Quantitative evaluation method for oil and gas transmission capacity of reverse fault of forward and reverse rotation structure

Abstract

The invention provides a quantitative evaluation method for oil and gas transmission capacity of a reverse fault of a forward and reverse structure. The evaluation method comprises the following steps: determining a flexural horizon; constructing a fault fracture development index T, a source-fault coupling degree index R and a fault longitudinal sealing index Smax; according to the T, the R and the Smax, calculating a reverse fault oil and gas transmission capability index G; counting a parameter F related to the reservoir forming scale in the positive and negative rotation structure; and establishing a G and F relation layout, and predicting the reservoir forming scale of the to-be-evaluated trap. According to the evaluation method, the three parameters of the oil and gas transmission capacity of the reverse fault of the forward and reverse structure are constructed, the attributes of the fault such as scale, fault displacement and fault dip angle are considered, the section ridge amplitude and the included angle between the fault trend and the regional principal stress are provided, and meanwhile, the source-fault coupling degree is combined to evaluate the oil and gas transmission capacity of the reverse fault of the forward and reverse structure. And the sealing property of the fault under the action of extrusion stress is considered, so that accurate quantitative evaluation of the oil-gas conduction capability of the reverse fault of the reverse structure is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas geological exploration, and relates to a method for quantitatively evaluating the oil and gas conduction capacity of reverse faults in positive-reverse structures. Background Art

[0002] During the tectonic evolution process, due to the change in the nature of the stress field, the early extensional basin undergoes positive-reverse transformation under the later compression to form an anticline structure. During this process, the normal faults formed by the early extensional faulting are compressed and reversed into reverse faults. Such faults are collectively referred to as reverse faults. Reverse faults usually show normal faults at the bottom and reverse faults at the top in terms of fault displacement, that is, the deep part is still a normal fault, while the middle layer shows a reverse fault displacement, and there is no obvious fault displacement in the shallow layer but it often causes formation flexure. Affected by the difference in compression intensity, the reverse fault displacement varies, and the flexure horizons also vary in depth. Reverse faults control the development of anticlines, are large in scale, and can communicate with source rocks downward. They are important oil source faults in positive-reverse structures, and it is necessary to focus on evaluating the oil and gas conduction capacity of such faults in oil and gas exploration.

[0003] Since the oil and gas generated by source rocks first need to undergo vertical migration through oil source faults and then be horizontally injected along sand bodies before finally forming reservoirs, the evaluation of the oil and gas conduction capacity of faults is very important in oil and gas exploration. Currently, the widely used evaluation techniques for fault conduction capacity mainly target normal faults, which are formed in extensional structures and have a negative pressure environment, facilitating vertical oil and gas conduction. For reverse faults widely developed in positive-reverse structures, due to the superimposed horizontal compression, their closure is stronger than that of normal faults, which restricts the vertical conduction of oil and gas along the faults to a certain extent. Therefore, the evaluation of the oil and gas migration capacity of such faults is more difficult, and there are few research reports, which seriously restricts the exploration evaluation direction and process of favorable hydrocarbon accumulation targets in positive-reverse structures. Summary of the Invention

[0004] To solve the technical problems existing in the prior art, the present invention provides a method for quantitatively evaluating the oil and gas conduction capacity of reverse faults in positive-reverse structures. By constructing three parameters for the oil and gas conduction capacity of reverse faults in positive-reverse structures, this evaluation method not only considers the properties of the faults themselves, such as scale, fault displacement, and fault dip angle, but also proposes the amplitude of the fault surface ridge and the angle between the fault strike and the regional principal stress. At the same time, it combines the source-fault coupling degree and considers the sealing property of the faults under compressive stress, realizing an accurate quantitative evaluation of the oil and gas conduction capacity of reverse faults in reverse structures.

