CN112081560A

CN112081560A - Development method of deep-sea high-temperature overpressure gas reservoir

Info

Publication number: CN112081560A
Application number: CN202010903572.6A
Authority: CN
Inventors: 王璐; 何勇明; 刘名名; 金鑫; 黄亮; 徐兴丽; 凌晓杰; 谢汪洋
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2020-09-01
Filing date: 2020-09-01
Publication date: 2020-12-15
Anticipated expiration: 2040-09-01
Also published as: CN112081560B

Abstract

The invention belongs to the technical field of natural gas development, and discloses a method for developing an offshore deep high-temperature overpressure gas reservoir, which comprises the following steps: determining the gas production capacity and influencing factors of the target area gas reservoir; determining the influence of different types of water sources on gas reservoir development, and judging the influence of different water sources on different water-cut gas wells of the gas reservoir in the target area; determining the change rule of the reservoir characteristic parameters after the gas reservoir breaks through water through analyzing the experimental result; determining the development strategy of the gas reservoir and the boundary of effective development key parameters, generating a development scheme, and developing the deep offshore high-temperature overpressure gas reservoir. The invention determines the effective development strategy and key parameter limit of the research block by deeply researching the seepage mechanism and the failure rule of the gas reservoir, the water break mechanism and the change of the key parameters of the reservoir after water break, and based on the research results of the physical simulation experiment and the mathematical model, thereby realizing the aims of high-efficiency development and long-term stable production of the gas reservoir.

Description

Development method of deep-sea high-temperature overpressure gas reservoir

Technical Field

The invention belongs to the technical field of natural gas development, and particularly relates to a method for developing an offshore deep high-temperature overpressure gas reservoir.

Background

Currently, an abnormally high pressure gas reservoir is one in which the pressure of the gas reservoir is higher than the hydrostatic pressure and the pressure coefficient is greater than 1.2. Because the pressure coefficient of the abnormal high-pressure gas reservoir is high, the pressure coefficient of part of the gas reservoir even reaches more than 2.0, in order to safely develop the abnormal high-pressure gas reservoir, a production well of the existing exploitation method needs to adopt a multi-casing sequence, high-material pipes and gas exploitation equipment, the safety level of a well head and ground equipment is greatly improved, the investment of a single well is about 3 times that of a conventional well, the exploitation investment is greatly increased, and the part of abnormal high-pressure natural gas resources are difficult to economically and effectively use. Because the reservoir temperature and pressure are extremely high, no relevant research for simulating the physical simulation experiment under the high-temperature and high-pressure conditions exists; (2) high CO content in natural gas component₂CO in the gas component has not been taken into consideration₂The influence of the content on the micro-seepage mechanism and macro-production characteristics; (3) the gas reservoir gas well is characterized in that water is produced in part of gas wells at the initial stage of testing, and in the production process, a plurality of gas wells produce water in different degrees, so that the water invasion mechanism is very complex, the gas wells have various water source types and unclear sources, the research of corresponding simulation experiments aiming at water source identification is not carried out, and the prior art does not aim at a deep offshore deep layer high-temperature overpressure gas reservoir development method.

Through the above analysis, the problems and defects of the prior art are as follows: the prior art does not aim at a development method of a deep high-temperature overpressure gas reservoir on the sea.

The difficulty in solving the above problems and defects is:

(1) the deep oil and gas reservoir is buried deeply (> 4500m), the temperature and pressure conditions are extremely high, and the conventional experimental device and experimental method are difficult to completely simulate the temperature and pressure conditions of an actual reservoir, so that the experimental result is different from the actual condition.

(2) Water saturation of deep hydrocarbon reservoir and CO in natural gas component₂The content difference is large, so that the seepage mechanism of the gas reservoir is very complex, and different water saturation conditions and different CO can be simulated₂The difficulty of physical simulation experiment research under the content condition is high.

(3) The water-breakthrough characteristics of the deep high-temperature and overpressure gas reservoir part in the production process of the gas well are greatly different, the water breakthrough mechanism is unclear, the influence on the productivity and the recovery ratio of the gas well after water breakthrough is difficult to determine, and the identification difficulty of different types of gas well water sources is high.

(4) The deep high-temperature overpressure gas reservoir can induce complex water-rock reaction for long-term gas-water CO-production, and the high-content CO2 can change the physical and chemical properties of formation water, so that the difficulty in evaluating the multiple damage mechanism of the reservoir after water breakthrough and the influence of the multiple damage mechanism on the gas well productivity is high.

(5) High temperature, high pressure, low permeability and water saturation and CO for such gas reservoirs₂The content difference is large, and the like, so that the key parameters for effective development are determined, and the corresponding efficient development technical policy and scheme are difficult to formulate.

The significance of solving the problems and the defects is as follows: (1) the mechanism is a complex seepage mechanism for revealing deep high-temperature overpressure gas reservoirs; (2) the application aspect is the establishment of an efficient development scheme for guiding the gas reservoir.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for developing an offshore deep high-temperature overpressure gas reservoir.

The invention is realized in such a way that the method for developing the offshore deep high-temperature overpressure gas reservoir comprises the following steps:

step one, setting different initial water saturation and different CO₂Content, setting different displacement pressure differences for the core respectively, and discharging according to the core outletDetermining the seepage capability of each rock core by the gas flow after the end is stabilized, and comparing and analyzing the initial water saturation difference and CO in the gas component₂The influence of the content difference on the single-phase seepage capability and the seepage rule of the gas determines the gas production capability and the influence factors of the target area gas reservoir;

simulating reservoirs without bottom water and with low water saturation as reference standards through depletion development seepage experiments, respectively performing a bottom water reservoir water breakthrough mechanism experiment and a high water content reservoir water breakthrough mechanism experiment, determining the influence of different types of water sources on gas reservoir development under different production conditions by analyzing the dynamic change rules of production parameters such as pressure, gas production rate, water-gas ratio, extraction degree and the like in the experiment process, and judging the influence of different types of water sources on different water breakthrough gas wells of the target gas reservoir on which water sources are influenced;

performing water drive experiments of different degrees on the natural rock core, simulating different stages of gas well water production, respectively measuring mineral content, pore structure characteristics and permeability after each water drive experiment is finished, and determining the change rule of the reservoir characteristic parameters after the gas reservoir water breakthrough by analyzing the experiment results;

and step four, determining a development strategy of the gas reservoir and the boundary of effective development key parameters based on the influence factors and the parameter change rules determined in the steps one to three, generating a development scheme, and developing the deep offshore high-temperature overpressure gas reservoir.

