Method for determining gas-oil interface of oil and gas reservoir

Abstract

The invention relates to the technical field of oil exploration and development, in particular to a method for determining a gas-oil interface of an oil-gas reservoir, and the method comprises the following steps: S1, obtaining oil-gas reservoir data of a target oil-gas reservoir; s2, determining a hydrocarbon reservoir by using well drilling and logging display data; s3, determining an oil and gas reservoir according to well logging, oil testing and pilot production data; s4, judging gas-water and oil-water interfaces according to well logging interpretation results and rock core display; and S5, judging the gas-oil interface by using the excavation effect of the gas layer displayed on the neutron and density curve. According to the method, the judgment of the gas-oil interface in the oil-gas reservoir such as a gas-cap reservoir or a gas reservoir with an oil base is realized, the gas-oil interface can be determined in the early development stage of the oil-gas reservoir, and a good foundation is laid for improving the recovery ratio of the oil-gas reservoir.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum exploration and development, and in particular to a method for determining a gas-oil interface in an oil and gas reservoir. Background Art

[0002] Gas-cap reservoirs refer to oil and gas coexisting reservoirs in which both gas and oil reservoirs exist in the rock formation, and the gas reservoir is located above the oil reservoir. In this type of reservoir, the distribution of oil and gas is vertically layered, with the gas reservoir at the top and the oil reservoir at the bottom, with a clear interface between the two. The gas reservoir has a lighter density and is located in the upper layer; the oil reservoir has a heavier density and is located in the lower layer. This type of reservoir usually exists in areas with complex geological structures, such as fold belts, fault zones, etc.

[0003] Gas cap reservoirs are an important type of oil and gas reservoirs in some oil fields, and are generally medium-porosity and medium-high permeability reservoirs. However, due to the large thickness of the gas layer, in the early stage of development, the development wells obtained condensate gas when opening the target layer for trial production, and most of the development wells were horizontal wells. Therefore, the development of condensate gas reservoirs was mainly carried out in the early stage. As the development progressed, it was later discovered that there was an oil layer under the gas layer.

[0004] The problem with the gas-oil interface identification method of conventional oil and gas reservoirs is that the drilling, core and conventional logging curves are not obvious, resulting in the oil layer below the gas layer being difficult to discover, especially in the early stages of development. Generally, after development to a certain extent, when the development wells deployed in the middle and low parts of the oil and gas reservoir show oil well characteristics, it is discovered that there is an oil layer below the gas layer, while at this time the upper gas layer has been developed for a long time, which has resulted in a significant decrease in recovery rate.

[0005] In order to improve the recovery rate of oil and gas reservoirs, it is necessary to determine the gas-oil interface in time in the early stage of development, and then determine the type of oil and gas reservoirs, formulate scientific and reasonable development policies, and ensure that the oil and gas reservoirs can achieve a higher recovery rate.

[0006] Therefore, there is an urgent need for a method for determining the gas-oil interface in oil and gas reservoirs, which can be used to determine the gas-oil interface in the early stages of oil and gas reservoir development. Summary of the invention

[0007] In order to avoid the above problems existing in the prior art, the object of the present invention is to provide a method for determining the gas-oil interface in an oil and gas reservoir.

[0008] To achieve the above object, the present invention provides the following technical solution: A method for determining the gas-oil interface of an oil and gas reservoir, comprising the following steps:

[0009] S1. Obtaining oil and gas reservoir data of the target oil and gas reservoir;

[0010] S2. Determine whether the target layer is an oil and gas layer by using the drilling and logging display data;

[0011] S3. Determine the oil and gas layer and water layer sections of the target layer using well logging, oil testing and production test data;

[0012] S4. Use logging interpretation results and core displays to determine the location of the gas-water or oil-water interface;

[0013] S5. Utilize the mining effect of the gas layer in the neutron and density curves and combine it with the position of the gas-water or oil-water interface to determine the gas-oil interface.

