CN113405962A - Storage space evaluation method and device for carbonate reservoir - Google Patents
Storage space evaluation method and device for carbonate reservoir Download PDFInfo
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Abstract
The application discloses a storage space evaluation method and device for a carbonate reservoir, and belongs to the technical field of carbonate reservoirs. The embodiment of the application provides a storage space evaluation method of a carbonate reservoir, which is used for obtaining a rock sample of a target carbonate reservoir; performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map; converting the relaxation time proportion distribution map into a pore radius proportion distribution map; determining the volume fraction of each type of reservoir space according to the pore radius fraction profile; the seepage capability of the target carbonate reservoir was evaluated according to the volume fraction of each type of reservoir space. According to the method, each type of reservoir space is identified and quantitatively characterized according to the pore radius ratio distribution map, and the volume ratio of each type of reservoir space is obtained, so that the seepage capability of the carbonate reservoir can be accurately evaluated, and the development of the carbonate reservoir can be effectively guided.
Description
Technical Field
The application relates to the technical field of carbonate reservoirs. In particular to a storage space evaluation method and a storage space evaluation device for a carbonate reservoir.
Background
The storage space of the carbonate reservoir is more complex than that of sandstone, and various storage spaces such as intercrystalline pores, erosion pores, cracks and the like develop. The different seepage capacities of the reservoirs corresponding to the different types of reservoir spaces are different, the better the seepage capacity is, and the better the development effect of the carbonate reservoir is. Therefore, the evaluation of different types of reservoir spaces of the carbonate rock is of great significance for guiding the development of carbonate rock reservoirs.
In the related technology, a rock sample of a carbonate reservoir is mainly observed through a scanning electron microscope, and when the observed rock sample has large pores, the seepage capability of the carbonate reservoir is considered to be good; carbonate reservoirs are considered to have poor permeability when the observed porosity of the rock sample is small.
However, the pore size observed in the related art cannot completely reflect the seepage capability of the carbonate reservoir, so that the evaluation of the carbonate reservoir is inaccurate, and the development of the carbonate reservoir cannot be effectively guided.
Disclosure of Invention
The embodiment of the application provides a storage space evaluation method and device for a carbonate reservoir, which can be used for identifying and quantitatively representing each type of storage space and accurately evaluating the seepage capability of the carbonate reservoir. The specific technical scheme is as follows:
in one aspect, an embodiment of the present application provides a reservoir space evaluation method for a carbonate reservoir, where the method includes:
obtaining a rock sample of a target carbonate rock reservoir, wherein the rock sample comprises at least one type of reservoir space in reservoir spaces corresponding to intercrystalline pores, reservoir spaces corresponding to erosion pores and reservoir spaces corresponding to cracks;
performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map;
converting the relaxation time fraction distribution map into a pore radius fraction distribution map;
determining the volume fraction of each type of reservoir space according to the pore radius fraction profile;
evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space;
and the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole.
In one possible implementation, the converting the relaxation time proportion map into a pore radius proportion map includes:
acquiring the surface relaxation rate and the shape factor of the target carbonate reservoir;
converting the relaxation time in the relaxation time proportion distribution map into a pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain a pore radius proportion distribution map;
the formula I is as follows: r ═ ρ FST2
Wherein r is the pore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
In another possible implementation, the determining a volume fraction of each type of reservoir space from the pore radius fraction profile includes:
acquiring a pore radius range corresponding to each type of reservoir space;
and integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
In another possible implementation manner, the integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space includes:
integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain at least one integration peak;
and taking the peak area corresponding to the integral peak as the volume ratio of the storage space to obtain the volume ratio of each type of storage space, wherein one integral peak corresponds to one type of storage space.
In another possible implementation, the obtaining the pore radius range corresponding to each type of reservoir space includes:
obtaining a sample rock sample of the target carbonate reservoir, and carrying out electronic computed tomography scanning on the sample rock sample;
and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result.
