Sandstone reservoir identification method based on common constraint of three elements

Abstract

The invention provides a sandstone reservoir identification method based on common constraint of three elements. The sandstone reservoir identification method comprises the following steps: establishing an isochronous stratigraphic framework according to a seismic interpretation profile, a drilling lithology comprehensive histogram and logging curve data of a research area; under the isochronous stratigraphic framework, sedimentary microfacies identification mark establishment and sedimentary microfacies division are carried out according to drilling core data and logging curve data, and the sedimentary microfacies distribution range of a research area is determined; in the sedimentary microfacies distribution range, according to well drilling core data, well logging curve data and well drilling coring data, sand body types are identified, and sand body distribution conditions are determined; drawing a cross plot according to various logging curves; establishing a sedimentary microfacies-sand body distribution-logging intersection identification sandstone reservoir scheme; and counting the thickness of the sandstone reservoir according to the sandstone reservoir, and drawing a thickness contour map of the sandstone reservoir. The sandstone reservoir can be identified more efficiently and clearly, and the prediction method has universality.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum exploration, and in particular to a sandstone reservoir identification method based on the common constraints of three elements. Background Art

[0002] Sandstone reservoirs are one of the most predominant reservoir types in my country's oil and gas fields. Considerable quantities of oil and gas have been developed in thin sandstone-mudstone reservoirs in many large oil and gas fields worldwide. Sandstone reservoirs are also found in large domestic oil and gas fields such as Daqing, Shengli, and Lunnan. Their primary characteristic is the development of thin interbeds of sandstone and mudstone. Therefore, identifying sandstone reservoirs is a key focus in the exploration phase of similar oil and gas reservoirs in my country. Currently, existing methods include seismic, numerical simulation, model prediction, well logging intersection, neural networks, and artificial intelligence learning. Compared to traditional reservoir identification methods that rely on lithologic and lithofacies combinations and reservoir parameter prediction, the proposed new method offers superior quantitative prediction and intelligent identification capabilities. The seismic method uses seismic reflection data of different lithologies to identify facies and then identify and predict reservoirs. However, seismic data has the disadvantages of multiple solutions and inconsistent quality. The numerical simulation method usually uses logging data such as lithologic data, physical data, and electrical data to establish reservoir identification standards and use this to carry out reservoir identification work. The disadvantage of the numerical simulation method is that the lithologies of different oil and gas reservoirs are slightly different, and their lithologies, physical properties, electrical properties and oil and gas content are all different. The same set of standards is not universally applicable to different oil and gas reservoirs, and one standard is required for each reservoir. The model prediction method uses modeling software to establish data similar to the various properties of the reservoir. The limitation of the value model is that it cannot fully simulate reservoir changes, and the prediction results often deviate from the actual situation. The well logging curve intersection method extracts lithologic identification boundaries based on the response of different lithologies to the logging curve, thereby conducting reservoir identification. However, for reservoirs with rapid vertical and horizontal changes, the well logging curve intersection method cannot accurately identify and predict unknown areas between wells. Neural network methods and artificial intelligence methods are relatively new reservoir prediction methods, with big data support and machine autonomous learning features. However, their disadvantages are that they are difficult to operate, the data accumulation phase is long, and the recognition accuracy is limited by the data volume. Therefore, all the current mainstream reservoir identification and prediction methods have certain limitations.

[0003] Sandstone reservoirs are primarily distributed in fluvial, deltaic, tidal flat, and shallow lake sedimentary facies. Their unique terrestrial or marine-continental transitional environments result in rapid changes in sedimentary facies. Furthermore, variations in provenance and other factors lead to rapid and complex sandstone-mudstone assemblages. This ultimately manifests as rapid changes in reservoir geophysical properties, making reservoir prediction extremely difficult. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a sandstone reservoir identification method based on the common constraints of three factors, which overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of the present invention, a sandstone reservoir identification method based on three-factor joint constraint is provided, the identification method comprising:

[0006] Step S1: Establish an isochronous stratigraphic framework based on seismic interpretation profiles, drilling lithology comprehensive histograms, and well logging curve data in the study area;

[0007] Step S2: establishing sedimentary microfacies identification marks and dividing sedimentary microfacies according to drilling core data and well logging curve data under the isochronous stratigraphic framework to clarify the distribution range of sedimentary microfacies in the study area;

[0008] Step S3: identifying the sand body type and determining the sand body distribution within the sedimentary microfacies distribution range based on drilling core data, well logging curve data, and drilling coring data;

[0009] Step S4: Draw an intersection diagram based on various logging curves; compare the intersection areas based on the oil test interpretation results, and establish a sedimentary microfacies-sand body distribution-logging intersection scheme for identifying sandstone reservoirs;

[0010] Step S5: Count the thickness of the sandstone reservoir and draw a thickness contour map of the sandstone reservoir according to the sandstone reservoir.

