Outcrop profile and well fine stratigraphic correlation method

Abstract

This invention provides a method for fine stratigraphic correlation between outcrop profiles and well logging, belonging to the field of stratigraphic correlation technology. It solves the problems in existing technologies for stratigraphic correlation studies in inter-basin regions, where the fine stratigraphic divisions obtained from well logging within the basin cannot be accurately compared with the outcrop strata, leading to difficulties in large-area fine stratigraphic distribution, sedimentary facies research, and prediction of hydrocarbon source rocks and reservoirs. The method includes collecting fine stratigraphic division schemes from well logging within the basin and comparing them with standard outcrop profile divisions to identify differences; collecting full-core wells with conventional logging in the outcrop area to establish a correspondence between well logging stratigraphic divisions and core lithology and rock assemblages, and establishing rock-electrical response indicators; using gamma-ray measurement to construct virtual well logging curves for the outcrop profile and combining this with comprehensive information from full-core wells at the basin margin, outcrop profile rock assemblages, sequence cycles, and paleontology to establish basin-mountain stratigraphic correlation relationships, thus achieving a method for fine regional stratigraphic correlation.

Description

Technical Field

[0001] This invention belongs to the field of stratigraphic correlation technology, specifically to a method for fine stratigraphic correlation between outcrop profiles and well drilling. Background Technology

[0002] In the process of geological exploration and research, stratigraphic correlation between wells and between wells and outcrops is often involved. Detailed stratigraphic correlation is the premise for stratigraphic thickness distribution, sedimentary facies analysis and prediction of oil and gas source rocks and reservoirs. The main basis for correlation is stratigraphic lithology, paleontology, well logging curves and other characteristics.

[0003] In the early stages of oil and gas exploration, stratigraphic correlation within the basin mainly relied on the standard profile of outcrops at the basin margin for stratification and correlation based on group names. However, as exploration progressed, stratigraphic correlation by group could no longer meet the needs of detailed correlation studies of oil and gas wells within the basin. Based on the groups, various oilfield companies used logging curve characteristics to perform more detailed segmentation or sub-layer division. Based on logging curve characteristics, not only was the difficulty of direct lithological correlation due to the fact that most wells in the basin were not cored, but the digitized curves also facilitated automatic stratigraphic division and identification. For example, patent publication number CN116291414A discloses a stratigraphic correlation method and device, and patent publication number CN116122804B discloses a stratigraphic correlation method and system, computer equipment and storage medium. The core of these methods is to analyze logging curve data using mathematical methods and combine the location of singular values ​​and the standard well correlation depth range to perform stratigraphic division. Therefore, well logging stratigraphic correlation is the primary method for inter-well correlation within a basin, and the resulting stratigraphic thickness maps, sedimentary facies maps, and reservoir prediction maps below the section level are also mainly based on well logging stratigraphic divisions. However, when it comes to large-scale basin-mountain stratigraphic correlation and sedimentary facies studies, it is difficult to establish correlations between well logging stratigraphy and the stratification of outcrops or paleontology in the field. Detailed well logging stratigraphic divisions cannot be correlated with outcrop profiles in the field, resulting in fine-grained basin-mountain stratigraphic correlation and short-section sedimentary facies studies being confined to the basin itself.

[0004] Patent CN106772679A discloses a method and apparatus for stratigraphic correlation, proposing to use standard field profiles to correct and classify well-drilled stratigraphic correlation within a basin, thereby promoting well-drilled correlation within the basin. However, methods for more refined segment or sub-layer correlation, and methods for extending well-logged stratigraphic correlation to outcrops in the field, are still lacking. Therefore, in the past, when it came to basin-mountain correlation, correlation and mapping were often carried out by groups, and it was difficult to extend the segments or sub-layers classified by well logging to outcrops outside the basin for correlation. Therefore, there is a need to invent a method for stratigraphic correlation connecting basin drilling and outcrop profiles, effectively comparing well-logged curves, rock assemblages, and paleontology between basins and mountains, achieving correlation based on a unified well-logged stratigraphic division between basins and mountains. At the same time, outcrop profiles can, in turn, promote the interpretation of lithological assemblages and geological ages of well-logged stratigraphic sequences, ultimately promoting fine stratigraphic correlation, sedimentary facies research, and correlation and prediction of hydrocarbon source rocks and reservoirs in large areas. Summary of the Invention

