Evaluation method of oil and gas transport capacity of premature oil source faults

Abstract

The invention relates to an oil and gas conductivity evaluation method for a premature oil source fault, and belongs to the technical field of oil and gas exploration. The oil and gas conductivity evaluation method comprises the following steps: determining the longitudinal cutting layer system of the fault according to the existing seismic data results, and judging whether the fault is a premature oil source fault; calculating the fault distance and fault dip of the premature oil source fault according to the measured horizontal distance and vertical distance of the premature oil source fault disconnecting the top surface of the source rock layer system, and the angle between the fault strike and the survey line; calculating the cross-sectional normal pressure of the premature oil source fault according to the cross-sectional depth, fault dip, formation water density and overlying stratum density of the premature oil source fault; establishing a conductivity coefficient calculation model of the premature oil source fault according to the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of the premature oil source fault, so as to quantitatively evaluate the oil and gas conductivity of the premature oil source fault.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration, and in particular relates to a method for evaluating the oil and gas conductivity of an early-aging oil source fault. Background Art

[0002] After the source rock is deep underground and is subjected to geological conditions such as high temperature and high pressure to generate oil and gas, these oil and gas need to pass through channels to migrate to the reservoir. The premature oil source fault is a special type of fault in the field of petroleum geology. Its main function is to connect the source rock (the rock that generates oil and natural gas) and the reservoir, providing a channel for the migration of oil and gas. The premature oil source fault is like a "highway", and oil and gas can migrate upward along the cracks and broken zones of the fault. Therefore, the oil and gas transport capacity of the premature oil source fault will directly affect the migration efficiency and effect of oil and gas.

[0003] At present, there is a lack of systematic and precise methods for studying the transport capacity of premature oil-source faults, which makes it difficult to accurately determine their contribution to the oil and gas migration process, limiting the in-depth understanding of the distribution laws of oil and gas reservoirs and the improvement of exploration efficiency.

[0004] Therefore, designing a method that can scientifically and effectively evaluate the transport capacity of premature oil-source faults is of great significance to oil and gas exploration and development. Summary of the invention

[0005] In view of the shortcomings existing in the related technologies, the present invention provides a method for evaluating the oil and gas conductivity of a premature oil source fault. Based on the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of the premature oil source fault, a conductivity coefficient calculation model for the premature oil source fault is established, and the conductivity of the premature oil source fault is quantitatively evaluated according to the calculation results of the model.

[0006] The present invention provides a method for evaluating the oil and gas conductivity of an early-aging oil source fault, comprising the following steps:

[0007] Steps for identifying premature oil source faults: Determine the vertical cutting layer of the fault based on the existing seismic data results, and determine whether the fault is a premature oil source fault based on whether the fault breaks into the underlying source rock layer and does not break into the overlying sedimentary strata during the reservoir formation period;

[0008] Calculation steps of fault throw and fault dip: Calculate the fault throw and fault dip of the premature oil source fault according to the measured horizontal distance and vertical distance of the premature oil source fault from the top surface of the source rock formation system and the angle between the fault strike and the survey line;

[0009] Calculation steps of cross-section normal pressure: Calculate the cross-section normal pressure of the premature oil source fault according to the cross-section depth, fault dip, formation water density and overlying formation density of the premature oil source fault;

[0010] Conductivity evaluation steps: According to the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of the premature oil source fault, a conductivity coefficient calculation model of the premature oil source fault is established to quantitatively evaluate the oil and gas conductivity of the premature oil source fault.

[0011] This technical solution classifies the faults that cut into the source rock system and have not been broken to the corresponding sedimentary strata in the accumulation period as premature oil source faults based on the interpretation results of faults and strata in the seismic profile; characterizes the fault distance and fault dip characteristics of premature oil source faults; calculates the normal pressure of the fault section based on the logging and well logging data of the wells drilled near the fault, and establishes a conductivity coefficient calculation model by comprehensively considering factors such as fault distance, fault dip, section normal pressure, and formation pressure, and quantitatively characterizes the conductivity capacity of premature oil source faults for oil and gas based on the calculation results of the model.

[0012] In some of the embodiments, in the step of identifying the early-degradation oil source fault, if the fault breaks into the underlying source rock layer and does not break to the overlying sedimentary strata during the reservoir formation period, the fault is identified as a premature oil source fault.

[0013] In some of the embodiments, in the step of calculating the fault throw and fault dip, the calculation formula for the fault throw of the early-decay type oil source fault is:

[0014]

[0015] Where T is the fault distance; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

[0016] In some of the embodiments, in the step of calculating the fault throw and fault dip, the calculation formula for the fault dip of the early-decay type oil source fault is:

[0017]

[0018] In the formula, is the fault dip; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

[0019] In some of the embodiments, in the cross-section normal pressure calculation step, the density of the overlying strata of the premature oil source fault is calculated based on the density logging data of a single well near the premature oil source fault; the calculation formula for the density of the overlying strata of the premature oil source fault is:

[0020]

[0021] In the formula, is the density of the overlying strata; DEN is the density logging; H is the section depth.

