil, and can simply, quickly and accurately obtain the coking rate of any heavy oil under different conditions. Compared with traditional testing methods, the method has the advantages of high efficiency and low cost.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0008] The present invention determines the cracking conversion coking rates of saturated fractions, aromatic fractions, colloids and asphaltenes under different conditions, and establishes a four-component coking model under corresponding reaction conditions; based on the characteristics of the four components of the heavy oil to be predicted and the coking model, the cracking conversion coking rate of the heavy oil under the corresponding reaction conditions is predicted.

[0009] A method for predicting coke generation by cracking and conversion of heavy oil based on a four-component model comprises the following steps in sequence:

[0010] S1. Heavy oil is divided into four components: saturates, aromatics, colloids and asphaltene, and the cracking coke yield of each component under different conditions is measured;

[0011] S2. Based on the cracking coke production rate of each component, a four-component cracking coke production model of heavy oil is established:

[0012]

[0013] Among them, β Coke is the coke production rate of heavy oil cracking under different conditions, that is, the mass of coke produced is proportional to the mass of heavy oil sample, %; w i is the content of each component of heavy oil in heavy oil. When i is equal to 1, 2, 3, and 4, it corresponds to saturated fraction, aromatic fraction, colloid, and asphaltene, respectively; v i is the mass loss rate of each component of heavy oil under different conditions, %; β i is the coke production rate of each component of heavy oil under different conditions, %;

[0014] S3. Based on the characteristics of each component of the heavy oil to be predicted and the four-component cracking and coking model, the cracking conversion coking rate of the heavy oil under the corresponding reaction conditions is predicted.

[0015] Furthermore, the cracking coke yield of each component refers to the ratio of the mass of the solid residue generated by cracking each component after being soaked and washed with toluene to the mass of the coke-forming part of each component.

[0016] Furthermore, the cracking is thermal cracking or oxidative cracking.

[0017] Furthermore, the different conditions include a heating rate and a heating time, such as but not limited to a heating rate of 5° C. / min and a heating time of 120 min.

[0018] Furthermore, the four-component cracking coke production model is a four-component thermal cracking coke production model or an oxidative cracking coke production model. If the thermal cracking coke production rate of each component is substituted into the model, the model is a four-component thermal cracking coke production model; if the oxidative cracking coke production rate of each component is substituted into the model, the model is a four-component oxidative cracking coke production model.

[0019] Furthermore, the mass loss rate is the mass loss rate of each component during the evaporation stage of the thermal cracking or oxidative cracking process.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention establishes a four-component coking model under different conditions based on experimental data, which can simply, quickly and accurately predict the coking rate of heavy oil with different compositions during thermal cracking or oxidative cracking, and has the characteristics of strong operability, strong adaptability and wide application range. Predicting the coking rate of heavy oil cracking is of great significance for selecting heavy oil reservoir mining technology and determining construction parameters. The application of this method can greatly improve decision-making efficiency and improve work efficiency on the oil field site. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic flow chart of the method for predicting coke production by cracking and conversion of heavy oil based on the four-component model of the present invention.

[0023] Figure 2 This is a comparison chart between the model prediction value and the experimental value (5℃ / min, 120min). DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to the accompanying drawings and examples, so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, they are all protected.

[0025] Example

[0026] A method for predicting coke generation from heavy oil cracking conversion based on a four-component model (refer to Figure 1 ), the specific steps are as follows:

[0027] S1. Determine the cracking coke yield of saturates, aromatics, colloids and asphaltene components under different conditions. When the heating rate is 5°C / min and the heating time is 120min, the thermal cracking coke yields of saturates, aromatics, colloids and asphaltene components are 1.6%, 3.7%, 19.5% and 44.8%, respectively. The oxidative cracking coke yields of saturates, aromatics, colloids and asphaltene components are 10.3%, 28.2%, 58.1% and 89.9%, respectively.

[0028] S2. A four-component thermal cracking and oxidative cracking coking model is established based on the coking rate of each component:

[0029]

[0030] Among them, β Coke is the coke yield of heavy oil cracking under different conditions, that is, the mass of coke produced is proportional to the mass of heavy oil sample, %, w i is the content of each component in the heavy oil. When i is equal to 1, 2, 3, and 4, it corresponds to saturated fraction, aromatic fraction, colloid, and asphaltene, respectively. i is the mass loss rate of each component of heavy oil during the evaporation stage under different conditions, %, β i is the coke production rate of each component of heavy oil under different conditions, %;

[0031] S3. Based on the characteristics of the four components of the heavy oil to be predicted and the aforementioned four-component coking model, the thermal cracking and oxidative cracking conversion coking rates of the heavy oil under the corresponding reaction conditions are predicted respectively.

[0032] For example, the mass loss rates of saturated fraction, aromatic fraction, colloid and asphaltene in the thermal cracking evaporation stage of heavy oil sample A are 87%, 37%, 13% and 0% respectively; when the heating rate is 5℃ / min and the heating time is 120min, the β i (i=1, 2, 3, 4) are 1.6, 3.7, 19.5, 44.8 respectively. The β i (i=1, 2, 3, 4) are 10.3, 28.2, 58.1, 89.9 respectively; when the heating rate is 5℃ / min and the heating time is 120min, the thermal cracking and oxidative cracking conversion coking rates of heavy oil sample A are 7.5% and 31.4% respectively.

[0033] Figure 2 The comparison between the prediction results and experimental results of different samples under different conditions is shown, and the comparison results show that the model has high reliability.

[0034] The above description is not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for predicting coke formation during the cracking conversion of heavy oil based on a four-component model, successively including the following steps: S1. Heavy oil is divided into four components: saturates, aromatics, resins, and asphaltenes, and the coke formation rates of each component under different conditions are measured; S2. Based on the coke formation rates of each component, a four-component cracking coke formation model for heavy oil is established: Among them, is the cracking coking rate of heavy oil under different conditions, that is, the mass ratio of the produced coke to the mass of the heavy oil sample, %; is the content of each component of heavy oil in heavy oil. When is equal to 1, 2, 3, and 4, it corresponds to saturates, aromatics, resins, and asphaltenes respectively, %; is the mass loss rate of each component of heavy oil under different conditions, %; is the cracking coking rate of each component of heavy oil under different conditions, %; The four-component cracking coke formation model is a four-component thermal cracking coke formation model or an oxidative cracking coke formation model. If the thermal cracking coke formation rates of each component are substituted into the model, the model is a four-component thermal cracking coke formation model; if the oxidative cracking coke formation rates of each component are substituted into the model, the model is a four-component oxidative cracking coke formation model; The mass loss rate is the mass loss rate during the evaporation stage in the thermal cracking or oxidative cracking process corresponding to each component; S3. Based on the characteristics of each component of the heavy oil to be predicted and the four-component cracking coke formation model, the coke formation rate of the cracking conversion of the heavy oil under the corresponding reaction conditions is predicted.

2. The method for predicting coke formation during the cracking conversion of heavy oil based on a four-component model according to claim 1, characterized in that the coke formation rate of each component is the mass ratio of the solid residue generated after each component undergoes cracking and is soaked and washed with toluene to the mass of the part of each component participating in coke formation.

3. The method for predicting coke formation during the cracking conversion of heavy oil based on a four-component model according to claim 1, characterized in that the cracking is thermal cracking or oxidative cracking.

4. The method for predicting coke formation during the cracking conversion of heavy oil based on a four-component model according to claim 1, characterized in that the different conditions include the heating rate and the heating time.

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