Further, the first step comprises:

(1) carrying out seepage experiments under different water-containing conditions;

(1.1) cleaning and drying the prepared rock core for 8 hours to obtain a dry weight, and measuring basic physical property parameters of the rock core, including length, diameter, porosity and permeability;

(1.2) putting the dry rock core into an ultrahigh-temperature high-pressure multifunctional rock core displacement experimental device for sealing, heating the rock core holder by using a heating belt, and stabilizing for 8 hours after the rock core holder is heated to 190 ℃;

(1.3) confining pressure is applied to the rock core to 5MPa by using a confining pressure pump, a displacement pump is started to displace an intermediate container of gas, and the confining pressure and the flow pressure of a rock core system are synchronously increased; when the gas in the intermediate container is used up, supplementing gas to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to the flowing pressure;

(1.4) when the confining pressure is increased to 95MPa, the flow pressure is increased to 90MPa, the upstream pressure and the downstream pressure are kept stable, different back pressures are respectively set through a back pressure pump and a back pressure valve, different displacement pressure differences are simulated to carry out a displacement experiment, the gas flow under the different displacement pressure differences is measured after the gas flow at the outlet end is stable, and a gas flow-experiment pressure difference curve graph is drawn;

(1.5) preparing standard saline water with related mineralization according to analysis data of the gas reservoir formation water composition of the target area, adding the saline water into an intermediate container, pressurizing to 90MPa, and connecting to an experimental device;

(1.6) respectively controlling a gas intermediate container and a water intermediate container by using two pumps of a double-plunger displacement pump, setting different displacement flows according to the permeability of a rock core, injecting gas and water into a rock sample according to the set proportion of 30%, 40%, 50%, 60% and 70% by adopting a steady state method, measuring the pressure difference between an inlet and an outlet and the gas flow after the flow is stable, and drawing a gas flow-experimental pressure difference curve chart;

(2) carrying out different CO₂A content infiltration experiment;

(2.1) cleaning and drying the prepared rock core for 8 hours to obtain a dry weight, and measuring basic physical property parameters of the rock core, including length, diameter, porosity and permeability;

(2.2) putting the dry rock core into an experimental device for sealing, heating the rock core holder by using a heating belt, and stabilizing for 8 hours after the temperature is raised to 190 ℃; firstly, confining pressure is applied to a rock core to be 5MPa by using a confining pressure pump, a displacement pump is started to displace an intermediate container filled with water, and the confining pressure and the flow pressure of a rock core system are synchronously increased;

(2.3) when the saline water in the intermediate container is used up, supplementing the saline water to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to flowing pressure;

(2.4) when the confining pressure is increased to 95MPa, the flow pressure is increased to 90MPa, the upstream pressure and the downstream pressure are kept stable, the saturation of the bound water under the conditions of high temperature and overpressure is established in a gas-driven water mode, and the rock core is displaced in the positive direction in the displacement process until water is no longer produced at the outlet end;

(2.5) keeping the upstream pressure unchanged, respectively setting different back pressures through a back pressure pump and a back pressure valve, simulating different displacement pressure differences to perform a displacement experiment, measuring the gas flow under the different displacement pressure differences after the gas flow at the outlet end is stable, and drawing a gas flow-experiment pressure difference curve chart;

(2.6) adding N₂And CO₂Adding the mixture into an intermediate container according to the proportion of the experimental design, namely 14%, 28%, 42%, 56% and 70%, pressurizing to 90MPa, and then connecting into an experimental device;

(2.7) before displacement, the upstream and downstream valves are closed to trap water and CO in the core₂And after full contact, carrying out displacement experiments under different displacement differential pressures, and drawing a gas flow-experiment differential pressure curve chart.

Further, the second step comprises:

1) carrying out a failure development seepage experiment;

2) experiment of water breakthrough mechanism of edge-bottom water reservoir

3) Carrying out water breakthrough mechanism experiment on high-water-content reservoir

4) Determining a critical movable water saturation;

5) acquiring dynamic change rules of production parameters of pressure, gas production, water-gas ratio and extraction degree based on the steps 1) to 4); analyzing the influence of the pressure difference on the failure mining dynamic law; analyzing pressure difference and water body dissolved CO₂Influence on water breakthrough and production characteristics; analyzing the influence of the pressure difference and the initial water-containing condition on water breakthrough and production characteristics; predicting the critical movable water saturation of the target area gas reservoir; and determining the water breakthrough mechanisms of different water breakthrough gas wells of the target gas reservoir.

Further, in step 1), the performing a failure development seepage experiment comprises:

1.1) cleaning and drying the prepared rock core for 8 hours to obtain dry weight, measuring basic physical property parameters related to the length, diameter, porosity and permeability of the rock core, and calculating the overall physical property of the spliced long rock core;

1.2) putting the long rock core saturated with the bound water into a full-simulation experiment device for sealing, heating the rock core holder by using a heating belt, and stabilizing for 8 hours after the heating is carried out to 190 ℃;

1.3) confining pressure is applied to the rock core to 5MPa by using a confining pressure pump, a displacement pump is started to displace an intermediate container of gas, and the confining pressure and the flow pressure of a rock core system are synchronously increased; when the gas in the intermediate container is used up, supplementing gas to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to the flowing pressure;

1.5) when the confining pressure is increased to 95MPa, the flowing pressure is increased to 90MPa, and when the upstream pressure and the downstream pressure are stable, the core system reaches an initial formation temperature and pressure system; and closing the upstream air inlet valve, opening the downstream air outlet valve, respectively setting different back pressures through the back pressure pump and the back pressure valve, simulating different exhaustion pressure differences to perform exhaustion development experiments, and recording the change data of upstream pressure, downstream pressure and gas production rate in real time.