[0011] Optionally, the isochronous stratigraphic framework includes: an isochronous stratigraphic framework top interface, an isochronous stratigraphic framework bottom interface, an isochronous stratigraphic interface of a sand layer group, and an isochronous sand layer group stratum.

[0012] Optionally, the establishing of the isochronous stratigraphic framework further includes: identifying continuous strong reflection interfaces of the stratigraphic layers in the seismic interpretation data as isochronous stratigraphic top interfaces and isochronous stratigraphic bottom interfaces.

[0013] Optionally, identifying continuous strong reflection interfaces of strata in seismic interpretation data further includes:

[0014] Under the constraints of the isochronous stratigraphic top and bottom interfaces, the interfaces of different lithologic cycles are identified as the isochronous stratigraphic interfaces of the sandstone group.

[0015] Optionally, the strata between the isochronous strata interfaces of the sand layer group are identified as isochronous sand layer group strata.

[0016] Optionally, step S2, under the isochronous stratigraphic framework, establishes sedimentary microfacies identification marks and divides sedimentary microfacies based on drilling core data and logging curve data to clarify the distribution range of sedimentary microfacies in the study area, specifically including:

[0017] Based on the observation of drilling cores, the lithology, sedimentary microfacies, sedimentary structure, and sedimentary cycle are judged and identified, and the sedimentary microfacies identification marks of drilling cores are established;

[0018] Identify different logging phases based on the basic element characteristics of the logging curve;

[0019] Based on the established core sedimentary microfacies identification marks and the established logging curve sedimentary microfacies identification marks, carry out detailed characterization of single well sedimentary microfacies;

[0020] Under the isochronous stratigraphic framework, based on the single-well sedimentary microfacies characterized in the third step, the sedimentary microfacies distribution range of the study area was characterized, and a comparison map of the wells connected by the sedimentary microfacies in the study area and a plane distribution map were obtained.

[0021] Optionally, the identification marks of the sedimentary microfacies include: core color, grain sequence changes, and sedimentary structure.

[0022] Optionally, the basic elements of the logging curve include the combination form of the logging curve, the amplitude of the logging curve, the top and bottom contact relationship of the logging curve, and the smoothness of the logging curve.

[0023] Optionally, the step S3 of identifying the sand body type and determining the sand body distribution within the sedimentary microfacies distribution range based on drilling core data, well logging curve data, and drilling coring data specifically includes:

[0024] Combined with the results of sedimentary microfacies division, sand bodies can be identified;

[0025] Draw a sand body well-connected cross-section and use the top interface of the identified isochronous stratigraphic framework as the isochronous surface for top leveling;

[0026] Based on the characteristics of well logging curves, the sand body type is identified by taking the lithologic combination, sedimentary structure, and morphological characteristics of the well logging curves. The same type of sand bodies with similar characteristics are connected to determine the vertical superposition and lateral distribution patterns of the sand bodies.

[0027] Optionally, step S4, drawing an intersection diagram based on various logging curves; comparing the intersection areas based on the oil test interpretation results, and establishing a sedimentary microfacies-sand body distribution-logging intersection scheme for identifying sandstone reservoirs specifically includes:

[0028] The logging curve types with higher sensitivity to sandstone and mudstone were selected from the logging curve data in the study area.

[0029] In the selected logging curves, combine them in pairs, select two different logging curves multiple times to draw intersection diagrams, and fill the intersection area with color;

[0030] Based on the comprehensive histogram of curve intersection in the single well logging area and the results of oil test interpretation, the sandstone reservoir identification results under the constraints of sedimentary microfacies, sandbody distribution and logging curve intersection were compared to establish a sandstone reservoir identification scheme based on sedimentary microfacies, sandbody distribution and logging intersection.

[0031] According to the obtained sandstone reservoir identification scheme, the sandstone reservoir of a single well in the study area was identified.

[0032] The present invention provides a sandstone reservoir identification method based on the joint constraints of three factors. The identification method includes: step S1, establishing an isochronous stratigraphic framework based on seismic interpretation profiles, drilling lithology comprehensive histograms and logging curve data of a study area; step S2, within the isochronous stratigraphic framework, establishing sedimentary microfacies identification marks and dividing sedimentary microfacies based on drilling core data and logging curve data, and clarifying the sedimentary microfacies distribution range of the study area; step S3, identifying sand body types and determining sand body distribution within the sedimentary microfacies distribution range based on drilling core data, logging curve data and drilling coring data; step S4, drawing intersection diagrams based on various logging curves; comparing intersection areas based on oil test interpretation results, and establishing a sedimentary microfacies-sand body distribution-logging intersection identification scheme for sandstone reservoirs; and step S5, statistically analyzing the sandstone reservoir thickness based on the sandstone reservoir, and drawing a sandstone reservoir thickness contour map. A sandstone reservoir identification method based on the joint constraints of sedimentary microfacies, sand body distribution and logging curve intersection factors is provided. It can identify sandstone reservoirs more efficiently and clearly, and this prediction method is universal.