[0022] In some of the embodiments, in the cross section normal pressure calculation step, the cross section normal pressure of the premature oil source fault is calculated as follows:

[0023]

[0024] In the formula, is the cross-sectional positive pressure; is the density of the overlying strata; H is the depth of the section; is the formation water density; is the fault dip angle.

[0025] In some of the embodiments, in the conductivity evaluation step, the calculation model of the conductivity coefficient of the premature oil source fault is:

[0026]

[0027] Where, C is the conductivity coefficient of the early-aging oil source fault; T is the fault distance; is the fault dip; is the formation pressure coefficient; is the cross-sectional positive pressure.

[0028] Based on the above technical scheme, the method for evaluating the oil and gas conductivity of the premature oil source fault in the embodiment of the present invention is based on the factors such as the fault distance, fault dip, cross-section normal pressure, formation pressure, etc. of the premature oil source fault, and establishes an oil and gas conductivity coefficient calculation model. The oil and gas conductivity of the premature oil source fault is quantitatively characterized according to the calculation results of the model, thereby realizing a scientific and effective evaluation of the oil and gas conductivity of the premature oil source fault. It not only solves the problem that the oil and gas conductivity of the premature oil source fault is difficult to evaluate in the past, but also the evaluation results can be effective and accurate. The evaluation results of the oil and gas conductivity of the premature oil source fault are applied to the analysis of oil and gas migration volume and favorable migration direction, which can provide a direct basis for the prediction of favorable areas and effectively reduce drilling risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0030] Figure 1 It is a flow chart of an embodiment of a method for evaluating the oil and gas conductivity of a premature oil source fault of the present invention;

[0031] Figure 2 A cross-sectional view of the oil source fault of the survey line No. 6729 in the Y area of ​​the Xihu Sag, one embodiment of the method for evaluating the oil and gas conductivity of the premature oil source fault of the present invention;

[0032] Figure 3This is a cross-sectional view of the oil source fault at survey line No. 7300 in the Y area of ​​the Xihu Sag, one embodiment of the method for evaluating the oil and gas conductivity of the premature oil source fault of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0035] The terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Early-degradation oil source faults are channels connecting source rock layers with sedimentary strata during the accumulation period. The location of early-degradation oil source faults is generally between source rock layers and sedimentary strata during the accumulation period. The cracks and fracture zones of early-degradation oil source faults provide a migration path for oil and gas, allowing oil and gas to migrate from deep source rock layers to shallow sedimentary strata during the accumulation period.

[0038] Source rock layers are usually located deep underground. The organic matter in the source rock is converted into oil and gas under certain temperature and pressure conditions.

[0039] The sedimentary strata during the accumulation period are at the top. These strata are deposited after the source rocks generate oil and gas, and provide a place for the accumulation of oil and gas. Reservoirs such as sandstone layers in the sedimentary strata during the accumulation period can store oil and gas that migrate from the oil source fault.

[0040] In an exemplary embodiment of the method for evaluating the oil and gas conductivity of an early-aging oil source fault of the present invention, as shown in the attached Figure 1 As shown, the method for evaluating the oil and gas conductivity of the premature oil source fault includes the following steps:

[0041] Steps for identifying premature oil source faults: Determine the vertical cutting layer of the fault based on the existing seismic data results, and determine whether the fault is a premature oil source fault based on whether the fault breaks into the underlying source rock layer and does not break into the overlying sedimentary strata during the reservoir formation period;

[0042] Calculation steps of fault throw and fault dip: Calculate the fault throw and fault dip of the premature oil source fault according to the measured horizontal distance and vertical distance of the premature oil source fault from the top surface of the source rock formation system and the angle between the fault strike and the survey line;

[0043] Calculation steps for section normal pressure: Calculate the section normal pressure of the premature oil source fault according to the section depth, fault dip, formation water density and overlying stratum density of the premature oil source fault. It should be noted that the section normal pressure of the premature oil source fault is the section normal pressure of the top surface of the source rock layer.

[0044] Conductivity evaluation steps: According to the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of the premature oil source fault, a conductivity coefficient calculation model of the premature oil source fault is established to quantitatively evaluate the oil and gas conductivity of the premature oil source fault.

[0045] In the above-mentioned method for evaluating the oil and gas conductivity of premature oil source faults, the faults that cut into the source rock system and have not been broken to the corresponding sedimentary strata in the accumulation period are classified as premature oil source faults according to the interpretation results of faults and strata in the seismic profile; for premature oil source faults, the fault distance and fault dip characteristics are characterized, and the fault section normal pressure is calculated based on the logging and well logging data of the wells near the fault, and a conductivity coefficient calculation model is established by comprehensively considering the fault distance, fault dip, section normal pressure, formation pressure and other factors, and the oil and gas conductivity of premature oil source faults is quantitatively characterized according to the calculation results of the model, so as to conduct a scientific and effective evaluation of the conductivity of premature oil source faults.

