CN118242040A - Method for improving recovery ratio of fracture-cavity carbonate rock oil-gas reservoir - Google Patents

Abstract

The invention provides a method for improving recovery ratio of a fracture-cavity carbonate rock oil-gas reservoir. The method comprises the following steps: determining the scale of a target oil and gas reservoir, a reservoir structure, residual dynamic reserves and stratum energy, wherein the reservoir structure comprises reservoir types and communication conditions among fracture holes; determining whether the water injection mode of each fracture-cavity unit of the target oil-gas reservoir is water injection oil displacement, water injection pressure maintaining, high-pressure water injection or unit water injection based on the scale, reservoir structure, residual dynamic reserve and stratum energy of the target oil-gas reservoir and combining the gas-oil ratio, and performing water injection development of the target oil-gas reservoir according to the determined water injection development mode; based on the injection pattern and reservoir structure of the fracture-cavity unit after the water injection failure of the target oil-gas reservoir unit, determining whether the improved water injection mode adopted by the fracture-cavity unit after the water injection failure of the unit is injection-production direction adjustment, injection-production parameter adjustment, injection medium regulation and control or injection runner regulation and control, and performing the water injection development of the fracture-cavity unit after the water injection failure of the target oil-gas reservoir unit according to the determined improved water injection mode.

Description

Method for improving recovery ratio of fracture-cavity carbonate rock oil-gas reservoir

Technical Field

The invention relates to the technical field of oil and gas reservoir development, in particular to a method for improving recovery ratio of a fracture-cavity carbonate rock oil and gas reservoir.

Background

At present, the development of fracture-cavity carbonate rock oil and gas reservoirs generally has the problems of low production benefit, short economic life of production wells and the like. How to improve the water injection and gas injection development scheme of the fracture-cavity type carbonate hydrocarbon reservoir and improve the recovery ratio of the fracture-cavity type carbonate hydrocarbon reservoir is one of the difficulties in the development of the carbonate hydrocarbon reservoir at present.

Disclosure of Invention

The invention aims to provide a technical scheme capable of quantitatively describing fracture-cavity carbonate rock-oil-gas reservoir fracture-cavity aggregate.

In order to achieve the above object, the present invention provides a method for enhancing recovery efficiency of a fracture-cavity carbonate hydrocarbon reservoir, wherein the method comprises:

Determining the scale, reservoir structure, remaining dynamic reserves, and formation energy of the target reservoir; the reservoir structure comprises a reservoir body type and a communication condition between the fracture holes;

Determining whether the water injection mode of each fracture-cavity unit of the target oil-gas reservoir is water injection oil displacement, water injection pressure maintaining, high-pressure water injection or unit water injection based on the scale, reservoir structure, residual dynamic reserve and stratum energy of the target oil-gas reservoir and by combining the gas-oil ratio; and then carrying out water injection development of the target oil and gas reservoir according to the determined water injection development mode;

Determining whether an improved water injection mode adopted by the seam hole unit after the water injection failure of the unit is injection and production direction adjustment, injection and production parameter adjustment, injection medium regulation and control or injection runner regulation and control based on a pattern of a gas injection well and a reservoir structure of the seam hole unit after the water injection failure of the target hydrocarbon reservoir unit; and then the water injection development of the fracture-cavity unit after the water injection failure of the target oil and gas reservoir unit is carried out according to the determined water injection improving mode.

According to the fracture-cavity carbonate hydrocarbon reservoir enhanced recovery method, preferably, determining the scale, reservoir structure, remaining dynamic reserves, and formation energy of the target hydrocarbon reservoir includes:

acquiring a water injection indication curve, an energy indication curve and a well test curve of a target oil and gas reservoir;

And determining the scale, the reservoir structure, the residual dynamic reserves and the stratum energy of the target hydrocarbon reservoir based on the water injection indication curve, the energy indication curve and the well test curve of the target hydrocarbon reservoir.

According to the method for improving recovery ratio of the fracture-cavity carbonate rock-hydrocarbon reservoir, preferably, determining whether the water injection mode of each fracture-cavity unit of the target hydrocarbon reservoir is water injection oil replacement, water injection pressure maintaining, high-pressure water injection or unit water injection based on the scale, reservoir structure, residual dynamic reserve and stratum energy of the target hydrocarbon reservoir and gas-oil ratio comprises:

combining the communication condition among the fracture holes of the target oil and gas reservoirs to respectively determine whether each fracture hole unit of the target oil and gas reservoir is a single-well fracture hole unit or a multi-well fracture hole unit;

For a multi-well fracture-cavity unit, adopting a unit water injection mode in a water injection development mode; the unit water injection mode is a mode of water injection development under the cooperation of a water injection well and a production well;

