High-angle unconformity reservoir horizontal well comparison method

Abstract

This invention provides a horizontal well correlation method for high-angle unconformity reservoirs. The method includes: Step 1, using sequence stratigraphy to perform preliminary stratigraphic correlation of vertical wells; Step 2, performing seismic stratigraphic calibration and constructing a preliminary structural model; Step 3, combining well-seismic analysis to determine the stratigraphic correlation results of the vertical wells; Step 4, performing detailed closure interpretation across the entire area, delineating erosion lines, and compiling structural maps; Step 5, combining well-seismic analysis to determine the major stratigraphic boundaries of the horizontal wells based on seismic profiles; and Step 6, performing minor stratigraphic correlation of the horizontal wells. This horizontal well correlation method for high-angle unconformity reservoirs solves the problem of horizontal well correlation in unconformity reservoirs, providing guidance for horizontal well correlation in such reservoirs. Its application prospects are broad, and its economic and social benefits are significant.

Description

Technical Field

[0001] This invention relates to the field of fine stratigraphic correlation technology for high-angle unconformity reservoirs, and in particular to a horizontal well correlation method for high-angle unconformity reservoirs. Background Technology

[0002] Unconformity reservoirs hold enormous resource potential in my country. To control more geological reserves, horizontal well development technology is generally employed. For unconformity reservoir development, domestic horizontal well deployment methods mainly include tunnel wells parallel to structural lines and "penetrating wells" perpendicular to or oblique to structural lines. Among these, the "penetrating wells," with their horizontal well trajectories obliquely intersecting the formation, ensure that multiple oil layers are encountered vertically, effectively expanding the drainage area and significantly improving reserve utilization and recovery rates. With the continuous deepening of oil and gas exploration and development in my country, many advanced stratigraphic correlation techniques have been developed. From the early "cycle correlation, graded control, and step-by-step closure" small-layer correlation techniques, it has evolved to a comprehensive interpretation of 3D seismic and drilling data, constrained by seismic inversion technology and seismic stratigraphic tracking interpretation, and comprehensive correlation based on conductivity curves and other data, forming a stratigraphic correlation method with an isochronous stratigraphic correlation framework. However, for unconformity reservoirs, the reservoir below the unconformity surface is in angular unconformity contact with the unconformity surface. New strata will continuously appear along the dip of the formation. In multi-layered sandstone and mudstone profiles, it is difficult to achieve the correlation of horizontal wells through the unconformity reservoir using only existing methods.

[0003] Chinese patent application CN201811064478.5 discloses a reservoir geological steering method, which includes: tracing the target depth of a horizontal well to be drilled laterally using seismic profile data; establishing a formation comparison map between the horizontal well to be drilled and adjacent wells; establishing a three-dimensional geological model, including a pre-drilling static geological model and a dynamic geological model of the horizontal well to be drilled; in the dynamic geological model, creating two-dimensional slices based on the closure azimuth of the horizontal well to observe whether the designed trajectory passes through the oil layer and adjusting the trajectory in a timely manner; predicting the formation dip angle; ensuring precise trajectory landing; controlling the trajectory of the horizontal section, predicting the position of the drill bit in the longitudinal profile of the reservoir, and adjusting the wellbore trajectory. This invention uses logging-while-drilling data from the horizontal well to be drilled as a basis, combined with formation comparison maps of adjacent wells, and uses software to establish a three-dimensional geological model to guide the trajectory drilling, effectively ensuring an improved oil layer encounter rate.