[0005] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for quantitatively evaluating the oil and gas conduction capacity of reverse faults in positive-reverse structures, and this evaluation method includes:

[0007] Determine the flexure horizon;

[0008] Construct the fault fracture development index T, the source-fault coupling degree index R, and the fault longitudinal sealing index S max ;

[0009] According to T, R, and S max Calculate the reverse fault oil and gas conduction capacity index G;

[0010] Statistically analyze the parameter F related to the hydrocarbon accumulation scale in the positive and reverse structures;

[0011] Establish the relationship map between G and F to predict the hydrocarbon accumulation scale of the trap to be evaluated.

[0012] As a preferred technical solution of the present invention, the parameters used to construct the fault fracture development index T include the fault length L of horizon i i , the fault throw V i , the fault dip angle θ, the angle β between the principal stress direction and the fault direction, the development amplitude H of the fault plane ridge, the curvature K of the fault plane ridge, the angle δ between the fault plane ridge and the fault strike, the elevation Z i and the elevation Z of the intersection point of the fault and the top surface of the source rock f .

[0013] As a preferred technical solution of the present invention, the calculation formula of the fault fracture development index T is shown in Equation 1:

[0014]

[0015] As a preferred technical solution of the present invention, constructing the source-fault coupling degree index R includes drawing the structural morphology map of the top surface of the source rock through the seismic profile to determine the source-fault coupling mode.

[0016] As a preferred technical solution of the present invention, the parameters used to construct the source-fault coupling degree index R include the oblique distance D from the high point of the source rock to the spill point and the angle between the fault and the flank formation of the source rock

[0017] As a preferred technical solution of the present invention, the calculation formula of the source-fault coupling degree index R is shown in Equation 2:

[0018]

[0019] As a preferred technical solution of the present invention, constructing the fault longitudinal sealing index S max includes calculating the normal pressure F exerted on the fault under the gravity of the overlying sedimentary strata according to Equation 3 i ;

[0020] F i =Z i *cosθ*(ρ r -ρ w)*g + σ*sinβ*sinθ

[0021] Equation 3

[0022] Where ρ r is the density of the overlying formation, and ρ w is the density of formation water;

[0023] Calculate the shale content K of the fault rock according to Equation 4 i ;

[0024] K i = V sh / V i

[0025] Equation 4

[0026] Where V sh is the total shale content from the position of the i-th layer in the downthrown block upwards to the offset formation of the i-th layer in the upthrown block.

[0027] As a preferred technical solution of the present invention, the calculation formula of the longitudinal sealing index S of the fault is as shown in Equation 5: max

[0028]

[0029] Where A, b, and c are regional parameters.

[0030] As a preferred technical solution of the present invention, the calculation formula of the hydrocarbon conduction capacity index G of the reverse fault is as shown in Equation 6:

[0031] G = T * R / S max

[0032] Equation 6.

[0033] As a preferred technical solution of the present invention, the parameter F related to the hydrocarbon accumulation scale includes the hydrocarbon filling degree F1 of the hydrocarbon accumulation series controlled by the reverse fault and / or the abnormal thickness F2 of the single sand layer hydrocarbon show of the anticlinal structure damaged by the late fault.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] (1) The present invention provides a quantitative evaluation method for the hydrocarbon conduction capacity of reverse faults in positive-reverse structures. By constructing three parameters for the hydrocarbon conduction capacity of reverse faults in positive-reverse structures, this evaluation method not only considers the properties of the fault itself, such as scale, fault throw, and fault dip angle, but also proposes the amplitude of the fault plane ridge and the angle between the fault strike and the regional principal stress. Based on the above parameters, an index T is constructed as a new property of the fault, and this index is creatively linked to the fracture development intensity of the fault.

