CN114737936B - Supercritical CO2Device and method for integrally developing middle-low mature shale oil - Google Patents

Abstract

The present invention discloses a device and method for developing medium- and low-maturity shale oil by supercritical CO2 integration, which belongs to the technical field of physical simulation in oil and gas production room, and includes a core holder, a liquid receiving tank, a displacement device, a throughput device and a thermogravimetric analyzer; the core holder is provided with a heating and heat preservation device; the liquid receiving tank is used to collect the fluid at the outlet of the core holder; the displacement device is used to inject formation water, shale oil and proppant into the core holder respectively; the throughput device includes an injection device and a backflow device respectively connected to the inlet of the core holder, the injection device is used to inject heated carbon dioxide, and the backflow device is used to perform gas-liquid separation on the backflow material and perform component analysis on the gas; the thermogravimetric analyzer is used to measure the pyrolysis of shale oil under different CO2 injection rates and different heating rates. The present invention can study the lightening and extraction mechanism of continental medium- and low-maturity shale oil by high-temperature supercritical CO2.

Description

A supercritical CO2 integrated development device and method for low-maturity shale oil

Technical Field

The present invention belongs to the technical field of indoor physical simulation of oil and gas production, and in particular relates to a device and method for supercritical CO2 integrated development of low-mature shale oil.

Background technique

Continental shale oil refers to petroleum hydrocarbons, asphalt and various unconverted organic matter contained in continental organic-rich shale formations with a burial depth of more than 300 meters and a vitrinite reflectance (Ro value) greater than 0.5%. Solid organic matter and liquid retained hydrocarbons coexist in the shale, which has the characteristic of great convertible resource potential.

China's continental medium-low maturity shale oil (0.5% <Ro <1.0%) resources are large, with technically recoverable reserves reaching 70-90 billion tons. China's medium-low maturity shale oil reservoirs have the following characteristics: ① The reservoir pores and throats are extremely small (micro-nano-nano level); the permeability is extremely low ( ^{10-4 μm2} ~ ^{10-6 μm2} ); ② The shale oil reservoir is buried deep (3000-5000 meters); ③ The reservoir physical properties are poor and the seepage resistance is large; ④ The occurrence form is complex (free state, adsorbed state, dissolved state); ⑤ The degree of thermal evolution is low, of which the unconverted organic matter accounts for 40% to 90%, and the retained hydrocarbons account for 5% to 60%. The conventional development methods (water drive production, depletion production, chemical drive, gas drive, etc.) cannot achieve the efficient development of medium-low maturity shale oil.

Studies at home and abroad have shown that high-temperature supercritical _CO2 in-situ light-weighting and extraction technology is a cutting-edge technology for the efficient development of medium- and low-maturity shale oil. China's research in this field is still in the early stages of indoor experiments and numerical simulations. There are problems to be overcome, such as the lack of adaptability of existing development technologies, unclear high-temperature "gas-liquid-solid" mutual feedback mechanism, and inaccurate development prediction methods. A theoretical and technical system applied to oil fields has not been formed. Existing research on the development of shale oil supercritical _CO2 mainly considers extraction, viscosity reduction, diffusion and other mechanisms, but does not consider reservoir fracturing, kerogen pyrolysis, and light-weighting of retained hydrocarbons, and cannot achieve accurate prediction of high-temperature supercritical _CO2 development of shale oil. In order to realize the industrial application of high-temperature supercritical _CO2 light-weighting and extraction technology in China's continental medium- and low-maturity shale oil, it is necessary to carry out research on the mechanism of high-temperature supercritical _CO2 light-weighting and extraction of continental medium- and low-maturity shale oil.

Summary of the invention

In view of the above problems, the present invention provides a supercritical CO2 integrated development device and method for low-maturity shale oil. The present invention provides the following technical solutions:

A supercritical CO2 integrated development device for low-mature shale oil comprises a core holder, a liquid receiving tank, a displacement device, a throughput device and a thermogravimetric analyzer; a heating and heat preservation device is arranged outside the core holder, a core is placed in the core holder and a pressure sensor is arranged for measuring the pressure of the core; the liquid receiving tank is used to collect the fluid at the core holder outlet; the displacement device is connected to the core holder inlet and is used to inject formation water, shale oil and proppant into the core holder respectively; the throughput device comprises an injection device and a flowback device respectively connected to the core holder inlet, the injection device is used to inject heated carbon dioxide into the core holder, and the flowback device is used to perform gas-liquid separation on the material flowed back in the core holder and perform component analysis on the gas; the thermogravimetric analyzer is used to measure the pyrolysis of shale oil under different CO2 injection rates and different heating rates.

