Well location deployment method for deep low-permeability reservoir in low-exploration-degree area

Abstract

The invention provides a method for deploying a deep low-permeability reservoir well location in a low-exploration-degree area. The method comprises the steps that the source, sedimentary facies, fault characteristics and sand body distribution characteristics of a target area are analyzed; according to analysis results of material sources, sedimentary facies, fault features and sand body distribution features, an exploration area sedimentary mode is established, and an exploration favorable area is determined; and drilling target evaluation is carried out on the exploration favorable area, a reservoir forming mode is established, and a well location deployment scheme is determined. According to the method, a sedimentary mode is established and a favorable area is optimized by analyzing object sources, sedimentary facies, fault characteristics and sand body distribution characteristics, and then drilling target evaluation, reservoir forming mode establishment and well location deployment scheme determination are carried out on the favorable area. According to the method, interference of complicated analysis means is removed, analysis of key problems is mainly mastered, the accuracy and efficiency of evaluation are improved, and the accuracy is improved by 50% and reaches 95%; the working efficiency is improved, invalid work is avoided, the workload of five persons and 60 days is reduced to be completed by four persons and 30 days, and deployment of the deep low-seepage well position is assisted.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, and specifically relates to a method for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels. Background Technology

[0002] The traditional meaning of exploration level refers to the input of physical work such as seismic surveys and drilling in an exploration area, as well as the degree of resource discovery. The level of exploration is an important basis for classifying exploration stages, but it does not always accurately represent the exploration potential of an area. Tight oil and gas (deep, low-permeability oil and gas) is typically characterized by its presence in low-porosity, tight sandstone, with conventional reservoir permeability generally less than 1.00 mD (overburden matrix permeability not greater than 0.10 mD), and single wells generally having no natural production capacity or a natural production capacity below the lower limit of industrial gas flow. Tight oil and gas is an important component of unconventional oil and gas and has received widespread attention both domestically and internationally.

[0003] Zhao Xin's "Study on the Sedimentary System of the Funing Formation in the Northern Jinhu Depression," published in June 2022, describes the distribution characteristics of sedimentary facies in the study area, the comprehensive stratigraphic distribution characteristics, and the analysis of the control effect of ancient valley slope breaks on sedimentary evolution, establishing a sedimentary facies model map consistent with the depositional period of the Funing Formation in the entire study area. Hou Zhiteng's "Study on Sedimentary Microfacies of the Paleogene Fushan Formation 3 in the Jinhu Depression," published in May 2018, describes an in-depth study of the sedimentary system of the Fushan Formation 3 in the Jinhu Depression, analyzing the development characteristics and distribution patterns of sedimentary microfacies and sedimentary facies, establishing a sedimentary model, reconstructing paleowater depth, paleogeography, paleowind field, and paleosource, and clarifying the control effect of various factors on the development of beach-bar sand bodies. The article "Analysis of the Provenance Characteristics and Tectonic Background of the Paleogene Fusan Member in the Subei Basin" published by Wang Xuying et al. in March 2021 in *Modern Geology*, Volume 28, Issue 2, states that, based on the analysis of clastic components, gravel composition, rare earth elements, sandstone content distribution, and conglomerate distribution characteristics, the Paleogene Fusan Member in the Subei Basin has six main provenance areas. The article "Sequence Stratigraphy Analysis and Sedimentary Regularities in Areas with Low Exploration Levels—Taking the Jurassic System in the Wudun Depression as an Example" published by Yin Wen in January 2025 in *Journal of Jilin University (Earth Science Edition)*, Volume 55, Issue 1, states that, through the comprehensive application of well logging, seismic, core, and analytical data, the study of the Middle and Lower Jurassic sequence stratigraphy and regional sequence stratigraphic framework in the Wudun Depression was conducted. The article "Segmented Growth Characteristics of Low-Angle Normal Faults in the Western Segment of the Bohai Bay Basin's Bohai South Low Uplift and Their Hydrogeological Significance," published by Lou Rui et al. in June 2024 in *Petroleum and Natural Gas Geology*, Volume 45, Issue 3, describes the segmented growth process and differential evolution characteristics of faults based on the latest 3D seismic data. Combined with the regional tectonic background, it explores the fault formation mechanism and its controlling role in hydrocarbon accumulation. The article "Quantitative Characterization of Fault Segmented Growth and Its Application in Hydrocarbon Accumulation Research," published by Fu Xiaofei et al. in 2015 in *Journal of China University of Mining and Technology*, Volume 44, Issue 2, describes the application of the "maximum fault displacement subtraction method" to quantitatively reconstruct the fault formation and evolution process. The article "Establishment of Quantitative Judgment Criteria for Fault Segment Growth and Its Geological Significance - Taking the Sartu Oil Layer in Xingbei Development Zone of Songliao Basin as an Example" published by Wang Haixue et al. in Volume 60, Issue 6 of Geological Review in 2014 states that a quantitative judgment criterion for fault segment growth in plane was established based on the fault "transformation displacement / distance (D / S)".