[0046] Based on the fault distance, fault dip, cross-section normal pressure, formation pressure and other factors of the premature oil-source fault, a calculation model for the oil and gas conductivity coefficient is established. The oil and gas conductivity of the premature oil-source fault is evaluated according to the calculation results of the model. This not only solves the problem of the difficulty in evaluating the oil and gas conductivity of the premature oil-source fault, but also quantifies the evaluation results in a scientific, effective and accurate manner. The evaluation results of the oil and gas conductivity of the premature oil-source fault are applied to the analysis of oil and gas migration volume and favorable migration direction, which can provide a direct basis for the prediction of favorable areas and effectively reduce drilling risks.

[0047] In the step of identifying the early-degradation oil source fault, if the fault breaks into the underlying source rock layer and does not break to the overlying sedimentary strata during the reservoir formation period, the fault is identified as a premature oil source fault.

[0048] Through the seismic data, the longitudinal cutting layer system of the fault is determined, and the early-degradation oil source faults that break into the underlying source rock layer but not into the overlying sedimentary strata during the reservoir formation period are selected from the numerous faults as the research objects, and then the research work on the early-degradation oil source faults is carried out.

[0049] In the calculation step of fault throw and fault dip, the calculation formula of the fault throw of the early-decay type oil source fault is:

[0050]

[0051] Where T is the fault distance; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

[0052] In the calculation steps of fault throw and fault dip, the calculation formula of the fault dip of the early-decay type oil source fault is:

[0053]

[0054] In the formula, is the fault dip; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

[0055] It should be noted that fault throw and fault dip are important geometric parameters for describing fault morphology. Fault throw reflects the magnitude of the relative displacement of rocks on both sides of the fault, while fault dip reflects the degree of inclination of the fault. Quantification of these parameters helps to more accurately understand the spatial morphology of premature oil source faults. Fault throw and fault dip will affect the flow direction and difficulty of oil and gas in the fault zone.

[0056] In the cross-section normal pressure calculation step, the density of the overlying strata of the premature oil source fault is calculated based on the density logging data of a single well near the premature oil source fault. The calculation formula for the density of the overlying strata of the premature oil source fault is:

[0057]

[0058] In the formula, is the density of the overlying strata; DEN is the density logging; H is the section depth.

[0059] In the cross-section normal pressure calculation step, the calculation formula for the cross-section normal pressure of the early-aging oil source fault is:

[0060]

[0061] In the formula, is the cross-sectional positive pressure; is the density of the overlying strata; H is the depth of the section; is the formation water density; is the fault dip angle.

[0062] Deep underground, the migration of oil and gas is often affected by various pressures, and cross-section normal pressure is one of the key factors. Clarifying the cross-section normal pressure can determine whether the oil and gas have enough power to migrate in the special channel of the fault. Moreover, the cross-section normal pressure of the early-degradation oil source fault is equal to the cross-section normal pressure on the top of the source rock layer, which is also helpful to accurately analyze the initial migration dynamics of oil and gas in the fault channel after being discharged from the source rock.

[0063] In the conductivity evaluation step, the calculation model of the conductivity coefficient of the early-aging oil source fault is:

[0064]

[0065] Where, C is the conductivity coefficient of the early-aging oil source fault; T is the fault distance; is the fault dip; is the formation pressure coefficient; is the cross-sectional positive pressure.

[0066] By establishing a calculation model for the conductivity coefficient of premature oil-source faults, multiple factors affecting oil and gas conductivity can be integrated together to more objectively and accurately judge the role of the fault in the oil and gas migration process, that is, how much oil and gas it can transport and the efficiency of transporting oil and gas, thereby providing important decision-making basis for oil and gas exploration and development, such as determining whether it is worthwhile to carry out oil and gas exploitation near the fault.

[0067] Taking the premature oil source fault in the Y area of ​​Xihu Sag as an example, the evaluation method of the oil and gas conductivity of the premature oil source fault is introduced in detail.

[0068] The above-mentioned method for evaluating the oil and gas conductivity of the premature oil source fault comprises the following steps:

[0069] S1. Steps for identifying premature oil source faults

[0070] The fault interpretation results of the Y area were used to determine the vertical cutting strata of the fault. The strata in the Y area are, from top to bottom, Santan Formation, Liulang Formation, Yuquan Formation, Longjing Formation, Huashang Member, Huaxia Member and Pinghu Formation. Among them, the Pinghu Formation is the source rock layer, and the Santan Formation is the sedimentary stratum during the reservoir formation period. According to whether the fault breaks into the Pinghu Formation and does not break into the Santan Formation, 8 early-degradation oil source faults were identified, see Figure 2 and Figure 3 It should be noted that the eight early-aging oil-source faults are named F1, F2, F3, F4, F5, F6, F7, and F8 respectively.