As a specific embodiment of the present invention, the displacement device includes a liquid storage tank, a displacement pump and an intermediate container connected in sequence. There are three intermediate containers, which are respectively filled with formation water, shale oil and proppant, and the three intermediate containers are arranged in parallel and respectively connected to the inlet of the core clamp.

As a specific embodiment of the present invention, the injection device includes a CO2 gas cylinder, a gas booster and a gas heater which are connected in sequence, and the gas heater is connected to the inlet of the core holder.

As a specific implementation of the present invention, the flowback device includes a gas-liquid separator and a gas mass spectrometer connected in sequence, and the gas-liquid separator is connected to the inlet of the core holder.

A method for using the above device comprises the following steps:

S1. Using the injection device in the throughput device to inject high-temperature CO2 into the core holder to perform shale fracturing; then using the displacement device to inject proppant into the core holder to establish an irregular artificial fracture network;

S2, injecting formation water into the core holder using a displacement device to saturate the core with formation water;

S3, injecting shale oil into the core holder using a displacement device to saturate the core with shale oil;

S4, closing the liquid outlet of the core holder, and injecting high-temperature supercritical CO2 fluid into the core holder using the injection device in the throughput device;

S5, until the system pressure is stable, then close the injection device, use the flowback device to separate the shale oil and gas from the flowback flow in the core holder, and measure the gas;

S6. Using a thermogravimetric analyzer, the pyrolysis of the raw shale oil and the return shale oil in the core clamp at different CO2 injection rates and different heating rates is measured;

S7. Use the measured data to conduct a comprehensive analysis of the high-temperature supercritical CO2 throughput of shale oil.

Beneficial effects: The invention can carry out high-temperature supercritical _CO2 fracturing-huff-and-puff integrated experiments. The device can be used to carry out research on the high-temperature supercritical _CO2 lightening and extraction mechanism of continental medium and low maturity shale oil.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a flow chart of a supercritical CO2 integrated development of low-mature shale oil unit;

Figure 2 shows the TG curve of pyrolysis of low-maturity shale oil;

Figure 3 shows the DTG curve of pyrolysis of low-maturity shale oil;

Fig. 4 Arenius curves at different conversion rates;

In the figure: 1. constant flow displacement pump; 2. liquid storage tank; 3. CO2 cylinder; 4. gas booster; 5. gas heater; 6. formation water; 7. shale oil; 8. proppant; 9. needle valve; 10. throughput device; 11. heating and insulation device; 12. core clamp; 13. pressure collection device; 14. liquid receiving tank; 15. gas-liquid separator; 16. gas phase mass spectrometer; 17. pressure regulator; 18. pointer pressure gauge; 19. thermogravimetric analyzer; 20. computer.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. The words "include" or "comprise" and the like used in the present disclosure mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

The present invention is further described below in conjunction with the accompanying drawings and embodiments.

A supercritical CO2 integrated development device for low-mature shale oil, comprising a core holder 12, a liquid receiving tank 14, a displacement device, a throughput device and a thermogravimetric analyzer; the core holder 12 is provided with a heating and heat preservation device 11, a core (not shown in the figure) is placed in the core holder 12 and a pressure sensor 13 is provided for measuring the pressure of the core; the liquid receiving tank 14 is connected to the outlet of the core holder 12 and is used to collect the fluid at the outlet of the core holder 12; the displacement device is connected to the inlet of the core holder 12 The core holder 12 is connected to inject formation water 6, shale oil 7 and proppant 8 respectively; the throughput device includes an injection device and a flowback device respectively connected to the inlet of the core holder 12, the injection device is used to inject heated carbon dioxide into the core holder 12, and the flowback device is used to separate the gas and liquid of the material returned from the core holder 12 and perform component analysis on the gas; the thermogravimetric analyzer 19 is used to determine the pyrolysis of shale oil under different CO2 injection rates and different heating rates.