[0033] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A flow chart of a sandstone reservoir identification method based on three common constraints provided by an embodiment of the present invention;

[0036] Figure 2 Identify the top and bottom interfaces of the isochronous grid in accordance with an embodiment of the present invention;

[0037] Figure 3This is a comprehensive histogram of the isochronous stratigraphic framework of a single well in an embodiment of the present invention;

[0038] Figure 4 This is a cross-sectional view of a sand layer group well connection according to an embodiment of the present invention;

[0039] Figure 5 This is a comprehensive histogram of sedimentary microfacies of a single well in an embodiment of the present invention;

[0040] Figure 6 This is a cross section of a micro-connected well deposited in an embodiment of the present invention;

[0041] Figure 7 This is a plane distribution diagram of the sedimentary microphase according to an embodiment of the present invention;

[0042] Figure 8 This is a crossplot of single well logging curves according to an embodiment of the present invention;

[0043] Figure 9 This is a contour map of sandstone reservoir thickness in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0045] The terms "comprises" and "comprising" and any variations thereof in the description, embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0046] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0047] like Figure 1 As shown in FIG, a sandstone reservoir identification method based on the joint constraints of the three elements of "sedimentation-sand body-logging curve" includes the following steps:

[0048] Step 1: Establish an isochronous stratigraphic framework based on the seismic interpretation profile, drilling lithology comprehensive histogram and logging curve data of the study area.

[0049] Step 2: Based on the isochronous stratigraphic framework obtained in step 1, establish sedimentary microfacies identification marks and divide sedimentary microfacies according to drilling core data and well logging curve data to clarify the distribution range of sedimentary microfacies in the study area;

[0050] Step 3: Within the sedimentary microfacies distribution range obtained in step 2, identify the sand body type and determine the sand body distribution based on the drilling core data, well logging curve data, and drilling coring data;

[0051] Step 4: Draw an intersection diagram based on various logging curves; compare the intersection areas based on the oil test interpretation results, and establish a sandstone reservoir identification scheme using sedimentary microfacies-sand body distribution-logging intersection;

[0052] Step 5: Based on the sandstone reservoir identified in step 4, calculate the thickness of the sandstone reservoir and draw a contour map of the sandstone reservoir thickness.

[0053] This method, based on seismic data, drilling data, and logging data, establishes an isochronous stratigraphic framework, clarifies sedimentary microfacies, characterizes sandbody distribution, and combines well logging curve intersection to carry out sandstone reservoir identification under the joint constraints of multiple factors. This method can not only clearly and efficiently identify sandstone reservoirs, but also has good universality and is suitable for most sand-mud interbedded formations.

[0054] In order to solve the problem of isochronous stratigraphic framework division, preferably, in step 1, the isochronous stratigraphic framework includes an isochronous stratigraphic framework top interface, an isochronous stratigraphic framework bottom interface, an isochronous stratigraphic interface of a sand layer group, and an isochronous sand layer group stratum.

[0055] In order to solve the problem of isochronous stratigraphic framework division, an isochronous stratigraphic framework was established based on seismic interpretation profiles, drilling lithology comprehensive histograms and logging curve data in the study area.

[0056] In order to solve the problem of isochronous stratigraphic framework division, the continuous strong reflection interface of the stratigraphic layer in the seismic interpretation data is identified as the isochronous stratigraphic top interface and the isochronous stratigraphic bottom interface.

[0057] In order to solve the problem of isochronous stratigraphic framework division, under the constraints of isochronous stratigraphic top and bottom interfaces, the interfaces of different lithologic cycles are identified as isochronous stratigraphic interfaces of sandstone groups.

[0058] In order to solve the problem of isochronous stratigraphic framework division, the strata between the isochronous stratigraphic interfaces of the sand layer group are identified as isochronous sand layer group strata.

[0059] To solve the problem of clarifying the distribution range of sedimentary microfacies in the study area, step 2 includes the following steps:

[0060] The first step is to identify lithology, sedimentary microfacies, sedimentary structure, sedimentary cycle, etc. based on drilling core observations, and establish drilling core sedimentary microfacies identification marks.

[0061] The second step is to identify different logging phases based on the basic element characteristics of the logging curve.