For a single well fracture-cavity unit, when the gas-oil ratio is smaller than 300m ³/t, if the single well is fast in decrease (the decrease in month exceeds 30%) and the recovery degree is low (not more than 10%) because the conventional water injection and acid pressure cannot realize the efficient expansion of the far well region, adopting a high-pressure water injection mode with the water injection pressure larger than 50MPa for the water injection development mode, otherwise adopting a water injection oil replacement mode for the water injection development mode with the reservoir body type being the karst cavity type;

For a single-well fracture-cavity unit, when the gas-oil ratio is more than 300m ³/t, the water injection development mode adopts a water injection pressure maintaining mode; the water injection pressure maintaining mode is a water injection mode which enables the oil reservoir pressure to be higher than the reservoir saturation pressure in the development process through water injection;

More preferably, the unit water injection mode adopts low-injection high-mining or seam injection hole mining;

more preferably, the water injection timing of the water injection pressure maintaining mode is not later than the time when the oil reservoir enters the solution gas flooding.

According to the method for improving recovery ratio of the fracture-cavity carbonate hydrocarbon reservoir, preferably, based on the injection well network and the reservoir structure of the fracture-cavity unit after the water injection failure of the target hydrocarbon reservoir unit, determining whether the improved water injection mode adopted by the fracture-cavity unit after the water injection failure of the unit is injection-production direction adjustment, injection-production parameter adjustment, injection medium regulation or injection runner regulation comprises:

for a fracture-cavity unit after water injection failure, the reservoir body type is a non-karst cavity type, if the well pattern is perfect (namely, the injection-production correspondence is satisfied) and dominant cracks develop (namely, cracks with good development opening property and good dredging property) the injection-production parameter adjustment mode is adopted for improving the water injection mode;

for the fracture-cavity unit after water injection failure, the reservoir type is non-karst cavity type, if the well pattern is imperfect (namely, the injection-production correspondence is not satisfied) or the storage control degree is low, the injection-production direction adjustment mode is adopted for improving the water injection mode;

for a fracture-cavity unit with a reservoir body type of karst cavity type after water injection failure, if the karst cavity is communicated with a well and a channeling channel is positioned at the middle lower part of the karst cavity, improving the water injection mode by adopting an injection medium regulation mode;

for a fracture-cavity unit after water injection failure, which is of a karst cavity type, if the karst cavity is communicated with a well and channeling is caused by fracture difference, an injection runner regulation and control mode is adopted for improving the water injection mode;

More preferably, the injection and production parameter adjustment comprises adjusting the injection rate and/or the planar adjustment injection and production ratio;

More preferably, the injection and production direction adjustment comprises a perfected well pattern and/or injection and production well adjustment;

more preferably, the injection medium conditioning comprises gas injection (e.g., nitrogen injection) or flexible gel injection or suspended particle + flexible gel injection;

More preferably, injection runner tuning includes injecting low density particles (capable of being suspended in formation water) +foam or foam gel.

According to the method for improving recovery efficiency of the fracture-cavity carbonate hydrocarbon reservoir, preferably, the method comprises the following steps: performing gas injection development on all or part of the fracture-cavity units in the target oil and gas reservoir;

More preferably, the gas injection development of all or part of the fracture-cavity units in the target hydrocarbon reservoir comprises: and selecting a fracture-cavity unit for gas injection development from the fracture-cavity units adopting water injection to replace oil, and performing single-well gas injection development.

In a specific embodiment, the following conditions are satisfied by the hole units for gas injection development selected in the process of selecting the hole units for gas injection development from the hole units for oil injection replacement:

The residual oil mode of part or all of the residual oil in the fracture-cavity unit accords with at least one of five typical residual oil modes suitable for gas injection development; wherein, the five typical residual oil modes suitable for gas injection development include: the method comprises the steps of (1) reservoir high-position residual oil, bottom water coning sealing residual oil, horizontal well upper residual oil, acid pressure communication peripheral seam hole bodies and interwell water injection sealing residual oil;

the accumulated oil yield is more than 5000 tons;

the wellbore and the reservoir body have good channel connectivity (i.e. no occurrence of reservoir collapse, crack closure, asphaltene blockage, mud production and fish-out);

the well mouth, the pipe column and the casing well cementation quality and the extrusion resistance of the production pipe column meet the requirement of gas injection construction;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions: the type of the reservoir body is cave type;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions: the water content rising type of the production well positioned in the fracture-cavity unit is a step rising type or a quick rising type, and the production well positioned in the fracture-cavity unit is provided with an effective production or long-term water self-injection;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions: medium formation energy-strong.

In a specific embodiment, a hole unit for gas injection development is selected from hole units for oil injection, and parameters for gas injection development of a single well are as follows in the process of gas injection development of a single well:

For a water injection oil replacement failure well, when the gas injection time is when the oil-water replacement rate is more than 0.2; for the well with water content rising period, the gas injection time is when the water content is more than 80%;

For a water injection oil replacement failure well, the gas injection mode is continuous gas injection; for the well in the water rising period, the gas injection mode is gas-water alternate injection;

For a water injection oil replacement failure well, the gas injection amount is 0.3-0.4PV in the early stage and 0.1PV in the later stage; for wells with a water lift, the gas injection is 1 time the water intrusion volume;

For the type of the reservoir body which is a cave type, the time of well stewing is 7-10 days; for the reservoir body type which is crack type, the well stewing time is 15-20 days;

The well opening system is a working system in normal production before gas injection development.