[0005] To address the problem in stratigraphic correlation studies of basin-mountain regions where the fine stratigraphic divisions (sections or sub-layers) obtained from well logging within the basin cannot be accurately compared with the outcrop strata, leading to difficulties in large-area fine stratigraphic distribution, sedimentary facies studies, and prediction of hydrocarbon source rocks and reservoirs, this invention aims to provide a method for comparing outcrop profiles with fine stratigraphic data obtained from well logging. This method utilizes gamma-ray array measurements to construct virtual well logging curves of outcrop profiles and combines this with comprehensive information from basin margin core wells, outcrop profile rock assemblages, sequence cycles, and paleontology to establish basin-mountain stratigraphic correlation relationships, thus achieving a method for fine regional stratigraphic correlation.

[0006] The technical solution adopted in this invention is as follows: A method for correlating outcrop profiles with detailed formation data from well drilling includes the following steps: S1: Collect detailed classification schemes of well logging formations within the basin and compare them with standard outcrop profile classifications to identify differences between the two; collect full-core wells with conventional logging in the outcrop area, establish the correspondence between well logging formation classification and core lithology and rock assemblage, and establish rock-electric response indicators; S2: Use portable gamma meters and profile measurement tools to obtain geological and geophysical information of the outcrop profile, form virtual electrical logging curves of the outcrop profile, compare and match the virtual electrical logging curves with the drilling electrical logging curves, and perform fine stratigraphic division of the outcrop profile according to the well logging stratigraphic division scheme in the basin. S3: Combine the rock-electric response markers of the core wells established in step S1 with the outcrop profiles divided by well logging, and conduct petrological, sedimentary facies, biofossils and sequence stratigraphy analysis on the outcrops. Summarize the lithosomes, sedimentary characteristics, sequence cycles and paleontological markers of each stratum in the outcrop profiles divided by well logging. S4: Apply the fine geological stratification markers of outcrops to other outcrop profiles that have not undergone GR measurement for fine stratigraphic division. At the same time, use outcrop profiles with logging and drilling inside and outside the basin and with virtual logging trunks for stratification correction, so as to achieve fine stratification of outcrop profiles and drilling in the whole area according to a unified stratification standard.

[0007] Preferably, the specific steps of step S2 are as follows: S21. Complete and continuous outcrops of the Maokou Formation at the basin margin were exposed. The profile was measured using tools and the layers were stratified in the field. A comprehensive columnar section of thickness, lithology and sedimentation was compiled. S22. Use a portable gamma meter to measure the gamma value of the profile rock. When measuring, measure at 1m intervals from bottom to top according to the field layer, with one measurement point corresponding to each meter. Record the measurement point number and measurement value included in the field layer. S23. Obtain the virtual gamma curve of the outcrop profile. Calculate the true depth of the profile corresponding to each measurement point using the method for calculating the true thickness of the profile, and connect each point into a line to obtain the virtual logging curve of the outcrop profile. S24. Utilizing the consistent cyclicity of virtual logging curves with that of downhole logging curves, the outcrop profile can be finely divided according to the gamma curve cyclicity and elevation based on the formation division scheme of the basin logging.

[0008] Preferably, the tools used in step S21 include a measuring tape, spray paint, a geological compass, and a camera.

[0009] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: A method for establishing basin-mountain stratigraphic correlation was developed by using gamma-ray meter measurements to construct virtual logging curves of outcrop profiles and combining this with comprehensive information from basin margin core wells, outcrop profile rock assemblages, sequence cycles, and paleontology. This method enables fine-grained regional stratigraphic correlation. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the stratigraphic division scheme of the Maokou Formation in the Sichuan Basin and its surrounding area provided in an embodiment of the present invention. Figure 3This is a schematic diagram of well logging stratification and rock-electric relationship establishment in a cored well at the basin margin provided in an embodiment of the present invention; Figure 4 A schematic diagram showing the GR measurement of the outcrop profile at the basin edge and its comparison with the drilling formation within the basin, provided in an embodiment of the present invention. Figure 5 A schematic diagram of field outcrop markers corresponding to well logging stratification of the Maokou Formation on the southern margin of the Sichuan Basin, provided in an embodiment of the present invention. Figure 6 This is a schematic diagram of the conodont zone corresponding to the well logging stratification of the Maokou Formation on the southern margin of the Sichuan Basin, provided in an embodiment of the present invention. Figure 7 A schematic diagram of formation comparison and correction with well logging drilling, outcrop profile with virtual well logging trunk and outcrop profile without virtual well logging provided for embodiments of the present invention; Figure 8 This is a schematic diagram of the stratigraphic thickness in a large basin-mountain region, compiled according to a fine stratigraphic division, provided for an embodiment of the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0013] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0014] In the description of this invention, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0015] The following is combined with Figures 1-8 The present invention will be described in detail below.