[0062] The third step is to carry out detailed characterization of the sedimentary microfacies of a single well based on the sedimentary microfacies identification marks of the core established in the first step and the sedimentary microfacies identification marks of the logging curve established in the second step.

[0063] The fourth step is to characterize the distribution range of sedimentary microfacies in the study area based on the isochronous stratigraphic framework obtained in step 1 and the single-well sedimentary microfacies characterized in step 3, and obtain a comparison map and a plane distribution map of the sedimentary microfacies connected wells in the study area.

[0064] In order to solve the problem of sedimentary microfacies identification marks, preferably, in the first step of step 2, the identification marks of the sedimentary microfacies include at least core color, grain sequence changes, and sedimentary structure.

[0065] In order to solve the problem of logging phase identification, preferably, in the second step of step 2, the basic elements of the logging curve include at least the combination form of the logging curve, the amplitude of the logging curve, the top and bottom contact relationship of the logging curve, and the smoothness of the logging curve.

[0066] To solve the problem of determining the distribution of sand bodies, step 3 includes the following steps:

[0067] The first step is to identify the sand body based on the sedimentary microfacies division results obtained in step 2.

[0068] The second step is to draw a sand body well-connected profile (or sand body well-connected comparison diagram), using the top interface of the isochronous stratigraphic framework identified in step 1 as the isochronous surface for top flattening. Based on the characteristics of the well logging curve, the sand body type is identified by taking the lithologic combination, sedimentary structure, and logging curve morphology. The same type of sand bodies with similar characteristics are connected to determine the vertical superposition and lateral distribution patterns of the sand bodies.

[0069] To solve the problem of establishing a sedimentary microfacies-sand body distribution-logging intersection scheme for identifying sandstone reservoirs, step 4 includes the following steps:

[0070] The first step is to select the logging curve type that is more sensitive to sandstone and mudstone from the logging curve data in the study area.

[0071] Step 2: In the well logging curves selected in step 1 of step 4, combine them in pairs, select two different well logging curves multiple times to draw intersection diagrams, and fill the intersection area with color;

[0072] The third step is to compare the sandstone reservoir identification results under the constraints of sedimentary microfacies-sandbody distribution-logging curve intersection based on the comprehensive histogram of curve intersection in the single well logging area and the oil test interpretation results, and establish a sandstone reservoir identification scheme based on sedimentary microfacies-sandbody distribution-logging intersection.

[0073] The fourth step is to identify the sandstone reservoirs in the study area in a single well according to the sandstone reservoir identification scheme obtained in the third step of step 4.

[0074] Example 1

[0075] This embodiment provides a sandstone reservoir identification method based on the joint constraints of the three factors of "sedimentation, sand body, and well logging curves". The main technical idea is: first, an isochronous stratigraphic framework is established using information such as seismic interpretation profiles, drilling cores, and well logging curve data. Within this framework, the distribution range of sedimentary microfacies, the distribution range of sand bodies, and the intersection range of well logging curves are sequentially characterized. The sandstone reservoir prediction results constrained by the three factors are compared with the well logging interpretation results to determine the sandstone reservoir identification plan, and sandstone reservoir identification is performed in the study area.

[0076] This example takes the sand-mud formation in the middle subsection of the third member of the Shahejie Formation in the Linpan area of ​​the Huimin Sag as an example. The study area has a large number of wells drilled and a high well density, but the formations are frequently interbedded with sand and mud, and the sandy reservoirs change rapidly, making reservoir prediction and identification in areas where no wells are drilled difficult.

[0077] The specific implementation process is as follows:

[0078] Step 1: In this embodiment, an isochronous stratigraphic framework is established based on the seismic interpretation profile, drilling lithology comprehensive histogram, and well logging data of the study area. The specific process is as follows:

[0079] Step 1: Based on the seismic interpretation data, identify the continuous strong reflection interface of the middle subsection of the third member of the Shahejie Formation as the isochronous formation interface, and establish the top and bottom interfaces of the isochronous formation framework of the middle subsection of the third member of the Shahejie Formation; Figure 2 As shown, the T3 reflection interface is identified as the top interface of the isochronous stratigraphic framework of the middle sub-section of the Shahejie Formation 3; and the T4 reflection interface is identified as the bottom interface of the isochronous stratigraphic framework of the middle sub-section of the Shahejie Formation 3.

[0080] Step 2: Within the top and bottom interfaces of the isochronous stratigraphic framework established in the first step, based on the lithologic data recorded in the comprehensive drilling lithologic histogram, identify the interfaces of different lithologic cycles as interfaces between different sand layer groups, and establish the isochronous stratigraphic interfaces of the sand layer groups. Specifically, in this embodiment:

[0081] Six isochronous stratigraphic interfaces of sand layers were identified in the middle subsection of the third member of the Shahejie Formation, namely interfaces 1, 2, 3, 4, 5, and 6. Their identification characteristics are as follows:

[0082] ① Interface No. 1: With the bottom interface of the isochronous stratigraphic framework of the middle sub-section of the third member of Shahejie Formation identified in the first step upward, the lithologic interface between the thick carbonaceous mudstone and the thin limy mudstone is identified as Interface No. 1.