Further, in the step 2), the performing of the water breakthrough mechanism experiment of the bottom water reservoir comprises:

2.1) cleaning and drying the prepared rock core for 8 hours to obtain a dry weight, measuring the length, diameter, porosity and permeability of the rock core, and calculating the overall physical properties of the spliced long rock core;

2.2) putting the long rock core saturated with the bound water into a full-simulation experiment device for sealing, heating the rock core holder by using a heating belt, and stabilizing for 8 hours after the temperature is 190 ℃; injecting prepared brine into a high-pressure intermediate container, and then preparing CO₂Gas samples with the content of 35 percent and 70 percent are excessively injected into a high-pressure intermediate container;

2.3) wrapping an electric heating sleeve in the intermediate container, heating to 190 ℃, connecting the intermediate container to a booster pump, pressurizing to 90MPa in a constant pressure mode, maintaining the pressure, standing for 24 hours, and enabling water and CO to react₂Fully contacting;

2.4) after the system is stabilized, opening a top valve, emptying undissolved redundant gas in the intermediate container, closing the valve when formation water flows out, pressurizing the pressure of the intermediate container to 90MPa by using a booster pump, and connecting the intermediate container into an experimental device to be used as a simulated edge bottom water body;

2.5) confining pressure is applied to the rock core to 5MPa by using a confining pressure pump, then a displacement pump is started to displace an intermediate container of gas, and the confining pressure and the flow pressure of a rock core system are synchronously increased, when the gas in the intermediate container is used up, the intermediate container is supplemented with gas, a pressurizing system is used for pressurizing the intermediate container, and the intermediate container is connected to the experimental device again after being pressurized to the flow pressure;

2.6) when confining pressure increases to 95MPa, the flowing pressure increases to 90MPa, when upper reaches and low reaches pressure reach the stability, close upstream air inlet valve, open upstream water inlet valve and low reaches liquid outlet valve, set up different back pressures through back pressure pump and back pressure valve respectively, the different exhaustion pressure differential of simulation carries out the exhaustion development experiment under the limit bottom water condition, real-time recording upper and lower stream pressure and gas production, water production change data.

Further, in the step 3), the performing of the water breakthrough mechanism experiment of the high-water-content reservoir comprises the following steps:

3.1) cleaning and drying the prepared rock core for 8 hours to obtain dry weight, measuring the length, diameter, porosity and permeability of the rock core, and calculating the overall physical properties of the spliced long rock core;

3.2) placing the long core with unsaturated water into an experimental device for sealing, heating the core holder by using a heating belt, and stabilizing for 8 hours after the core holder is heated to 190 ℃;

3.3) confining pressure is applied to the rock core to 5MPa by using a confining pressure pump, a displacement pump is started to displace an intermediate container filled with water, and the confining pressure and the flow pressure of a rock core system are synchronously increased; when the saline water in the intermediate container is used up, supplementing the saline water to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to flowing pressure;

3.4) when the confining pressure is increased to 95MPa, the flow pressure is increased to 90MPa, when the upstream pressure and the downstream pressure are stable, two pumps of the double-plunger displacement pump are used for respectively controlling the gas intermediate container and the water intermediate container, corresponding displacement flow is set for displacement according to the designed gas-water ratio, namely 35% and 70%, and the displacement is stopped when the gas-water ratio at the outlet end reaches the designed ratio;

3.5) closing an upstream air inlet valve, opening a downstream air outlet valve, respectively setting different back pressures through a back pressure pump and a back pressure valve, simulating different exhaustion pressure differences to carry out exhaustion development experiments, and recording the change data of upstream and downstream pressures, the gas yield and the water yield in real time.

Further, in step 4), the determining the critical movable water saturation comprises:

4.1) obtaining Nuclear magnetic resonance T under different displacement experiments₂Drawing movable water identification charts of reservoirs with different physical properties by combining the basic physical properties of the core subjected to the nuclear magnetic resonance test;

4.2) determining the critical water saturation range of the reservoir by combining the physical property parameter range of the reservoir in the target area;

and 4.3) determining the original water saturation and physical property of each stratum by combining single well logging interpretation results, and judging whether the reservoir contains movable water.

Further, the third step includes:

determining the change of key parameters of a microscopic reservoir after water breakthrough;

firstly, cleaning and drying a prepared rock core for 8 hours to obtain dry weight; cutting about 50g of sample on the core, grinding to a particle size of less than 40 μm and weighing; separating clay minerals with particle size less than 10 μm by suspension method, and weighing to obtain total amount of clay minerals;

secondly, measuring the content of each non-clay mineral by adopting a K value method of powder XRD; recording the total amount of clay minerals and the content of each non-clay mineral, and calculating the relative content of the clay minerals and the common non-clay minerals; extracting clay minerals with the particle size of less than 2 mu m and clay sample smear samples by adopting a centrifugal method, and sequentially carrying out natural XRD (X-ray diffraction) measurement, EG saturation sheet XRD measurement and high-temperature sheet XRD measurement to determine the relative content of the unusual clay minerals;

cutting a sample on the rock core into 10mm multiplied by 5mm, and taking a representative and flat fresh end face as an analysis face; naturally drying the sample at room temperature, blowing off scraps and dust on the surface of the sample by using an ear washing ball during the period, and keeping the fresh end face of the sample clean; plating a thin gold layer on the end surface of the sample by using a vacuum coating instrument, and putting the sample into a dryer for analysis;

then, stabilizing the scanning electron microscope for more than 30min after starting up, and observing the scanning electron microscope after the instrument stability reaches the standard of JJJG 550; after two tests under the initial condition of the rock core are finished, vacuumizing the rock core, saturating formation water, and establishing bound water by adopting a gas drive method until water does not flow out from an outlet end; connecting an experimental device according to an experimental flow chart, putting the rock core containing bound water into a full-simulation experimental flow, sealing, adding confining pressure to 5MPa, and communicating a downstream end with the atmosphere;

finally, opening an upstream end valve, controlling a water intermediate container by using a displacement pump, and performing a water drive experiment by adopting a constant-flow displacement mode; measuring the injected water amount by a displacement pump, stopping the experiment when the injected water amount reaches 30PV, taking out the core, performing X-ray diffraction and scanning electron microscope tests, and repeating the steps;

