CN116411906A - A fire flooding development method and system for medium and low mature shale - Google Patents

Abstract

The invention provides a medium-low mature shale fire flooding development method and a system, wherein the method comprises the following steps: arranging an injection well and a production well in a shale reservoir respectively, and perforating the middle lower part of the shale reservoir; respectively putting coiled tubing into an injection well and a production well; performing high-temperature ignition by using a continuous oil pipe of the injection well; and (5) producing combustion tail gas and crude oil by using a coiled tubing of the production well. According to the invention, an injection well is arranged in an oil shale reservoir, high-temperature combustion in the layer is realized by injecting high-temperature air, solid kerogen in the oil shale is promoted to be quickly converted into liquid hydrocarbon, and the liquid hydrocarbon is pushed to a production well to be produced. Compared with an in-situ conversion technology, the method can quickly improve the formation temperature, can realize kerogen conversion earlier, realizes quick conversion of medium-low mature shale, and effectively improves the heating efficiency and the energy utilization rate.

Description

A fire flooding development method and system for medium and low mature shale

technical field

The invention belongs to the technical field of shale oil and gas exploration and development, and in particular relates to a fire flooding development method and system for middle and low maturity shale.

Background technique

In recent years, with the rapid development of the economy, crude oil production has been far from meeting the needs of economic construction. It has become an urgent need to ensure energy security to find alternative areas for oil resources, to ensure stable or even increased production of crude oil, and to reduce dependence on foreign crude oil. However, the discovery of high-quality oil reserves and the stability of production are currently facing enormous challenges: on the one hand, the degree of proven oil resources in major oil and gas-bearing basins is getting higher and higher, and it is more difficult to find reserves with economies of scale; The difficulty is increasing, the water cut is increasing year by year, and the new production capacity is difficult to make up for the declining production of the old oilfields. Therefore, only by making breakthroughs in technology and theory, and obtaining scale-effective reserves and production outside the existing oil and gas exploration and development fields, can the energy security situation be fundamentally improved.

In this context, continental shale oil can be divided into medium-high maturity shale oil (Ro=1.0%-1.5%) and medium-low maturity shale oil (medium-low maturity shale: vitrinite reflectance (R _o ) is an important index to characterize the maturity of source rocks, and the shale with R _o =0.5%-1.0% is defined as medium-low maturity shale) two types. The development of medium and low maturity oil shale mainly uses in-situ mining technology to heat the oil shale reservoir at high temperature, and the solid kerogen in the oil shale (kerogen refers to the sedimentary rock that is insoluble in alkali, non-oxidizing acid and non-oxidizing Dispersed organic matter in polar organic solvents) is converted into liquid hydrocarbons, which are then extracted through traditional oil and gas drilling and recovery processes. At present, the existing in-situ conversion technology of medium and low maturity oil shale is mainly based on small-spacing downhole electric heating technology, which has the advantages of flexible and easy-to-control heating methods. For example, in the prior art, downhole electric heating technology with small spacing is used, in which vertical wells are production wells and horizontal wells are process heating wells. Downhole heating is realized by running a high-voltage cable into the process heating well, and the formation is heated to a conversion temperature of about 340°C after 2-4 years of heating time. This technology can evenly heat the formation to the set temperature, and the downhole electric heating is easy to control in engineering. However, there are the following disadvantages: due to the small heating interval of the technical solution, the deployment of heating wells is intensive, and the initial investment cost is high; the heat conduction of electric heating is slow, and it takes 2-4 years to heat the formation to a target temperature of 340°C or higher, and The energy utilization rate of the electric heating technology itself is not high, and a high recovery rate of liquefied hydrocarbons is required to ensure the return on investment. It can be seen that the existing in-situ conversion technology has the problems of low heating efficiency and low energy utilization.

Contents of the invention

In view of the above problems, the present invention provides a fire flooding development method and system for middle and low maturity shale. In order to achieve the above purpose, the following technical solutions are adopted:

A fire flooding development method for middle and low maturity shale, comprising the following steps:

Arrange injection wells and production wells in shale reservoirs, and perforate in the middle and lower parts of shale reservoirs;

Run the coiled tubing in the injection well and the production well respectively;

High-temperature ignition using coiled tubing in injection wells;

Coiled tubing in production wells is used to produce combustion tail gas and crude oil.