[0004] A predictive method for the distribution of fine-grained terrestrial facies in low-exploration areas (CN114076993B) discloses the following: identifying subsidence and sedimentary centers through geological structure analysis; determining facies types through outcrop and well facies analysis; inferring facies types through source geochemical analysis of oil and gas; predicting the distribution of fine-grained facies based on lithological grain size variations; determining the distribution of fine-grained facies based on facies models; and inferring facies types and boundaries based on seismic facies.

[0005] A method for determining the spatial segmentation, growth history, and true length of a fault (CN114296135A) discloses that: based on the characteristics of the fault dip and strike displacement curves, the displacement propagation mode and growth connection pattern of fault activity are determined, and the complete evolution process of the fault and the kinematic relationship between the interactions are explained through the characteristics of the fault spatial segmentation.

[0006] Although the above-mentioned classification scheme solves some problems, its application to well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels still has certain limitations as described in the background technology. Summary of the Invention

[0020] This application provides a method for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels. This method can comprehensively, quickly, and effectively propose well location deployment plans, thereby improving the accuracy of well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels.

[0021] This application provides a method for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels, including:

[0022] S101, analyze the source, sedimentary facies, fault characteristics and sand body distribution characteristics of the target area; S103. Based on the analysis results of provenance, sedimentary facies, fault characteristics and sand body distribution characteristics, a sedimentary model for the exploration area was established to identify favorable exploration areas. S105 involves evaluating drilling targets in favorable exploration areas, establishing reservoir formation models, and determining well location deployment plans.

[0023] In step S101, heavy mineral analysis is used to clarify the provenance system of the study area. Different regions have the same heavy mineral types, but different proportions of different heavy mineral types. The same source has the same representative heavy minerals. Well logging curves and core observation characteristics are used to determine sedimentary microfacies characteristics. By comparing the characteristics of well-drilled areas and low-exploration areas, the provenance extension range is determined.

[0024] In step S101, the characteristics of faults and sand-controlling mechanisms during the depositional period in the low-exploration area are clarified. By analyzing the thickness difference between the uplift and downlift blocks of the fault corresponding to the strata during the depositional period, it is determined whether the fault during the depositional period controlled the deposition. If it is a syn-depositional fault, the strata thickness of the uplift and downlift blocks will differ. If it is a fault from a different depositional period, the strata thickness of the uplift and downlift blocks will be the same. A fault from a different depositional period is a location where the fault during the depositional period does not exist, and sand bodies can advance and deposit along this location. The ratio of the thickness of the downlift block strata to the thickness of the uplift block strata is w. If w is 1, it is a location where the fault during the depositional period does not exist. If w is greater than 1, it is a location where the fault during the depositional period exists.