[0004] Chinese patent application CN201610971436.4 discloses a well-seismic integrated horizontal well geological steering modeling method, comprising: Step 1, collecting data from adjacent wells and small-scale 3D seismic data within the work area; Step 2, performing stratigraphic comparison and subdividing based on the collected adjacent well data; Step 3, establishing a 3D digital geological body for the work area using ordinary kriging interpolation based on the adjacent well layer data; Step 4, cutting a 2D profile from the 3D geological body along the well trajectory; Step 5, processing the 3D seismic data using the time-depth relationship within the work area and cutting a 2D profile along the well trajectory, then overlaying it with the stratigraphic model cut from the 3D geological body; Step 6, adjusting the stratigraphic model according to the morphology of the seismic profile phase axis to ensure that the stratigraphic model morphology matches the seismic phase axis morphology. This well-seismic integrated horizontal well geological steering modeling method improves the accuracy of structural description and reservoir prediction, providing strong technical support for horizontal well geological steering.

[0005] Chinese patent application CN202110379797.0 discloses a method and apparatus for determining a horizontal well paving strategy. The method includes: acquiring historical production logging data; analyzing saturation data, production profile test data, and production dynamic characteristic data from the historical production logging data to determine the water intrusion patterns of the gas well and / or gas field; identifying low-permeability layers of the gas well and / or gas field through formation correlation and dynamic monitoring; and determining a horizontal well paving strategy on the low-permeability layers based on the water intrusion patterns. This invention improves the accuracy of horizontal well paving and enhances the comprehensiveness and efficiency of historical production logging data analysis, thereby effectively improving the reserve utilization and recovery rate of large, thick, abnormally high-pressure gas reservoirs.

[0006] The existing technologies described above are significantly different from the present invention and have failed to solve the technical problem we want to address. Therefore, we have invented a new method for horizontal well correlation based on high-angle unconformity reservoirs. Summary of the Invention

[0007] The purpose of this invention is to provide a method for horizontal well correlation in high-angle unconformity reservoirs that solves the problem of horizontal well correlation in unconformity reservoirs.

[0008] The objective of this invention can be achieved through the following technical measures: a horizontal well correlation method based on high-angle unconformity reservoirs, which includes:

[0009] Step 1: Use sequence stratigraphy to conduct preliminary stratigraphic correlation of the vertical well;

[0010] Step 2: Determine seismic horizons and build a preliminary structural model;

[0011] Step 3: Combine well and seismic data to determine the stratigraphic correlation results for the vertical well;

[0012] Step 4: Perform detailed closure interpretation of the entire area, delineate the location of erosion lines, and compile a structural map;

[0013] Step 5: Combining well and seismic analysis, determine the major layer boundaries of the horizontal well based on the seismic profile;

[0014] Step 6: Perform small-layer correlation of the horizontal well.

[0015] The objective of this invention can also be achieved through the following technical measures:

[0016] In step 1, sequence stratigraphy is used, combined with geological sedimentary characteristics, and regional and local markers are used to conduct preliminary stratigraphic correlation of vertical wells in the horizontal well area.

[0017] In step 2, based on the stratigraphic correlation results of the vertical wells in the horizontal well area, well-seismic stratigraphic positioning is performed, and stratigraphic tracking and interpretation are carried out for major layers and key sand groups. Seismic data is interpreted, and the planar distribution pattern of faults is clarified through seismic attributes. The location of major fault edges is described in detail, and a preliminary structural model is built.

[0018] In step 3, well-seismic analysis is combined with seismic analysis. By referring to the seismic sequence sedimentary characteristics and fault development of the seismic profile, regional and local markers are used to resolve the contradictions between well-seismic analysis and to determine the sub-layer data of vertical wells in the horizontal well area.

[0019] In step 4, the stratigraphic positions of each main layer are finely synthesized and calibrated, the seismic reflection characteristics of the main layers are clarified, a fine closure interpretation of the entire area is performed, the location of the erosion line is delineated, and a structural map is compiled.

[0020] In step 5, a reservoir distribution map of the horizontal well is created. Based on the distribution pattern of the erosion lines and the seismic profile through the horizontal well, the sand group to which each oil sand body of the horizontal well belongs is roughly determined, and the major layer boundaries of the horizontal well are preliminarily determined.

[0021] Step 5 also includes creating cross-sectional views of the horizontal and vertical wells.