[0014] The present invention is further configured such that the oil and gas reservoir data in step S1 includes core data, drilling data, logging data, well logging data, oil test data, production test data and fluid high-pressure physical property data.

[0015] The present invention is further configured that step S2 is specifically to determine the oil and gas layer according to the different levels of oil and gas displays in the core of the oil and gas layer section, because the drilling time of the oil and gas-bearing sandstone is low and the gas logging is abnormal during the drilling process, and the methane content of the gas layer is high.

[0016] The present invention is further configured such that, in step S3, the oil and gas layers are preliminarily judged based on the logging curve characteristics of the oil and gas layers and the water layers and the logging interpretation results; and then the oil layer section, water layer section and gas layer section are further determined in combination with the well testing and oil testing results.

[0017] The present invention is further configured such that the test and oil testing results include test layer section liquid production, oil and gas production conditions, and pressure data.

[0018] The present invention is further configured that the logging curve of the oil and gas layer section shows low natural gamma, negative abnormal natural potential, regular well diameter, the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, and RILD≥0.6Ω.m;

[0019] If the production well has gas production during testing and the gas-oil ratio is greater than 600m 3 / d, the target layer is judged to be a gas layer; if there is oil and gas production during oil testing, and the gas-oil ratio is lower than 600m 3 / d. Determine that the target layer is an oil layer.

[0020] The present invention is further configured such that the logging curve of the water layer section shows low gamma, negative natural potential anomaly, regular well diameter, and the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, and RILD≤0.3Ω.m.

[0021] It should be noted that RILD, RILM and RFOC are three terms related to rock property measurements.

[0022] They represent different types of measurement methods and results. The specific explanations are as follows:

[0023] 1. RILD (Resistivity Induction Logs Deep): RILD refers to deep induction resistivity logging, which measures the resistivity of the formation through an induction resistivity instrument. It can provide information about the conductivity and porosity of the formation rock. Resistivity induction logging is widely used in oil exploration and production to determine the properties of underground formations and their potential for oil and gas.

[0024] 2. RILM (Resistivity Induction Logs Medium): RILM refers to medium induction resistivity logging, which is also a resistivity measurement method, but compared with RILD, it measures the resistivity of the invasion zone of the formation. The measurement depth range of RILM is usually between RILD and RFOC, and can provide resistivity information of the invasion zone formation.

[0025] 3.RFOC (Resistivity Focused Laterolog): RFOC refers to lateral resistivity logging, which is a focused measurement instrument used to measure the resistivity of the formation. Unlike induction logging, RFOC uses electrodes to directly contact the formation and calculates the resistivity by measuring current and voltage. RFOC is usually used for resistivity measurement in the flushing zone of the formation.

[0026] The present invention is further configured such that, in step S4, the gas-water and oil-water interfaces are determined based on the logging interpretation of the gas-water interface of a single well in the well area and the oil and gas display of the core, combined with the test results of laboratory tests and analysis.

[0027] It should be noted that core display refers to the display and description of core samples obtained from the drilling process. In the process of oil exploration and production, core sampling is usually carried out, that is, underground rock layers are taken out from the borehole to obtain detailed information about geological characteristics and rock properties.

[0028] Well logging interpretation of gas-water and oil-water interface results refers to the determination of the interface position of gas, oil and water in the reservoir through the analysis and interpretation of well logging data. This interface is usually called gas-water and oil-water interface.

[0029] Well logging is to obtain information about formation characteristics and reservoir properties by measuring the electrical, acoustic, nuclear magnetic resonance and other physical properties of underground reservoirs. In well logging interpretation, commonly used logging curves include density, acoustic wave velocity, resistivity, etc.

[0030] The present invention is further configured such that the logging interpretation includes density logging, and based on the density of water> density of oil> density of gas, the existence of gas, oil and water is distinguished, and the gas-oil, gas-water, and oil-water interfaces are determined.