Preferably, the high-temperature ignition using the coiled tubing of the injection well includes:

Nitrogen is injected from the coiled tubing of the injection well to preheat, and then high-temperature air is injected into the formation for high-temperature ignition.

Preferably, the high-temperature ignition using the coiled tubing of the injection well also includes:

Air is continuously injected into the formation from the coiled tubing of the injection well to maintain the continuous combustion of the formation.

Preferably, the following steps are also included:

When the oxygen content in the combustion tail gas exceeds 3%, the gas injection into the injection well is stopped and the perforation channel of the perforation section of the injection well is blocked to end the production.

Preferably, the oil shale of the medium-low maturity shale satisfies the following conditions: thickness>10m, oil content>5% and average porosity>1%.

Preferably, the length of the perforation section where the perforation is located is 10-30 m, and the distance between the perforation sections of the injection well and the production well is 50-100 m.

Preferably, the nitrogen is preheated until the temperature of the formation within 3m of the perforation section of the gas injection well reaches 300°C or above; the temperature of the re-injected high-temperature air is ≥450°C.

Preferably, the flow rate of the re-injected high-temperature air is 1000-20000 Sm ³ /day.

Preferably, the wellbores of the injection and production wells are completed with casing and the cement is returned to the surface.

Preferably, a packer is used to seal off the annular space between the coiled tubing of the injection well and the casing of the injection well.

A medium-low maturity shale fire flooding development system, using the medium-low maturity shale fire flooding development method, including

The well layout module is used to respectively arrange injection wells and production wells in shale reservoirs, and perform perforation in the middle and lower parts of shale reservoirs;

The running module is used to run the coiled tubing in the injection well and the production well respectively;

Ignition module for high temperature ignition using coiled tubing in injection wells;

Development of modules for producing combustion tail gas and crude oil using coiled tubing from production wells;

The stop module is used to stop the gas injection into the injection well and block the perforation channel of the perforation section of the injection well when the oxygen content in the combustion tail gas exceeds 3%, so as to end the production.

The present invention has the following beneficial effects: the technical scheme of the present invention adopts the arrangement of an injection well in the oil shale reservoir, and realizes high-temperature combustion in the layer by injecting high-temperature hot air, and promotes the rapid conversion of solid kerogen in the oil shale to liquid hydrocarbons, And push liquid hydrocarbons to production wells for production. Compared with the in-situ conversion technology, the present invention can rapidly increase formation temperature, see kerogen conversion earlier, realize rapid conversion and production of middle and low mature shale, and effectively improve heating efficiency and energy utilization rate.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure pointed out in the written description, claims hereof as well as the appended drawings.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 shows a schematic diagram of a typical injection-production well group in an embodiment of the present invention;

In the figure: 1—igniter, oil shale reservoir, 2—gas injection pipe, 3—injection well, 4—perforation section of injection well, 5—production well, 6—coiled tubing, 7—production string, 8— Production well perforation section.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Fire flooding technology is one of the main methods to enhance the recovery of heavy oil. It is a development method that achieves high-temperature combustion displacement by injecting hot air into the formation and igniting the crude oil in the formation. It has high temperature, high recovery and high The peak combustion temperature generally exceeds 600°C. In order to improve the problems of slow heating efficiency and low energy utilization rate of the in-situ conversion technology, the present invention designs a new underground in-situ development technology combined with the fire flooding technology: medium and low mature shale fire flooding development method and system.

Example

A fire flooding development method for middle and low maturity shale, comprising the following steps:

Step 1: Arrange injection wells in the shale reservoir, and perforate in the middle and lower part of the shale reservoir: select a suitable block, and determine the location of the well arrangement. A vertical well is drilled as an injection well, and its perforation section is located in the middle and lower part of the shale reservoir. The entire wellbore is completed with casing and the cement is returned to the surface. The completion quality complies with the relevant requirements for thermal recovery completion;

Step 2: Arrange production wells in the shale reservoir and perforate in the middle and lower part of the shale reservoir: drill a vertical well as the production well, and its perforation section is located in the middle and lower part of the reservoir. The entire wellbore is completed with casing and the cement is returned to the surface. Completion quality should meet the relevant requirements of thermal recovery well completion;

Step 3: run coiled tubing in the injection well: run a coiled tubing to the perforation section of the gas injection well as a gas injection string, and use a packer to seal the annular space between it and the casing; perforate The length of the perforation section where it is located is 10-30m; the packer should have certain high temperature resistance, and can maintain stable mechanical properties for a long time under the condition of not lower than 300°C, so as to ensure the tightness between the gas injection pipe and the casing during the gas injection process. The annulus is well sealed;

Step 4: Run the coiled tubing in the production well: Run a coiled tubing to the production well as a production string; the production string can be run directly to the perforation section of the production well. If the liquid supply capacity of the formation is very strong and the dynamic liquid level is high, the production string run in should always be below the dynamic liquid level;

Step 5: Use the coiled tubing of the injection well for high-temperature ignition: inject high-temperature nitrogen from the gas injection string to preheat, until the formation temperature within 3m of the perforation section of the gas injection well reaches 300°C or above, then transfer high-temperature air into the formation, and then transfer high-temperature injection The temperature of the air is ≥450°C, the flow rate is 1000-20000Sm ³ /day, and high-temperature ignition is carried out; the daily gas injection volume of the air is related to the thickness of the formation and the duration of fire flooding. In order to ensure the stable advancement of the combustion front and achieve good development results, Professional and meticulous design is required according to relevant theories of reservoir engineering;

Step 6: Continuously inject air into the formation through the gas injection pipe string to maintain the continuous combustion of the formation;

Step 7: Use the coiled tubing of the production well to produce combustion tail gas and crude oil: produce combustion tail gas and crude oil from the production string, and monitor the components of the produced gas in real time. Monitor injection and other parameters in the production process and make necessary adjustments to keep the combustion front advancing stably in the formation. Specifically, real-time monitoring of the oxygen, hydrogen, hydrogen sulfide and methane gas content in the produced gas requires timing (such as Daily or weekly) to monitor the carbon dioxide content in the produced gas. In addition, parameters such as daily oil production, daily liquid production, bottomhole flow pressure (production section) and gas injection pressure need to be recorded every day. According to these parameters, relevant principles of reservoir engineering can be used to carry out regulation and control to keep the fire flooding front stably advancing;

Step 8: After the oxygen content in the output gas in the production string exceeds 3%, stop gas injection, use cement ash plug and other wellbore plugging technologies to block the perforation channel in the perforation section of the injection well, end production or change to next cycle of production. When plugging the perforation section, the amount of cement should be strictly controlled, and the amount of cement should be reduced as much as possible on the basis of ensuring the plugging effect, so as to prevent the production section from being blocked by too much cement.

Further, the oil shale of the middle and low maturity shale satisfies the following conditions: thickness > 10m, oil content > 5% and average porosity > 1%; the distance between the perforation sections of the injection well and the production well is 50 -100m. Favorable factors of low-medium maturity shale include: high horizontal permeability, no interlayer, continuous distribution of sand bodies, and uniform distribution of sweet spots; unfavorable factors include: high clay content, strong heterogeneity, low pressure coefficient, crude oil viscosity is too big. Parameters such as the position of the two perforation sections of the injection well and the production well, the length of the perforation section, and the distance between the perforation sections (referred to as the injection-production interval) need to be determined according to the formation conditions and crude oil physical properties, using laboratory experiments or reservoir engineering Related theories are designed. The location of the perforation section should be designed in the well section with good formation physical properties. The length of the perforation section is 10-30m. The higher the formation permeability and the stronger the homogeneity, the shorter the length of the perforation section. The injection-production interval is 50-100m, which is related to the fluidity of formation crude oil under the formation conditions before the application of this technology; the greater the mobility, the larger the injection-production interval; the design of the injection-production interval should ensure that the injected air can Inject into the oil layer below the fracture pressure.