[0022] In step 6, based on the cross-sectional diagrams of the horizontal and vertical wells, the small-layer comparison work of the horizontal well is completed.

[0023] In step 6, based on the structural map, the vertical well is projected onto the trajectory of the horizontal well along the structural line. For unconformity reservoirs, it is necessary to combine the formation occurrence and perform adjacent well structural correction to generate profile maps of the horizontal and vertical wells, thus completing the comparative study of the horizontal and vertical wells.

[0024] The method for horizontal well correlation based on high-angle unconformity reservoirs also includes, after step 6, step 7, compiling a plan view of the main layer based on the sub-layer stratification data and structural map, verifying the formation correlation data through data such as sub-layer oil-water and production dynamics, and adjusting the stratification or structure if there are problems to resolve the contradiction between oil and water development.

[0025] This invention presents a horizontal well correlation method for high-angle unconformity reservoirs, breaking away from the conventional method of relying on sequence stratigraphy correlation. It utilizes seismic profiles and a combination of well and seismic data to determine the location of major horizontal well layers. On the seismically interpreted structural map, vertical wells are projected along structural lines onto the horizontal well trajectory, and structural differences between adjacent wells are corrected. This generates profile maps of both horizontal and vertical wells, allowing for layered correlation. The correlation results of each oil-bearing sub-layer are verified through oil-water relationships and production dynamics. Ultimately, this method enables horizontal well correlation studies in unconformity reservoirs. This invention solves the problem of horizontal well correlation in unconformity reservoirs, providing guidance for horizontal well correlation in such reservoirs. Its application prospects are broad, and its economic and social benefits are significant. Attached Figure Description

[0026] Figure 1 This is a flowchart of a specific embodiment of the horizontal well correlation method for high-angle unconformity reservoirs according to the present invention;

[0027] Figure 2 This is a stratigraphic sedimentary profile in a specific embodiment of the present invention;

[0028] Figure 3 This is an overlay diagram of erosion lines in a specific embodiment of the present invention;

[0029] Figure 4 This is a horizontal well reservoir distribution diagram in a specific embodiment of the present invention;

[0030] Figure 5 This is a seismic profile of a horizontal well G12-P2 in a specific embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of a vertical well projected onto a horizontal well in a specific embodiment of the present invention, showing the bottom surface structure of hole 6.

[0032] Figure 7 This is a depth correction diagram of the vertical well projection onto the horizontal well structure on the bottom surface structure diagram of hole 6 in a specific embodiment of the present invention;

[0033] Figure 8 This is a cross-sectional view of a horizontal well and a vertical well after adjacent well correction in a specific embodiment of the present invention;

[0034] Figure 9 This is a plan view of the main sub-layer in a specific embodiment of the present invention. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0037] This invention relates to a method for stratigraphic correlation of horizontal wells in high-angle unconformity reservoirs, combining well-seismic analysis with fine structural model guidance. First, vertical wells in the horizontal well area are correlated using sequence stratigraphy and sedimentary characteristics, aided by regional and local markers. Second, seismic interpretation is used to calibrate the stratigraphic correlation data, interpreting the boundaries of major layers and sandstone groups, and constructing a structural model. Based on this model, a full-area closure interpretation of the target layer is completed, and a structural map is created. Then, based on the structural map, a horizontal well reservoir distribution map is created. According to the distribution pattern of erosion lines and seismic profiles passing through horizontal wells, the sandstone groups to which each oil sand body belongs in the horizontal well are roughly identified, and the major layer boundaries of the horizontal well are preliminarily determined. The vertical wells are projected onto the horizontal well trajectory along the structural lines, and structural corrections are performed to generate profile maps of both the horizontal and vertical wells. Ultimately, this method achieves the goal of stratigraphic correlation between horizontal wells and surrounding vertical wells in complex fault-block unconformity reservoirs.

[0038] The following are several specific embodiments of the application of the present invention.