In another possible implementation manner, the obtaining of the rock sample of the target carbonate reservoir includes:
obtaining a rock core of the target carbonate reservoir within a first preset diameter range;
drilling a rock pillar with a second preset diameter range from the rock core;
and displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
In another aspect, an embodiment of the present application provides a reservoir space evaluation apparatus for a carbonate reservoir, the apparatus including:
the acquisition module is used for acquiring a rock sample of a target carbonate rock reservoir, wherein the rock sample comprises at least one type of reservoir space in reservoir spaces corresponding to intercrystalline pores, reservoir spaces corresponding to erosion pores and reservoir spaces corresponding to cracks;
the experiment module is used for carrying out nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map;
a conversion module for converting the relaxation time proportion distribution map into a pore radius proportion distribution map;
the determining module is used for determining the volume ratio of each type of reservoir space according to the pore radius ratio distribution map;
the evaluation module is used for evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space;
and the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole.
In one possible implementation, the conversion module is further configured to obtain a surface relaxation rate and a shape factor of the target carbonate reservoir; converting the relaxation time in the relaxation time proportion distribution map into a pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain a pore radius proportion distribution map;
the formula I is as follows: r ═ ρ FST2
Wherein r is the pore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
In another possible implementation manner, the determining module is further configured to obtain a pore radius range corresponding to each type of reservoir space; and integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
In another possible implementation manner, the determining module is further configured to integrate the pore radius ratio distribution map according to a pore radius range corresponding to each type of reservoir space, so as to obtain at least one integrated peak; and taking the peak area corresponding to the integral peak as the volume ratio of the storage space to obtain the volume ratio of each type of storage space, wherein one integral peak corresponds to one type of storage space.
In another possible implementation manner, the determining module is further configured to obtain a sample rock sample of the target carbonate reservoir, and perform electronic computed tomography scanning on the sample rock sample; and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result.
In another possible implementation manner, the obtaining module is further configured to obtain a core of the target carbonate reservoir within a first preset diameter range; drilling a rock pillar with a second preset diameter range from the rock core; and displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
The technical scheme provided by the embodiment of the application has the following beneficial effects:
the embodiment of the application provides a storage space evaluation method of a carbonate reservoir, which is used for obtaining a rock sample of a target carbonate reservoir; performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map; converting the relaxation time proportion distribution map into a pore radius proportion distribution map; determining the volume fraction of each type of reservoir space according to the pore radius fraction profile; evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space; the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole. According to the method, a nuclear magnetic resonance experiment is carried out on a rock sample to convert a relaxation time ratio distribution map into a pore radius ratio distribution map, and each type of reservoir space is identified and quantitatively characterized according to the pore radius ratio distribution map, so that the volume ratio of each type of reservoir space is obtained, the seepage capability of the carbonate reservoir can be accurately evaluated, and the development of the carbonate reservoir can be effectively guided.
Drawings
Fig. 1 is a flow chart of a reservoir space evaluation method for a carbonate reservoir according to an embodiment of the present application;
FIG. 2 is a relaxation time ratio distribution graph provided by an embodiment of the present application;
FIG. 3 is a pore radius ratio distribution graph obtained after converting the relaxation time ratio distribution graph of FIG. 2 according to an embodiment of the present disclosure;
FIG. 4 is a schematic illustration of different types of reservoir spaces obtained by performing an electron computed tomography scan on a sample rock sample according to an embodiment of the present disclosure;
fig. 5 is an identification diagram of a reservoir space corresponding to an intergranular pore, an erosion pore and a fracture, which is obtained by identifying the pore radius ratio distribution diagram shown in fig. 3 according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of a reservoir space evaluation device for a carbonate reservoir provided in an embodiment of the present application;
FIG. 7 is a relaxation time ratio distribution diagram corresponding to rock samples 1, 2, 3 and 4 provided in the embodiments of the present application;
fig. 8 is a pore radius ratio distribution map obtained by converting the relaxation time ratio distribution map of fig. 7 according to an embodiment of the present disclosure;
fig. 9 is an identification diagram of a reservoir space corresponding to an intergranular pore, an erosion pore and a fracture, which is obtained by identifying the pore radius distribution diagram shown in fig. 8 according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions and advantages of the present application more clear, the following describes the embodiments of the present application in further detail.
The embodiment of the application provides a reservoir space evaluation method of a carbonate reservoir, and the method comprises the following steps of:
step 101: and obtaining a rock sample of the target carbonate reservoir.