[0036] ​(2) The present invention provides a method for quantitatively evaluating the oil and gas conduction capacity of reverse faults with normal-reverse structures. This evaluation method additionally considers the coupling relationship between faults and the top surface of hydrocarbon source rocks, and proposes a parameter R. Based on the compressive tectonic environment generated by reverse faults, regional stress effects are added to the formula for normal stress on the fault plane, and the normal stress is related to the shale content. It is creatively considered that the combined action of these two factors will reduce the oil and gas conduction capacity of fault fractures. Description of the Drawings

[0037] Figure 1

[0038] The following further details the present invention. However, the following examples are merely simple examples of the present invention and do not represent or limit the scope of the rights protected by the present invention. The scope of protection of the present invention shall be subject to the claims. Detailed Embodiment

[0039] The technical solution of the present application will be further described below through specific embodiments.

[0040] The detailed embodiment of the present invention provides a method for quantitatively evaluating the oil and gas conduction capacity of reverse faults with normal-reverse structures, and this evaluation method includes:

[0041] Determine the flexural horizon;

[0042] Construct the fault fracture development index T, the source-fault coupling degree index R, and the fault longitudinal sealing index S max ;

[0043] According to T, R, and S max Calculate the oil and gas conduction capacity index G of the reverse fault;

[0044] Statistically analyze the parameter F related to the hydrocarbon accumulation scale in the normal-reverse structure;

[0045] Establish a relationship map between G and F to predict the hydrocarbon accumulation scale of the trap to be evaluated.

[0046] In the present invention, the ability of a fault to conduct oil and gas lies in its geological structure. During the formation of a fault, induced fractures and secondary fractures are associated and generated in the limited areas above and below the fault plane, and their permeability is significantly better than that of the surrounding rock. Therefore, during the fault movement process, oil and gas can migrate upward along the fracture zone under the action of buoyancy. The more developed the fractures are, the greater the permeability and the stronger the oil and gas conduction capacity. Therefore, the present invention constructs a new parameter, the fault fracture development index T, to characterize the fracture development situation.

[0047] In a specific embodiment of the present invention, the parameters used to construct the fault fracture development index T include the fault length L of horizon i i , the fault throw V i, fault dip angle θ, the angle β between the principal stress direction and the fault direction, the development amplitude H of the fault plane ridge, the curvature K of the fault plane ridge, the angle δ between the fault plane ridge and the fault strike, and the elevation Z i and the elevation Z of the intersection point of the fault and the top surface of the source rock f .

[0048] In a specific embodiment of the present invention, horizon i is equivalent to the naming or reference to a certain layer, and it does not have a mathematical meaning itself.

[0049] In a specific embodiment of the present invention, horizon i has an obvious fault throw on the seismic section, and the seismic event should have a certain stability and traceability on both sides of the fault.

[0050] In a specific embodiment of the present invention, the fault length L i can be directly read on the seismic section, and this parameter determines the development degree of the fault fracture zone.

[0051] In a specific embodiment of the present invention, the fault throw V i can be obtained through the depth-domain section or by performing time-depth conversion on the seismic section.

[0052] In a specific embodiment of the present invention, the fault dip angle θ can be directly calculated from the fault throw and the lateral displacement of horizon i offset by the fault, and this parameter determines the magnitude of the component of the oil and gas buoyancy along the fault plane.

[0053] In a specific embodiment of the present invention, the angle β between the principal stress direction and the fault direction determines the opening degree of the fault fracture zone, and the determination method includes: (1) using image logging to determine the principal stress direction; (2) statistically analyzing the dominant orientation of joints through a rose diagram; (3) using the anisotropy of rock wave velocity to determine the principal stress direction.

[0054] In a specific embodiment of the present invention, the development amplitude H of the fault plane ridge, the curvature K of the fault plane ridge, and the angle δ between the fault plane ridge and the fault strike are determined by modeling fault i.

[0055] In a specific embodiment of the present invention, the elevation Z of fault i i and the elevation Z of the intersection point of the fault and the top surface of the source rock f can be obtained through depth-domain seismic or by performing time-depth conversion.