[0039] Example 1

[0040] In a specific embodiment 1 of the present invention, the horizontal well correlation method based on high-angle unconformity reservoirs includes the following steps:

[0041] (1) Geologists used sequence stratigraphy and combined it with sedimentary characteristics to conduct preliminary stratigraphic correlation of all vertical wells in the horizontal well area with the help of regional and local markers.

[0042] (2) Based on the stratigraphic correlation results, the structural interpretation personnel will conduct well-seismic stratigraphic positioning, perform stratigraphic tracking and interpretation of major layers and key sand groups, finely delineate the fault edges of major faults, and build a preliminary structural model.

[0043] (3) Combine well and seismic analysis, carry out fine stratigraphic comparison with alternating well and seismic analysis and resolve well and seismic contradictions, and determine the stratigraphic comparison results of vertical wells in the horizontal well area.

[0044] (4) Seismic interpreters completed the full-area closed interpretation of each major sub-layer and produced a structural map.

[0045] (5) Combining well and seismic analysis, the boundary of the major layer of the horizontal well is determined based on the seismic profile.

[0046] (6) Geological researchers project the vertical well along the structural line onto the trajectory of the horizontal well based on the structural map. Since the area is an unconformity reservoir, it is necessary to combine the stratigraphic occurrence and perform structural correction of adjacent wells to generate profile maps of horizontal and vertical wells and complete the comparative study of horizontal and vertical wells.

[0047] Example 2

[0048] In a specific embodiment 2 of the present invention, such as Figure 1 As shown, Figure 1 The flowchart below shows the horizontal well correlation method based on high-angle unconformity reservoirs according to the present invention. This method includes the following steps:

[0049] Step 101: Using sequence stratigraphy, combined with geological sedimentary characteristics and regional and local markers, conduct preliminary stratigraphic correlation of vertical wells in the horizontal well area. Proceed to step 102.

[0050] Step 102: Based on the stratigraphic correlation results of the vertical wells in the horizontal well area, the seismic structural interpreters perform well-seismic stratigraphic calibration, and perform stratigraphic tracing and interpretation of major layers and key sand groups; interpret the seismic data, clarify the planar distribution pattern of faults through seismic attributes, finely describe the location of major fault edges, and build a preliminary structural model. Step 103.

[0051] Step 103: Well-seismic integration. Referring to the seismic sequence sedimentary characteristics and fault development of the seismic profile, and using regional and local markers to resolve well-seismic discrepancies, determine the sub-layer data of vertical wells in the horizontal well area. Proceed to step 104.

[0052] Step 104: The structural interpretation personnel perform detailed synthetic record stratigraphic positioning of each main layer, clarify the seismic reflection characteristics of the main layers, perform detailed closed interpretation of the entire area, delineate the location of erosion lines, and compile structural maps. Step 105:

[0053] Step 105: Create a horizontal well reservoir distribution map. Based on the distribution pattern of erosion lines and the seismic profile through the horizontal well, roughly determine the sand group to which each oil sand body in the horizontal well belongs, and preliminarily determine the major layer boundaries of the horizontal well. Proceed to step 106.

[0054] Step 106: Create cross-sectional views of the horizontal and vertical wells, then proceed to step 107.

[0055] Step 107: Based on the cross-sectional diagrams of the horizontal and vertical wells, complete the small-layer comparison work of the horizontal well, and proceed to step 108.

[0056] Step 108: Geological researchers compile a plan view of the main layer based on the sublayer stratification data and structural map. They then verify the stratigraphic correlation data using sublayer oil and water, production dynamics, and other data. If any problems are found, adjustments are made to the stratification or structure to resolve the contradictions in oil and water development, and the process ends.

[0057] Example 3

[0058] In a specific embodiment 3 of the present invention, the Gao 963 complex fault block is located in the Kongdian Formation area of ​​the Gaoqing Oilfield, in the southwestern part of the Dongying Depression, on the uplifted plate of the Gaoqing-Pingnan Fault, and on the northern slope of the Qingcheng Uplift. The Kongdian Formation strata are eroded layer by layer from north to south, exhibiting an imbricate distribution. The Guantao Formation strata, mainly composed of mudstone, overlie different Paleogene strata, forming multiple unconformity traps. These traps are further complicated by multiple faults with displacements of 10–30 meters, at depths of 940–1420 meters. The current problem with this block is the complex fault system, the presence of multiple unconformity systems, and the bottleneck in horizontal well correlation. Research on horizontal well correlation methods is urgently needed to identify reservoirs and clarify the distribution patterns of remaining oil.

[0059] The horizontal well correlation method for high-angle unconformity reservoirs of the present invention includes the following steps:

[0060] (1) By combining multiple data sources for analysis, a bottom-up sedimentary development model of the strata was established, clarifying the unconformity contact relationship between the strata in Block 963. First, by analyzing the correlation changes of 35 vertical wells, three stable correlation markers were identified for Block 963. Second, under the control of the marker layers, through analysis of the regional stratigraphic and sedimentary background and combined with high-precision three-dimensional seismic profiles, a correlation model of stratigraphic deposition in this area was established, showing that the strata underlying the Kongdian Formation and the Guantao Formation are in a high-angle unconformity contact. For example... Figure 2 As shown. Guided by the stratigraphic sedimentary model, the stratigraphy and sub-layers of 35 vertical wells in the horizontal well area were correlated and divided into 7 sand layer groups and 43 sub-layers, of which 23 are the main sub-layers.

[0061] (2) Based on the delineation results of the vertical well sandstone formation boundaries in the horizontal well area, and on the basis of reasonable and accurate stratigraphic calibration, stratigraphic and fault tracking interpretation was carried out through well-seismic fusion. Through seismic reflection characteristics, the bottom surfaces of six large formations (Guantao, Sha-4, Kong-4, Kong-5, Kong-6, and Mesozoic) with unified characteristics and stable and continuous energy were selected for full-area tracking interpretation. Hourly window coherence attributes and ant-body attributes were extracted to guide the fine interpretation of low-order fault profiles, establishing a refined three-dimensional structural framework. Top surface structural maps of the Guantao Formation, Kongdian-5 sandstone formation, and Kongdian-6 sandstone formation were compiled, clarifying the planar distribution pattern of erosion lines in Kongdian-2, 3, 4, 5, and 6 sandstone formations. For example... Figure 3 .

[0062] (3) Based on the well logging interpretation results, read the top and bottom depth data of each oil sand body in each horizontal well, calculate the corresponding planar position (x, y, z) of each oil sand body's top and bottom depth, and create a horizontal well reservoir distribution map based on this. Figure 4 Based on the distribution pattern of erosion lines, the sand layer group to which each oil sand body in the horizontal well belongs is roughly determined, and the division boundary of the sand layer group of the horizontal well is initially determined. Secondly, through well-seismic integration, seismic profiles are extracted along the trajectory of the horizontal well within the seismic interpretation body where the stratigraphic and fault interpretations have been completed. The influence of faults is eliminated, and the sand layer group boundary of the horizontal well that has been initially determined is further verified or fine-tuned from the seismic profile. Finally, the layering boundary of the sand layer group of the horizontal well is obtained.

[0063] (4) Create profile diagrams of horizontal and vertical wells. Based on the bottom structural maps of Guantao and Kong 6, first read the elevation depth of Kong 6 encountered by wells Gao 12-42 and Gao 12-21, project it along the structural lines of the bottom structural map of Kong 6 onto the trajectory of the horizontal well, and combine the occurrence and structural dip of the Guantao Formation with the structural line extraction function of GPT software to refine it. Then, perform adjacent well structural correction on the vertical wells, such as... Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown, take height 12-level 2 as an example.