The technical scheme provided by the invention is that the fracture-cavity type carbonate hydrocarbon reservoir enhanced recovery technology is provided on the basis of deepening the knowledge of the fracture-cavity type carbonate hydrocarbon reservoir and defining the development mechanism of the fracture-cavity type carbonate hydrocarbon reservoir. The fracture-cavity type carbonate hydrocarbon reservoir enhanced recovery technology provided by the invention effectively solves the problems of low production benefit and short economic life of a production well of the fracture-cavity type carbonate hydrocarbon reservoir, and can be used for guiding the development and comprehensive treatment of the fracture-cavity type carbonate hydrocarbon reservoir.

Drawings

FIG. 1 is a graph of a well production curve.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.

By researching the pressure gradient, the flow speed and the flow rule of crude oil flowing in cracks with different dimensions, the method is as follows: crude oil exhibits a feature of fidaxy flow when flowing in a fracture with a fracture width of 100 μm or more, and the wider the fracture, the closer to free flow. The method is characterized in that: the pressure gradient and the flow velocity of the crude oil flowing in the crack with the width of more than 100 μm are obvious nonlinear relation; when the opening of the crack is smaller than 50 mu m, especially smaller than 10 mu m, the pressure gradient and the flow speed of the crude oil flow in the crack are in obvious linear relation, and the flow state of the crude oil flow is seepage, so that the flow capacity is poor. It was thus determined that a crack with a slit width above the center slit plays a decisive role in the crude oil flow, and that a narrow slit contributes less to the crude oil flow. The width of the crack has great influence on the flow rule of the oil-water two phases. When the seam width of the crack is more than 50 mu m, the oil-water relative permeability curve is nearly X-shaped, the influence of the crack on the oil-water flow is small, and the oil-water two-phase flow shows a free flow characteristic; and when the seam width of the crack is less than 50 mu m, the relative permeability of the water phase is upward convex, the relative permeability curve of the oil phase is downward concave, and the oil phase is discontinuous and prevents the movement of the water phase to a certain extent. The oil-water relative permeability curves under different seam widths further prove that the cracks with the seam widths above the center seam are main flow channels, and the flow capacity of the narrow seams is poor.

Experimental researches on the seam-hole system show that: in a single cave system, gravity is the most important factor influencing the flow and distribution of oil and water, and is influenced by gravity difference caused by oil-water density difference, water phase is always distributed below an oil phase interface, and along with the lifting of the water phase interface, the oil phase is continuously driven out of a karst cave. In the cave and hole system, under the action of gravity after the water phase enters the karst cave, the water phase is gathered at the bottom of the cave at first, and along with the increase of injected water, an oil-water interface is continuously lifted, and oil in the hole at the lower part is slowly driven out in the later period of exploitation; it follows that in the cavity + cavity system, the cavity is the most dominant flow space and further determines the key role of gravity in the flow process. In a crack communication dual-cavity system, bottom water enters an upper cavity from a bottom cavity through a crack, oil in the upper cavity is gradually driven out, and the oil-water flowing process in the cavity is similar to that in a single-cavity system. In summary, the fracture acts primarily as a flow channel within the slot-hole system. According to the oil-water distribution change in the water flooding process in the three seam-hole systems, the following can be known: gravity in the cavity is a main factor influencing flow and oil-water distribution, the holes mainly play a role in supplying liquid, and the cracks play a role in communicating channels. This rule is also demonstrated in a typical well development process: the oil pressure and the yield of a typical well are in a descending trend after production, and the descending slopes of the oil pressure and the yield at the earlier stage are basically consistent and relatively larger; after the pressure of the later stratum is reduced by 8-10MPa, the oil pressure keeps the early reduction rate and the yield reduction rate to be obviously slowed down, because the liquid supply amount is increased after the production pressure difference is increased in the later hole reservoir, and the yield slope is obviously slowed down (as shown in figure 1).

In the development process of the fracture-cavity carbonate hydrocarbon reservoir, the inventor provides a brand new fracture-cavity carbonate hydrocarbon reservoir recovery improvement method on the premise that gravity in a cavity is a main factor influencing flow and oil-water distribution, holes mainly play a role in supplying liquid and cracks play a role in communicating channels. The method can effectively solve the problems of low production benefit and short economic life of the production well of the prior fracture-cavity carbonate hydrocarbon reservoir, and improves the development effect of the fracture-cavity carbonate hydrocarbon reservoir.

