Method for judging formation time of reservoir cracked asphalt by using solid cracked asphalt-saline two-phase inclusion

Abstract

The invention belongs to the field of petroleum geology, and particularly discloses a method for judging formation time of reservoir cracked asphalt by using a solid cracked asphalt-saline water two-phase inclusion. According to the method, the lithofacies characteristics of the fluid inclusion in the fluid inclusion slice are determined, the types of various fluid inclusion developed in the reservoir diagenetic minerals are determined according to the lithofacies characteristics, and the solid cracked asphalt-salt water two-phase inclusion is found in the various types of inclusion; the method comprises the following steps: carrying out microscopic uniform temperature test on an inclusion to obtain the uniform temperature and freezing point of the inclusion, carrying out PVT simulation on the fluid inclusion by using the uniform temperature and freezing point to obtain the capture temperature of the fluid inclusion, and then inputting the obtained capture temperature data to a burial history curve of the region, thereby finally accurately obtaining the formation time of the cracked asphalt. The method is simple and efficient, and a new thought and method are provided for limiting the forming period of the cracked asphalt.

Description

Technical Field

[0001] The invention belongs to the field of petroleum geology, and in particular relates to a method for determining the formation time of reservoir cracked asphalt by using solid cracked asphalt-brine two-phase inclusions. Technical Background

[0002] At present, the existence of cracked asphalt is very widespread in sedimentary basins. Almost all common oil and gas reservoirs are accompanied by the development of cracked asphalt to a greater or lesser extent. The cracked asphalt in the reservoir is almost all formed by the in-situ cracking of early crude oil. Its carbonization degree is extremely high and usually only exists in the solid phase. At present, the research on the determination method of oil and gas filling time in the reservoir by predecessors has been very mature. For example, the formation period of oil and gas is limited by lithofacies, diagenetic sequence, geochemical data analysis, fluid inclusion analysis and fault activity analysis. However, there are some gaps in the research on the formation period of cracked asphalt, another important hydrocarbon in the reservoir. It is worth noting that the formation time of cracked asphalt can be accurately determined by Re-Os isotope dating, but this isotope analysis method, apart from the complex and time-consuming process, is also extremely costly and is almost not suitable for large-scale popularization.

[0003] To study the solid cracked asphalt in the reservoir, we must clarify the information of the fluid in the reservoir. To clarify the information of the original fluid, we must find a commonly seen sample for studying microscopic geological processes. Fluid inclusions, as the most direct natural geological sample that can record the information of the original fluid, have an irreplaceable position in the analysis and study of geological processes such as diagenesis, mineralization, basin fluid evolution, and fluid migration. Therefore, we try to find methods from the perspective of fluid inclusions. At the same time, it is feasible to use fluid inclusion analysis methods to limit the formation period of cracked asphalt, an important hydrocarbon in the reservoir, both from a theoretical and technical perspective. It is low-cost, simple and efficient. Summary of the invention

[0004] The present invention provides a method for accurately determining the formation time of reservoir cracking asphalt by using solid cracking asphalt-brine two-phase inclusions, which can effectively limit the formation period of solid cracking asphalt in the reservoir in a simple and efficient manner.

[0005] To achieve the above object, the present invention adopts the following technical solutions: Fluid inclusion thin sections made from reservoir rock samples; Determine the petrographic characteristics contained in the fluid inclusion combination, wherein the petrographic characteristics include the size, shape, structure, occurrence, phase combination and phase volume ratio characteristics, internal material composition, and fluid inclusion stage of the fluid inclusion; According to the petrographic characteristics, various types of fluid inclusions developed in the reservoir diagenetic minerals are determined, specifically including: natural gas-liquid hydrocarbon-solid cracking asphalt three-phase inclusions; brine-solid cracking asphalt two-phase inclusions; natural gas-liquid hydrocarbon two-phase inclusions; brine inclusions; natural gas-solid cracking asphalt two-phase inclusions; single natural gas phase inclusions; single solid cracking asphalt inclusions, etc.

[0006] We found the research samples we needed among various types of inclusions - solid cracked asphalt-brine two-phase inclusions.

[0007] Then the inclusion was subjected to a microscopic uniform temperature test to obtain the uniform temperature and freezing point of the inclusion.

[0008] The capture temperature of fluid inclusions is obtained by PVT simulation using uniform temperature and freezing point.