(II) determining the change of the key parameters of the macroscopic reservoir after water breakthrough

(a) Cleaning and drying a prepared core for 8h to obtain a dry weight, and measuring the length, diameter, porosity and permeability of the core;

(b) vacuumizing the rock core, saturating formation water, and establishing bound water by adopting a gas drive method until no water is discharged from an outlet end;

(c) putting the rock core into an experimental device and heating and pressing the rock core to an initial formation temperature and pressure condition;

(d) opening an upstream end valve, controlling a water intermediate container by using a displacement pump, and performing a water drive experiment by adopting a constant-flow displacement mode;

(e) and measuring the injected water amount through a displacement pump, stopping the experiment every time the injected water amount reaches 5 PV, 15 PV or 30PV, taking out the core to measure the permeability, and drawing a permeability change curve before and after water flooding.

By combining all the technical schemes, the invention has the advantages and positive effects that: according to the invention, through deeply researching the seepage mechanism and the failure rule of the gas reservoir, the water breakthrough mechanism and the change research of the key parameters of the reservoir after water breakthrough, and based on the research results of the physical simulation experiment and the mathematical model, the effective development strategy and the key parameter limit of the research block are determined, and the aims of efficient development and long-term stable yield of the gas reservoir are realized.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

FIG. 1 is a flow chart of a method for developing a deep-sea high-temperature overpressure gas reservoir provided by an embodiment of the invention.

Fig. 2 is a schematic view of an ultrahigh-temperature and high-pressure multifunctional core displacement experimental apparatus provided by an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Aiming at the problems in the prior art, the invention provides a method for developing an offshore deep high-temperature overpressure gas reservoir, which is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the method for developing an offshore deep high-temperature overpressure gas reservoir provided by the embodiment of the invention comprises the following steps:

s101: by setting different initial water saturation, different CO₂Content, respectively setting different displacement pressure differences for the rock cores, determining the seepage capability of each rock core according to the gas flow after the outlet end of the rock core is stabilized, and performing comparative analysis on the initial water saturation difference and CO in the gas component₂The influence of the content difference on the single-phase seepage capability and the seepage rule of the gas determines the gas production capability and the influence factors of the target area gas reservoir;

s102: simulating reservoirs without bottom water and with low water saturation as reference standards through depletion development seepage experiments, respectively performing a bottom water reservoir water breakthrough mechanism experiment and a high water content reservoir water breakthrough mechanism experiment, determining the influence of different types of water sources on gas reservoir development under different production conditions through analyzing the dynamic change rules of production parameters such as pressure, gas production rate, water-gas ratio, extraction degree and the like in the experiment process, and judging the influence of different types of water sources on different water breakthrough gas wells of a target area gas reservoir;

s103: performing water drive experiments of different degrees on the natural rock core, simulating different stages of gas well water production, respectively measuring mineral content, pore structure characteristics and permeability after each water drive experiment is finished, and determining the change rule of reservoir characteristic parameters after water breakthrough of a gas reservoir by analyzing the experiment results;

s104: and determining a development strategy of the gas reservoir and the limit of effective development key parameters based on the influence factors and the parameter change rules determined from S101 to S103, generating a development scheme, and developing the deep offshore high-temperature overpressure gas reservoir.

Step S101 provided in the embodiment of the present invention includes:

(2) carrying out different CO₂A content infiltration experiment;

(2.6) adding N₂And CO₂The intermediate vessels were added at the ratios in the experimental design, i.e. 14%, 28%, 42%, 56% and 70%Pressurizing to 90MPa, and connecting the pressure to an experimental device;

Step S102 provided in the embodiment of the present invention includes:

1) carrying out a failure development seepage experiment;

2) experiment of water breakthrough mechanism of edge-bottom water reservoir

4) Determining a critical movable water saturation;

In step 1), the experiment for performing failure development seepage provided by the embodiment of the present invention includes:

In step 2), the experiment for performing the water breakthrough mechanism of the bottom-edge water reservoir provided by the embodiment of the invention comprises the following steps:

In step 3), the experiment for carrying out the water breakthrough mechanism of the high-water-content reservoir provided by the embodiment of the invention comprises the following steps:

In step 4), the determining of the critical movable water saturation provided by the embodiment of the present invention includes:

Step S103 provided in the embodiment of the present invention includes:

The technical effects of the present invention will be further described with reference to specific embodiments.

Example 1:

the zone 10 of the Ledong is positioned at a position near a concave part of the east slope of the origanum in the origanum marigolensis, has the water depth of 87.0-90.5 m, belongs to a structure and lithologic gas reservoir, is controlled by lithologic property, is divided into a plurality of gas-water systems in the plane and the longitudinal direction, and each system has different pressure systems. The original formation pressure coefficient of the Ledong 10 area is high (the pressure coefficient is 2.174-2.306), the pressure is 84.1-92.5 MPa, the temperature of a normal ground temperature system (the ground temperature gradient is 3.97 ℃/100m), and the formation temperature is about 190 ℃. The reservoir mainly comprises a yellow flow group and a Meishan group, belongs to a low-porosity, low-permeability to ultra-low-permeability reservoir and a local development medium-permeability reservoir. The pure hydrocarbon content of natural gas is 26% -86%, belonging to dry gas reservoir. The phenomenon of water production occurs in the multi-mouth exploratory well in the zone 10 of Ledong in the test process, the water-gas ratio reaches 2.1-138.0 m3/104m3 in the test, the water outlet mechanism is complex, and the subsequent development and evaluation and related research difficulty are high.