The invention provides a method for improving recovery ratio of a fracture-cavity carbonate rock oil-gas reservoir, which comprises the following steps:

step S1: determining the scale, reservoir structure, remaining dynamic reserves, and formation energy of the target reservoir; the reservoir structure comprises a reservoir body type and a communication condition between the fracture holes;

Step S2: determining whether the water injection mode of each fracture-cavity unit of the target oil-gas reservoir is water injection oil displacement, water injection pressure maintaining, high-pressure water injection or unit water injection based on the scale, reservoir structure, residual dynamic reserve and stratum energy of the target oil-gas reservoir and by combining the gas-oil ratio; and then carrying out water injection development of the target oil and gas reservoir according to the determined water injection development mode;

Step S3: determining whether an improved water injection mode adopted by the seam hole unit after the water injection failure of the unit is injection and production direction adjustment, injection and production parameter adjustment, injection medium regulation and control or injection runner regulation and control based on a pattern of a gas injection well and a reservoir structure of the seam hole unit after the water injection failure of the target hydrocarbon reservoir unit; and then the water injection development of the fracture-cavity unit after the water injection failure of the target oil and gas reservoir unit is carried out according to the determined water injection improving mode.

In one embodiment, step S1 of determining the size, reservoir structure, remaining dynamic reserves, formation energy of the target reservoir includes:

step S11: acquiring a water injection indication curve, an energy indication curve and a well test curve of a target oil and gas reservoir;

step S12: and determining the scale, the reservoir structure, the residual dynamic reserves and the stratum energy of the target hydrocarbon reservoir based on the water injection indication curve, the energy indication curve and the well test curve of the target hydrocarbon reservoir.

According to the optimal technical scheme, the three-line four-dimensional research method is adopted for target oil and gas reservoir evaluation, namely, the water injection indication curve, the energy indication curve and the well test curve of the target oil and gas reservoir are utilized to determine the scale, the reservoir structure, the residual dynamic reserves and the stratum energy of the target oil and gas reservoir, so that the development of the target oil and gas reservoir is guided quantitatively, and the benefit development of the target oil and gas reservoir is realized. The water injection indication curve is a relation curve of accumulated water injection quantity and water injection pressure, can well reflect the change condition of water injection pressure along with the increase of accumulated water injection quantity in the water injection process, provides reliable basis for preliminary analysis of reservoir body types and scales, and is beneficial to realizing reservoir structure determination and single well residual dynamic reservoir volume determination. The energy indication curve is a relation curve of oil pressure and accumulated production fluid, and the descending trend of the oil pressure along with the accumulated production fluid in the production process can be reflected through the change of the slope of a line segment, so that the energy indication curve can be used for primarily judging the type of a reservoir body (belonging to a fracture type, a fracture hole type or a cave type (single hole and multiple holes)), and can also be used for determining the residual dynamic reserve, evaluating the stratum energy, the water body size and the like. The well test curve is a pressure and pressure derivative curve formed by processing well test monitoring data based on corresponding technologies and principles, and can reflect the real dynamic state of the stratum. The corresponding mode of the well test curve-fracture-cavity unit-dynamic characteristic can be established according to the type, the development condition and the seepage storage performance of the reservoir body in the fracture-cavity type carbonate reservoir stratum by combining the well test interpretation curve characteristic. Different well test curves have different stage characteristics, and different forms and curve positions of each stage correspond to reservoir types, reservoir properties and boundary reactions of the region where the well is located. Corresponding stratum parameters can be determined through a fracture-cavity well test curve equation, namely a fluctuation-pipe seepage coupling equation, and the residual dynamic reserve is judged. The purpose of quantitatively guiding the development of the target oil and gas reservoir can be achieved through comprehensive analysis of the water injection indication curve, the energy indication curve and the well test curve.

In one embodiment, step S2, determining whether the water injection mode of each hole unit of the target hydrocarbon reservoir is water injection for oil replacement, water injection for pressure maintaining, high pressure water injection or unit water injection based on the scale, reservoir structure, remaining dynamic reserves, and formation energy of the target hydrocarbon reservoir and gas-oil ratio includes:

combining the communication condition among the fracture holes of the target oil and gas reservoirs to respectively determine whether each fracture hole unit of the target oil and gas reservoir is a single-well fracture hole unit or a multi-well fracture hole unit;

For a multi-well fracture-cavity unit, adopting a unit water injection mode in a water injection development mode; the unit water injection mode is a mode of water injection development under the cooperation of a water injection well and a production well;

For a single well fracture-cavity unit, when the gas-oil ratio is smaller than 300m ³/t, if the single well is fast in decrease (the decrease in month exceeds 30%) and the recovery degree is low (not more than 10%) because the conventional water injection and acid pressure cannot realize the efficient expansion of the far well region, adopting a high-pressure water injection mode with the water injection pressure larger than 50MPa for the water injection development mode, otherwise adopting a water injection oil replacement mode for the water injection development mode with the reservoir body type being the karst cavity type;

For a single-well fracture-cavity unit, when the gas-oil ratio is more than 300m ³/t, the water injection development mode adopts a water injection pressure maintaining mode; the water injection pressure maintaining mode is a water injection mode which enables the oil reservoir pressure to be higher than the reservoir saturation pressure in the development process through water injection;

further, a unit water injection mode adopts low-injection high-mining or seam injection hole mining;

further, the water injection time of the water injection pressure maintaining mode is not later than the time of the oil reservoir entering the solution gas drive; furthermore, the time of the oil reservoir entering the solution gas drive is predicted based on the pressure measurement data and various indication curves of the oil well.