[0064] (5) Based on the profile maps of horizontal and vertical wells, sequence stratigraphy was used to classify and compare sub-layers in horizontal wells, taking into account geological sedimentary characteristics, oil-water relationships, and production conditions. Sub-layer classification was completed for eight horizontal wells with a "tanghulu" (a type of oil-bearing layer) pattern. Sub-layer plan maps of 23 oil-bearing sub-layers were compiled. The stratigraphic correlation data was verified using sub-layer oil-water and production dynamics data to determine the final horizontal well stratigraphic correlation results. Taking the Kongdian Formation 6-1 sub-layer plan map as an example... Figure 9 As shown.

[0065] This invention offers a clear technical approach and simple application, providing a practical method for horizontal well correlation in high-angle unconformity reservoirs and serving as a pioneering demonstration for the development of similar reservoirs. The method was applied in the Gao 963 complex fault block area of ​​the Chunliang Oil Production Plant in the Gaoqing Oilfield. Based on detailed stratigraphic correlation and structural interpretation, it completed the reservoir characteristics, oil reservoir characteristics, reserve calculation, and potential area prediction for the Gao 963 block. It clarified the distribution pattern of remaining oil in the block and proposed four potential well locations, providing a reliable geological basis for subsequent well network adjustments and remaining oil potential tapping.

[0066] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0067] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A horizontal well correlation method for high-angle unconformity reservoirs, characterized in that: This method for horizontal well correlation based on high-angle unconformity reservoirs includes: Step 1: Using sequence stratigraphy, conduct preliminary stratigraphic correlation of vertical wells, including: using sequence stratigraphy, combined with geological sedimentary characteristics, and with the help of regional and local markers, to conduct preliminary stratigraphic correlation of vertical wells in the horizontal well area; Step 2 involves seismic stratigraphic calibration and the construction of a preliminary structural model. This includes: calibrating seismic stratigraphic positions based on the vertical well stratigraphic correlation results in the horizontal well area; interpreting the stratigraphic positions of major layers and key sand groups; interpreting the seismic data; clarifying the planar distribution of faults through seismic attributes; precisely describing the location of major fault edges; and constructing a preliminary structural model. Step 3, combining well and seismic analysis to determine the stratigraphic correlation results of vertical wells, including: combining well and seismic analysis, referring to the seismic sequence sedimentary characteristics and fault development of seismic profiles, resolving well-seismic discrepancies with the help of regional and local markers, and determining the sub-layer data of vertical wells in horizontal well areas; Step 4: Perform detailed closure interpretation of the entire area, delineate the location of erosion lines, and compile structural maps. This includes: finely calibrating the synthetic record layers of each main layer, clarifying the seismic reflection characteristics of the main layers, performing detailed closure interpretation of the entire area, delineating the location of erosion lines, and compiling structural maps. Step 5, combining well and seismic analysis, based on the seismic profile, determine the major layer boundaries of the horizontal well, including: creating a reservoir distribution map of the horizontal well; according to the distribution pattern of the erosion lines and the seismic profile passing through the horizontal well, roughly determine the sand group to which each oil sand body of the horizontal well belongs, and preliminarily determine the major layer boundaries of the horizontal well; and creating profile maps of the horizontal well and the vertical well. Step 6: Perform small-layer comparison of horizontal wells, including: based on the structural map, project the vertical well along the structural line onto the trajectory of the horizontal well. For unconformity reservoirs, it is necessary to combine the formation occurrence and perform structural correction of adjacent wells to generate profile maps of horizontal and vertical wells, and complete the comparative study of horizontal and vertical wells; based on the profile maps of horizontal and vertical wells, complete the small-layer comparison of horizontal wells.

2. The horizontal well correlation method for high-angle unconformity reservoirs according to claim 1, characterized in that, The method for horizontal well correlation based on high-angle unconformity reservoirs also includes, after step 6, step 7, compiling a plan view of the main layer based on the sub-layer stratification data and structural map, verifying the formation correlation data through data such as sub-layer oil-water and production dynamics, and adjusting the stratification or structure if there are problems to resolve the contradiction between oil and water development.

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