At present, the evaluation of offshore deep high-temperature overpressure gas reservoirs (the formation temperature is more than 180 ℃, the formation pressure coefficient is more than 2.1 and the average permeability of a reservoir is 1.1mD) in China has no experience and can be used for reference, and the Ledong 10 area faces a plurality of bottlenecks in the development, evaluation and research process: (1) the seepage mechanism of the high-temperature overpressure gas reservoir at the deep sea comprises different water saturation degrees and different CO₂Seepage characteristics at content; (2) water production phenomenon occurs in the process of testing the deep sea high-temperature overpressure gas reservoir, the water-break mechanism and the water-break characteristics are not clear, and the influence on the productivity after water break is caused; (3) influence on reservoir characteristic parameters after water breakthrough in production of the offshore deep high-temperature overpressure gas reservoir; (4) aiming at the characteristics of high temperature and overpressure, low permeability, water production and the like of the gas reservoir, a feasible development strategy is formulated for the gas reservoir, the boundary of key parameters is effectively developed and determined, and a feasible research and development scheme is formed. Therefore, the above bottleneck problem needs to be solved by the research of the present invention.

2. Subject experiment setup protocol

2.1 experiment of seepage law of deep high-temperature overpressure gas reservoir at sea

2.1.1 principle of the experiment

The experiment is based on Darcy's law, and different initial water saturation and different CO are set₂Content, respectively setting different displacement pressure differences for the rock cores, determining the seepage capability of each rock core according to the gas flow after the outlet end of the rock core is stabilized, and comparing and analyzing the initial water saturation difference and CO in the gas component₂The influence of the content difference on the gas single-phase seepage capability and the seepage rule, and further the gas production capability and the influence factors of the target area gas reservoir are researched.

2.2.2 Experimental conditions

(1) Selecting a natural core with the permeability of a yellow flow interval range of 0.3-3.0mD according to the distribution rule of the physical properties of an LD10-1 block reservoir;

(2) the experimental process completely simulates the conditions of high temperature and overpressure (temperature 190 ℃ and pressure 95MPa) of the reservoir;

(3) in the experimental process, high-purity nitrogen with the purity of 99.9 percent is adopted to simulate natural gas, and standard saline (the salinity: 12800mg/L) meeting the salinity of a target reservoir is configured according to a water complete analysis detection report provided by Party A to simulate formation water;

(4) according to the logging data of the LD10-1-1 well, the initial water saturation of the reservoir is 31.1% -68.7%, so the experimental process sets 6 initial water saturations of 0, 30%, 40%, 50%, 60% and 70%;

(5) according to the test data of LD10-1 block, CO in gas component₂The content is 6.18% -69.10%, so the experimental process configures 6 CO types including 0, 14%, 28%, 42%, 56% and 70%₂Content of a simulated gas.

2.2.3 Experimental apparatus and flow charts

The experiment adopts an independently researched and developed ultrahigh-temperature high-pressure multifunctional rock core displacement experiment device, and the configuration and the experiment flow of the experiment device are shown in table 3 and fig. 2. The set of experimental equipment can be applied to seepage rule experiments, water-break mechanism experiments and characteristic parameter change experiments after water break, and is not repeated in subsequent experimental schemes.

TABLE 3 ultra-high temperature and high pressure multifunctional core displacement experimental device configuration

2.2.4 Experimental procedure-seepage test under different Water-containing conditions

(1) Cleaning and drying a core prepared in advance for 8 hours to obtain a dry weight, and then measuring basic physical property parameters of the core, including length, diameter, porosity and permeability;

(2) connecting an experimental device according to an experimental flow chart, putting a dry rock core into a full-simulation experimental flow for sealing, heating a rock core holder by using a heating belt, and stabilizing for 8 hours after the temperature is 190 ℃ to ensure that the internal temperature of the rock core meets the requirement;

(3) firstly, confining pressure is applied to the rock core to be 5MPa by using a confining pressure pump, then a displacement pump displacement gas intermediate container is started, and the confining pressure and the flow pressure of a rock core system are synchronously increased at the same time, so that the influence of a stress sensitivity effect on an experimental result is prevented;

(4) when the gas in the intermediate container is used up, supplementing gas to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to the flowing pressure;

(5) when the confining pressure is increased to 95MPa, the flow pressure is increased to 90MPa, and when the upstream pressure and the downstream pressure are stable, the core system reaches an initial formation temperature pressure system;

(6) keeping the upstream pressure unchanged, respectively setting different back pressures through a back pressure pump and a back pressure valve, simulating different displacement pressure differences (0.1-10MPa) to perform a displacement experiment, measuring gas flow under different displacement pressure differences after the gas flow at the outlet end is stable, and drawing a gas flow-experiment pressure difference curve chart;

(7) standard saline water with equal mineralization degree is prepared according to analysis data of the gas reservoir stratum water composition of the target area, and the saline water is added into an intermediate container to be pressurized to 90MPa and then is connected into an experimental device;

(8) and (3) respectively controlling the gas intermediate container and the water intermediate container by utilizing two pumps of the double-plunger displacement pump, setting different displacement flows (according to the test result in the step (6)) according to the permeability of the rock core, injecting gas and water into the rock sample according to the set proportion (30%, 40%, 50%, 60% and 70%) by adopting a steady state method, measuring the inlet and outlet pressure difference and the gas flow after the flow is stable, and drawing a gas flow-experiment pressure difference curve chart.

2.2.5 Experimental procedure-different CO₂Content infiltration experiment

(3) firstly, confining pressure is applied to a rock core to be 5MPa by using a confining pressure pump, then a displacement pump is started to displace an intermediate container filled with water, and the confining pressure and the flow pressure of a rock core system are synchronously increased at the same time, so that the influence of a stress sensitivity effect on an experimental result is prevented;

(4) when the saline water in the intermediate container is used up, supplementing the saline water to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to flowing pressure;

(5) when the confining pressure is increased to 95MPa, the flowing pressure is increased to 90MPa, and when the upstream pressure and the downstream pressure are stable, the core system reaches an initial formation temperature and pressure system and is 100% saturated formation water;

(6) establishing the saturation of the bound water under the conditions of high temperature and overpressure by adopting a gas-water displacement mode until the outlet end does not produce water any more, and displacing the rock core in a positive direction in the displacement process so as to uniformly distribute the bound water;

(7) keeping the upstream pressure unchanged, respectively setting different back pressures through a back pressure pump and a back pressure valve, simulating different displacement pressure differences (0.1-10MPa) to perform a displacement experiment, measuring gas flow under different displacement pressure differences after the gas flow at the outlet end is stable, and drawing a gas flow-experiment pressure difference curve chart;

(8) handle N₂And CO₂Adding the mixture into an intermediate container according to the proportion (14%, 28%, 42%, 56% and 70%) in the experimental design, pressurizing to 90MPa, and connecting into an experimental device;

(9) before each displacement, the upstream and downstream valves are closed to trap water and CO in the core₂After full contact, carrying out displacement experiments under different displacement differential pressures (0.1-10MPa), and drawing a gas flow-experiment differential pressure curve chart.