Different water injection modes have different functions, and four different water injection modes, namely oil replacement, water injection pressure maintaining, high-pressure water injection and unit water injection, suitable for water injection development of the fracture-cavity carbonate rock oil-gas reservoir are explored and formed according to the fracture-cavity carbonate rock oil-gas reservoir characteristics and the difference of gas-oil ratios. The fracture-cavity type carbonate rock oil and gas reservoir can be divided into a single-well fracture-cavity unit and a multi-well fracture-cavity unit according to the communication condition among the fracture cavities in the reservoir body. The multi-well fracture-cavity unit water injection development can adopt a unit water injection mode to transversely or longitudinally displace residual oil among wells; in the water injection development process, the water injection well is a well with poor development degree of the reservoir body, the production well is a well with good development degree of the reservoir body, and the modes of low injection high production and hole injection production can be adopted. The single-well fracture-cavity unit adopts natural energy to naturally mine at the initial stage, the natural energy gradually weakens along with the progress of mining, the self-injection production cannot be realized, and the well is restarted after the energy supplementing water injection is completed. For a fracture-cavity type carbonate rock oil-gas reservoir with the gas-oil ratio smaller than 300m ³/t, if the reservoir body type is karst cavity type, and no single well is quickly decreased and the production degree is low because the conventional water injection and acid pressure can not realize the high-efficiency capacity expansion of a far well area, the water injection and oil displacement mode can be adopted for water injection development; the karst cave type reservoir body usually has the phenomena of emptying, leakage or overflow in the well drilling process, and the seismic section of the karst cave type reservoir body has an obvious beaded structure and has strong reflection. When the water injection and oil replacement mode is adopted to carry out water injection development on the fracture-cavity unit with the reservoir body type of karst cavity type, the water injection time and the well-flushing time are required to be mastered. For the fracture-cavity type carbonate rock-oil-gas reservoir with the gas-oil ratio smaller than 300m ³/t, if the single well is quickly decreased and the extraction degree is low because the conventional water injection and acid fracturing can not realize the high-efficiency capacity expansion of the far well region, the high-pressure water injection technology can be adopted, the water injection pressure is larger than 50MPa, and the high-pressure injected water is used as an energy carrier to break through the isolated fracture-cavity barrier so as to realize the effective capacity expansion. The volatile oil reservoir with the gas-oil ratio of more than 300m ³/t has the problems of rapid yield decrease and high difficulty in stable yield, and the pressure of the oil reservoir is kept higher than the saturation pressure of the oil reservoir during exploitation, so that low recovery ratio caused by formation degassing is avoided; and selecting proper water injection time for the oil reservoir units, and judging the time of the oil reservoir units entering the dissolved gas drive by combining pressure measurement data and various indication curves of the oil well, so as to perform water injection and pressure maintaining in time.

In an embodiment, step S3, based on the injection pattern and the reservoir structure of the hole-seam unit after the water injection failure of the target hydrocarbon reservoir unit, determining whether the improved water injection mode adopted by the hole-seam unit after the water injection failure of the unit is injection-production direction adjustment, injection-production parameter adjustment, injection medium regulation or injection runner regulation includes:

for a fracture-cavity unit after water injection failure, the reservoir body type is a non-karst cavity type, if the well pattern is perfect (namely, the injection-production correspondence is satisfied) and dominant cracks develop (namely, cracks with good development opening property and good dredging property) the injection-production parameter adjustment mode is adopted for improving the water injection mode;

for the fracture-cavity unit after water injection failure, the reservoir type is non-karst cavity type, if the well pattern is imperfect (namely, the injection-production correspondence is not satisfied) or the storage control degree is low, the injection-production direction adjustment mode is adopted for improving the water injection mode;

for a fracture-cavity unit with a reservoir body type of karst cavity type after water injection failure, if the karst cavity is communicated with a well and a channeling channel is positioned at the middle lower part of the karst cavity, improving the water injection mode by adopting an injection medium regulation mode;

for a fracture-cavity unit after water injection failure, which is of a karst cavity type, if the karst cavity is communicated with a well and channeling is caused by fracture difference, an injection runner regulation and control mode is adopted for improving the water injection mode;

further, injection and production parameter adjustment comprises adjustment of water injection quantity and/or plane adjustment of injection and production ratio;

further, injection and production direction adjustment comprises well pattern perfecting (realizing injection and production correspondence) and/or injection and production well adjustment;

further, injection medium conditioning includes gas injection (e.g., nitrogen injection) or ductile gel injection or suspended particle + ductile gel injection;

further, injection runner tuning includes injecting low density particles (capable of being suspended in formation water) +foam or foam gel.