[0031] The present invention is further configured such that the logging interpretation also includes acoustic logging, and according to the different acoustic velocities of the fluid, the positions of the gas-water and oil-water interfaces are determined based on velocity anomalies and reflection characteristics by analyzing the acoustic logging curves.

[0032] The present invention is further configured such that the logging interpretation also includes resistivity logging, measuring the radial distribution of the resistivity of the formation, and inferring the position of the oil-water or gas-water interface based on the difference in electrical conductivity of water, oil and gas.

[0033] The present invention is further configured that the core oil and gas display refers to the presence or signs of oil and gas observed in the core sample, including observing the form of oil and gas, core color and texture, bubble and gas release, and determining whether there is a smell of oil or natural gas by smell.

[0034] It should be noted that the above observations and judgments are only preliminary core displays and are not sufficient to quantitatively determine the content and quality of oil and gas. Further laboratory tests and analyses, such as permeability tests of core samples and oil and gas component analysis, are required to conduct more detailed research to confirm the content and type of oil and gas in the rock.

[0035] The present invention is further configured such that step S5 specifically comprises: using the neutron density curve overlap method to delineate the gas-oil interface of a single well, that is, overlapping the neutron and density curves of the water layer near the target layer of the development well, observing the amplitude difference of the neutron and density curves in the oil and gas layer, the amplitude difference of the gas layer is greater than that of the oil layer, and for reservoirs containing both gas and oil, the amplitude difference is larger at the top and smaller at the bottom, and at the position where the amplitude difference is significantly reduced, the half-amplitude point of the curve change is selected as the gas-oil interface.

[0036] In summary, the beneficial effects of the above technical solution of the present invention are as follows:

[0037] 1. The present invention realizes the determination of the gas-oil interface in oil and gas reservoirs such as gas-cap oil reservoirs or oil-bottom gas reservoirs, and can determine the gas-oil interface in the early stage of oil and gas reservoir development, laying a good foundation for improving the recovery rate of oil and gas reservoirs. It can provide important parameter support for determining the type of oil and gas reservoirs in the development of clastic oil and gas reservoirs, and provide a basis for the formulation of oil and gas reservoir development strategies, and has a relatively broad application and promotion prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1 The present invention is a flow chart of a method for determining a gas-oil interface in an oil and gas reservoir.

[0040] Figure 2 This is a flow chart of a method for determining the gas-oil interface of an oil and gas reservoir based on clastic rocks in a certain location in Example 2 of the present invention.

[0041] Figure 3 This is a schematic diagram of the conventional gas-water interface division in a certain clastic oil and gas reservoir example.

[0042] Figure 4 The diagram is a gas-oil and oil-water interface division diagram of an embodiment of a clastic oil and gas reservoir in a certain place according to the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, other similar embodiments obtained by ordinary technicians in the field without making any creative work should all fall within the scope of protection of the present invention.

[0044] In addition, the directional words mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only reference directions of the drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0045] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0046] Embodiment 1:

[0047] like Figure 1 As shown in the figure, a preferred embodiment of the present invention is a method for determining the gas-oil interface of an oil and gas reservoir, comprising the following steps:

[0048] S1. Obtaining oil and gas reservoir data of the target oil and gas reservoir; the oil and gas reservoir data includes core data, drilling data, logging data, well logging data, oil test data, production test data and fluid high-pressure physical property data.

[0049] S2. Use drilling and logging display data to determine whether the target layer is an oil and gas layer.

[0050] Since the drilling time of oil and gas-bearing sandstone is low and the gas logging is abnormal during the drilling process, and the methane content of the gas layer is high in the gas logging, the oil and gas layer is determined based on the oil and gas displays of different levels in the core of the oil and gas layer section.

[0051] S3. Use logging, oil testing and test production data to determine the oil and gas layer sections and water layer sections of the target layer.