2.2.6 Experimental details

2.2.7 Experimental records Table

2.2.8 expected results

(1) Obtaining a single-phase gas seepage characteristic curve under the conditions of high temperature and overpressure;

(2) analysis of different water saturation and different CO₂The effect of content on gas permeability;

(3) prediction of different water conditions, different CO₂Gas production capacity of the reservoir under the content condition;

(4) the experimental result can provide data support for determining the lower limit of the physical property of the effective reservoir by the capacity simulation method.

2.2 Water breakthrough mechanism experiment of deep high-temperature overpressure gas reservoir at sea

2.2.1 principle of the experiment

The experiment is based on the national industry standard (GB/T28912-; in the method, reservoirs without edge bottom water and with low water saturation are simulated through a failure development seepage experiment as reference standards, then an edge bottom water reservoir water breakthrough mechanism experiment and a high water content reservoir water breakthrough mechanism experiment are respectively carried out, the influence of different types of water sources on gas reservoir development is researched through analyzing the dynamic change rules of pressure, gas production rate and extraction degree in the experiment process, and the influence of different water breakthrough gas wells of the target area gas reservoir on which water sources are influenced is further judged.

2.2.2 Experimental conditions

(1) According to the distribution rule of the physical properties of an LD10-1 block reservoir, 3 rock cores with the same permeability range (0.3-3.0mD) of a yellow flow interval are selected and spliced to form a long rock core, so that the boundary effect of a single plunger rock core is reduced;

(4) according to the logging data of the LD10-1-1 well, the initial water saturation of the reservoir is 31.1% -68.7%, so the experimental process sets that the water saturation is 35% and 70% respectively represent a lower water-bearing layer and an upper water-bearing layer;

(5) according to the test data of LD10-1 block, CO in gas component₂The content is 6.18% -69.10%, therefore, the experimental process respectively leads CO to be₂Injecting simulated gas with content of 35% and 70% into water intermediate container, and standing sufficiently to make CO₂Fully contact with brine and then drain the water out of the intermediate vessel to simulate a lower CO content₂And higher CO content₂And (4) edge bottom water body.

(6) According to the test data of the LD10-1 block, the pressure differences at the 3-well 4 level were 12.2MPa, 32.6MPa, 62.7MPa and 62.9MPa, respectively, so experimental pressure differences of 5, 10, 15 and 30MPa were set to represent different production pressure differences (15, 30, 45 and 60MPa), respectively.

(7) According to a three-phase diagram of water, the pressure required when the water is vaporized from liquid to gas at 190 ℃ is about 1.5MPa, and the pressure in the core is always higher than 1.5MPa, so that the vaporization phenomenon of the water does not need to be considered in the experiment; and a condensing device is arranged in the metering system of the water at the outlet end of the experiment, and the vaporized water can be condensed into liquid for metering.

2.2.3 Experimental procedure-seepage experiment for failure development

(1) Cleaning and drying a prepared core for 8h to obtain a dry weight, measuring basic physical parameters of the core, including length, diameter, porosity and permeability, and calculating the overall physical properties of the spliced long core;

(2) connecting an experimental device according to an experimental flow chart, putting the long rock core saturated with bound water into a full-simulation experimental flow for sealing, heating the rock core holder by using a heating belt, and stabilizing for 8 hours after the temperature is 190 ℃ to ensure that the internal temperature of the rock core meets the requirement;

(6) and closing the upstream air inlet valve, opening the downstream air outlet valve, respectively setting different back pressures through the back pressure pump and the back pressure valve, simulating different exhaustion pressure differences (5, 10, 15 and 30MPa) to carry out exhaustion development experiments, and recording the change data of the upstream pressure, the downstream pressure and the gas production rate in real time in the experiment process.

2.2.4 Experimental step-experiment of Water breakthrough mechanism in edge-bottom Water reservoir

(3) injecting prepared brine into a high-pressure intermediate container, and then preparing CO₂Gas samples with the content of 35 percent and 70 percent are excessively injected into a high-pressure intermediate container;

(4) wrapping the intermediate container with an electric heating jacket, heating to 190 deg.C, connecting the intermediate container to a booster pump, pressurizing to 90MPa in constant pressure mode, maintaining the pressure, standing for 24 hr to allow water and CO to react₂Fully contacting;

(5) after the system is stabilized, the formation water is at the bottom of the intermediate container. Opening a top valve, emptying undissolved redundant gas in the intermediate container, closing the valve when formation water flows out, pressurizing the pressure of the intermediate container to 90MPa by using a booster pump, and accessing the intermediate container into an experimental device to be used as a simulated edge-bottom water body;

(6) firstly, confining pressure is applied to the rock core to be 5MPa by using a confining pressure pump, then a displacement pump displacement gas intermediate container is started, and the confining pressure and the flow pressure of a rock core system are synchronously increased at the same time, so that the influence of a stress sensitivity effect on an experimental result is prevented;

(7) when the gas in the intermediate container is used up, supplementing gas to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to the flowing pressure;

(8) when the confining pressure is increased to 95MPa, the flow pressure is increased to 90MPa, and when the upstream pressure and the downstream pressure are stable, the core system reaches an initial formation temperature pressure system;

(9) and closing an upstream air inlet valve, opening an upstream water inlet valve and a downstream liquid outlet valve, respectively setting different back pressures through a back pressure pump and a back pressure valve, simulating different exhaustion pressure differences (5, 10, 15 and 30MPa) to carry out exhaustion development experiments under the condition of bottom water, and recording the variation data of the upstream pressure, the downstream pressure, the gas yield and the water yield in real time in the experiment process.