Aiming at the multi-well fracture-cavity unit of the fracture-cavity carbonate rock-oil-gas reservoir, the inventor performs the study on the communication condition, the distribution of residual oil and the mechanism among the fracture-cavities, and then forms four schemes for improving water injection after the water injection failure of the unit, wherein the schemes are as follows: the injection and production direction adjusting scheme, the injection and production parameter adjusting scheme, the injection and production medium adjusting scheme and the injection and production flow channel adjusting scheme belong to the injection and production adjusting technology, and the injection and production medium adjusting scheme and the injection and production flow channel adjusting scheme belong to the injection and production adjusting technology. The purpose of improving the water injection effect is achieved by adopting corresponding schemes under different applicable conditions, as shown in table 1. The reserve utilization scale can be increased to a greater extent through injection and production parameter adjustment and injection and production direction adjustment, and residual oil at a non-dominant channel is further displaced, so that further digging of a communication well group after unit water injection failure is facilitated. The injection medium is adjusted by utilizing the residual oil at the top seam hole position which can not be reached by injection gas and gel with injection water, and simultaneously plugging a water channeling channel formed in the earlier stage. The injection runner adjustment can also play the role, the characteristics of different media are exerted through density difference, the replacement of oil and injection media is completed, the dynamic profile control is completed, and the recovery ratio is improved.

TABLE 1

In one embodiment, step S4, performing gas injection development on all or part of the fracture-cavity units in the target hydrocarbon reservoir;

Further, step S4, performing gas injection development on all or part of the fracture-cavity units in the target hydrocarbon reservoir includes:

And selecting a fracture-cavity unit for gas injection development from the fracture-cavity units adopting water injection to replace oil, and performing single-well gas injection development.

In an embodiment, the following conditions are satisfied by the hole units for gas injection development selected in the process of selecting the hole units for gas injection development from the hole units for oil injection replacement:

The residual oil mode of part or all of the residual oil in the fracture-cavity unit accords with at least one of five typical residual oil modes suitable for gas injection development; wherein, the five typical residual oil modes suitable for gas injection development include: the method comprises the steps of (1) reservoir high-position residual oil, bottom water coning sealing residual oil, horizontal well upper residual oil, acid pressure communication peripheral seam hole bodies and interwell water injection sealing residual oil;

the accumulated oil yield is more than 5000 tons;

the wellbore and the reservoir body have good channel connectivity (i.e. no occurrence of reservoir collapse, crack closure, asphaltene blockage, mud production and fish-out);

the well mouth, the pipe column and the casing well cementation quality and the extrusion resistance of the production pipe column meet the requirement of gas injection construction;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions:

The type of the reservoir body is cave type;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions:

the water content rising type of the production well positioned in the fracture-cavity unit is a step rising type or a quick rising type, and the production well positioned in the fracture-cavity unit is provided with an effective production or long-term water self-injection;

Further, the selected hole-injecting unit for gas injection development also satisfies the following conditions:

medium formation energy-strong.

In an embodiment, a hole unit for gas injection development is selected from hole units for oil injection, and parameters for gas injection development of a single well are as follows in a single well gas injection development process:

For a water injection oil replacement failure well, when the gas injection time is when the oil-water replacement rate is more than 0.2; for the well with water content rising period, the gas injection time is when the water content is more than 80%;

For a water injection oil replacement failure well, the gas injection mode is continuous gas injection; for the well in the water rising period, the gas injection mode is gas-water alternate injection;

For a water injection oil replacement failure well, the gas injection amount is 0.3-0.4PV in the early stage and 0.1PV in the later stage; for wells with a water lift, the gas injection is 1 time the water intrusion volume;

For the type of the reservoir body which is a cave type, the time of well stewing is 7-10 days; for the reservoir body type which is crack type, the well stewing time is 15-20 days;

The well opening system is a working system in normal production before gas injection development.