[0083] ② Interface No. 2: With interface No. 1 identified in the second step facing upward, the lithologic interface between thin-layered limy mudstone and thick-layered sandstone interbedded with thin-layered mudstone is identified as interface No. 2.

[0084] ③ Interface No. 3: With Interface No. 2 identified in the second step upward, the lithologic interface between thick sandstone interbedded with thin mudstone and middle sandstone interbedded with thin mudstone is identified as Interface No. 3.

[0085] ④ Interface No. 4: With Interface No. 3 identified in the second step upward, the lithologic interface between the middle sandstone interbedded with thin mudstone and the thick mudstone is identified as Interface No. 4.

[0086] ⑤ Interface No. 5: With interface No. 4 identified in the second step upward, the lithologic interface between the thick mudstone and siltstone is identified as interface No. 5.

[0087] ⑥ Interface No. 6: With interface No. 5 identified in the second step upward, the lithologic interface between siltstone and mudstone is identified as interface No. 6.

[0088] In the third step, based on the six interfaces identified in the second step, seven sets of isochronous sand layer groups were identified within the framework of the top and bottom interfaces of the middle sub-section of the third member of the Shahejie Formation completed in the first step, namely sand layer groups 1, 2, 3, 4, 5, 6, and 7.

[0089] ① No. 1 sand layer group: The mudstone-dominated stratum between the top interface of the middle sub-section of the third member of the Shahejie Formation identified in the first step and the other No. 6 interface identified in the second step is identified as the No. 1 sand layer group.

[0090] ② Sand layer group No. 2: The stratum mainly composed of siltstone between the No. 5 interface and the No. 6 interface identified in the second step is identified as sand layer group No. 2.

[0091] ③ Sand layer group No. 3: The stratum mainly composed of thick mudstone and siltstone between the No. 4 interface and the No. 5 interface identified in the second step is identified as sand layer group No. 3.

[0092] ④ No. 4 sand layer group: The stratum between the No. 3 interface and the No. 4 interface identified in the second step, which is mainly composed of middle-layer sandstone interbedded with thin-layer mudstone, is identified as the No. 4 sand layer group.

[0093] ⑤ Sand layer group No. 5: The stratum between interface No. 2 and interface No. 3 identified in the second step, which is mainly composed of thick sandstone and thin mudstone, is identified as sand layer group No. 5.

[0094] ⑥ Sand layer group No. 6: The stratum between interface No. 1 and interface No. 2 identified in the second step, which is mainly composed of thin layers of gray mudstone interbedded with thin layers of sandstone, is identified as sand layer group No. 6.

[0095] ⑦Sandbed No. 7: The stratum consisting mainly of thick carbonaceous mudstone between the No. 1 interface identified in the second step and the top interface of the middle sub-member of the Shahejie Formation No. 3 identified in the first step is identified as the No. 7 sandbed.

[0096] The fourth step is to carry out the isochronous stratigraphic framework division of the single well in the study area based on the top and bottom interfaces of the middle subsection of the third member of the Shahejie Formation identified in the first step, the six isochronous stratigraphic framework interfaces identified in the second step, and the seven isochronous sandstone formations divided in the third step. Figure 3 The figure shows a comprehensive histogram of the isochronous stratigraphic framework of a single well, taking Well Shang 547 as an example.

[0097] The fifth step is to draw the isochronous stratigraphic grid of the study area based on the comprehensive histogram of the single well isochronous stratigraphic grid divided in the fifth step of step 1, and obtain the isochronous stratigraphic grid of the middle subsection of the third member of the Shahejie Formation in the study area. Figure 4 , which is an isochronous stratigraphic framework well connection diagram.

[0098] Step 2: Based on the isochronous stratigraphic framework obtained in step 1, establish sedimentary microfacies identification marks and divide sedimentary microfacies according to drilling core data and well logging curve data to clarify the distribution range of sedimentary microfacies in the study area. The specific process is as follows:

[0099] The first step is to identify the lithology, sedimentary microfacies, sedimentary structure, sedimentary cycle, etc. based on the observation of the drilling core, and establish the drilling core sedimentary microfacies identification mark. Specifically, in this embodiment:

[0100] ① Identifying the color of the core, it was found that the sandstones in the study area are mostly reddish-brown, reflecting a shallow or slightly oxidizing sedimentary environment, which is the underwater distributary channel and estuary bar microfacies; the mudstone is darker in color, gray-green or purple-red, reflecting a slightly reducing sedimentary environment, which is the distributary bay microfacies.