[0056] In a specific embodiment of the present invention, the calculation formula of the fault fracture development index T is shown in Equation 1:

[0057]

[0058] In the present invention, the oil and gas generated by the source rock migrate vertically through faults. Therefore, the source-fault coupling degree controls the charging capacity of oil and gas from the source rock to the fault. The coupling degree mainly refers to the cutting mode of the oil-source fault and the top surface of the source rock, mainly including: outer cutting mode, where the fault does not cut at the high point of the top surface of the source rock; oblique cutting mode, where the fault cuts at the flank of the high point of the top surface of the source rock; top cutting mode: where the fault cuts at the structural high point of the top surface of the source rock. Therefore, the source-fault coupling degree is characterized by the source-fault coupling degree index R.

[0059] In a specific embodiment of the present invention, the parameters used to construct the source-fault coupling degree index R include the oblique distance D from the high point of the source rock to the spill point and the included angle between the fault and the formation on the flank of the source rock.

[0060] In a specific embodiment of the present invention, the calculation method of the oblique distance D from the high point of the source rock to the spill point can be to directly calculate the parameter D through the trigonometric function relationship after determining the elevation difference between the structural high point of the top surface of the source rock and the spill point and their horizontal lateral distance (which can be directly measured).

[0061] In a specific embodiment of the present invention, the included angle between the fault and the formation on the flank of the source rock The calculation method can be to use the horizontal distance measured when determining the value of D, the value of D, and the fault dip angle θ, and the included angle can be obtained through trigonometric calculation.

[0062] In a specific embodiment of the present invention, the calculation formula of the source-fault coupling degree index R is shown in Equation 2:

[0063]

[0064] In a specific embodiment of the present invention, to construct the longitudinal fault sealing index S max It includes calculating the normal pressure F on the fault under the action of the gravity of the overlying sedimentary formation according to Equation 3. i ;

[0065] F i =Z i *cosθ*(ρ r -ρ w )*g + σ*sinβ*sinθ

[0066] Equation 3

[0067] Among them, ρ r is the density of the overlying formation, and ρ w is the density of formation water.

[0068] In a specific embodiment of the present invention, the density ρ r of the overlying formation and the density ρ wIt can be obtained through well logging data, core samples from the rock wall, and analysis and testing data of water samples.

[0069] In a specific embodiment of the present invention, the shale content K of the fault rock is calculated according to Equation 4 i ;

[0070] K i = V sh / V i

[0071] Equation 4

[0072] where V sh is the total shale content from the position of the i-th layer in the downthrown block upwards to the offset formation of the i-th layer in the upthrown block.

[0073] In a specific embodiment of the present invention, V sh can be obtained by calculating through radioactive well logging data.

[0074] In a specific embodiment of the present invention, the longitudinal sealing index S of the fault max is calculated according to the following formula as shown in Equation 5:

[0075]

[0076] where A, b, and c are regional parameters.

[0077] In a specific embodiment of the present invention, the regional parameters A, b, and c can be obtained through physical simulation experiment analysis of existing rock samples.

[0078] In a specific embodiment of the present invention, the calculation formula of the oil and gas conduction capacity index G of the reverse fault is as shown in Equation 6:

[0079] G = T * R / S max

[0080] Equation 6.

[0081] In a specific embodiment of the present invention, the parameter F related to the reservoir scale includes the oil and gas filling degree F1 of the reservoir formation controlled by the reverse fault and / or the abnormal thickness F2 of the single sand layer oil and gas display of the anticlinal structure damaged by the late fault.

[0082] In a specific embodiment of the present invention, for the anticlinal structure damaged by the late fault (during the formation of the anticline by compression, due to lateral extensional adjustment, normal faults perpendicular or oblique to the strain direction are often formed at the top of the anticline. Such faults can damage the original gas reservoir and cause oil and gas to escape, and the filling degree cannot reflect the reservoir formation characteristics of the trap. Therefore, the abnormal thickness F2 of the single sand layer oil and gas display of the anticlinal structure is used to reflect the reservoir formation characteristics of the trap.