According to the characteristics of the fracture-cavity carbonate rock oil and gas reservoir, the gas injection development technology is mainly divided into single-well gas injection development and well group gas injection development. The inventor develops differential scheme researches of gas injection of fracture-cavity carbonate hydrocarbon reservoirs of different karst geological backgrounds based on oil reservoir fine description, determines main control factors influencing the gas injection effect of the fracture-cavity carbonate hydrocarbon reservoirs, and optimizes gas injection time, gas injection parameters and the like; and the classification evaluation research of the gas injection development mode of the hydrocarbon reservoir is carried out by combining different geological features of the fracture-cavity carbonate rock hydrocarbon reservoir. The single well gas injection development is mainly aimed at a single well fracture-cavity unit with relative constant volume, and the injected gas is subjected to gravity differential displacement to remove residual oil at the top which is not affected by water injection by means of non-miscible phase, artificial gas top drive, expansion and viscosity reduction, interfacial tension reduction, dissolution extraction and the like. The well group gas injection development mainly aims at a multi-well fracture-cavity unit with two or more communication wells, and is characterized in that residual oil among wells is injected through injection wells, an oil reservoir flow field is changed, bottom water coning is inhibited, stratum energy is supplemented, and discontinuous injection is generally carried out in the implementation process. On the basis of defining the single-well gas injection development action mechanism, the inventor combines field tests to develop optimization researches on 5 gas injection and production parameters such as gas injection time, gas injection mode, gas injection amount, well-stewed time, well-open working system and the like, and determines a single-well gas injection development technical means of the fracture-cavity unit, and particularly see table 2. According to the characteristics of the fracture-cavity carbonate rock oil and gas reservoir, the inventor combines field tests, considers the influence of 7 small factors in the aspects of geology, development and engineering 3, and determines a single-well gas injection development well selection principle. The wells with high upper reservoir development, high cumulative production, strong water energy, good cone pressing effect, large uncovering depth and deviating from the reservoir are mainly preferred, and are specifically shown in table 3.

TABLE 2

TABLE 3 Table 3

The main medium of the current gas injection development is nitrogen, and the purity can reach 99 percent.

Application example

The application example applies the fracture-cavity carbonate hydrocarbon reservoir enhanced recovery method provided by the detailed description of the invention to develop a fracture-cavity carbonate hydrocarbon reservoir.

The water injection and gas injection development of the target fracture-cavity carbonate hydrocarbon reservoir achieves a good development effect.

In the water injection development process of the target fracture-cavity carbonate rock-oil-gas reservoir, 144 water injection ports of a single well and 58 water injection ports of a well group are implemented, water is injected for 879.6 thousands of times in three years, oil is produced for 152.32 thousands of tons, the average annual oil increase is 38 thousands of tons, and the water injection amount and the oil increase amount are all in an ascending trend.

In the water injection development process of the target fracture-cavity type carbonate rock-oil-gas reservoir, 36 gas injection ports are implemented, wherein 13 gas injection ports of a single well are used for injecting gas, 23 gas injection ports of a unit are used for injecting gas, 8953 square and 13.24 ten thousand tons of oil are added.

The target fracture-cavity type carbonate rock oil-gas reservoir has the functions of three years of water injection, gas injection, oil increment of 165.56 ten thousand tons and annual average oil increment of 41.34 ten thousand tons.

The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims (11)

1. A method for enhancing recovery efficiency of a fracture-cavity carbonate hydrocarbon reservoir, wherein the method comprises the following steps:

Determining the scale, reservoir structure, remaining dynamic reserves, and formation energy of the target reservoir; the reservoir structure comprises a reservoir body type and a communication condition between the fracture holes;

Determining whether the water injection mode of each fracture-cavity unit of the target oil-gas reservoir is water injection oil displacement, water injection pressure maintaining, high-pressure water injection or unit water injection based on the scale, reservoir structure, residual dynamic reserve and stratum energy of the target oil-gas reservoir and by combining the gas-oil ratio; and then carrying out water injection development of the target oil and gas reservoir according to the determined water injection development mode;

Determining whether an improved water injection mode adopted by the seam hole unit after the water injection failure of the unit is injection and production direction adjustment, injection and production parameter adjustment, injection medium regulation and control or injection runner regulation and control based on a pattern of a gas injection well and a reservoir structure of the seam hole unit after the water injection failure of the target hydrocarbon reservoir unit; and then the water injection development of the fracture-cavity unit after the water injection failure of the target oil and gas reservoir unit is carried out according to the determined water injection improving mode.

2. The method of claim 1, wherein determining the size of the target reservoir, reservoir structure, remaining dynamic reserves, formation energy comprises:

acquiring a water injection indication curve, an energy indication curve and a well test curve of a target oil and gas reservoir;

And determining the scale, the reservoir structure, the residual dynamic reserves and the stratum energy of the target hydrocarbon reservoir based on the water injection indication curve, the energy indication curve and the well test curve of the target hydrocarbon reservoir.

3. The method of claim 1, wherein determining whether the water injection mode of each fracture-hole unit of the target reservoir is water injection for oil replacement, water injection pressure maintaining, high pressure water injection or unit water injection based on the size of the target reservoir, reservoir structure, remaining dynamic reserves, formation energy size, in combination with gas-to-oil ratio comprises:

combining the communication condition among the fracture holes of the target oil and gas reservoirs to respectively determine whether each fracture hole unit of the target oil and gas reservoir is a single-well fracture hole unit or a multi-well fracture hole unit;

For a multi-well fracture-cavity unit, adopting a unit water injection mode in a water injection development mode; the unit water injection mode is a mode of water injection development under the cooperation of a water injection well and a production well;

For a single well fracture-cavity unit, when the gas-oil ratio is smaller than 300m ³/t, if the single well is fast in descending and low in production degree due to the fact that conventional water injection and acid pressure cannot realize high-efficiency capacity expansion of a far well region, a water injection development mode adopts a high-pressure water injection mode with water injection pressure larger than 50MPa, otherwise, a water injection oil replacement mode is adopted for a water injection development mode with a reservoir body type of karst cavity;

For a single-well fracture-cavity unit, when the gas-oil ratio is more than 300m ³/t, the water injection development mode adopts a water injection pressure maintaining mode; the water injection pressure maintaining mode is a water injection mode which enables the oil reservoir pressure to be higher than the reservoir saturation pressure in the development process through water injection.