[0016] Example: A method for correlating outcrop profiles with detailed formation data from well drilling includes the following steps: S1: Collect detailed classification schemes of well logging formations within the basin and compare them with standard outcrop profile classifications to identify differences between the two; collect full-core wells with conventional logging in the outcrop area, establish the correspondence between well logging formation classification and core lithology and rock assemblage, and establish rock-electric response indicators; A detailed explanation is provided using the stratigraphic correlation of the Maokou Formation in and around the Sichuan Basin as an example: (1) Summary of outcrop stratigraphy at the basin margin: The standard section of the Maokou Formation is named at Maokouhe in Liuzhi Special District, Guizhou Province, on the southern margin of the Sichuan Basin. Based on the rock assemblage and fossil characteristics, it is divided into three sections from bottom to top: Xianrenmiao Section (dolomite and bioclastic limestone), Dazhai Section (containing chert limestone), and Honglakong Section (weakly dolomitized limestone), producing fossil assemblages of fusiformes, corals, etc. In the outcrops at the periphery of the Sichuan Basin, it can be divided into four sections: Maokou Section 1 is iridocorneal argillaceous limestone, rich in cryptolithic ternite; Maokou Section 2: light gray to gray massive micritic bioclastic limestone, containing thick-walled corals, pseudo-canine corals, yabe, zhusen, and Sumatran corals; the upper part contains chert nodule limestone. Maokou Section 3: light gray massive scleretic bioclastic limestone, containing Neo-Shivag, yabe, and zhusen; Maokou Section 4: light gray to gray intermediate micritic limestone interbedded with chert layers, containing zhusen, yabe, and Neo-Shivag.

[0017] (2) Drilling and logging stratification schemes within the basin and their differences from outcrops: Stratigraphic division schemes of the Maokou Formation within the Sichuan Basin of China National Petroleum Corporation were collected. Specifically, based on gamma curves (GR) and using cyclic stratigraphy, the Maokou Formation was divided into four sections: Maokou 1, Maokou 2, Maokou 3, and Maokou 4. Maokou 1 is further divided into four sub-sections, and Maokou 2 is divided into upper and lower sub-sections (e.g., ...). Figure 2 (As shown). Differences in stratigraphic division between outcrops and basins: Stratigraphic division in outcrop profiles is mainly based on rock assemblages and paleontology, while well logging strata are often demarcated by extremely high or low GR at the bottom of the cycle. Although the top and bottom divisions of the group are not significantly different, the number of segments, segment locations, and level of detail in well logging strata differ considerably from standard profiles. Therefore, the two cannot be directly compared.

[0018] (3) Collect and compare the formation of the core wells with conventional logging at the basin edge with the formation of the basin: the well can be a mineral, hydrological or oil and gas well, and must meet the requirements of logging and the target layer has physical rock cores; use the logging curves to perform fine formation division of the target layer of the core drilling at the basin edge according to the formation division scheme of the basin logging.

[0019] (4) Based on well logging stratigraphic division, conduct core observation or sampling identification of core samples from full-core wells to summarize the lithology, rock assemblage, paleontology, and boundary markers of each layer, and establish lithological-electrical property relationships: By collecting data from the basin margin full-core geological survey well YD1, the stratigraphy was re-divided according to the basin drilling Maokou Formation division scheme, and the rock-electrical property relationships were established using the above method. Specular sandstone limestone corresponds to extremely low gamma values, micritic limestone corresponds to medium gamma values, and iridocorneal argillaceous limestone has the highest gamma value. The bottom of each section of the Maokou Formation boundary is often a argillaceous band with high GR or containing argillaceous limestone (such as...). Figure 3 (As shown).