[0071] S2. Calculation steps of fault throw and fault dip

[0072] The horizontal and vertical distances of the premature oil source faults that cut off the top surface of the Pinghu Formation source rock strata, as well as the angle between the fault strike and the survey line were measured, and the fault throw and dip angle of each premature oil source fault were calculated. The results are shown in Table 1.

[0073] Table 1

[0074]

[0075] S3. Calculation steps of cross-section normal pressure

[0076] Based on the density logging results, the density of the overlying strata is calculated. Then, combined with the section location depth, fault dip angle and formation water density, the section normal pressure characteristics of each early-degradation oil source fault are calculated. The results are shown in Table 2.

[0077] Table 2

[0078]

[0079] S4. Conductivity evaluation steps

[0080] According to the factors such as fault throw, fault dip, cross-section normal pressure and formation pressure coefficient of each premature oil source fault, the conductivity of each premature oil source fault is calculated. The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] The above-mentioned method for evaluating the oil and gas conductivity of premature oil source faults is based on the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of premature oil source faults, and a calculation model for the conductivity coefficient of premature oil source faults is established. The oil and gas conductivity of premature oil source faults is quantitatively evaluated according to the calculation results of the model. Not only is the evaluation method simple but the evaluation results are scientific and accurate. The evaluation results of the oil and gas conductivity of premature oil source faults are applied to the analysis of oil and gas migration volume and favorable migration direction, which can provide a direct basis for the prediction of favorable areas and effectively reduce drilling risks.

[0084] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0085] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for evaluating the oil and gas conductivity of a premature oil source fault, characterized in that: The following steps are involved: Steps for identifying premature oil source faults: Determine the vertical cutting layer of the fault based on the existing seismic data results, and determine whether the fault is a premature oil source fault based on whether the fault breaks into the underlying source rock layer and does not break into the overlying sedimentary strata during the reservoir formation period; Calculation steps of fault throw and fault dip: Calculate the fault throw and fault dip of the premature oil source fault according to the measured horizontal distance and vertical distance of the premature oil source fault from the top surface of the source rock formation system and the angle between the fault strike and the survey line; Calculation steps of cross-section normal pressure: Calculate the cross-section normal pressure of the premature oil source fault according to the cross-section depth, fault dip, formation water density and overlying formation density of the premature oil source fault; Conductivity evaluation steps: according to the fault distance, fault dip, cross-sectional normal pressure and formation pressure coefficient of the premature oil source fault, a conductivity coefficient calculation model of the premature oil source fault is established to quantitatively evaluate the oil and gas conductivity of the premature oil source fault; The calculation model of the conductivity coefficient of the premature oil source fault is: Where, C is the conductivity coefficient of the early-aging oil source fault; T is the fault distance; is the fault dip; is the formation pressure coefficient; is the cross-sectional positive pressure.

2. The method for evaluating the oil and gas conductivity of a premature oil source fault according to claim 1, characterized in that: In the step of identifying the premature oil source fault, if the fault breaks into the underlying source rock layer and does not break into the overlying sedimentary strata during the reservoir formation period, the fault is identified as a premature oil source fault.

3. The method for evaluating the oil and gas conductivity of a premature oil source fault according to claim 1, characterized in that: In the step of calculating the fault throw and fault dip, the calculation formula for the fault throw of the early-decay type oil source fault is: Where T is the fault distance; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

4. The method for evaluating the oil and gas conductivity of a premature oil source fault according to claim 1 or 3, characterized in that: In the step of calculating the fault throw and fault dip, the calculation formula for the fault dip of the early-aging oil source fault is: In the formula, is the fault dip; TV is the vertical distance; TH is the horizontal distance; θ is the angle between the fault strike and the survey line.

5. The method for evaluating the oil and gas conductivity of a premature oil source fault according to claim 1, characterized in that: In the cross-section normal pressure calculation step, the density of the overlying strata of the premature oil source fault is calculated based on the density logging data of a single well near the premature oil source fault. The calculation formula for the density of the overlying strata of the premature oil source fault is: In the formula, is the density of the overlying strata; DEN is the density logging; H is the section depth.

6. The method for evaluating the oil and gas conductivity of a premature oil source fault according to claim 1 or 5, characterized in that: In the cross-sectional normal pressure calculation step, the cross-sectional normal pressure of the premature oil source fault is calculated as follows: In the formula, is the cross-sectional positive pressure; is the density of the overlying strata; H is the depth of the section; is the formation water density; is the fault dip angle.

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