Exemplarily, a shale section in Changqing, China, as shown in Figure 1 ("production well" in Figure 1 is the production well), the main buried depth is 700-1700m, corresponding to R _O <0.8%, and the shale thickness is 100m , The average porosity is 1.35%, the area is large, the continuity is good, and the organic matter content is high. Now a pair of injection-production vertical wells are deployed in this area for fire flooding development of medium and low mature shale. The specific development steps and parameters are as follows:

(1) Select the target well location. The well area with good shale homogeneity and convenient ground conditions was selected as the target well location. A pair of injection-production vertical wells (including injection well 3 and production well 5) are arranged in the shale layer, and the distance between the injection-production well and the shale bottom is designed to be 15m. The borehole size is not less than 9 inches (22.86cm);

(2) Well completion. The casing is used to complete the well, and the cement is returned to the wellhead. The inner diameter of the completion casing is not less than 7 inches (17.78cm), perforated at a distance of 5m from the end of the injection well, and the length of the perforation section 4 of the injection well and the perforation section 8 of the production well is set to 30m;

(3) inject trachea 2 under. A 2-inch coiled tubing 6 is lowered into the injection well 3 as a gas injection pipe 2 to the vicinity of the perforation section 4 of the injection well. Utilizing a packer to block the annular space between the gas injection pipe 2 and the casing;

(4) Lower the production string 7. 2-inch coiled tubing 6 is lowered into the production well 5;

(5) Preheating and ignition. Inject 450°C high-temperature nitrogen into the formation through the gas injection pipe 2 for preheating, and continue injecting for 3 days. Then inject 450°C high-temperature air into the formation, and realize electric heating and ignition by the igniter 1 . There will be a burning interface with a temperature exceeding 450°C underground, and the igniter can be turned off at this time to stop heating;

(6) Inject air into the formation. Continuously inject air into the formation, with a daily gas injection rate of 1000Sm ³ /day, to maintain a stable supply of oxygen at the combustion interface;

(7) Oil and gas are recovered from the production string 7 by using a mechanical lifting process. At the initial stage, the bottomhole flow pressure is maintained at about 1MPa, and when the daily gas production is basically equal to the daily gas injection volume, the gas production rate is slightly lower than the daily gas injection volume. Real-time monitoring of the components of the produced gas (oxygen, carbon dioxide, hydrogen sulfide, methane content) during production, recording parameters such as daily oil production, daily liquid production, bottomhole flow pressure and gas injection pressure;

(8) Adjustment of daily gas injection volume. After one month, if the production conditions are stable, the daily gas injection volume can be increased step by step, as shown in Table 1. The daily gas injection volume can be carried out according to the table below. The production string 7 adjusts the daily gas production in real time based on the principle of maintaining injection-production balance;

Table 1 Daily gas injection volume at different times

(9) When the oxygen content in the production string 7 exceeds 3%, the gas injection is stopped, the gas injection pipe 2 is taken out, and the perforation section 4 of the injection well is sealed with cement ash plug.

Exemplarily, the present invention adopts the above-mentioned development method (i.e. the burning oil reservoir method) and the conventional electric heating method to develop respectively, and tests the energy utilization rate and heating efficiency of the two development methods, and the results are shown in Table 2:

Table 2 Energy utilization and heating efficiency results of different development methods

The results show that the energy utilization rate of the method for burning the oil reservoir by adopting the present invention reaches 100% (without considering the heat carried by the air), and the peak temperature > 450° C.; the energy utilization rate of the electric heating method reaches 60% (the wellbore heat loss is 35%, the resistance heat loss of 5%), the peak temperature only reaches 340°C. Therefore, the invention used in the present invention has higher energy utilization rate and heating efficiency.