[0020] S2: Obtain geological and geophysical information of the outcrop profile using a portable gamma ray meter and profile measurement tools, generate virtual electrical logging curves for the outcrop profile, compare and match the virtual electrical logging curves with drilling electrical logging curves, and perform fine stratigraphic division of the outcrop profile according to the well logging stratigraphic division scheme within the basin; the specific steps of step S2 are as follows: S21, a complete and continuous outcrop of the Maokou Formation at the basin margin is exposed, and the profile is measured in the field using tools, and the layers are divided in the field to compile a comprehensive columnar section of thickness, lithology, and sedimentation; S22, the gamma ray value of the rock in the profile is measured using a portable gamma ray meter, and the measurement is performed according to the field stratification... Measurements are taken at 1-meter intervals from bottom to top, with one measurement point per meter. The measurement point number and measurement value included in the field stratification are recorded. S23: Obtain the virtual gamma curve of the outcrop profile. Calculate the true depth of the profile corresponding to each measurement point using the actual profile thickness calculation method based on the measured values ​​in meters recorded by the gamma curve. Connect each point to form a line to obtain the virtual logging curve of the outcrop profile. S24: Utilizing the consistency between the cyclicity reflected by the virtual logging curve and the cyclicity of the downhole logging curve, the outcrop profile can be finely divided into strata based on the gamma curve cyclicity and elevation according to the basin logging formation division scheme. The tools in step S21 include a measuring tape, spray paint, geological compass, and camera.

[0021] Specifically: (1) Based on traditional geological survey methods, complete and continuous outcrops of the Maokou Formation at the basin margin were exposed. The profile was measured using tools such as tape measure, spray paint, geological compass, and camera, and the field stratification was carried out to compile a comprehensive columnar section of thickness, lithology, and sedimentation; (2) The gamma value of the profile rocks was measured using a portable gamma meter. During the measurement, the field stratification was measured at 1m intervals from bottom to top, with one measurement point corresponding to each meter. The measurement point number and measurement value included in the field stratification were recorded (e.g., Figure 4(3) Obtain the virtual gamma curve of the outcrop profile. Calculate the true depth of the profile corresponding to each measurement point using the actual thickness calculation method of the profile, based on the measured value in meters of the gamma record. Connect each point to form a line to obtain the virtual logging curve of the outcrop profile. (4) Since the downhole logging company and the portable gamma meter manufacturer are different, the measured value of this virtual logging curve cannot correspond to the absolute value of the drilling logging. However, the high and low trends of the gamma curves of the two are consistent. The cyclicity reflected by the virtual curve is consistent with the cyclicity of the downhole logging curve. Using this rule, the outcrop profile can be finely divided into layers according to the gamma curve cyclicity and height based on the formation division scheme of the basin logging (e.g., Figure 4 (As shown).

[0022] S3: Combine the rock-electric response markers of the core wells established in step S1 with the outcrop profiles divided by well logging, and conduct petrological, sedimentary facies, biofossils and sequence stratigraphy analysis on the outcrops. Summarize the lithosomes, sedimentary characteristics, sequence cycles and paleontological markers of each stratum in the outcrop profiles divided by well logging. Specifically: (1) Through field investigation and summarization, the lithology, rock assemblage, and sequence cycle markers of the southern margin of the Sichuan Basin, as defined by well logging, are shown in Table 1. Figure 5 As shown, (2) through systematic sampling, the conodont zones corresponding to each logging layer were identified, and the geological age corresponding to each layer was determined. Figure 6 This system established the rock assemblage, sedimentary characteristics, sequence cycles, and paleontological markers for each stratum in the outcrop section.

[0023] Table 1 Geological markers of well logging outcrops in the Maokou Formation on the southern margin of the Sichuan Basin S4: Apply the fine geological stratification markers of outcrops to other outcrop profiles that have not undergone GR measurement for fine stratigraphic division. At the same time, use outcrop profiles with logging and drilling inside and outside the basin and with virtual logging trunks for stratification correction, so as to achieve fine stratification of outcrop profiles and drilling in the whole area according to a unified stratification standard.