2.2.5 Experimental step-Water breakthrough mechanism experiment of high water-cut reservoir

(2) connecting an experimental device according to an experimental flow chart, putting the long core with unsaturated water into a fully-simulated experimental flow for sealing, heating the core holder by using a heating belt, and stabilizing for 8 hours after the core holder is heated to 190 ℃ to ensure that the internal temperature of the core meets the requirement;

(5) when the saline water in the intermediate container is used up, supplementing the saline water to the intermediate container, pressurizing the intermediate container by using a pressurization system, and connecting the intermediate container to the experimental device again after pressurizing to flowing pressure;

(6) when the confining pressure is increased to 95MPa, the flowing pressure is increased to 90MPa, and when the upstream pressure and the downstream pressure are stable, the core system reaches an initial formation temperature and pressure system and is 100% saturated formation water;

(7) respectively controlling an air intermediate container and an underwater intermediate container by using two pumps of a double-plunger displacement pump, setting corresponding displacement flow for displacement according to designed air-water proportion (35 percent and 70 percent), and stopping when the air-water proportion at an outlet end reaches the designed proportion, wherein the core system reaches different initial water-containing conditions;

(8) and closing the upstream air inlet valve, opening the downstream air outlet valve, respectively setting different back pressures through the back pressure pump and the back pressure valve, simulating different exhaustion pressure differences (5, 10, 15 and 30MPa) to carry out exhaustion development experiments, and recording the change data of upstream and downstream pressures, the gas yield and the water yield in real time in the experiment process.

2.2.6 Experimental procedure-Critical Mobile Water saturation study

(1) Obtaining nuclear magnetic resonance T under different displacement experiments₂Spectrogram, provided by Party A (southwest university of Petroleum)

(2) Drawing movable water identification charts of reservoirs with different physical properties by combining the basic physical properties of the core subjected to the nuclear magnetic resonance test;

(3) determining the critical water saturation range of the reservoir by combining the physical property parameter range of the reservoir in the target area;

(4) and determining the original water saturation and physical properties of each stratum by combining the single well logging interpretation result, and judging whether the reservoir contains movable water.

2.2.7 Experimental details

2.2.8 Experimental records Table

2.2.9 expected result

(1) Acquiring a dynamic change rule of pressure, yield and recovery ratio in the failure exploitation process;

(2) analyzing the influence of the pressure difference on the failure mining dynamic law;

(3) analyzing pressure difference and water body dissolved CO₂Influence on water breakthrough and production characteristics;

(4) analyzing the influence of the pressure difference and the initial water-containing condition on water breakthrough and production characteristics;

(5) predicting the critical movable water saturation of the target area gas reservoir;

(6) and (3) disclosing water breakthrough mechanisms of different water breakthrough gas wells of the target gas reservoir.

2.3 change of key parameters of reservoir stratum after water breakthrough of deep high-temperature overpressure gas reservoir at sea

2.3.1 principle of the experiment

The experiment is based on the oil and natural gas industry standard (SY/T5163-. And after each water flooding experiment is finished, measuring the mineral content, the pore structure characteristics and the permeability, researching the change rule of the characteristic parameters of the reservoir after the gas reservoir breaks into water from a micro level and a macro level by analyzing the experiment result, and judging whether the reservoir can produce water for a long time.

2.3.2 Experimental conditions

(2) the water drive experiment for measuring macroscopic parameters is carried out under the conditions of high temperature and overpressure, the X-ray diffraction and the electron microscope scanning for measuring microscopic parameters are carried out under the indoor temperature and pressure condition, and the microscopic parameter characteristics after water drive before and after water drive are respectively measured;

(4) in the experiment, 3 water body multiples of 5 PV, 15 PV and 30PV are designed to carry out constant pressure difference (10 MPa and 20MPa) water drive experiments, and the short-term, medium-term and long-term water invasion processes are simulated respectively.

2.3.3 Experimental procedures-change in key parameters of microscopic reservoir after Water breakthrough

(1) Cleaning and drying a core prepared in advance for 8 hours to obtain dry weight;

(2) cutting about 50g of sample on the core, grinding to a particle size of less than 40 μm and weighing;

(3) separating clay minerals with particle size less than 10 μm by suspension method, and weighing to obtain total amount of clay minerals;

(4) measuring the content of each non-clay mineral by adopting a powder XRD (X-ray diffraction) K value method;

(5) recording the total amount of clay minerals and the content of each non-clay mineral, and calculating the relative content of the clay minerals and the common non-clay minerals;

(6) then extracting clay minerals with the particle size of less than 2 microns by a centrifugal method, smearing the clay sample with the sample, and sequentially carrying out natural XRD (X-ray diffraction) measurement, EG saturation sheet XRD measurement and high-temperature sheet XRD measurement to determine the relative content of the unusual clay minerals;

(7) cutting a sample on the rock core into 10mm multiplied by 5mm, and taking a representative and flat fresh end face as an analysis face;

(8) naturally drying the sample at room temperature, blowing off scraps and dust on the surface of the sample by using an ear washing ball during the period, and keeping the fresh end face of the sample clean;

(9) plating a thin gold layer on the end surface of the sample by using a vacuum coating instrument, and putting the sample into a dryer for analysis;

(10) stabilizing the scanning electron microscope for more than 30min after starting up, and observing the scanning electron microscope after the instrument stability reaches the standard of JJJG 550;

(11) after two tests under the initial condition of the rock core are finished, vacuumizing the rock core, saturating formation water, and establishing bound water by adopting a gas drive method until water does not flow out from an outlet end;

(12) connecting an experimental device according to an experimental flow chart, putting the rock core containing bound water into a full-simulation experimental flow, sealing, adding confining pressure to 5MPa, and communicating a downstream end with the atmosphere;

(13) opening an upstream end valve, controlling a water intermediate container by using a displacement pump, and performing a water drive experiment by adopting a constant-flow displacement mode;

(14) and (3) measuring the injected water amount through a displacement pump, stopping the experiment when the injected water amount reaches 30PV, taking out the core, performing X-ray diffraction and scanning electron microscope tests, and repeating the steps (1) to (10).