Specifically, the displacement device includes a liquid storage tank 2, a constant flow displacement pump 1 and an intermediate container connected in sequence. There are three intermediate containers, which are filled with formation water 6, shale oil 7 and proppant 8 respectively. The three intermediate containers are arranged in parallel and are respectively connected to the inlet of the core clamp 12. The inlet and outlet of each intermediate container are provided with a needle valve 9. The injection device includes a CO2 gas cylinder 17, a gas booster 4 and a gas heater 5 connected in sequence. The gas heater 5 is connected to the inlet of the core clamp 12. The backflow device includes a gas-liquid separator 15 and a gas phase mass spectrometer 16 connected in sequence. The gas-liquid separator 15 is connected to the inlet of the core clamp 12. The gas phase mass spectrometer 16 is used to determine the gas phase composition in the gas-liquid separator 15. The _CO2 gas cylinder 17 is also connected to a pressure regulator 17, and the pressure regulator 17 is also connected to a correcting pressure gauge 18 and a thermogravimetric analyzer 19, which are used to control the input of CO2 into the thermogravimetric analyzer to simulate the pyrolysis of shale oil with or without CO2. The gas phase mass spectrometer 16, the thermogravimetric analyzer 19 and the computer 20 are used to perform a comprehensive analysis of the high temperature supercritical CO2 throughput using the collected data.

The working principle of the present invention is: first, high-pressure proppant and high-temperature fracturing cause the reservoir to form a complex fracture network structure, which is convenient for the convection of the heat-carrying medium. Secondly, the heat-carrying medium contacts the oil reservoir and conducts the carried heat to the shale oil through the matrix, realizing the long-distance transmission of heat. Finally, kerogen is pyrolyzed in a high-temperature supercritical _CO2 atmosphere, the retained hydrocarbons are lightened, and the modified oil (pyrolysis oil, lightened oil) is extracted. In order to study the high-temperature pyrolysis characteristics of kerogen, kerogen pyrolysis experiments were carried out in parallel.

Shale oil high temperature supercritical _CO2 fracturing-huff and puff integrated experimental device usage steps:

S1. Using the injection device in the throughput device to inject high-temperature CO2 into the core holder to perform shale fracturing; then using the displacement device to inject proppant into the core holder to establish an irregular artificial fracture network;

S2, injecting formation water into the core holder using a displacement device to saturate the core with formation water;

S3, injecting shale oil into the core holder using a displacement device to saturate the core with shale oil;

S4, closing the liquid outlet of the core holder, and injecting high-temperature supercritical CO2 fluid into the core holder using the injection device in the throughput device;

S5, until the system pressure is stable, then close the injection device, use the flowback device to separate the shale oil and gas from the flowback flow in the core holder, and measure the gas;

S6. The pyrolysis of the raw shale oil and the shale oil returned in the core clamp at different CO2 injection rates and different heating rates was measured using a thermogravimetric analyzer, and the pyrolysis weight loss curve (see Figure 3) and the pyrolysis weight loss rate curve (see Figure 4) were obtained.

S7. Import the data collected from the experiment into the computer to conduct a comprehensive analysis of the high-temperature supercritical CO2 throughput of shale oil.

The comprehensive analysis of high-temperature supercritical CO2 throughput of shale oil includes analysis of the shale oil throughput process and analysis of the pyrolysis characteristics of shale oil.

The analysis of shale oil huff-and-puff process mainly includes the effect of rock fracturing, the oil production law of high-temperature supercritical CO2 huff-and-puff, and the pyrolysis, lightening and upgrading of kerogen in medium and low maturity shale oil in high-temperature supercritical CO2 atmosphere.

The analysis of shale oil pyrolysis characteristics mainly includes the division of the three-stage temperature range of shale oil weight loss, the temperature mark corresponding to the maximum weight loss rate, the maximum weight loss temperature drift law under different heating rates and the calculation of shale oil pyrolysis kinetic parameters. The calculation method of shale oil pyrolysis kinetic parameters is as follows:

The present method for calculating the pyrolysis kinetic parameters is based on the following two assumptions: (1) the pyrolysis process consists of many independent irreversible reactions, and the reaction order of these reactions is 1; (2) the apparent activation energy is a continuous function of temperature, and each reaction has a certain apparent activation energy value.

Based on these assumptions, the weight loss process of a material at a certain stage in the pyrolysis process can be described as equation (1):

Where: w _t ——sample mass at time t (mg); w ₀ ——initial sample mass (mg); w _t /(w ₀ -w _∞ )——conversion rate α; k ₀ ——reaction frequency factor (s ^-1 ). β——heating rate (℃/min). Ea——apparent activation energy (kJ/mol). R——ideal gas constant (8.314J/(mol·K)); T——sample temperature (K); f(Ea)——apparent activation energy distribution function, here it is taken as 1.

Equation (1) can be simplified to equation (2).

in:

Then there are:

The latter term in equation 4 is a constant term, which can be replaced by the constant symbol A:

The steps for calculating the kinetic parameters according to formula (4) mainly include:

S1. Determine the weight loss curve under different heating rates β through thermogravimetric experiments.