[0025] In step S101, the thickness, distribution, and sedimentary microfacies characteristics of the sand body are determined. The drilled strata in the area are divided into sub-sections based on electrical properties, lithology, marker beds, and sedimentary cycles. The division principles are established to form a backbone profile for stratigraphic division. The location of sandstone layer development is determined by combining the resistivity curves, spontaneous potential curves, natural gamma curves, and well logging interpretation results of the drilled wells. The thickness and percentage of sandstone in the sub-sections in the vertical direction of a single well are statistically analyzed. Sandstone thickness maps and sandstone percentage maps are compiled. The distribution characteristics of the sand body are preliminarily determined. The sedimentary microfacies characteristics are analyzed by combining well logging curves and core observations.

[0026] In step S101, geophysical prediction of sand body distribution characteristics is performed, multi-element seismic attribute prediction and reservoir inversion prediction are carried out, and the prediction result with the highest agreement with the actual drilling is selected.

[0027] In step S101, the phase control high-precision inversion method is used to carry out quantitative reservoir prediction, well logging curve quality control is carried out, rock physical analysis is performed using well logging curves to clarify the sensitive parameters of sand bodies, and then the seismic waveform indication inversion method is used to quantitatively predict the thickness of sand bodies in each sub-section.

[0028] In step S103, based on the source of sediments, sedimentary microfacies characteristics, fault-controlled sand control mechanisms, and geophysical prediction results, a planar sandstone thickness map and a sandstone percentage content map are compiled to clarify the sand body distribution characteristics, establish a sedimentary model for the exploration area, and identify favorable exploration areas.

[0029] In step S105, the drilling target evaluation for the exploration favorable area includes: trap confirmation degree evaluation, hydrocarbon accumulation condition evaluation, resource scale, engineering difficulty, drilling significance and risk analysis. The trap confirmation degree evaluation includes data quality, reliability and trap characteristics. The hydrocarbon accumulation condition evaluation includes oil and gas injection conditions, reservoir conditions and preservation conditions. Based on the drilling target evaluation results, a hydrocarbon accumulation model is established, and finally the well location deployment plan is determined.

[0030] This application also provides a method for selecting favorable targets in low-exploration areas, including the method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas as described in any of the above claims.

[0031] The method for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels, as described in this application, has the following beneficial effects: This application comprehensively utilizes key technologies to establish sedimentary models and select favorable areas by analyzing provenance, sedimentary facies, fault characteristics, and sand body distribution characteristics. It then evaluates drilling targets within these favorable areas, establishes reservoir formation models, and determines well placement plans. This technical solution eliminates interference from complex analytical methods, focusing on the analysis of key issues, thus improving the accuracy and efficiency of the evaluation. The accuracy rate has increased by 50 percentage points, reaching 95%. It also improves work efficiency, avoiding ineffective work and reducing the workload from 60 days for 5 people to 30 days for 4 people. This facilitates the deployment of deep, low-permeability wells, opening up new exploration ideas and methods. The deployment of well Q21X is expected to achieve a major breakthrough in the exploration of new areas and new strata in deep, low-permeability fields. It comprehensively, efficiently, and accurately solves the problem of selecting favorable targets in areas with low exploration levels, providing important support for increasing reserves and production in old oilfields in the east and securing energy resources. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to an embodiment of this application; Figure 2 Characteristic maps of heavy minerals in typical wells in different zones of the JH Depression; Figure 3 Sedimentary facies diagram of the third member of the Funing Formation in the SG area of ​​the JH Depression; Figure 4 For TX11 well E1f3 1 Single-well facies diagram; Figure 5 YX6 well E1f3 1 ~E1f3 2 Single-well facies diagram; Figure 6 For FX7 well E1f3 1 Single-well facies diagram; Figure 7 For well F2 E1f3 3 Single-well facies diagram; Figure 8 For well S218 E1f3 1 Single-well facies diagram; Figure 9 For BG1 well E1f3 1 Single-well facies diagram; Figure 10 For Q20X well E1f3 1 Single-well facies diagram; Figure 11 A columnar section of well E1f3 in the central shallow lake area of ​​L1; Figure 12This is a local fault feature map of the SG fault during its depositional period; Figure 13 This indicates the location where the SG fault did not exist during its depositional period; Figure 14 This is the main stratigraphic section of the Fusan Member in the eastern part of the JH Depression; Figure 15 For SG region E1f3 1 E1f3 2 E1f3 3 Plan view of reservoir prediction at 15Hz amplitude in sub-segment; Figure 16 For SG region E1f3 1 E1f3 2 E1f3 3 Sub-segment reservoir inversion plane; Figure 17 For SG region E1f3 1 E1f3 2 E1f3 3 Sub-section stratigraphic thickness map; Figure 18 For SG region E1f3 1 E1f3 2 E1f3 3 Percentage content of sandstone in sub-section strata; Figure 19 A diagram illustrating the depositional model of the E1f3 sand body in the SG fault; Figure 20 For target block T3 1 Construction diagram; Figure 21 A schematic diagram of a favorable target hydrocarbon accumulation model for the Fusan Member of the SG fault zone. Detailed Implementation