The rock sample comprises at least one type of reservoir space in the reservoir space corresponding to the intercrystalline pores, the reservoir space corresponding to the erosion pores and the reservoir space corresponding to the cracks.
This step can be realized by the following steps (1) to (3), including:
(1) and obtaining the rock core of the target carbonate reservoir within a first preset diameter range.
The core may be one obtained during drilling or one removed from a reservoir by coring techniques. In the embodiments of the present application, this is not particularly limited.
The first preset diameter range may be set and modified as needed, and is not particularly limited in the embodiment of the present application. For example, the first predetermined diameter range is 8-10 cm.
(2) And drilling a rock pillar with a second preset diameter range from the rock core.
The second preset diameter range is smaller than the first preset diameter range, and may also be set and changed as needed, which is not specifically limited in the embodiment of the present application. For example, when the first predetermined diameter range is 8-10 cm, the second predetermined diameter range is 1.8-2 cm.
The length of the rock pillar can also be set and changed according to the needs, and in the embodiment of the present application, this is not particularly limited. For example, the length of the rock pillar may be 5-8 cm.
(3) And displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
In the embodiment of the application, the rock sample can be obtained by using water to simulate formation water to displace the rock pillar and simulate the state of the rock pillar in the formation until the rock pillar is saturated.
The water for displacing the rock pillar can be clear water or treated water extracted from the stratum. In the embodiments of the present application, this is not particularly limited.
Step 102: and performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time ratio distribution map.
In the nmr phenomenon, after the rf pulse is terminated, the protons return to their original equilibrium state, a process called relaxation. The emitted radio-frequency pulses also cause the vibrating protons to move synchronously at the same speed, in phase, so that the protons point in the same direction at the same time, forming transverse magnetization. After stopping the rf pulse, the vibrating protons are in different phases and the transverse magnetization gradually disappears to 37% of the original magnetization, the time required is called the relaxation time.
In the embodiment of the application, a nuclear magnetic resonance experiment can be performed on a rock sample according to 'rock sample nuclear magnetic resonance parameter experiment measurement specification' (SY/T6490-2014), and an obtained relaxation time proportion distribution map can be shown in fig. 2.
Step 103: the relaxation time occupancy profile is converted into a pore radius occupancy profile.
This step can be realized by the following steps (1) to (2), including:
(1) and acquiring the surface relaxation rate and the shape factor of the target carbonate reservoir.
Each reservoir has its corresponding surface relaxation rate. In the embodiment of the application, the surface relaxation rate of the target carbonate reservoir can be obtained by a maximum value method, a peak value method or an overlap method.
For a spherical pore, the corresponding shape factor value is 3; for a columnar void, the corresponding shape factor value is 2. In the embodiment of the present application, the intergranular pores belong to spherical pores, and therefore, the shape factor value corresponding to the intergranular pores is 3; the erosion holes and cracks belong to columnar pores, and therefore, the corresponding shape factor value of the erosion holes and cracks is 2.
It should be noted that the type of the reservoir space corresponding to each peak can be determined from the positions of the peaks appearing in the relaxation time proportion distribution map, and based on this, the shape factor value in the relaxation time range corresponding to each peak can be determined.
(2) Converting the relaxation time in the relaxation time ratio distribution map into the pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain the pore radius ratio distribution map.
The formula I is as follows: r ═ ρ FST2
Wherein r is the pore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
According to the step (1), the surface relaxation rate and the shape factor are both constant, the surface relaxation rate and the shape factor are substituted into the formula I, a relational expression between the pore radius and the relaxation time can be obtained, and the relaxation time in the relaxation time proportion distribution map is converted into the pore radius according to the relational expression, so that the pore radius proportion distribution map is obtained.
In addition, r is in nm, ρ is in nm/ms, FSWithout unit, T2Is not only a sheetThe bits are ms.
Referring to fig. 3, fig. 3 is a pore radius ratio distribution graph obtained after conversion of the relaxation time ratio distribution graph of fig. 2.
Step 104: pore radius ranges corresponding to each type of reservoir space are obtained.
In a possible implementation manner, a sample rock sample of a target carbonate reservoir can be obtained, and the sample rock sample is subjected to electronic Computed Tomography (CT) scanning; and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result. The number of the sample rock samples may be set and changed as needed, and is not particularly limited in the embodiments of the present application.