S2. Prepare according to the data of each weight loss curve The curve is shown in Figure 4.

S3, in Draw an Arrhenius straight line on the curve with the same conversion rate at different heating rates. The slope of the straight line is / > From this value, Ea can be obtained, and then k ₀ can be obtained.

Based on this, it can be calculated that the apparent activation energy of shale oil at 300℃, 400℃ and 500℃ is 89kJ/mol, 121kJ/mol and 260kJ/mol respectively, and the reaction frequency factor is 4.2×10 ⁸ s ^-1 .

The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this 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 fall within the scope of the technical solution of the present invention.

In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims (3)

1. A method for using a medium-low mature shale oil device in supercritical CO ₂ integrated development is characterized in that,

The medium-low mature shale oil device for supercritical CO ₂ integrated development comprises a core holder, a liquid receiving tank, a displacement device, a throughput device and a thermogravimetric analyzer; the core holder is provided with a heating and heat-preserving device, and is internally provided with a core and a pressure sensor for measuring the pressure of the core; the liquid receiving tank is used for collecting fluid at the outlet of the core holder; the displacement device is communicated with the inlet of the core holder and is used for respectively injecting formation water, shale oil and propping agent into the core holder; the handling device comprises an injection device and a flowback device which are respectively communicated with the inlet of the core holder, wherein the injection device is used for injecting carbon dioxide after temperature rise into the core holder, and the flowback device is used for carrying out gas-liquid separation on materials flowback in the core holder and carrying out component analysis on the gas; the thermogravimetric analyzer is used for measuring shale oil pyrolysis conditions under different CO ₂ injection rates and different heating rates; the displacement device comprises a liquid storage tank, a displacement pump and three intermediate containers which are sequentially connected, wherein the three intermediate containers are respectively filled with stratum water, shale oil and propping agent, are arranged in parallel and are respectively connected with an inlet of the rock core holder;

the application method of the medium-low mature shale oil device for supercritical CO ₂ integrated development comprises the following steps:

S1, injecting high-temperature CO ₂ into a core holder by using an injection device in a huff and puff device to carry out shale fracturing; then, using a displacement device to inject propping agent into the core holder to establish an irregular artificial fracture network;

s2, injecting formation water into the rock core holder by using a displacement device, and saturating the rock core with the formation water;

S3, injecting shale oil into the core holder by using a displacement device, and carrying out shale oil saturation on the core;

S4, closing a liquid outlet of the core holder, and injecting high-temperature supercritical CO2 fluid into the core holder by using an injection device in the throughput device;

S5, closing the injection device until the system pressure is stable, separating flowback materials in the core holder by using the flowback device, separating shale oil and gas, and measuring the gas;

S6, determining pyrolysis conditions of the raw shale oil and the flowback shale oil in core clamping under different CO ₂ injection rates and different heating rates by using a thermogravimetric analyzer;

s7, carrying out shale oil high-temperature supercritical CO ₂ throughput comprehensive analysis by using the measured data;

The comprehensive analysis comprises the steps of obtaining activation energy and frequency factors of shale oil pyrolysis reaction;

The calculation formula of shale oil pyrolysis activation energy and reaction frequency factor is as follows:

Wherein, beta is the temperature rising rate, T is the sample temperature, ea is the apparent activation energy, R is the ideal gas constant, k ₀ is the reaction frequency factor, alpha is the pyrolysis conversion rate, and A is the constant;

The steps for obtaining the shale oil pyrolysis activation energy and the reaction frequency factor are as follows:

Sub1, determining a weight loss curve under different heating rates beta through a thermogravimetric experiment;

Sub2, data preparation according to each weightlessness curve A curve;

Sub3, at Arrhenius straight line with the same conversion rate at different heating rates is made on the curve, and the slope of the straight line is/>Ea is obtained through the slope, the intercept of the straight line and the vertical axis is constant A, and k ₀ is obtained through a shale oil pyrolysis reaction frequency factor calculation formula.

2. The method for using the medium and low mature shale oil device in supercritical CO ₂ integrated development according to claim 1, wherein the injection device comprises a CO ₂ gas cylinder, a gas booster and a gas heater which are connected in sequence, and the gas heater is connected with the core holder inlet.

3. The method for using the medium-low mature shale oil device in supercritical CO ₂ integrated development according to claim 1, wherein the flowback device comprises a gas-liquid separator and a gas-phase mass spectrometer which are connected in sequence, and the gas-liquid separator is connected with the inlet of the core holder.