[0009] The captured temperature data obtained are projected onto the burial history curve of the area, thus ultimately accurately obtaining the time of formation of cracked asphalt.

[0010] Through the scheme provided in the embodiment of the present invention, a fluid inclusion thin section made from a reservoir rock sample is obtained; the petrographic characteristics contained in the fluid inclusion combination are determined; the various types of fluid inclusions developed in the reservoir diagenetic minerals are determined based on the petrographic characteristics; the research sample we need, namely, a solid cracked asphalt-brine two-phase inclusion, is found among the various types of inclusions; then the inclusion is subjected to a microscopic uniform temperature test to obtain the uniform temperature and freezing point of the inclusion; the uniform temperature and freezing point are used to perform PVT simulation on the fluid inclusion to obtain its capture temperature; the obtained capture temperature data is projected onto the burial history curve of the area, thereby ultimately and accurately obtaining the time when the cracked asphalt was formed.

[0011] The present invention has the following beneficial effects: This method can effectively limit the formation period of solid cracked asphalt in the reservoir by simply applying petrographic observation of fluid inclusions, laser Raman spectroscopy analysis of fluid inclusions, microscopic homogenization temperature testing of fluid inclusions, PVT simulation pressure calculation and correspondence of burial history maps. It cleverly avoids the complexity of obtaining accurate geochemical data and limits the formation period of cracked asphalt from the perspective that fluid inclusion records can record the original fluid in the reservoir diagenesis process. It is simple and efficient.

[0012] The present invention can provide assistance for relevant research on the formation period of solid cracked asphalt in reservoirs of oil and gas basins, and provides a new idea and method for limiting the formation period of the cracked asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A schematic flow chart of a method for accurately determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions provided by the present invention; Figure 2 This is a specific experimental flow chart of the present invention for accurately determining the formation time of reservoir cracking asphalt; Figure 3 The invention sorts out the pattern diagram of the types of inclusions developed in the diagenetic minerals and cements by in-situ cracking of crude oil in the reservoir; Figure 4 It is a schematic diagram for selecting solid cracking asphalt-brine two-phase inclusions in the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0015] The following is a description of the solution of the present application in conjunction with the accompanying drawings. Figure 1 As shown, Figure 1 A schematic flow chart of a method for determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions provided by the invention includes: S1. Fluid inclusion thin sections made from reservoir rock samples.

[0016] Collect rock samples and make fluid inclusion thin sections according to the petroleum industry standard SY / T 5913-2004.

[0017] S2. Determine the petrographic characteristics contained in the fluid inclusion thin sections made from reservoir rock samples.

[0018] Through microscopic observation of fluid inclusions combined with laser Raman spectroscopy analysis, and ultimately a comprehensive analysis and judgment of fluid inclusion petrography and laser Raman spectroscopy, the petrographic characteristics of fluid inclusions such as size, morphology, structure, occurrence, phase combination and phase volume ratio characteristics, internal material composition, and fluid inclusion stage in the fluid inclusions are determined. Figure 2 A schematic diagram of a process for accurately determining the formation time of reservoir cracking asphalt provided in an embodiment of the present application.

[0019] S3. Determine the type and combination of the fluid inclusions based on the petrographic characteristics of the inclusions and laser Raman component analysis.

[0020] Before determining the types of various fluid inclusions developed in the reservoir diagenetic minerals according to the petrographic characteristics, it is necessary to clearly determine the types of host minerals where the inclusions are developed in the reservoir samples through microscopic observation. If the inclusions are developed in the clastic particles, secondary inclusions that are often distributed along microcracks must be selected, because only the secondary inclusions developed in the clastic particles can record the fluid generation properties during the diagenesis process. If the inclusions are developed in the pore cement, both primary and secondary inclusions can be used for research, because both primary and secondary inclusions developed in the pore cement can represent the formation during the diagenesis process and reflect the properties of the fluid during the diagenesis process.

[0021] After the above work is completed, the morphology and structure of the inclusion are used to distinguish whether it is a FIA under a transmitted light microscope and a fluorescence microscope respectively. Then, taking FIA as the research object, the type of fluid inclusion is distinguished by observing the phase combination and phase volume ratio characteristics, internal material composition, and fluid inclusion stage of the fluid inclusion.