[0033] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0034] In the following description, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The following description provides multiple embodiments of the invention, which can be substituted or combined with each other. Therefore, this application can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more other possible combinations of features A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0035] The technical approach of this scheme addresses the scarcity of data in low-exploration areas. Previous studies in these areas have primarily focused on zonal evaluation, often emphasizing risk factors such as geological complexity, exploration limitations, development uncertainties, and economic volatility, or on the process of predicting favorable areas. However, they have not focused on evaluating favorable exploration targets and well placement. This scheme employs technical methods that can be implemented for well placement, effectively advancing the exploration process. In its implementation, this scheme provides a complete and systematic technical process. Unlike conventional methods, which are relatively fragmented, often focusing on a single point of analysis and employing cumbersome evaluation methods, this scheme emphasizes grasping key points and solving problems. By establishing a "dual-mode" approach—from "establishing a sedimentary model and selecting favorable areas" to "evaluating favorable targets and establishing a hydrocarbon accumulation model"—it ultimately determines the well placement plan. This technical approach can provide effective exploration strategies and practical well placement methods for exploration areas with similar geological characteristics.

[0036] Example 1 like Figure 1 As shown, the method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas in this application includes: S101, analyzing the source, sedimentary facies, fault characteristics, and sand body distribution characteristics of the target area; S103, establishing a sedimentary model for the exploration area and identifying favorable exploration areas based on the analysis results of the source, sedimentary facies, fault characteristics, and sand body distribution characteristics; S105, evaluating drilling targets in favorable exploration areas, establishing reservoir formation models, and determining well location deployment schemes.

[0037] The method described in this application can comprehensively, quickly, and effectively propose well location deployment schemes, thereby improving the reliability of well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels.

[0038] Example 2 The method for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels, as described in this application, includes: The first step is to determine the source direction and clarify the source system of the study area. By using well logging curves and core observations, the sedimentary microfacies characteristics of the well-drilled area and the low-exploration area are clarified. The study area includes both well-drilled and low-exploration areas.

[0039] First, heavy mineral analysis was used to clarify the provenance system of the study area. While the types of heavy minerals were the same in different regions, the proportions of different heavy mineral types varied. Representative heavy minerals were common to the same provenance. Further, sedimentary microfacies characteristics were determined using natural gamma ray (GR) or spontaneous potential (SP) curve morphology, well logging lithology, and core observation features. By comparing the characteristics of well-explored and low-exploration areas, the extent of provenance extension was determined.

[0040] The second step is to clarify the characteristics of faults and sand-controlling mechanisms during the depositional period in low-exploration areas. By analyzing the thickness differences between the uplift and downlift blocks of the fault corresponding to the strata during the depositional period, it is determined whether the fault controlled deposition. If it is a syn-depositional fault, the strata thicknesses on the two blocks will differ; the two blocks refer to the uplift and downlift blocks. If it is a fault from a different depositional period, the strata thicknesses on both blocks will be the same. A syn-depositional fault is a location where the fault did not exist during the depositional period, and sand bodies can advance and deposit along this location. The ratio of downlift block strata thickness to uplift block strata thickness equals w. If w equals 1, the location is where the fault did not exist during the depositional period; if w is greater than 1, the location is where the fault existed during the depositional period.