[0052] The oil and gas layers are initially determined based on the logging curve characteristics and logging interpretation results of the oil and gas layers and water layers; the oil layer section, water layer section and gas layer section are further determined in combination with the well testing and oil testing results. The test and oil testing results include the test layer section liquid production, oil and gas production, and pressure data.

[0053] The logging curves of the oil and gas layer section show low natural gamma, negative abnormal natural potential, regular wellbore, and the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, and RILD≥0.6Ω.m;

[0054] If the production well has gas production during testing and the gas-oil ratio is greater than 600m 3 / d, the target layer is judged to be a gas layer; if there is oil and gas production during oil testing, and the gas-oil ratio is lower than 600m 3 / d. Determine that the target layer is an oil layer.

[0055] The logging curves of the water layer section show low gamma, negative natural potential anomaly, regular well diameter, and the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, RILD≤0.3Ω.m.

[0056] S4. Use logging interpretation results and core displays to determine the location of the gas-water or oil-water interface.

[0057] The gas-water and oil-water interfaces are determined based on the logging interpretation of the gas-water interface and the core oil and gas indications of the single wells in the well area, combined with the test results of laboratory tests and analysis.

[0058] Core display refers to the display and description of core samples obtained from the drilling process. In the process of oil exploration and production, core sampling is usually carried out, that is, underground rocks are taken out from the borehole to obtain detailed information about geological characteristics and rock properties.

[0059] Fluid high-pressure physical property data refers to the physical properties of oil at reservoir pressure and temperature, including state, density, viscosity, etc. This data is direct evidence for determining oil and gas reservoirs, and can also assist in determining the gas-oil interface. However, the number of such tests is generally small, especially in the early stages of oil and gas reservoir development.

[0060] Well logging interpretation of gas-water and oil-water interface results refers to the determination of the gas-water and oil-water interface positions in the reservoir through analysis and interpretation of well logging data.

[0061] Well logging is to obtain information about formation characteristics and reservoir properties by measuring the electrical, acoustic, nuclear magnetic resonance and other physical properties of underground reservoirs. In well logging interpretation, commonly used logging curves include density, acoustic wave velocity, resistivity, etc.

[0062] By analyzing these logging curves, logging interpreters can identify gas-water or oil-water interfaces. Specific methods may involve the following aspects:

[0063] 1. Density Log: Density log measures the density of the formation. Water usually has a higher density, followed by oil, while gas (such as natural gas) has a lower density. Therefore, density log can be used to distinguish the presence of gas-oil and oil-water, and determine the gas-oil and oil-water interfaces.

[0064] 2. Acoustic Log: Acoustic logging measures the propagation velocity of sound waves in the formation. Different fluids (such as gas and water) have different sound wave velocities. By analyzing the acoustic logging curve, the location of the gas-water interface can be determined based on velocity anomalies and reflection characteristics.

[0065] 3. Resistivity Log: Resistivity logging can measure the radial distribution of resistivity of the formation. According to the difference in electrical conductivity of water, oil and gas, the position of the oil-water or gas-water interface can be inferred.

[0066] Oil and gas shows on cores refer to the presence or signs of oil and gas observed in core samples. When core samples are taken out of the well and analyzed, geologists, core interpreters or core engineers will pay attention to the following aspects to determine the oil and gas shows in the rock:

[0067] 1. Observe the form in which the oil and gas appear: You can observe the form in which the oil and gas appear, such as oil in liquid form, or bubbles or gas funnels in gas form.

[0068] 2. Observe the color and texture of the core: Rocks containing oil and gas usually have certain color changes, such as greasy sheen, gray or yellow color, and changes in rock texture, such as signs of oil immersion or penetration.

[0069] 3. Bubble and gas release: Bubble release or gas release can be observed in core samples, which may mean the presence of gas in the rock.

[0070] 4. Smell: Observe the smell of oil or natural gas by smelling it. This is a way to determine whether there is oil or gas in the core.

[0071] S5. Utilize the mining effect of the gas layer in the neutron and density curves and combine it with the position of the gas-water or oil-water interface to determine the gas-oil interface.