Referring to fig. 4, fig. 4 is a schematic illustration of different types of reservoir spaces obtained by performing an electron computed tomography scan of a sample rock sample. As can be seen on the scale of fig. 4: the pore radius range of the storage space corresponding to the intercrystalline pores is smaller than that of the storage space corresponding to the erosion pores, and the pore radius range of the storage space corresponding to the erosion pores is smaller than that of the storage space corresponding to the cracks.
In another possible implementation, the pore radius range corresponding to each type of reservoir space may also be determined from survey experience. Generally, the pore radius range of the reservoir space corresponding to the intercrystalline pores is in the nanometer level; the pore radius range of the reservoir space corresponding to the erosion hole is in micron level; the pore radius range of the reservoir space corresponding to the fracture is larger than the pore radius range of the reservoir space corresponding to the erosion hole, and is micrometer or millimeter.
In another possible implementation, the pore radius range corresponding to each type of reservoir space may also be determined based on the electron computed tomography results and the exploration experience.
Step 105: and integrating the pore radius ratio distribution diagram according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
In the step, integrating a pore radius ratio distribution map according to a pore radius range corresponding to each type of reservoir space to obtain at least one integration peak; then, the peak area corresponding to the integration peak is used as the volume ratio of the storage space, so that the volume ratio of each type of storage space is obtained, and one integration peak corresponds to one type of storage space.
Continuous integrated peaks correspond to one type of reservoir space, and when the integrated peaks are discontinuous, the type of the corresponding reservoir space is changed.
With continued reference to fig. 3, it can be seen from fig. 3 that: there are 3 integration peaks, one corresponding to each type of reservoir space.
According to step 104, the pore radius range of the storage space corresponding to the intergranular hole is smaller than the pore radius range of the storage space corresponding to the erosion hole, and the pore radius range of the storage space corresponding to the erosion hole is smaller than the pore radius range of the storage space corresponding to the fracture. In this step, the peak area corresponding to the integrated peak with the smallest pore radius range is used as the volume fraction of the storage space corresponding to the intercrystalline pore, the peak area corresponding to the integrated peak with the largest pore radius range is used as the volume fraction of the storage space corresponding to the fracture, and the peak area corresponding to the integrated peak with the pore radius range between the smallest range and the largest range is used as the volume fraction of the storage space corresponding to the erosion pore.
Referring to fig. 5, fig. 5 is an identification diagram of the reservoir space corresponding to the intergranular pores, the erosion pores and the cracks obtained by identifying the pore radius ratio distribution diagram shown in fig. 3. As can be seen from fig. 5: the integral peak with the largest area is a storage space corresponding to intercrystalline pores, the integral peak with poor continuity and the peak value of the integral peak larger than 0.5 mu m is a storage space corresponding to corrosion pores, the integral peak with poor continuity and the peak value of the integral peak larger than 0.5 mu m is a storage space corresponding to cracks, the volume ratio of the storage space corresponding to the intercrystalline pores in the rock sample is the largest, the corrosion pores are formed in the second place, and the cracks are formed in the last place.
In the embodiment of the application, the rock samples of the carbonate reservoirs under the condition of 100% saturated simulated formation water are subjected to nuclear magnetic resonance experiments, so that the storage spaces of different types of the carbonate reservoirs can be identified, and the quantitative characterization of the storage spaces of different types in the carbonate reservoirs is realized. The method adds a new method and thought for recognizing the structural characteristics of the compact reservoir, and enriches and perfects the theoretical basis of compact gas reservoir exploration and development.
Step 106: the seepage capability of the target carbonate reservoir was evaluated according to the volume fraction of each type of reservoir space.
The seepage capability of the reservoir space corresponding to the crack is superior to that of the reservoir space corresponding to the erosion hole; the seepage capability of the reservoir space corresponding to the erosion hole is better than that of the reservoir space corresponding to the intercrystalline hole. Under the condition that other reservoir conditions are the same, the larger the volume ratio of the reservoir space corresponding to the erosion hole to the reservoir space corresponding to the fracture is, the better the seepage capability of the carbonate reservoir is, and the better the development effect of the carbonate reservoir is.