4. The method of claim 3, wherein,

The unit water injection mode adopts low-injection high-mining or seam injection hole mining;

The water injection timing of the water injection pressure maintaining mode is not later than the time of the oil reservoir entering the dissolved gas flooding.

5. The method of claim 1, wherein determining whether the improved water injection mode adopted by the fracture-cavity unit after the water injection failure of the unit is injection-production direction adjustment, injection-production parameter adjustment, injection medium regulation or injection runner regulation based on the injection pattern and the reservoir structure of the fracture-cavity unit after the water injection failure of the target hydrocarbon reservoir unit comprises:

For a fracture-cavity unit after water injection failure, the reservoir body type is non-karst cavity type, if the well pattern is perfect and dominant cracks develop, the water injection mode is improved by adopting a water injection and production parameter adjustment mode;

for the fracture-cavity unit after water injection failure, the reservoir type is non-karst cavity type, if the well pattern is imperfect or the storage control degree is low, the fracture-cavity unit after water injection failure is improved, and the water injection mode adopts the injection-production direction adjustment mode;

for a fracture-cavity unit with a reservoir body type of karst cavity type after water injection failure, if the karst cavity is communicated with a well and a channeling channel is positioned at the middle lower part of the karst cavity, improving the water injection mode by adopting an injection medium regulation mode;

For the fracture-cavity unit after the water injection failure, the reservoir body type is karst cavity type, if the karst cavity is communicated with the well and the channeling is caused by the fracture difference, the water injection mode is improved by adopting an injection runner regulation mode.

6. The method of claim 5, wherein,

The injection and production parameter adjustment comprises the adjustment of water injection quantity and/or the adjustment of injection and production ratio in a plane;

The injection and production direction adjustment comprises well pattern perfecting and/or injection and production well adjustment;

the injection medium regulation comprises gas injection, toughness gel injection, suspension particle injection and toughness gel injection;

Injection flow channel regulation includes injecting low density particles + foam or injecting foam gel.

7. The method according to claim 1, wherein the method comprises: and selecting a fracture-cavity unit for gas injection development from the fracture-cavity units adopting water injection to replace oil, and performing single-well gas injection development.

8. The method of claim 7, wherein the gas injection development slit hole units selected in the process of selecting the gas injection development slit hole units from the slit hole units adopting water injection for oil substitution satisfy the following conditions:

The residual oil mode of part or all of the residual oil in the fracture-cavity unit accords with at least one of five typical residual oil modes suitable for gas injection development; wherein, the five typical residual oil modes suitable for gas injection development include: the method comprises the steps of (1) reservoir high-position residual oil, bottom water coning sealing residual oil, horizontal well upper residual oil, acid pressure communication peripheral seam hole bodies and interwell water injection sealing residual oil;

the accumulated oil yield is more than 5000 tons;

The pit shaft and the reservoir body have good channel communication;

The well mouth, the pipe column and the casing well cementation quality and the extrusion resistance of the production pipe column meet the requirement of gas injection construction.

9. The method of claim 8, wherein the selected hole cell for gas injection development further satisfies:

the reservoir type is a cave type.

10. The method of claim 8, wherein the selected hole cell for gas injection development further satisfies:

The water content rising type of the production well positioned in the fracture-cavity unit is a step rising type or a quick rising type, and the production well positioned in the fracture-cavity unit is provided with an effective or long-term water-carrying self-injection.

11. The method of claim 7, wherein the single well gas injection development parameters are as follows in the single well gas injection development process by selecting a hole cell for gas injection development from hole cells using water injection to replace oil:

For a water injection oil replacement failure well, when the gas injection time is when the oil-water replacement rate is more than 0.2; for the well with water content rising period, the gas injection time is when the water content is more than 80%;

For a water injection oil replacement failure well, the gas injection mode is continuous gas injection; for the well in the water rising period, the gas injection mode is gas-water alternate injection;

For a water injection oil replacement failure well, the gas injection amount is 0.3-0.4PV in the early stage and 0.1PV in the later stage; for wells with a water lift, the gas injection is 1 time the water intrusion volume;

For the type of the reservoir body which is a cave type, the time of well stewing is 7-10 days; for the reservoir body type which is crack type, the well stewing time is 15-20 days;

The well opening system is a working system in normal production before gas injection development.