[0022] like Figure 3 As shown, according to the various fluid inclusion types developed in the diagenetic minerals of the crude oil cracking reservoir, they specifically include: natural gas-liquid hydrocarbon-solid cracking asphalt three-phase inclusions; brine-solid cracking asphalt two-phase inclusions; natural gas-liquid hydrocarbon two-phase inclusions; brine inclusions; natural gas-solid cracking asphalt two-phase inclusions; single natural gas phase inclusions; single solid cracking asphalt inclusions, etc.

[0023] S4. Identify and screen out the research samples we need from various types of inclusions - solid cracked asphalt-brine two-phase inclusions.

[0024] Through a large number of experimental observations, it is found that due to the complexity of fluids, multiple inclusions with different components are often developed in reservoir diagenetic minerals, such as liquid hydrocarbon inclusions, liquid hydrocarbon-water inclusions, liquid hydrocarbon-natural gas inclusions, asphalt-natural gas inclusions, asphalt-water inclusions and three-phase liquid hydrocarbon-water-asphalt inclusions, and even liquid hydrocarbon-natural gas-water-asphalt four-phase inclusions. Among them, the solid asphalt-water two-phase inclusions can be used as the research object for us to understand the asphalt filling period.

[0025] like Figure 4As shown in the figure, the formation of this kind of solid asphalt-water two-phase inclusion in the reservoir is due to the capture of solid asphalt and brine in the reservoir during the diagenesis process. Therefore, the temperature and pressure conditions of the solid asphalt and brine captured in the same inclusion are consistent, which can be called a perfect FIA. The conventional FIA we mentioned refers to the combination of inclusions with the same occurrence in petrography that capture the same period of fluid, and the fluid information recorded by their inclusions is consistent. In oil and gas basins, the temperature and pressure conditions of oil and gas accumulation and the period of oil and gas accumulation are usually restored by using brine inclusions with the same FIA ​​as the liquid hydrocarbon inclusions. According to Roedder's three principles, if the homogenization temperature data of the inclusion is to be valid, the following conditions must be met: ① The inclusion captures a single, uniform fluid phase; ② The volume of the inclusion has not changed since the capture (isovolumetric system); ③ The composition of the inclusion has not changed since the capture. For the solid asphalt-brine two-phase inclusions in which the initial captured asphalt is solid, it is reasonable to meet Roedder's three principles, and it is effective to test the homogenization temperature on them. Because the initial solid asphalt will not mix with the brine of the same period, the capture of the brine phase also meets the condition of uniform capture. In addition, solid asphalt is solid, and its volume will not change after being captured into the inclusion, so the entire system also meets the principle of isochoric system after healing and closure. Therefore, using this inclusion for microscopic temperature testing can best ensure the contemporaneity of asphalt and brine. Because in the standard FIA, there is also a time difference in the healing of each inclusion, and the recorded physical and chemical properties are more or less different. The only two substances captured simultaneously into the same inclusion can be called a perfect FIA.

[0026] It is worth mentioning that the asphalt in the solid cracked asphalt-brine two-phase inclusion needs to be strictly screened. Based on microscopic observation and Raman shift asphalt reflectivity recovery, ensure that the selected asphalt is solid cracked asphalt. Solid cracked asphalt is solid under a microscope, often appearing in the form of plates, sheets and aggregates, with sharp edges and corners, and its asphalt reflectivity is generally greater than 1.4%. The asphalt in the solid cracked asphalt-brine two-phase inclusion must be solid in a wide temperature range to theoretically meet the uniform capture and isochoric system in Roedder's three principles to ensure the validity of the inclusion uniform temperature test data.

[0027] S5. Then, the inclusion is subjected to a microscopic uniform temperature test to obtain the uniform temperature and freezing point of the inclusion, and the uniform temperature and freezing point are used to simulate the PVT of the fluid inclusion to obtain its capture temperature.

[0028] Before conducting microscopic homogeneous temperature tests on solid cracked asphalt-brine two-phase inclusions and obtaining the homogeneous temperature and freezing point of the inclusions, it is necessary to confirm whether the gas phase contained in the FIA ​​is only water vapor formed by gas-liquid separation of liquid water due to temperature reduction through laser Raman spectroscopy and the bubble volume ratio of the brine inclusions in the same fluid inclusion assemblage (FIA). If the gas-liquid ratio of solid cracked asphalt-brine two-phase inclusions and ordinary brine inclusions in the same FIA ​​tends to be consistent, it is preliminarily shown that the bubbles are not mixed gases, but only water vapor (in petrography, the gas volume ratio of mixed gases is generally greater than that of water vapor). The most critical and accurate method is to use Raman spectroscopy to directly analyze the composition of the bubbles to directly identify the gas composition. If the bubble composition of the solid cracked asphalt-brine two-phase inclusions is only water, then this inclusion is the ideal sample for our study.