Based on the above, in the step, the seepage capability of the target carbonate reservoir can be evaluated according to the volume ratio of the storage space corresponding to the intercrystalline pores, the volume ratio of the storage space corresponding to the erosion pores and the volume ratio of the storage space corresponding to the fractures.
It should be noted that in the embodiment of the present application, effective identification and quantitative characterization of intercrystalline pores, erosion pores and fractures in a carbonate reservoir are achieved through a nuclear magnetic resonance experiment, and pore distribution characteristics and volume fractions of different types of reservoir spaces are obtained, so that the seepage capability of the carbonate reservoir can be effectively reflected, and further, the development effect of the carbonate reservoir can be judged.
In one possible implementation, the test oil production of carbonate reservoirs may also be evaluated based on the volumetric proportion of each type of reservoir space. When the volume ratio of the storage space corresponding to the erosion hole and the volume ratio of the storage space corresponding to the fracture are larger than a certain value, the carbonate reservoir development effect is better, and the test oil yield is higher.
The embodiment of the application provides a storage space evaluation method of a carbonate reservoir, which is used for obtaining a rock sample of a target carbonate reservoir; performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map; converting the relaxation time proportion distribution map into a pore radius proportion distribution map; determining the volume fraction of each type of reservoir space according to the pore radius fraction profile; the seepage capability of the target carbonate reservoir was evaluated according to the volume fraction of each type of reservoir space. According to the method, a nuclear magnetic resonance experiment is carried out on a rock sample to convert a relaxation time ratio distribution map into a pore radius ratio distribution map, and each type of reservoir space is identified and quantitatively characterized according to the pore radius ratio distribution map, so that the volume ratio of each type of reservoir space is obtained, the seepage capability of the carbonate reservoir can be accurately evaluated, and the development of the carbonate reservoir can be effectively guided.
The embodiment of the application provides a storage space evaluation device of carbonate reservoir, refer to fig. 6, and the device includes:
the acquisition module 601 is configured to acquire a rock sample of a target carbonate rock reservoir, where the rock sample includes at least one type of reservoir space among a reservoir space corresponding to an intercrystalline pore, a reservoir space corresponding to a corrosion pore, and a reservoir space corresponding to a fracture;
an experiment module 602, configured to perform a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map;
a conversion module 603, configured to convert the relaxation time proportion distribution map into a pore radius proportion distribution map;
a determining module 604 for determining a volume fraction of each type of reservoir space from the pore radius fraction profile;
an evaluation module 605 for evaluating the seepage capability of the target carbonate reservoir according to the volume fraction of each type of reservoir space;
the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole.
In one possible implementation, the conversion module 603 is further configured to obtain a surface relaxation rate and a shape factor of the target carbonate reservoir; converting relaxation time in a relaxation time ratio distribution map into pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain a pore radius ratio distribution map;
the formula I is as follows: r ═ ρ FST2
Wherein r is the pore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
In another possible implementation, the determining module 604 is further configured to obtain a pore radius range corresponding to each type of reservoir space; and integrating the pore radius ratio distribution diagram according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
In another possible implementation manner, the determining module 604 is further configured to integrate the pore radius ratio distribution map according to a pore radius range corresponding to each type of reservoir space, so as to obtain at least one integrated peak; and taking the peak area corresponding to the integral peak as the volume ratio of the storage space to obtain the volume ratio of each type of storage space, wherein one integral peak corresponds to one type of storage space.
In another possible implementation manner, the determining module 604 is further configured to obtain a sample rock sample of the target carbonate reservoir, and perform electronic computed tomography on the sample rock sample; and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result.
In another possible implementation manner, the obtaining module 601 is further configured to obtain a core of the target carbonate reservoir within a first preset diameter range; drilling a rock pillar with a second preset diameter range from the rock core; and displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
The embodiment of the application provides a storage space evaluation device of a carbonate reservoir, which is used for acquiring a rock sample of a target carbonate reservoir; performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map; converting the relaxation time proportion distribution map into a pore radius proportion distribution map; determining the volume fraction of each type of reservoir space according to the pore radius fraction profile; evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space; the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole. The device converts the relaxation time ratio distribution map into a pore radius ratio distribution map by performing a nuclear magnetic resonance experiment on the rock sample, identifies and quantitatively characterizes each type of reservoir space according to the pore radius ratio distribution map, and obtains the volume ratio of each type of reservoir space, so that the seepage capability of the carbonate reservoir can be accurately evaluated, and the development of the carbonate reservoir can be effectively guided.