[0072] The mining effect of gas layers in neutron and density curves refers to a method of determining the location and properties of gas layers by analyzing and interpreting the differences between neutron and density record curves when there are differences between them. In the process of oil exploration, well logging tools are usually used to measure the neutron and density responses of gas layers in the well. Neutron records are used to determine the hydrogen content in the gas layer, while density records are used to measure the density of the rock. When a gas layer exists, the gas layer portion will produce an obvious "mining" effect in the neutron and density curves due to the low density and low neutron response of the gas. This mining effect can help geological engineers determine the existence and boundaries of gas layers, and then make correct decisions on oil exploration and development.

[0073] Embodiment 2:

[0074] like Figure 2-Figure 4 As shown in the figure, a method for determining the gas-oil interface of an oil and gas reservoir according to Example 1 of the present invention is shown. Figure 3 An example of determining the gas-oil interface in a clastic oil and gas reservoir in a certain place is shown.

[0075] like Figure 2 As shown, step S1, obtaining the oil and gas reservoir data of the target oil and gas reservoir AT1 in the middle oil group of the Triassic system.

[0076] Specifically, the oil and gas reservoir data of the AT1 Triassic Zhongyou Formation include core data, drilling data, logging data, well logging data, oil test data, production test data and fluid high-pressure physical property data.

[0077] Step S2, determining the oil and gas layer using the drilling and logging display data.

[0078] During the drilling process, the drilling time is low and the gas logging is abnormal. The methane content in the gas layer is relatively high. The cores of the oil and gas layer sections often have oil and gas displays of different levels, and the target layer is determined to be the oil and gas layer.

[0079] Step S3, determining the oil and gas layer using the well logging, oil testing and production testing data.

[0080] The oil and gas layers are preliminarily determined based on the logging curve characteristics and logging interpretation results of the oil and gas layers and water layers. The oil layer section, water layer section and gas layer section are further determined based on the well testing and oil testing results. For example, the logging interpretation of the target layer of a well is an oil and gas layer, and the production well test shows a certain gas production, and the gas-oil ratio is greater than 600m 3 / d, the target layer is generally judged to be a gas layer; if there is a certain oil and gas production during oil testing, and the gas-oil ratio is lower than 600m 3 / d. The target layer is generally judged to be an oil layer. At the same time, if there is high-pressure physical property test data of the production well, it is also the basis for judging the oil and gas layer.

[0081] Step S4, using logging interpretation, core and fluid high pressure physical property data display to determine the gas-water interface.

[0082] like Figure 3 As shown, the gas-water interface of the target layer is determined based on the well logging interpretation results of the gas-water interface of the single well in the target well area and the oil and gas display of the core, combined with the test results of subsequent further laboratory tests and analysis.

[0083] Step S5, using the mining effect of the gas layer in the neutron and density curve to determine the gas-oil interface.

[0084] refer to Figure 4 , on the well-connected profile, select the well-connected profile of vertical wells and altitude depth; select natural potential, natural gamma, well diameter, deep and shallow induction resistivity, neutron, and density curves as the main curves for oil and gas layer division. On the profile, overlap the neutron and density curves of the water layer near the oil and gas layer of the development well, and observe the amplitude difference of the neutron and density curves of the oil and gas layer. The amplitude difference of the gas layer is significantly greater than that of the oil layer. For reservoirs containing both gas and oil, the amplitude difference is larger at the top and smaller at the bottom. At the position where the amplitude difference is significantly reduced, the half-amplitude point of the curve change is selected as the gas-oil interface. The original gas-water interface is transformed into the oil-water interface. Example: After the production wells in the well section below the perforated gas-oil interface are put into production, the gas-oil ratio is lower than 400m 3 / t, which is a characteristic of reservoir production, proving that the gas-oil interface determined by this method is reliable.