[0029] Based on the above work, a microscopic uniform temperature test was carried out on the inclusions to obtain the uniform temperature and freezing point of the inclusions, and the uniform temperature and freezing point were used to simulate the PVT of the fluid inclusions to obtain its capture temperature.

[0030] S6. Project the captured temperature data onto the burial history curve of the area, so as to finally and accurately obtain the time of formation of cracked asphalt.

[0031] Through the scheme provided by the embodiment of the present invention, a fluid inclusion thin section made from a reservoir rock sample is obtained; the petrographic characteristics contained in the fluid inclusion combination are determined; various fluid inclusion types developed in the reservoir diagenetic minerals are determined according to the petrographic characteristics; the research sample we need, solid cracked asphalt-brine two-phase inclusion, is found among various types of inclusions; a microscopic uniform temperature test is then performed on the inclusion to obtain the uniform temperature and freezing point of the inclusion; the PVT simulation of the fluid inclusion is performed using the uniform temperature and freezing point to obtain its capture temperature; the obtained capture temperature data is projected onto the burial history curve of the region, thereby finally accurately obtaining the time of formation of cracked asphalt (specific time is). This method only requires the application of petrographic observation of fluid inclusions, laser Raman spectroscopy analysis of fluid inclusions, microscopic uniform temperature testing of fluid inclusions, PVT simulation pressure calculation and correspondence of burial history diagrams to effectively limit the formation period of solid cracked asphalt in the reservoir, cleverly avoiding the complexity of obtaining accurate geochemical data, and limiting the formation period of cracked asphalt from the perspective that fluid inclusion records can record the original fluid in the reservoir diagenesis process, which is simple and efficient. The present invention can provide assistance for relevant research on the formation period of solid cracked asphalt in reservoirs of oil and gas basins, and provides a new idea and method for limiting the formation period of the cracked asphalt.

[0032] In summary, when solid cracked asphalt-brine inclusions are developed in reservoir samples, microthermometry can be performed directly on them, and then combined with fluid inclusion PVT simulation to restore the capture temperature of cracked asphalt and brine in the inclusions, and finally correspond to the burial history map of the study area, so as to obtain the formation period of solid cracked asphalt in the reservoir of the oil and gas basin.

[0033] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps or modules recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A method for determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions, characterized in that: The following steps are involved: S1. Fluid inclusion thin sections made from reservoir rock samples; S2. Determine the petrographic characteristics contained in the fluid inclusion thin sections made from the reservoir rock samples; S3, determining the type and combination of the fluid inclusions according to the petrographic characteristics of the inclusions and laser Raman component analysis; S4. Determine and screen out the required solid cracked asphalt-brine two-phase inclusion samples from various types of inclusions; S5. Then, the inclusion is subjected to a microscopic uniform temperature test to obtain the uniform temperature and freezing point of the inclusion, and the uniform temperature and freezing point are used to simulate the fluid inclusion PVT to obtain its capture temperature; S6. Project the captured temperature data onto the burial history curve of the area, so as to finally and accurately obtain the time of formation of cracked asphalt.

2. The method of determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions according to claim 1, characterized in that: In step S1, the fluid inclusion thin section is made according to the petroleum industry standard SY / T 5913-2004.

3. The method for determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions according to claim 1, characterized in that: In step S2, the size, morphology, structure, occurrence, phase combination and phase volume ratio characteristics, internal material composition and fluid inclusion period of the fluid inclusions are determined by microscopic observation of the fluid inclusions combined with laser Raman spectroscopy analysis, and finally a comprehensive analysis and judgment of the fluid inclusion petrography and laser Raman spectroscopy.

4. The method of determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions according to claim 1, characterized in that: In step S3, the types of fluid inclusions are distinguished by observing the phase combination and phase volume ratio characteristics, internal material composition, and fluid inclusion stages of the fluid inclusions.

5. The method of determining the formation time of reservoir cracked asphalt using solid cracked asphalt-brine two-phase inclusions according to claim 1, characterized in that: In step S4, microscopic observation and Raman shift asphalt reflectivity recovery are used to ensure that the selected asphalt is solid cracked asphalt.

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