The technical solution of the present application will be described in detail by specific examples below.
Step 1: 4 rock samples of a carbonate reservoir in a certain area are obtained.
The 4 rock samples were named rock sample 1, rock sample 2, rock sample 3, and rock sample 4, respectively.
In the step, 4 rock cores with the diameter range of 8-10 cm are obtained, then rock pillars with the diameter of 2cm are drilled from each rock core, and each rock pillar is displaced by water until the rock pillars are saturated, so that 4 rock samples are obtained.
Step 2: and (3) performing a nuclear magnetic resonance experiment on each rock sample according to 'rock sample nuclear magnetic resonance parameter experiment measurement specification' (SY/T6490-.
Referring to fig. 7, fig. 7 is a graph showing relaxation time ratio distributions corresponding to rock sample 1, rock sample 2, rock sample 3, and rock sample 4, respectively.
And step 3: and converting the relaxation time ratio distribution map into a pore radius ratio distribution map according to the formula I.
The empirical value of the surface relaxation rate rho of the carbonate reservoir in the region is 2-5 nm/ms, and in the embodiment, the rho value is 2 nm/ms.
Referring to fig. 8, fig. 8 is a pore radius ratio distribution map obtained by converting the relaxation time ratio distribution map of fig. 7.
And 4, step 4: and integrating the pore radius ratio distribution map to obtain the volume ratio of different types of reservoir spaces.
Referring to fig. 9, fig. 9 is an identification diagram of the reservoir space corresponding to the intergranular pores, the erosion pores and the fractures, which is obtained by identifying the pore radius distribution diagram shown in fig. 8. As can be seen in fig. 9: the reservoir spaces of the rock samples 1 and 2 have intergranular pores, eroded pores and fractures, and the reservoir spaces of the rock samples 3 and 4 have only intergranular pores and eroded pores.
And 5: pore radius ranges corresponding to each type of reservoir space are obtained.
Step 6: and determining the volume ratio of each type of reservoir space according to the pore radius range corresponding to each type of reservoir space.
Referring to table 1, table 1 is the volume fraction of the reservoir space obtained from the peak areas of the integrated peaks corresponding to the intercrystalline pores, the erosion pores and the cracks in fig. 9.
TABLE 1
And 7: the seepage capability of the target carbonate reservoir was evaluated according to the volume fraction of each type of reservoir space.
As can be seen from table 1: in 4 rock samples, no reservoir space corresponding to the fracture exists in the rock sample 3, the volume ratio of the reservoir space corresponding to the intercrystalline pores in the rock sample 3 is the largest, and the seepage capacity of the reservoir space corresponding to the intercrystalline pores is poor, so that the seepage capacity of the reservoir layer corresponding to the rock sample 3 is the worst. Although the rock sample 4 does not have a storage space corresponding to the fracture, the volume ratio of the storage space corresponding to the erosion hole in the rock sample 4 is greater than that of the storage space corresponding to the erosion hole in the rock sample 3. And the volume ratio of the reservoir space corresponding to the intercrystalline pores in the rock sample 4 is not greatly different from the volume ratio of the reservoir space corresponding to the intercrystalline pores in the rock sample 1 and the rock sample 2, so the seepage capacity of the reservoir layer corresponding to the rock sample 1, the rock sample 2 and the rock sample 4 is not greatly different.
The above description is only for facilitating the understanding of the technical solutions of the present application by those skilled in the art, and is not intended to limit the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (12)
1. A reservoir space evaluation method for a carbonate reservoir, the method comprising:
obtaining a rock sample of a target carbonate rock reservoir, wherein the rock sample comprises at least one type of reservoir space in reservoir spaces corresponding to intercrystalline pores, reservoir spaces corresponding to erosion pores and reservoir spaces corresponding to cracks;
performing a nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map;
converting the relaxation time fraction distribution map into a pore radius fraction distribution map;
determining the volume fraction of each type of reservoir space according to the pore radius fraction profile;
evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space;
and the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole.