A fire flooding development system for medium and low mature shale, adopting the above fire flooding development method for medium and low mature shale, including

The well layout module is used to respectively arrange injection wells and production wells in shale reservoirs, and perform perforation in the middle and lower parts of shale reservoirs;

The running module is used to run the coiled tubing in the injection well and the production well respectively;

Ignition module for high temperature ignition using coiled tubing in injection wells;

Development of modules for producing combustion tail gas and crude oil using coiled tubing from production wells;

The stop module is used to stop the gas injection into the injection well and block the perforation channel of the perforation section of the injection well when the oxygen content in the combustion tail gas exceeds 3%, so as to end the production.

In summary, the present invention arranges an injection well in the oil shale reservoir, realizes high-temperature combustion in the layer by injecting high-temperature hot air, promotes the rapid conversion of solid kerogen in the oil shale to liquid hydrocarbons, and pushes the liquid hydrocarbons to production wells. The invention can realize the large-scale production of medium-low mature shale, saves the initial investment cost of development compared with the existing technology, and at the same time, the heating rate, peak temperature and energy utilization rate of internal combustion are better than underground electric heating, which is beneficial to underground solidification. The rapid conversion of phase kerogen effectively improves heating efficiency and energy utilization.

Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that: they can still modify the technical solutions described in the aforementioned embodiments, or perform equivalent replacements for some of the technical features; and these The modification or replacement does not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (11)

1. A fire flooding development method for middle and low mature shale, characterized in that, comprising the following steps: Arrange injection wells and production wells in shale reservoirs, and perforate in the middle and lower parts of shale reservoirs; Run the coiled tubing in the injection well and the production well respectively; High-temperature ignition using coiled tubing in injection wells; Coiled tubing in production wells is used to produce combustion tail gas and crude oil. 2. The medium and low maturity shale fire flooding development method according to claim 1, characterized in that, the high-temperature ignition using the coiled tubing of the injection well comprises: Nitrogen is injected from the coiled tubing of the injection well to preheat, and then high-temperature air is injected into the formation for high-temperature ignition. 3. The medium and low maturity shale fire flooding development method according to claim 2, characterized in that, the high-temperature ignition using the coiled tubing of the injection well also includes: Air is continuously injected into the formation from the coiled tubing of the injection well to maintain the continuous combustion of the formation. 4. The medium and low mature shale fire flooding development method according to claim 1, further comprising the steps of: When the oxygen content in the combustion tail gas exceeds 3%, the gas injection into the injection well is stopped and the perforation channel of the perforation section of the injection well is blocked to end the production. 5. The fire flooding development method of middle and low maturity shale according to claim 1, characterized in that the oil shale of the middle and low maturity shale satisfies the following conditions: thickness>10m, oil content>5% and average porosity degree > 1%. 6. The middle-low mature shale fire flooding development method according to claim 1, characterized in that the length of the perforation section where the perforation is located is 10-30m, and the perforation section between the injection well and the production well The spacing is 50-100m. 7. The fire flooding development method for middle and low mature shale according to claim 2, characterized in that, the nitrogen is preheated until the formation temperature within 3m of the perforation section of the gas injection well reaches 300°C or above; The temperature is ≥450°C. 8. The fire flooding development method for middle and low mature shale according to claim 2, characterized in that the flow rate of the high-temperature air injection is 1000-20000 Sm ³ /day. 9. The fire flooding development method for middle and low maturity shale according to any one of claims 1-8, characterized in that the wellbore of the injection well and the production well is completed with casing and the cement is returned to the ground. 10. The fire flooding development method for middle and low maturity shale according to claim 9, characterized in that the annulus between the coiled tubing of the injection well and the casing of the injection well is sealed off by a packer. 11. A fire flooding development system for middle and low mature shale, characterized in that, adopting the middle and low maturity shale fire flooding development method as described in any one of claims 1-10, comprising The well layout module is used to respectively arrange injection wells and production wells in shale reservoirs, and perform perforation in the middle and lower parts of shale reservoirs; The running module is used to run the coiled tubing in the injection well and the production well respectively; Ignition module for high temperature ignition using coiled tubing in injection wells; Development of modules for producing combustion tail gas and crude oil using coiled tubing from production wells; The stop module is used to stop the gas injection into the injection well and block the perforation channel of the perforation section of the injection well when the oxygen content in the combustion tail gas exceeds 3%, so as to end the production.

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