[0024] Specifically: (1) In the southern margin of the Sichuan Basin, 7 main profiles were measured by both in-situ and portable GR measurements, and 15 profiles were measured only by in-situ (e.g. Figure 7 (As shown in the lower right figure), without GR measurement, effective field outcrop stratification was carried out by identifying geological markers and stratifying well logging stratification within the basin; (2) By correcting outcrops without GR logging through well logging in the region and outcrops with virtual logging trunks, the outcrop profiles and wells in the whole area were finely stratified according to a unified stratification standard.

[0025] This method utilizes gamma-ray array measurements to construct virtual logging curves of outcrop profiles and combines this with comprehensive information such as core samples from basin margins, outcrop profile rock assemblages, sequence cycles, and paleontology to establish basin-mountain stratigraphic correlation, thus achieving a method for fine regional stratigraphic correlation.

[0026] This method was successfully used to correlate more than 30 wells in the Sichuan Basin with more than 20 sections of the Maokou Formation in its southern outcrop area. This extended the stratification of drilling and logging within the Sichuan Basin to the southern edge of the basin and even to the mountainous areas of northern Guizhou and northeastern Yunnan. Stratigraphic thickness maps and sedimentary facies maps (such as those for Maokou Formation I, Maokou Formation II, Maokou Formation II, Maokou Formation III, and Maokou Formation IV) were successfully compiled. Figure 8 (As shown). Therefore, this invention enables segmented and detailed mapping of large-area strata, which can effectively guide the prediction of strata thickness, thereby guiding the design of well depths for oil and gas and mineral drilling. It can even guide the prediction of oil and gas source rocks and reservoirs through strata thickness and sediment mapping. This invention has broad application prospects in solving the problem of detailed stratigraphic correlation between wells and outcrops in large oil and gas basins in my country.

[0027] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for correlating outcrop profiles with detailed formation data from well drilling, characterized in that, Includes the following steps: S1: Collect detailed classification schemes of well logging formations within the basin and compare them with standard outcrop profile classifications to identify differences between the two; collect full-core wells with conventional logging in the outcrop area, establish the correspondence between well logging formation classification and core lithology and rock assemblage, and establish rock-electric response indicators; S2: Use portable gamma meters and profile measurement tools to obtain geological and geophysical information of the outcrop profile, form virtual electrical logging curves of the outcrop profile, compare and match the virtual electrical logging curves with the drilling electrical logging curves, and perform fine stratigraphic division of the outcrop profile according to the well logging stratigraphic division scheme in the basin. S3: Combine the rock-electric response markers of the core wells established in step S1 with the outcrop profiles divided by well logging, and conduct petrological, sedimentary facies, biofossils and sequence stratigraphy analysis on the outcrops. Summarize the lithosomes, sedimentary characteristics, sequence cycles and paleontological markers of each stratum in the outcrop profiles divided by well logging. S4: Apply the fine geological stratification markers of outcrops to other outcrop profiles that have not undergone GR measurement for fine stratigraphic division. At the same time, use outcrop profiles with logging and drilling inside and outside the basin and with virtual logging trunks for stratification correction, so as to achieve fine stratification of outcrop profiles and drilling in the whole area according to a unified stratification standard.

2. The method for correlating outcrop profiles with fine formation data from well drilling, as described in claim 1, is characterized in that... The specific steps of step S2 are as follows: S21. Complete and continuous outcrops of the Maokou Formation at the basin margin were exposed. The profile was measured using tools and the layers were stratified in the field. A comprehensive columnar section of thickness, lithology and sedimentation was compiled. S22. Use a portable gamma meter to measure the gamma value of the profile rock. When measuring, measure at 1m intervals from bottom to top according to the field layer, with one measurement point corresponding to each meter. Record the measurement point number and measurement value included in the field layer. S23. Obtain the virtual gamma curve of the outcrop profile. Calculate the true depth of the profile corresponding to each measurement point using the method for calculating the true thickness of the profile, and connect each point into a line to obtain the virtual logging curve of the outcrop profile. S24. Utilizing the consistent cyclicity of virtual logging curves with that of downhole logging curves, the outcrop profile can be finely divided according to the gamma curve cyclicity and elevation based on the formation division scheme of the basin logging.

3. The method for correlating outcrop profiles with fine formation data from well drilling, as described in claim 2, is characterized in that... The tools used in step S21 include a measuring tape, spray paint, a geological compass, and a camera.

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