2. The method of claim 1, wherein converting the relaxation time occupancy profile to a pore radius occupancy profile comprises:
acquiring the surface relaxation rate and the shape factor of the target carbonate reservoir;
converting the relaxation time in the relaxation time proportion distribution map into a pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain a pore radius proportion distribution map;
the formula I is as follows: r ═ ρ FST2
Wherein r isPore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
3. The method of claim 1, wherein determining the volume fraction of each type of reservoir space from the pore radius fraction profile comprises:
acquiring a pore radius range corresponding to each type of reservoir space;
and integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
4. The method of claim 3, wherein said integrating the pore radius ratio profile according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space comprises:
integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain at least one integration peak;
and taking the peak area corresponding to the integral peak as the volume ratio of the storage space to obtain the volume ratio of each type of storage space, wherein one integral peak corresponds to one type of storage space.
5. The method of claim 3, wherein the obtaining a pore radius range corresponding to each type of reservoir space comprises:
obtaining a sample rock sample of the target carbonate reservoir, and carrying out electronic computed tomography scanning on the sample rock sample;
and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result.
6. The method of claim 1, wherein obtaining the rock sample of the target carbonate reservoir comprises:
obtaining a rock core of the target carbonate reservoir within a first preset diameter range;
drilling a rock pillar with a second preset diameter range from the rock core;
and displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
7. A reservoir space evaluation apparatus for a carbonate reservoir, the apparatus comprising:
the acquisition module is used for acquiring a rock sample of a target carbonate rock reservoir, wherein the rock sample comprises at least one type of reservoir space in reservoir spaces corresponding to intercrystalline pores, reservoir spaces corresponding to erosion pores and reservoir spaces corresponding to cracks;
the experiment module is used for carrying out nuclear magnetic resonance experiment on the rock sample to obtain a relaxation time proportion distribution map;
a conversion module for converting the relaxation time proportion distribution map into a pore radius proportion distribution map;
the determining module is used for determining the volume ratio of each type of reservoir space according to the pore radius ratio distribution map;
the evaluation module is used for evaluating the seepage capability of the target carbonate reservoir according to the volume ratio of each type of reservoir space;
and the seepage capacity of the storage space corresponding to the fracture is superior to that of the storage space corresponding to the erosion hole, and the seepage capacity of the storage space corresponding to the erosion hole is superior to that of the storage space corresponding to the intercrystalline hole.
8. The apparatus of claim 7, wherein the conversion module is further configured to obtain a surface relaxation rate and a shape factor of the target carbonate reservoir; converting the relaxation time in the relaxation time proportion distribution map into a pore radius according to the surface relaxation rate and the shape factor by the following formula I to obtain a pore radius proportion distribution map;
the formula I is as follows: r ═ ρ FST2
Wherein r is the pore radius, ρ is the surface relaxation rate, FSIs a form factor, T2Is the relaxation time.
9. The apparatus of claim 7, wherein the determining module is further configured to obtain a pore radius range corresponding to each type of reservoir space; and integrating the pore radius ratio distribution map according to the pore radius range corresponding to each type of reservoir space to obtain the volume ratio of each type of reservoir space.
10. The apparatus of claim 9, wherein the determining module is further configured to integrate the pore radius ratio distribution map according to a pore radius range corresponding to each type of reservoir space to obtain at least one integrated peak; and taking the peak area corresponding to the integral peak as the volume ratio of the storage space to obtain the volume ratio of each type of storage space, wherein one integral peak corresponds to one type of storage space.
11. The apparatus of claim 9, wherein the determining module is further configured to obtain a sample rock sample of the target carbonate reservoir, perform an electronic computed tomography scan on the sample rock sample; and obtaining the pore radius range corresponding to each type of reservoir space according to the scanning result.
12. The apparatus of claim 7, wherein the obtaining module is further configured to obtain a core of the target carbonate reservoir within a first preset diameter range; drilling a rock pillar with a second preset diameter range from the rock core; and displacing the rock pillar with water until the rock pillar is saturated to obtain the rock sample.
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