[0083] In a specific embodiment of the present invention, the oil and gas filling degree F1 of the reservoir-forming series can be obtained by calculating the ratio of the oil and gas column height to the trap amplitude.

[0084] In a specific embodiment of the present invention, the abnormal thickness F2 of the oil and gas display in a single sand layer of an anticlinal structure can be obtained by calculating the ratio of the oil and gas display thickness to the total sand body thickness drilled.

[0085] In a specific embodiment of the present invention, the method for establishing the relationship map is a conventional method in the art and will not be further defined herein.

[0086] To better illustrate the present invention and facilitate understanding of its technical solutions, the typical but non-limiting embodiments of the present invention are as follows:

[0087] Example 1

[0088] This example provides a quantitative evaluation method for the oil and gas conduction capacity of a normal-reverse structure reverse fault. The quantitative evaluation method includes:

[0089] 1. Determine the formation flexure depth

[0090] The trap to be evaluated is located in a certain area. Identify the flexure horizon on the seismic profile and determine the spread range of the flexure section on the plane. There is no fault displacement above this flexure horizon, only formation flexure deformation, and oil and gas cannot migrate through the fault to above the flexure horizon.

[0091] 2. Construct the fault fracture development intensity index

[0092] Among them, the relevant parameters of a certain horizon i in the trap to be evaluated are shown in Table 1.

[0093] Table 1

[0094] Parameter name Parameter value <![CDATA[Fault length L i > 17.5 <![CDATA[Fault throw V i > 0.23 Fault dip angle θ 52 Angle β between the principal stress direction and the fault direction 82 Development amplitude H of the section ridge 1.7 Section ridge curvature K 0.3 Angle δ between the section ridge and the fault strike 25 <![CDATA[Altitude Z i > 3.0 <![CDATA[The elevation Z of the intersection point of the top surface of the hydrocarbon source rock f > 4.5

[0095] According to the parameters in Table 1, through Equation 1, the fracture development index T of fault i is calculated to be 13.2.

[0096]

[0097]

[0098] 3. Construct the source-fault coupling degree index

[0099] By calculation, the oblique distance D from the high point of the hydrocarbon source rock to the spill point is 2.1 km, and the included angle between the fault and the flank formation of the hydrocarbon source rock Furthermore, through Equation 2, the source-fault coupling degree index R is calculated to be 2.5

[0100]

[0101] 4. Construct the longitudinal sealing index of the fault

[0102] Calculate the normal pressure F exerted on the fault under the gravitational action of the overlying sedimentary strata according to Equation 3 i = 57.9.

[0103] F i = Z i * cosθ * (ρ r - ρ w ) * g + σ * sinβ * sinθ

[0104] Equation 3

[0105] Among them, the density of the overlying strata ρ r = 2.3 g / cm 3 , the density of formation water ρ w = 1.1 g / cm 3 .

[0106] Calculate the shale content K of the fault rock according to Equation 4 i = 0.13;

[0107] K i = V sh / V i

[0108] Equation 4

[0109] Among them, the total shale content V from the position of the i-th layer in the downthrown block to the offset strata of the i-th layer in the upthrown block sh = 29.9.

[0110] 5. Construct a quantitative evaluation method for the oil and gas conduction capacity of the fault

[0111] Calculate the reverse fault oil and gas conduction capacity index G of the i-th fault according to Equation 6 i = 71.4

[0112] G = T * R / S max

[0113] Equation 6

[0114] Calculate the reverse fault oil and gas conduction capacity index G of other faults according to the above calculation method, and count the oil and gas filling degree F1 of the reservoir formation controlled by the reverse fault and / or the abnormal thickness F2 of the single sand layer oil and gas show of the anticline structure damaged by the late fault, and construct a relationship chart of G and F for the reservoir formation within the regional scope, as Figure 1 shown. Through Figure 1It can be seen that for the positive - reverse structures damaged by late - stage faults, by calculating and comparing the hydrocarbon - conducting capacity index G of reverse faults and the abnormal thickness F of hydrocarbon shows in single sand bodies, there is a good positive correlation between the two, and overall, the higher the G value, the larger the F value. The plate results show that the present invention has reliability and practicability. In addition, if there are many drilled wells in the structure, a certain threshold value can be used to divide the poor - gas area (poor hydrocarbon shows) and the rich - gas area (good hydrocarbon shows), which can be used as a quantitative prediction plate for the hydrocarbon - accumulation scale of the traps to be evaluated.

[0115] The applicant declares that the present invention uses the above - mentioned embodiments to illustrate the detailed structural features of the present invention, but the present invention is not limited to the above - mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above - mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

[0116] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above - mentioned embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0117] In addition, it should be noted that, in the above - described specific embodiments, the various specific technical features described can be combined in any suitable way without contradiction. To avoid unnecessary repetition, the present invention does not separately describe various possible combination methods.

[0118] Furthermore, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A quantitative evaluation method for the hydrocarbon conduction capacity of a normal-reverse structural reverse fault, characterized in that, The evaluation method includes: Determining the flexural horizon; Construct the fault fracture development index T, source-fault coupling degree index R, and fault longitudinal sealing index S max ; According to the described T, R, and S max Calculate the reverse fault oil and gas conduction capacity index G; Statistically analyzing the parameter F related to the hydrocarbon accumulation scale in the positive and reverse structures; Establishing a relationship map between G and F to predict the hydrocarbon accumulation scale of the trap to be evaluated.

2. The evaluation method according to claim 1, wherein The parameters used to construct the fault fracture development index T include the fault length L of horizon i i , the fault throw V i , the fault dip angle θ, the angle β between the principal stress direction and the fault direction, the development amplitude H of the fault surface ridge, the curvature K of the fault surface ridge, the angle δ between the fault surface ridge and the fault strike, the elevation Z i and the elevation Z of the intersection point of the fault and the top surface of the source rock f .

3. The evaluation method according to claim 2, wherein The calculation formula of the fault fracture development index T is shown in Equation 1:

4. The evaluation method according to claim 1, characterized in that, Constructing the source-fault coupling degree index R includes drawing a structural map of the top surface of the source rock through a seismic profile to determine the source-fault coupling mode.

5. The evaluation method according to claim 4, characterized in that, The parameters used to construct the source-fault coupling degree index R include the oblique distance D from the high point of the source rock to the spill point and the included angle between the fault and the strata on the flank of the source rock 6. The evaluation method according to claim 5, characterized in that The calculation formula of the source-fault coupling degree index R is shown in Equation 2:

7. The evaluation method according to claim 1, wherein Construct the longitudinal sealing index S of the fault max including calculating the normal pressure F exerted on the fault under the gravity of the overlying sedimentary strata according to Equation 3 i ; F i = Z i * cosθ * (ρ r - ρ w ) * g + σ * sinβ * sinθ Equation 3 where ρ r is the density of the overlying formation, and ρ w is the density of formation water; Calculate the shale content K of fault rock according to Equation 4 i ; K i = V sh / V i Equation 4 Among them, V sh is the total shale content from the start of the i-th layer position of the downthrown block to the offset strata of the i-th layer of the upthrown block.

8. The evaluation method according to claim 7, characterized in that The longitudinal fault sealing index S max is calculated by Equation 5 as follows: Where A, b, and c are regional parameters.

9. The evaluation method according to claim 8, characterized in that The calculation formula of the reverse fault hydrocarbon conduction capacity index G is shown in Equation 6: G = T * R / S max Equation 6.

10. The evaluation method according to claim 1, wherein The parameter F related to the hydrocarbon accumulation scale includes the hydrocarbon saturation F1 of the hydrocarbon accumulation series controlled by the reverse fault and / or the abnormal thickness F2 of the single sand layer hydrocarbon display of the anticline structure damaged by the late fault.

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