[0101] ② Identify the changes in grain sequence of conglomerate, sandstone, siltstone and mudstone on the core. Identify the lithology dominated by medium sandstone and fine sandstone, with a positive grain sequence showing a finer grain size from bottom to top, as the underwater distributary channel microfacies; identify the lithology dominated by siltstone and fine sandstone, with a reverse grain sequence showing a coarser grain size from bottom to top, as the estuary bar microfacies; identify the lithology dominated by mudstone and silty mudstone as the distributary bay microfacies.

[0102] ③ Identify the sedimentary structures on the core and identify the parallel bedding as underwater distributary channel microfacies, such as Figure 4 Shown are parallel bedding of underwater distributary channel microfacies; developed cross-bedding is identified as estuary bar microfacies; visible bio-bores and horizontal bedding are identified as distributary bay microfacies.

[0103] The second step is to identify different logging phases based on the basic element features of the logging curve, where the basic element features of the logging curve include the combination form of the logging curve, the amplitude of the logging curve, the contact relationship between the top and bottom of the logging curve, the smoothness of the logging curve, etc. Specifically, in this embodiment:

[0104] ① Identify the natural gamma ray curve and the uranium-free gamma ray curve as a bell-shaped curve with gradually higher values ​​from bottom to top, or a box-shaped curve with a sudden change to high values ​​at the top and bottom interfaces and a relatively stable middle, or a bell-shaped or box-shaped curve alone or in combination as underwater distributary channel microfacies.

[0105] ② Identify the funnel-shaped, toothed funnel-shaped or superimposed funnel-shaped patterns that gradually approach lower values ​​from bottom to top in the natural gamma-ray curve and the uranium-free gamma-ray curve as estuary bar microfacies.

[0106] ③ Identify the natural gamma ray curve and the uranium-free gamma ray curve in a stable relatively high value area as the inter-distributary bay microfacies.

[0107] The third step is to carry out a detailed characterization of the single well sedimentary microfacies based on the core sedimentary microfacies identification marks established in the first step of step 2 and the logging curve sedimentary microfacies identification marks established in the second step, such as Figure 5 , which is a comprehensive histogram of sedimentary microfacies of a single well, taking Well Shang 645 as an example.

[0108] The fourth step is to characterize the distribution range of sedimentary microfacies in the study area based on the isochronous stratigraphic framework obtained in step 1 and the single well sedimentary microfacies characterized in step 2, step 3, and obtain the comparison map and plane distribution map of the sedimentary microfacies connected wells in the study area. Figure 6 , which is a comparison of sedimentary micro-connected wells among Shang 70, Shang 39, Shang 742 and Shang 72. Figure 7 , which is the planar distribution map of sedimentary microfacies of sand layer group No. 4 in the study area.

[0109] Step 3: Within the sedimentary microfacies distribution range obtained in step 2, identify the sand body type and determine the sand body distribution based on the drilling core data, well logging curve data, and drilling coring data. The specific process is as follows:

[0110] Step 1: Identify the sand body type based on the sedimentary microfacies classification results obtained in step 2. Specifically, in this embodiment:

[0111] Two types of sand bodies were identified, namely underwater distributary channel sand bodies and estuary bar sand bodies. The specific identification characteristics are as follows:

[0112] ① Sandbodies originating from underwater distributary channels typically exhibit the following characteristics: lithology is primarily medium and fine sandstone containing mud and gravel, with widespread development of sedimentary structures such as scour surfaces, oblique bedding, parallel bedding, and gravel imbrication, all of which are strongly hydrodynamic. Natural gamma ray logging curves often exhibit a bell-shaped pattern with gradually increasing values ​​from bottom to top, or a box-shaped pattern with abrupt changes in top and bottom interfaces and a relatively stable center. Frequently eroded and superimposed by the channel, sandbodies occur in combinations, with multiple cycles and a positive rhythm. Each cycle is often composed of thin reddish-brown mudstone at the top and mud-gravel sandstone at the bottom. Natural gamma ray and uranium-free gamma ray logs exhibit a bell-shaped pattern with gradually increasing values ​​from bottom to top, or a box-shaped pattern with abrupt changes in top and bottom interfaces and a relatively stable center, or a combination of bell and box-shaped patterns. Therefore, these characteristics can be used to identify sandbodies originating from underwater distributary channels.

[0113] ② Mouth-bar sandbodies typically exhibit the following characteristics: lithology is primarily medium sandstone and fine sandstone, occasionally containing mud and gravel; grain size exhibits an antirhythm of increasing coarseness upward; the top has a high shale content, and cross-bedding is often developed; natural gamma-ray logging curves often exhibit a funnel-shaped pattern with values ​​gradually decreasing from bottom to top; natural gamma-ray logging curves and uranium-free gamma-ray logging curves exhibit a funnel-shaped pattern, a toothed funnel-shaped pattern, or a combination of superimposed funnel-shaped patterns, all gradually decreasing from bottom to top. Therefore, these characteristics can be used to identify mouth-bar sandbodies.

[0114] Step 2: Draw a sand body well-connected profile (or sand body well-connected comparison diagram), use the top interface of the isochronous stratigraphic framework identified in step 1 as the isochronous surface for top flattening, and based on the characteristics of the well logging curve, select the same type of sand bodies with similar lithologic combinations, sedimentary structures, and well logging curve morphology for layer connection to determine the vertical superposition and lateral distribution patterns of the sand bodies.

[0115] Step 4: Draw an intersection diagram based on various logging curves within the sand body distribution range obtained in step 3; compare the intersection areas based on the oil test interpretation results to establish a sedimentary microfacies-sand body distribution-logging intersection scheme for identifying sandstone reservoirs. The specific process is as follows:

[0116] The first step is to select the logging curve type with high sensitivity to sandstone and mudstone from the logging curve data in the study area. In this embodiment, the natural gamma ray curve (GR), acoustic wave transit time curve (AC), spontaneous potential curve (SP) and resistivity (RNML) curve are selected.

[0117] Step 2: Draw a cross plot of the logging curve selected in Step 4 (1) using the natural gamma ray (GR) curve and the resistivity (RNML) curve. The natural gamma ray (GR) curve has a value range of 0-200 API and a normal scale. The resistivity curve has a value range of 0.001-100 Ω and a logarithmic scale with a base of 10. Fill the intersection area with color.

[0118] Step 3: In the logging curve selected in step 4, draw a cross plot with the acoustic transit time curve (AC) and the resistivity curve (RNML). The acoustic transit time curve (AC) has a value range of -100-0us / m and a normal scale; the resistivity curve has a value range of 0.01-1000Ω and a logarithmic scale with a base of 10; and fill the intersection area with color.

[0119] Step 4: In the logging curve selected in step 4, draw an intersection diagram with the acoustic transit time curve (AC) and the resistivity curve (RNML). The spontaneous potential curve (SP) value range is 50-500mV, and the scale is normal. The resistivity curve value range is 0.01-1000Ω, and the scale is logarithmic with a base of 10. Fill the intersection area with color.

[0120] The fifth step is to compare the sandstone reservoir identification results under the constraints of sedimentary microfacies-sandbody distribution-logging curve intersection based on the comprehensive histogram of single well logging area curve intersection and the oil test interpretation results, and establish a sandstone reservoir identification scheme based on sedimentary microfacies-sandbody distribution-logging intersection. Figure 8 , which is a comprehensive histogram comparing the logging curve intersection results and the oil test interpretation results, taking Well Shang 541 as an example.

[0121] Step 6: Identify the sandstone reservoirs in the study area in a single well according to the sandstone reservoir identification scheme obtained in step 4.

[0122] Step 5: Based on the sandstone reservoir identified in step 4, calculate the thickness of the sandstone reservoir and draw a contour map of the sandstone reservoir thickness. Figure 9 , which is the thickness contour map of the sandstone reservoir in the No. 4 sand layer group in the middle subsection of the third member of Shahejie Formation in the study area.

[0123] Beneficial effects: A sandstone reservoir identification method based on the joint constraints of sedimentary microfacies, sand body distribution and logging curve intersection factors is provided, which can more efficiently and clearly identify sandstone reservoirs, and the prediction method is universal.

[0124] Based on seismic data, drilling data, and logging data, an isochronous stratigraphic framework is established, sedimentary microfacies are clarified, and sand body distribution is depicted. Combined with the intersection of logging curves, sandstone reservoir identification under the joint constraints of multiple factors is carried out. This method can not only clearly and efficiently identify sandstone reservoirs, but also has good universality and is suitable for most sand-mud interbedded formations.

[0125] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sandstone reservoir identification method based on the common constraints of three factors, characterized in that: The identification method comprises: Step S1: Establish an isochronous stratigraphic framework based on seismic interpretation profiles, drilling lithology comprehensive histograms, and well logging curve data in the study area; Step S2: establishing sedimentary microfacies identification marks and dividing sedimentary microfacies according to drilling core data and well logging curve data under the isochronous stratigraphic framework to clarify the distribution range of sedimentary microfacies in the study area; Step S3: identifying the sand body type and determining the sand body distribution within the sedimentary microfacies distribution range based on drilling core data, well logging curve data, and drilling coring data; Step S4: Draw an intersection diagram based on various logging curves; compare the intersection areas based on the oil test interpretation results, and establish a sedimentary microfacies-sand body distribution-logging intersection scheme for identifying sandstone reservoirs; Step S5: Count the thickness of the sandstone reservoir and draw a thickness contour map of the sandstone reservoir according to the sandstone reservoir.

2. The sandstone reservoir identification method based on three-factor common constraint according to claim 1 is characterized in that: The isochronous stratigraphic framework includes: an isochronous stratigraphic framework top interface, an isochronous stratigraphic framework bottom interface, an isochronous stratigraphic interface of a sand layer group, and an isochronous sand layer group stratum.

3. The sandstone reservoir identification method based on three-factor common constraint according to claim 1 is characterized in that: The establishing of the isochronous stratigraphic framework further includes: identifying the continuous strong reflection interface of the stratigraphic layer in the seismic interpretation data as the isochronous stratigraphic top interface and the isochronous stratigraphic bottom interface.

4. The sandstone reservoir identification method based on three-factor common constraint according to claim 3 is characterized in that: The identification of continuous strong reflection interfaces of strata in seismic interpretation data also includes: Under the constraints of the isochronous stratigraphic top and bottom interfaces, the interfaces of different lithologic cycles are identified as the isochronous stratigraphic interfaces of the sandstone group.

5. The sandstone reservoir identification method based on three-factor common constraint according to claim 4 is characterized in that: The strata between the isochronous strata interfaces of the sand layer group are identified as isochronous sand layer group strata.

6. The sandstone reservoir identification method based on three-factor common constraint according to claim 1 is characterized in that: The step S2, under the isochronous stratigraphic framework, establishes sedimentary microfacies identification marks and divides sedimentary microfacies based on drilling core data and logging curve data, and clarifies the distribution range of sedimentary microfacies in the study area, specifically including: Based on the observation of drilling cores, the lithology, sedimentary microfacies, sedimentary structure, and sedimentary cycle are judged and identified, and the sedimentary microfacies identification marks of drilling cores are established; Identify different logging phases based on the basic element characteristics of the logging curve; Based on the established core sedimentary microfacies identification marks and the established logging curve sedimentary microfacies identification marks, carry out detailed characterization of single well sedimentary microfacies; Under the isochronous stratigraphic framework, based on the single-well sedimentary microfacies characterized in the third step, the sedimentary microfacies distribution range of the study area was characterized, and a comparison map of the wells connected by the sedimentary microfacies in the study area and a plane distribution map were obtained.

7. The sandstone reservoir identification method based on three-factor common constraint according to claim 6, characterized in that: The identification marks of the sedimentary microfacies include: core color, grain sequence changes, and sedimentary structure.

8. The sandstone reservoir identification method based on three-factor common constraint according to claim 6, characterized in that: The basic elements of the logging curve include the combination form of the logging curve, the amplitude of the logging curve, the contact relationship between the top and bottom of the logging curve, and the smoothness of the logging curve.

9. The sandstone reservoir identification method based on three-factor common constraint according to claim 1, characterized in that: The step S3 of identifying the sand body type and determining the sand body distribution within the sedimentary microfacies distribution range based on drilling core data, well logging curve data, and drilling coring data specifically includes: Combined with the results of sedimentary microfacies division, sand bodies can be identified; Draw a sand body well-connected cross-section and use the top interface of the identified isochronous stratigraphic framework as the isochronous surface for top leveling; Based on the characteristics of well logging curves, the sand body type is identified by taking the lithologic combination, sedimentary structure, and morphological characteristics of the well logging curves. The same type of sand bodies with similar characteristics are connected to determine the vertical superposition and lateral distribution patterns of the sand bodies.

10. The sandstone reservoir identification method based on three-factor common constraint according to claim 1, characterized in that: Step S4: drawing a crossplot based on various logging curves; Based on the comparison of the intersection area based on the oil test interpretation results, a sedimentary microfacies-sand body distribution-well logging intersection identification scheme for sandstone reservoirs was established, which specifically includes: The logging curve types with higher sensitivity to sandstone and mudstone were selected from the logging curve data in the study area. In the selected logging curves, combine them in pairs, select two different logging curves multiple times to draw intersection diagrams, and fill the intersection area with color; Based on the comprehensive histogram of curve intersection in the single well logging area and the results of oil test interpretation, the sandstone reservoir identification results under the constraints of sedimentary microfacies, sandbody distribution and logging curve intersection were compared to establish a sandstone reservoir identification scheme based on sedimentary microfacies, sandbody distribution and logging intersection. According to the obtained sandstone reservoir identification scheme, the sandstone reservoir of a single well in the study area was identified.

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