[0085] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for determining a gas-oil interface in an oil and gas reservoir, It is characterized in that The following steps are involved: S1. Obtaining oil and gas reservoir data of the target oil and gas reservoir; S2. Determine whether the target layer is an oil and gas layer by using the drilling and logging display data; S3. Determine the oil and gas layer and water layer sections of the target layer using well logging, oil testing and production test data; S4. Use logging interpretation results and core displays to determine the location of the gas-water or oil-water interface; S5. Utilize the mining effect of the gas layer in the neutron and density curves and combine it with the position of the gas-water or oil-water interface to determine the gas-oil interface.

2. A method for determining the gas-oil interface in an oil and gas reservoir according to claim 1, It is characterized in that The oil and gas reservoir data in step S1 include core data, drilling data, logging data, well logging data, oil test data, production test data and fluid high-pressure physical property data.

3. A method for determining the gas-oil interface in an oil and gas reservoir according to claim 1, It is characterized in that Step S2 is specifically as follows: during the drilling process, the drilling time of the oil and gas-bearing sandstone is low, the gas logging is abnormal, and the gas layer has a high methane content in the gas logging. The oil and gas layer is determined according to the oil and gas displays of different levels in the core of the oil and gas layer section.

4. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 1, It is characterized in that In step S3, the oil and gas layers are preliminarily determined based on the logging curve characteristics and logging interpretation results of the oil and gas layers and water layers; and the oil layer section, water layer section and gas layer section are further determined in combination with the well testing and oil testing results.

5. A method for determining the gas-oil interface in an oil and gas reservoir according to claim 4, It is characterized in that The test results include test layer liquid production, oil and gas production, and pressure data.

6. A method for determining the gas-oil interface in an oil and gas reservoir according to claim 5, It is characterized in that The logging curves of the oil and gas layer section show low natural gamma, negative abnormal natural potential, regular wellbore, and the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, and RILD≥0.6Ω.m; If the production well has gas production during testing and the gas-oil ratio is greater than 600m 3 / d, the target layer is judged to be a gas layer; if there is oil and gas production during oil testing, and the gas-oil ratio is lower than 600m 3 / d. Determine that the target layer is an oil layer.

7. A method for determining the gas-oil interface in an oil and gas reservoir according to claim 6, It is characterized in that The logging curves of the water layer section show low gamma, negative natural potential anomaly, regular well diameter, and the relationship between the three resistivity curves is RILD<RILM<RFOC, showing high invasion characteristics, RILD≤0.3Ω.m.

8. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 1, It is characterized in that In step S4, the gas-water interface and the oil-water interface are determined based on the well logging interpretation results of the single well in the well area and the oil and gas display of the core, combined with the test results of the laboratory test and analysis.

9. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 8, It is characterized in that The logging interpretation includes density logging, which distinguishes the existence of gas, oil and water based on the density of water> density of oil> density of gas, and determines the gas-oil, gas-water and oil-water interfaces.

10. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 9, It is characterized in that The logging interpretation also includes sonic logging, which determines the position of the gas-water and oil-water interfaces based on velocity anomalies and reflection characteristics by analyzing sonic logging curves according to different sonic velocities of the fluid.

11. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 10, It is characterized in that The logging interpretation also includes resistivity logging, which measures the radial distribution of resistivity of the formation and infers the position of the oil-water or gas-water interface based on the difference in electrical conductivity of water, oil and gas.

12. A method for determining a gas-oil interface in an oil and gas reservoir according to claim 1, It is characterized in that Step S5 specifically comprises the following steps: using the neutron density curve overlap method to define the gas-oil interface of a single well, that is, overlapping the neutron and density curves of the water layer near the target layer of the development well, and observing the amplitude difference of the neutron and density curves in the oil and gas layer. The amplitude difference of the gas layer is greater than that of the oil layer. For reservoirs containing both gas and oil, the amplitude difference is larger at the top and smaller at the bottom. At the position where the amplitude difference decreases, the half-amplitude point of the curve change is the gas-oil interface.

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