2.3.4 Experimental procedures-change in Key parameters of macroscopic reservoir after Water breakthrough

(2) vacuumizing the rock core, saturating formation water, and establishing bound water by adopting a gas drive method until no water is discharged from an outlet end;

(3) connecting an experimental device according to an experimental flow chart, putting a rock core, and heating and pressing to an initial formation temperature and pressure condition;

(4) opening an upstream end valve, controlling a water intermediate container by using a displacement pump, and performing a water drive experiment by adopting a constant-flow displacement mode;

(5) and measuring the injected water amount through a displacement pump, stopping the experiment every time the injected water amount reaches 5 PV, 15 PV or 30PV, taking out the core to measure the permeability, and drawing a permeability change curve before and after water flooding.

2.3.5 Experimental details

2.3.6 Experimental record sheet

2.3.7 expected results

(1) Revealing the change characteristics of the clay minerals and the pore structures of the reservoir under different water invasion degrees;

(2) revealing reservoir permeability change rules under different water invasion degrees;

(3) and analyzing the change of the key parameters of the reservoir after the water breakthrough of the gas well and the influence on the production from a macroscopic level and a microscopic level.

3. Experimental research scheduling

3.1 Experimental period

The high-temperature overpressure experiment period is long, the experiment preparation (pressurization, stabilization and pressure relief) and data processing need longer time, and the working time of 188 days is needed on the premise of ensuring 100% success rate. The success rate of high-temperature overpressure experiments is low, and the success rate of previous project experiments is about 70%. The specific experimental period is shown in the following table.

TABLE 4 Experimental period

3.2 progress of the experiment

The experimental period and the experimental success rate are comprehensively considered, and the experimental research part is expected to be completed in 2020 and 9 months; on the premise of ensuring the number of finished planned experiments, the number of the experiments is increased, and the requirement of an excess finished project is strived for.

TABLE 5 Experimental Schedule

3.3 core requirements

The failure rate of the high-temperature overpressure experiment is high, and the core is easy to damage, so that a standby core needs to be prepared, and the core is replaced in time after being damaged so as to avoid influencing the experiment progress and totally need 16 cores; the core with other subjects finished can be used under the premise of ensuring the integrity and permeability requirements.

TABLE 6 core requirements arrangement

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for developing an offshore deep high-temperature and overpressure gas reservoir is characterized by comprising the following steps:

step one, setting different initial water saturation and different CO₂Content, respectively setting different displacement pressure differences for the rock cores, determining the seepage capability of each rock core according to the gas flow after the outlet end of the rock core is stabilized, and performing comparative analysis on the initial water saturation difference and CO in the gas component₂The influence of the content difference on the single-phase seepage capability and the seepage rule of the gas determines the gas production capability and the influence factors of the target area gas reservoir;

simulating reservoirs without bottom water and with low water saturation as reference standards through depletion development seepage experiments, respectively performing a bottom water reservoir water breakthrough mechanism experiment and a high water content reservoir water breakthrough mechanism experiment, determining the influence of different types of water sources on gas reservoir development under different production conditions by analyzing the dynamic change rule of pressure, gas yield, water-gas ratio and extraction degree production parameters in the experiment process, and judging the influence of different types of water sources on different water breakthrough gas wells of the target gas reservoir on which water sources are influenced;

2. The method for developing an offshore deep high temperature and overpressure gas reservoir of claim 1 wherein said first step comprises:

(2) carrying out different CO₂A content infiltration experiment;

3. The method for developing an offshore deep high-temperature overpressure gas reservoir of claim 1, wherein the second step includes:

1) carrying out a failure development seepage experiment;

2) carrying out a water breakthrough mechanism experiment of the bottom-edge water reservoir;

3) carrying out a water breakthrough mechanism experiment of a high-water-content reservoir;

4) determining a critical movable water saturation;

5) acquiring dynamic change rules of production parameters of pressure, gas production, water-gas ratio and extraction degree based on the steps 1) to 4); analyzing the influence of the pressure difference on the failure mining dynamic law; analyzing pressure difference and water body dissolved CO₂Influence on water breakthrough and production characteristics; analyzing the influence of the pressure difference and the initial water-containing condition on water breakthrough and production characteristics; predicting the critical movable water saturation of the target area gas reservoir; determining water breakthrough mechanisms of different water breakthrough gas wells of the target area gas reservoir;

simulating reservoirs without bottom water and with low water saturation as reference standards through depletion development seepage experiments, respectively carrying out bottom water reservoir water breakthrough mechanism experiments and high water content reservoir water breakthrough mechanism experiments, determining the influence of different types of water sources on gas reservoir development under different production conditions through analyzing the dynamic change rules of pressure, gas production rate, water-gas ratio and production parameters of extraction degree in the experiment process, and judging the influence of different types of water sources on different water breakthrough gas wells of the target gas reservoir on which water sources are influenced.

4. The method for developing an offshore deep high-temperature overpressure gas reservoir of claim 3, wherein in step 1), the performing failure development seepage test includes:

5. The method for developing an offshore deep high-temperature overpressure gas reservoir as claimed in claim 3, wherein in the step 2), the performing of the experiment of the water breakthrough mechanism of the bottom water reservoir comprises:

2.3) wrapping the intermediate container with an electric heating jacket, heating to 190 deg.C, connecting the intermediate container to a booster pump, using a constant pressure modePressurizing to 90MPa, maintaining the pressure and standing for 24h to ensure that water and CO are mixed₂Fully contacting;

6. The offshore deep high-temperature overpressure gas reservoir development method of claim 3, wherein in step 3), the performing of the water breakthrough mechanism experiment of the high-water-content reservoir comprises:

7. The method for offshore deep high temperature and overpressure gas reservoir development of claim 3, wherein in step 4), said determining critical mobile water saturation comprises:

8. The method for developing an offshore deep high-temperature overpressure gas reservoir of claim 1, wherein the third step includes: