Method and device for calculating oil saturation of sandstone reservoir
By combining curve correction methods from open-hole and casing neutron lifetime logging, the problem of oil saturation error caused by inaccurate formation water capture section values was solved, achieving higher accuracy in oil saturation calculation and oil-water identification.
Patent Information
- Application Number
- CN202410622136.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2025-11-21
AI Technical Summary
In existing technologies, when calculating reservoir oil saturation using post-casing neutron lifetime logging, inaccurate input of formation water capture section values leads to significant errors in the calculation results.
By combining the compensated neutron curve from open-hole logging with the capture section curve from casing neutron lifetime logging, and adjusting the scale through sandstone skeleton correction, the two curves are made to coincide in the non-reservoir section. The envelope grid value is calculated in the oil-bearing section. The reservoir oil saturation is calculated by combining the compensated neutron value and the capture section value.
It improves the accuracy and reliability of oil saturation calculation, has wide applicability, can effectively identify oil and water properties in low-resistivity reservoirs, and is convenient and simple to calculate.
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Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to the technical field of sandstone reservoir logging evaluation, and particularly relates to a sandstone reservoir oil saturation calculation method and device. BACKGROUND
[0002] For sandstone reservoirs, the accurate calculation of oil saturation has always been the focus and difficulty of reservoir exploration and development. In recent years, in order to evaluate the oil content of the reservoir and calculate the oil saturation of the reservoir, the post-casing neutron lifetime logging technology has developed rapidly. The neutron lifetime logging uses a pulsed neutron source to emit a high-energy fast neutron pulse to irradiate the formation, and then uses a source distance or two source distance gamma ray detector to measure the gamma ray emitted by the captured thermal neutron, and then calculates the formation thermal neutron lifetime and the macroscopic capture cross section curve Σ of the thermal neutron, which is a logging method for studying the oil content of the formation in the cased well instead of resistivity logging.
[0003] In the prior art, the commonly used method for calculating the oil saturation of the reservoir by using post-casing neutron lifetime logging is to substitute the measured thermal neutron capture cross section curve Σ into the volume model formula: Σ = Σ ma (1-φ-V sh )+Σ w S w φ+Σ h (1-S w )φ+Σ sh V sh , to obtain the water saturation of the reservoir, and then to obtain the oil saturation. However, this method requires accurate input of the capture cross section value Σ w of the formation water. Because the mineralization degree and boron content of the formation water are different in different regions and layer systems, the capture cross section value of the formation water varies greatly between different regions and layer systems, and fluctuates within a large range, so it is difficult to accurately obtain the value, and therefore this method has a large error in calculating the oil saturation of the reservoir. SUMMARY
[0004] In view of the above problems, the present disclosure provides a sandstone reservoir oil saturation calculation method and device, which combines the compensated neutron curve of open hole logging and the capture cross section curve of post-casing neutron lifetime logging to calculate the oil saturation, thereby solving the problem of large error in the calculation result of the oil saturation due to inaccurate input of the capture cross section value Σ w of the formation water.
[0005] In a first aspect, a sandstone reservoir oil saturation calculation method is provided, which comprises:
[0006] For sandstone reservoirs, the compensated neutron curve of open hole logging and the capture cross section curve of post-casing neutron lifetime logging are corrected for sandstone skeleton to obtain two corrected curves;
[0007] The two corrected curves are displayed on the same track of the logging curve graph, the left and right scales are adjusted, and the two corrected curves are made to coincide in the non-reservoir section or the pure water section to obtain two set curves;
[0008] In the oil-bearing section, the envelope track value CSG between the two set curves is calculated;
[0009] The compensated neutron value and the capture cross-section value of the crude oil in the target area are placed in the scale track of the two set curves, and the track value CSGoil between the compensated neutron value and the capture cross-section value of the crude oil is calculated;
[0010] The reservoir oil-bearing porosity is calculated by the ratio of the envelope track value CSG to the track value CSGoil. oil The reservoir oil-bearing saturation is calculated by dividing the oil-bearing porosity by the total porosity of the reservoir.
[0011] Further, the compensated neutron curve of the open hole well logging and the capture cross-section curve of the after-casing neutron lifetime logging are corrected for the sandstone matrix to obtain two corrected curves, which are as follows:
[0012] CNL jz = CNL-V sand * CNL sand / 100;
[0013] ∑ jz =∑-V sand *∑ sand / 100;
[0014] In the formula, CNL is the compensated neutron curve obtained by logging, in percentage; CNL jz is the corrected compensated neutron curve, in percentage;∑ is the capture cross-section curve obtained by logging;∑ jz is the corrected capture cross-section curve; V sand represents the volume content of the sandstone matrix in the sandstone reservoir, in percentage; CNL sand represents the compensated neutron value of the sandstone matrix in the target area;∑ sand represents the capture cross-section value of the sandstone matrix in the target area.
[0015] Further, the two corrected curves are displayed on the same track of the logging curve graph, the left and right scales are adjusted, and the two corrected curves are made to coincide in the non-reservoir section or the pure water section to obtain two set curves, including:
[0016] The two corrected curves are displayed on the same scale track of the logging curve graph, the left and right scales CNL left , CNL right of the compensated neutron curve are fixed and unchanged, which are 45% and -15% respectively, and the left and right scales∑left ,∑ right ,∑
[0017] The compensated neutron curve value represents the hydrogen index of unit volume formation, and the capture cross section curve value represents the capture cross section value of unit volume formation. For sandstone reservoirs, the formation is composed of shale, sandstone skeleton, crude oil, and formation water. After sandstone skeleton correction, the compensated neutron curve shows the hydrogen index of shale, formation water, and crude oil, and the contribution of the hydrogen index in shale is mainly the bound water therein, so in the non-reservoir section or pure water layer section, the compensated neutron value after correction is mainly affected by the water in the formation. Similarly, after sandstone skeleton correction, the capture cross section curve shows the capture cross section value of shale, formation water, and crude oil, and the main contribution elements of the capture cross section in the formation are CI and Be, which mainly exist in the formation water, so the contribution of the capture cross section in shale is mainly the bound water therein, so in the non-reservoir section or pure water layer section, the capture cross section value after correction is mainly affected by the water in the formation.
[0018] Therefore, in the non-reservoir section or pure water layer section, the compensated neutron curve value after correction and the capture cross section curve value are both affected by the water in the formation. Therefore, by fixing the left and right scales of the compensated neutron curve after correction and adjusting the left and right scales of the capture cross section curve after correction, the two curves can always be coincided in the non-reservoir section or pure water layer section. For the same region and the same layer system, the properties of the formation water are the same, so the left and right scales of the capture cross section curve after adjustment are also the same.
[0019] Further, in the oil-bearing layer section, the envelope channel value CSG between the two aligned curves is calculated, including:
[0020] Under the premise of aligning the compensated neutron curve after correction and the capture cross section curve in the non-reservoir section or pure water layer section, the envelope of the two curves on the well logging channel in the oil-bearing layer is an indication of oil-bearing, and the scale channel is divided into N small grids, and the envelope channel value CSG of the two curves is calculated:
[0021]
[0022] In the formula, CNL left is the left scale value of the compensated neutron curve after correction; CNL right is the right scale value of the compensated neutron curve after correction; ∑ left is the left scale value of the capture cross section curve after skeleton correction; ∑ right is the right scale value of the capture cross section curve after skeleton correction; CNL jz is the compensated neutron curve after correction; ∑ jz is the capture cross section curve after correction.
[0023] Further, the compensated neutron value and the capture cross section value of the crude oil in the target area are placed in the scale channels of the two setting curves, and the channel gamma value CSG between the compensated neutron value and the capture cross section value of the crude oil is calculated oil , comprising:
[0024] The compensated neutron value and the capture cross section value of the crude oil in the target area are found, and are simulated to be placed in the scale channels of the two setting curves. The left and right scales of the compensated neutron value and the capture cross section value correspond to the previously adjusted scales. After the compensated neutron value and the capture cross section value of the crude oil are placed in the scale channels, the channel gamma value CSG between the two is calculated oil .
[0025] Further, the channel gamma value CSGoil between the compensated neutron value and the capture cross section value is calculated as follows:
[0026]
[0027] In the formula, CNL oil is the compensated neutron value of the crude oil in the target area; ∑ oil is the capture cross section value of the crude oil in the target area; N is the number of small channels in the scale channel; CNL left is the left scale value of the corrected compensated neutron curve; CNL right is the right scale value of the corrected compensated neutron curve; ∑ left is the left scale value of the capture cross section curve after the skeleton correction; ∑ right is the right scale value of the capture cross section curve after the skeleton correction.
[0028] Further, the reservoir oil-bearing porosity is calculated by the ratio of the envelope channel gamma value CSG to the channel gamma value CSG oil ; the reservoir oil saturation is calculated by dividing the oil-bearing porosity by the total porosity of the reservoir, and is calculated as follows:
[0029]
[0030]
[0031] In the formula, POR oil is the oil-bearing porosity, percentage; POR is the total porosity of the formation, percentage; S O is the oil saturation, percentage.
[0032] In the second aspect, a sandstone reservoir oil saturation calculation device comprises a correction unit, a channel gamma value calculation unit, and an oil saturation calculation unit.
[0033] The correction unit is used for, for a sandstone reservoir, performing sandstone skeleton correction on the compensated neutron curve of the open hole well logging and the capture cross section curve of the after-casing neutron lifetime logging to obtain two corrected curves.
[0034] The correction unit is further configured to display the two corrected curves on the same track of the well logging curve graph, and make the two corrected curves coincide in the non-reservoir section or the pure water layer section to obtain two set curves;
[0035] The CSG value calculation unit is configured to calculate the CSG value between the two set curves in the oil-bearing layer section of the two set curves.
[0036] The CSG value calculation unit is further configured to place the compensated neutron value and the capture cross section value of the crude oil in the target area in the scale track of the two set curves, and calculate the CSG value between the compensated neutron value and the capture cross section value. oil ;
[0037] The oil-bearing saturation calculation unit is configured to calculate the reservoir oil-bearing porosity through the ratio of the CSG value to the CSG value oil , and calculate the reservoir oil-bearing saturation through the oil-bearing porosity divided by the total porosity of the reservoir.
[0038] In a third aspect, an electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory complete communication with each other through the communication bus.
[0039] The memory stores a computer program.
[0040] The processor is configured to implement the sandstone reservoir oil-bearing saturation calculation method when executing the computer program stored on the memory.
[0041] In a fourth aspect, a computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the sandstone reservoir oil-bearing saturation calculation method.
[0042] The present disclosure has at least the following beneficial effects:
[0043] The present disclosure performs sandstone skeleton correction on the compensated neutron curve of the open hole well logging and the capture cross section curve of the post-casing neutron lifetime logging, displays the two corrected curves on the same well logging graph, adjusts the left and right scales to make the two curves coincide in the non-reservoir section or the pure water layer section, and the size of the envelope of the two curves in the oil-bearing layer section reflects the amount of oil in the reservoir, and thus the oil-bearing saturation can be calculated. Compared with the conventional neutron lifetime logging evaluation method which uses only one capture cross section curve to calculate the oil-bearing saturation, the present method has higher calculation accuracy and reliable theoretical basis, is convenient and simple to calculate, has strong universality, and has wide applicability. For low-resistance reservoirs, when the resistivity curve cannot be used to determine the fluid property, the present method can also be used to effectively identify oil and water, and has wide application prospects.
[0044] Additional features and advantages of the present disclosure will be set forth in the description which follows, and in part will be apparent from the description, or can be learned by practice of the present disclosure. The objectives and other advantages of the present disclosure will be realized and attained by the structure particularly pointed out in the description. BRIEF DESCRIPTION OF DRAWINGS
[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present disclosure, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.
[0046] Figure 1 The flow chart of the calculation method for the embodiments of the present disclosure is shown in Figure 1.
[0047] Figure 2 The structure schematic diagram of the calculation device for the embodiments of the present disclosure is shown in Figure 2.
[0048] Figure 3 The structure schematic diagram of the electronic device is shown in Figure 3.
[0049] Figure 4 The comprehensive diagram of the oil saturation logging curve of a certain well in a sandstone reservoir is shown in Figure 4.
[0050] Figure 5 The error analysis diagram of the oil saturation calculated by the disclosed method and the oil saturation analyzed by the core for a certain well in a sandstone reservoir is shown in Figure 5. DETAILED DESCRIPTION
[0051] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the following will combine the drawings in the embodiments of the present disclosure to make a clear and complete description of the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are some of the embodiments of the present disclosure, but not all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present disclosure.
[0052] The present disclosure combines the compensated neutron curve of the open hole logging and the capture cross section curve of the neutron lifetime logging after casing to calculate the oil saturation of the sandstone reservoir, which can effectively quantitatively evaluate the oil saturation of the sandstone reservoir.
[0053] In a first aspect, a method for calculating oil saturation of a sandstone reservoir, the method comprising:
[0054] S101, for a sandstone reservoir, performing sandstone skeleton correction on a compensated neutron curve of open hole logging and a capture cross section curve of neutron lifetime logging after casing to obtain two corrected curves;
[0055] S102, display the two corrected curves on the same well logging curve chart, adjust the left and right scales, and make the two corrected curves coincide in the non-reservoir section or the pure water layer section to obtain two set curves;
[0056] S103, calculate the envelope log value CSG between the two set curves in the oil-bearing layer section;
[0057] S104, place the compensated neutron value and the capture cross section value of the crude oil in the target area in the scale channel of the two set curves, and calculate the log value CSG between the compensated neutron value and the capture cross section value of the crude oil oil ;
[0058] S105, calculate the reservoir oil-bearing porosity by the ratio of the envelope log value CSG to the log value CSG oil , and calculate the reservoir oil-bearing saturation by dividing the oil-bearing porosity by the total porosity of the reservoir.
[0059] In the specific implementation, the following is introduced:
[0060] S101, for the sandstone reservoir, perform sand skeleton correction on the compensated neutron curve of the open hole well logging and the capture cross section curve of the post-casing neutron lifetime logging;
[0061] S102, display the two corrected curves on the same well logging curve chart, fix the left and right scales of the compensated neutron curve unchanged, which is generally 45% to -15%, adjust the left and right scales of the capture cross section curve, and make the two curves coincide in the non-reservoir section or the pure water layer section;
[0062] S103, in the oil-bearing layer section, the corrected compensated neutron curve and the capture cross section curve will produce different degrees of envelope in the scale channel, and the envelope log value CSG between the two curves is calculated;
[0063] S104, find the compensated neutron value and the capture cross section value of the crude oil in the target area, simulate the placement in the scale channel of step S102, the left and right scales of the two correspond to the previously adjusted scales and are unchanged, calculate the log value CSGoil between the compensated neutron value and the capture cross section value of the crude oil after placement in the scale channel;
[0064] S105, the ratio of the envelope log value CSG obtained in step S103 to the log value CSGoil obtained in step S104 is the reservoir oil-bearing porosity, and the reservoir oil-bearing saturation is the total porosity of the reservoir divided by the oil-bearing porosity;
[0065] In step S101, the compensated neutron curve of the open hole well logging and the capture cross section curve of the post-casing neutron lifetime logging are corrected for the sandstone skeleton;
[0066] CNL jz= CNL-V sand * CNL sand / 100 (1)
[0067] ∑ jz =∑-V sand *∑ sand / 100 (2)
[0068] In the formula, CNL is the compensated neutron curve obtained by logging, in percentage; CNL jz is the compensated neutron curve after correction, in percentage;∑ is the capture cross section curve obtained by logging;∑ jz is the capture cross section curve after correction; V sand represents the volume content of the sandstone framework in the sandstone reservoir, in percentage, excluding the shale and fluid; CNL sand represents the compensated neutron value of the sandstone framework in the target area, generally taken as -3.5 to -4%;∑ sand represents the capture cross section value of the sandstone framework in the target area, generally taken as 4 to 19 c.u.;
[0069] In step S102, the two corrected curves are displayed on the same scale channel of the logging curve chart, and the compensated neutron curve is fixed with the left and right scales CNL left , CNL right unchanged, generally 45% to -15%, and the left and right scales∑ left ,∑ right of the capture cross section curve are adjusted so that the two curves coincide in the non-reservoir section or the pure water layer section, and the left and right scales of the capture cross section curve of the same layer system in the same area are consistent.
[0070] According to the volume model principle, the compensated neutron curve value indicates the hydrogen index of unit volume formation, and the capture cross section curve value indicates the capture cross section value of unit volume formation. For a sandstone reservoir, the formation is composed of shale, sandstone framework, crude oil and formation water. After the sandstone framework correction, the compensated neutron curve displays the hydrogen index of shale, formation water and crude oil, and the contribution of the hydrogen index in shale is mainly the bound water therein, so in the non-reservoir section or the pure water layer section, the compensated neutron value after correction is mainly affected by the water in the formation. Similarly, after the sandstone framework correction, the capture cross section curve displays the capture cross section value of shale, formation water and crude oil, and the main contribution elements of the capture cross section in the formation: CI and Be, mainly exist in the formation water, so the contribution of the capture cross section in shale is mainly the bound water therein, so in the non-reservoir section or the pure water layer section, the capture cross section value after correction is mainly affected by the water in the formation.
[0071] Therefore, in the non-reservoir section or the pure water section, the compensated neutron curve value and the capture cross section curve value after correction are both affected by the water in the formation. Therefore, by fixing the left and right scales of the compensated neutron curve and adjusting the left and right scales of the capture cross section curve, the two curves can be made to coincide in the non-reservoir section or the pure water section. For the same region and the same layer, the properties of the formation water are the same, and therefore the left and right scales of the capture cross section curve are also the same.
[0072] In step S103, in the oil-bearing section, the compensated neutron curve and the capture cross section curve after correction will produce different degrees of envelope in the scale track, and the envelope track value CSG between the two curves is calculated.
[0073] On the premise that the compensated neutron curve and the capture cross section curve after correction have been made to coincide in the non-reservoir section or the pure water section, because the hydrogen index of oil is slightly higher than that of water, the capture cross section value of oil is much lower than that of water, and therefore the envelope of the two curves in the logging track in the oil-bearing layer is an indication of oil-bearing. The scale track is divided into 10 small grids, and the envelope track value CSG of the two curves is calculated.
[0074]
[0075] In the formula, CNL left is the left scale value of the compensated neutron curve after correction in step S102, and is generally 45%; CNL right is the right scale value, and is generally -15%; ∑ left is the left scale value of the capture cross section curve after correction in step S102, and ∑ right is the right scale value.
[0076] In step S104, the compensated neutron value and the capture cross section value of the crude oil in the target region are found, and are simulated in the scale track in step S102. The left and right scales of the two values correspond to the previously adjusted scales and are unchanged. After the compensated neutron value and the capture cross section value of the crude oil are placed in the scale track, the track value CSGoil between the two values is calculated.
[0077]
[0078] In the formula, CNL oil is the compensated neutron value of the crude oil in the target region, and is generally 102-109%; ∑ oil is the capture cross section value of the crude oil in the target region, and is generally 16-22 c.u.
[0079] In step S105, the ratio of the envelope track value CSG obtained in step S103 to the track value CSGoil obtained in step S104 is the oil-bearing porosity of the reservoir; and the oil-bearing porosity divided by the total porosity of the reservoir is the oil-bearing saturation of the reservoir.
[0080]
[0081]
[0082] In the formula, POR oil is the oil-bearing porosity, percentage; POR is the total porosity of the formation, percentage; S O is the oil saturation, percentage.
[0083] As Figure 2 shown, a sandstone reservoir oil saturation calculation device includes a correction unit 201, a Dug value calculation unit 202 and an oil saturation calculation unit 203;
[0084] The correction unit 201 is used for sandstone skeleton correction of the compensated neutron curve of the open hole well logging and the capture cross section curve of the after casing neutron lifetime logging in the sandstone reservoir, to obtain two correction curves;
[0085] The correction unit 201 is also used for displaying the two correction curves on the same track on the well logging curve chart, and making the two correction curves coincide in the non-reservoir section or the pure water layer section, to obtain two placement curves;
[0086] The Dug value calculation unit 202 is used for calculating the envelope Dug value CSG between the two placement curves in the oil-bearing layer section of the two placement curves;
[0087] The Dug value calculation unit 202 is also used for placing the compensated neutron value and the capture cross section value of the crude oil in the target area in the scale track of the two placement curves, and calculating the Dug value CSG oil between the compensated neutron value and the capture cross section value;
[0088] The oil saturation calculation unit 203 is used for calculating the reservoir oil-bearing porosity through the ratio of the envelope Dug value CSG to the Dug value CSG oil , and calculating the reservoir oil saturation through the oil-bearing porosity divided by the total porosity of the reservoir.
[0089] As Figure 3 shown, the present disclosure provides an electronic device, including a processor 301, a communication interface 302, a memory 303 and a communication bus 304, wherein the processor 301, the communication interface 302 and the memory 303 complete the communication among each other through the communication bus 304;
[0090] The memory 303 stores a computer program;
[0091] The processor 301 is used for executing the computer program stored on the memory 303, to realize the above-mentioned method.
[0092] The present disclosure provides a computer readable storage medium storing a computer program, which, when executed by a processor, implements the method described above.
[0093] The computer readable storage medium can be included in the device / apparatus described in the above embodiments, or can exist separately and not be assembled into the device / apparatus. The computer readable storage medium carries one or more programs, which, when executed, implement the method according to the embodiments of the present disclosure.
[0094] According to embodiments of the present disclosure, the computer readable storage medium can be a non-volatile computer readable storage medium, which can include, but is not limited to, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any appropriate combination thereof. In the present disclosure, the computer readable storage medium can be any tangible medium that contains or stores a program, which can be used by or in connection with an instruction execution system, apparatus, or device.
[0095] In order for those skilled in the art to better understand the present disclosure, the principles of the present disclosure are described below in conjunction with the accompanying drawings:
[0096] The present disclosure takes a well in a western sandstone reservoir as an example, and the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0097] Step S101: For a sandstone reservoir, the compensated neutron curve of the open hole well logging is corrected for the sandstone matrix with the capture cross section curve of the after-casing neutron lifetime logging;
[0098] CNL jz = CNL-V sand * CNL sand / 100;
[0099] ∑ jz =∑-V sand *∑ sand / 100;
[0100] CNL,∑ are the compensated neutron curve and the capture cross section curve obtained by well logging, and V Figure 4 is shown in the 6th track in FIG. 7. CNL jz ,∑ jz are the compensated neutron and capture cross section curves after correction, and V Figure 4 is shown in the 7th track in FIG. 7. V sand represents the volume content of the sandstone matrix in the sandstone reservoir, excluding the mud and fluid, in percentage, which is a known quantity in the present embodiment; CNLsand The compensated neutron value of the sandstone skeleton of the target area, -4% in this embodiment; ∑ sand The capture cross-section value of the sandstone skeleton of the target area, 4.3 c.u. in this embodiment.
[0101] Step S102: Display the corrected two curves on the same scale track of the well logging curve graph, fix the left and right scales CNL left , CNL right of the compensated neutron curve, and adjust the left and right scales ∑ left , ∑ right of the capture cross-section curve, so that the two curves coincide in the non-reservoir section or the pure water layer section.
[0102] Because the properties of the formation water of the same layer system in the same area are basically the same, the left and right scales of the corrected capture cross-section curves of the same layer system in the same area are consistent. In this embodiment, the left and right scales of the corrected capture cross-section curve are adjusted to 42 c.u.~2 c.u., and the left and right scales of the corrected compensated neutron curve are 45%~-15%, so that the two curves coincide in the non-reservoir section or the pure water layer section.
[0103] Step S103: In the oil-bearing layer section, the corrected compensated neutron curve and the corrected capture cross-section curve will produce different degrees of envelope on the scale track, and the envelope track grade value CSG between the two curves is calculated.
[0104] In this embodiment, the left and right scales of the corrected compensated neutron curve are 45%~-15%, and the left and right scales of the corrected capture cross-section curve are 42 c.u.~2 c.u. If the scale track is divided into 10 small grids, then the envelope track grade value of the two curves is:
[0105]
[0106] Among them, represents the track grid number of the corrected compensated neutron curve away from the right boundary, represents the track grid number of the corrected capture cross-section curve away from the right boundary, and the difference between the two is the envelope track grade value of the two curves, which is also Figure 4 the track grade value of the 7th shadow part in the figure.
[0107] Step S104: Find the compensated neutron value and the capture cross-section value of the crude oil in the target area, and simulate them in the scale track of step 2. The left and right scales of the two correspond to the previously adjusted scales and are unchanged. Calculate the track grade value CSGoil between the compensated neutron value and the capture cross-section value of the crude oil after they are placed in the scale track.
[0108] In the embodiment, the compensated neutron value of the target area crude oil is 109%, and the capture cross-section value of the crude oil is 16.5 c.u. When the formation is 100% crude oil, the difference between the two values is:
[0109]
[0110] wherein, represents the number of Doglegs of the compensated neutron value of the crude oil from the right boundary, represents the number of Doglegs of the capture cross-section value of the crude oil from the right boundary, and the difference between the two is the number of Doglegs between the two curves.
[0111] Step S105: The ratio of the envelope Dogleg value CSG obtained in step 3 to the Dogleg value CSGoil obtained in step 4 is the oil-bearing porosity of the reservoir; the oil-bearing porosity divided by the total porosity of the reservoir is the oil-bearing saturation of the reservoir:
[0112] CSG is the envelope Dogleg value of the compensated neutron and capture cross-section curves of the oil-bearing layer after correction, and the more oil-bearing, the larger the envelope. CSGoil is the number of Doglegs between the two when the formation is 100% oil-bearing. Then the ratio of CSG to CSGoil is the oil-bearing porosity of the reservoir.
[0113]
[0114] Figure 4 The eighth track in the middle is the oil-bearing porosity and the total porosity of the formation calculated in the embodiment. In the embodiment, the total porosity is a known quantity, which is generally calculated from the open hole logging data. The oil-bearing porosity divided by the total porosity of the reservoir is the oil-bearing saturation.
[0115]
[0116] Figure 4 The ninth track in the middle is a comparison chart of the oil-bearing saturation calculated in the embodiment of the disclosure and the oil-bearing saturation curve analyzed by the core. Figure 5 The error analysis chart of the oil-bearing saturation calculated by the disclosed method and the oil-bearing saturation analyzed by the core;
[0117] From Figure 4 and Figure 5 It can be seen that the oil-bearing saturation calculated by the embodiment according to the method is basically consistent with the oil-bearing saturation analyzed by the core, which verifies the reliability of the method, and the oil-bearing saturation of the sandstone reservoir can be accurately calculated.
[0118] Although the present disclosure is explained in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.
Claims
1. A method of calculating oil saturation in sandstone reservoirs, characterized in that, The method comprises: For sandstone reservoir, the compensated neutron curve of open hole logging and the capture cross section curve of post casing neutron lifetime logging are corrected for sandstone skeleton to obtain two corrected curves; The two corrected curves are displayed on the same well logging curve chart, the left and right scales are adjusted, and the two corrected curves are overlapped in non-reservoir section or pure water layer section to obtain two placed curves; In oil-bearing layer section, the envelope channel value CSG between the two placed curves is calculated; The compensated neutron value and the capture cross section value of crude oil in the target area are placed in the scale channel of the two placed curves, and the channel value CSGoil between the compensated neutron value and the capture cross section value of the crude oil is calculated; The reservoir oil-bearing porosity is calculated by the ratio of the envelope channel value CSG to the channel value CSGoil, and the reservoir oil-bearing saturation is calculated by dividing the oil-bearing porosity by the total porosity of the reservoir.
2. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein the compensated neutron curve of open hole logging and the capture cross section curve of post casing neutron lifetime logging are corrected for sandstone skeleton to obtain two corrected curves by the following method:
3. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein the two corrected curves are displayed on the same well logging curve chart, the left and right scales are adjusted, and the two corrected curves are overlapped in non-reservoir section or pure water layer section to obtain two placed curves, which comprises: CNL jz = CNL-V sand * CNL sand / 100; Σ jz =∑-V sand *∑ sand / 100; where CNL is the compensated neutron log, percent; CNL jz is the corrected compensated neutron log, percent; Σ is the capture cross section log; Σ jz is the corrected capture cross section log; V sand represents the volume fraction of the sandstone matrix, percent, in the sandstone reservoir, excluding shale and fluid; CNL sand represents the compensated neutron value of the sandstone matrix in the target area; Σ sand represents the capture cross section value of the sandstone matrix in the target area.
4. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein the envelope channel value CSG between the two placed curves is calculated in oil-bearing layer section, which comprises: On the premise that the compensated neutron curve and the capture cross section curve are overlapped in non-reservoir section or pure water layer section, the envelope of the two curves in the well logging chart channel in the oil-bearing layer is the indication of oil-bearing, the scale channel is divided into N small grids, and the envelope channel value CSG of the two curves is calculated: Display the two correction curves on the same scale of the well logging curve chart, fix the left and right scales of the compensated neutron curve CNL left , CNL right unchanged, adjust the left and right scales of the capture cross section curve Σ left , Σ right , so that the two curves coincide in the non-reservoir section or the pure water layer section, to obtain two set curves.
5. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein 6. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein the channel value CSGoil between the compensated neutron value and the capture cross section value of the crude oil is calculated as follows:
7. The sandstone reservoir oil-bearing saturation calculation method according to claim 1, wherein it comprises: where CNL left is the left scale value of the corrected compensated neutron curve; CNL right is the right scale value of the corrected compensated neutron curve; CNL left is the left scale value of the adjusted capture cross section curve with skeleton correction; CNL right is the right scale value of the adjusted capture cross section curve with skeleton correction; CNL jz is the corrected compensated neutron curve; CNL jz is the corrected capture cross section curve. a correction unit, a channel value calculation unit and an oil-bearing saturation calculation unit; placing the compensated neutron value and the capture cross section value of the crude oil of the target area in the scale channels of the two sets of normalization curves, and calculating the channel value CSG between the compensated neutron value and the capture cross section value oil , comprising: The compensated neutron value and the capture cross-section value of the crude oil in the target area are found, and the simulation is placed in the two scale channels of the setting curve. The left and right scales of the compensated neutron value and the capture cross-section value correspond to the previously adjusted scales. After the compensated neutron value and the capture cross-section value of the crude oil are placed on the scale channel, the channel gamma value CSG between the two is calculated oil . the correction unit is used for correcting the compensated neutron curve of open hole logging and the capture cross section curve of post casing neutron lifetime logging for sandstone skeleton to obtain two corrected curves for sandstone reservoir; the correction unit is further used for displaying the two corrected curves on the same well logging curve chart, adjusting the left and right scales, and overlapping the two corrected curves in non-reservoir section or pure water layer section to obtain two placed curves; CNL oil is the compensated neutron value of the target area crude oil; Σ oil is the capture cross section value of the target area crude oil; N is the number of small grids divided by the calibration track; CNL left is the left calibration value of the compensated neutron curve after correction; CNL right is the right calibration value of the compensated neutron curve after correction; Σ left is the left calibration value of the capture cross section curve after skeleton correction; Σ right is the right calibration value of the capture cross section curve after skeleton correction. the channel value calculation unit is used for calculating the envelope channel value CSG between the two placed curves in oil-bearing layer section; The reservoir oiliness porosity is calculated by the ratio of the envelope log value CSG to the log value CSG oil The reservoir oiliness porosity is calculated by the ratio of the envelope log value CSG to the log value CSG The reservoir oiliness saturation is calculated by dividing the reservoir oiliness porosity by the total porosity of the reservoir, calculated as follows: where POR is the oil-filled porosity, percent; POR is the total formation porosity, percent; SOR is the oil saturation, percent. oil O where POR is the oil-filled porosity, percent; POR is the total formation porosity, percent; SOR is the oil saturation, percent. 8. A sandstone reservoir oil saturation calculation device characterized by comprising: the channel value calculation unit is further used for placing the compensated neutron value and the capture cross section value of crude oil in the target area in the scale channel of the two placed curves, and calculating the channel value CSGoil between the compensated neutron value and the capture cross section value of the crude oil; an oil saturation calculation unit for calculating the reservoir oil porosity by the ratio of the envelope log value CSG to the log value CSG oil and calculating the reservoir oil saturation by dividing the oil porosity by the total porosity of the reservoir.
9. An electronic device, comprising: The device comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; The memory stores a computer program; The processor is configured to execute the computer program stored in the memory to implement the method for calculating oil saturation of a sandstone reservoir according to any one of claims 1-7.
10. A computer readable storage medium storing a computer program, characterized in that, The computer program is executed by the processor to implement the method for calculating oil saturation of a sandstone reservoir according to any one of claims 1-7.