[0041] The third step is to determine the sand body thickness, distribution, and sedimentary microfacies characteristics. The drilled strata within the area are delineated, using electrical properties, lithology, marker beds, and sedimentary cycles as standards to divide the strata to the sub-section level. Delineation principles are established, forming a core stratigraphic profile. The location of sandstone layers is determined by combining drilled resistivity curves, spontaneous potential curves, natural gamma curves, and well logging interpretation results. The sandstone thickness and percentage content within each sub-section in the vertical direction of a single well are statistically analyzed, and sandstone thickness and percentage content maps are compiled. The distribution characteristics of the sand bodies are preliminarily analyzed, and sedimentary microfacies characteristics are analyzed in conjunction with well logging curves and core observations.

[0042] The fourth step is to predict the distribution characteristics of sand bodies using geophysical methods. This involves conducting multi-element seismic attribute predictions and reservoir inversion predictions, and selecting the prediction results that best match the actual drilled wells.

[0043] The fifth step involves combining the provenance, sedimentary microfacies characteristics, fault-controlled sand control mechanisms, and geophysical prediction results to compile a planar sandstone thickness map and a sandstone percentage content map, clarify the sand body distribution characteristics, establish a sedimentary model for the exploration area, and identify favorable exploration areas.

[0044] The sixth step is to conduct drilling target evaluation for favorable areas, including evaluation of trap implementation (data quality, reliability and trap characteristics), evaluation of hydrocarbon accumulation conditions (oil and gas injection conditions, reservoir conditions and preservation conditions), resource scale, engineering difficulty, drilling significance and risk analysis, to establish hydrocarbon accumulation model and finally determine well location deployment plan.

[0045] This application's technical solution targets deep, low-permeability reservoirs in low-exploration areas. It utilizes provenance analysis, sedimentary facies analysis, sand body thickness and percentage content analysis, and fault growth mechanism analysis to establish sedimentary models, select favorable areas, and then evaluate drilling targets within these favorable areas to establish hydrocarbon accumulation models and determine well location deployment plans. This technical solution eliminates interference from complex technical methods, focuses on key analytical content, quickly identifies clear exploration directions, meets the requirements of high-efficiency and accurate exploration and production, and effectively solves the problem of selecting favorable targets in low-exploration areas.

[0046] Example 3 Taking the Q21X well in the third member (E1f3) of the Funing Formation in the SG area of ​​the JH Depression as an example, the method for well location deployment in deep, low-permeability reservoirs in low-exploration areas in this application includes: The first step is to determine the source direction and clarify the source system of the study area. By using well logging curves and core observations, the sedimentary microfacies characteristics of the well-drilled area and the low-exploration area are clarified. The study area includes both well-drilled and low-exploration areas.

[0047] Heavy mineral analysis clarifies the provenance system. Different regions may share the same heavy mineral types, but the proportions of different heavy mineral species may vary. For the same provenance, representative heavy minerals are common. "Representative" means that the percentage of heavy minerals present is relatively high.

[0048] like Figure 2 As shown, the heavy mineral composition of the JH Depression includes: most stable heavy minerals: zircon, tourmaline, and rutile; stable heavy minerals: garnet, magnetite, and hematite; unstable heavy minerals: epidote and zoisite; and minerals with a single mineral content of less than 0.5% are classified as other minerals. Representative heavy minerals differ across zones. In the eastern region, the main minerals are garnet, magnetite, and hematite, with hematite being the representative mineral. In the western region, the main minerals are garnet, magnetite, and zircon, with zircon being the representative mineral. In the central region, the main minerals are garnet, zircon, and tourmaline, with zircon and tourmaline being the representative minerals.

[0049] Table 1. Statistical table of heavy mineral content in typical wells in different zones of the JH Depression.

[0050] The sedimentary microfacies characteristics are determined by using natural gamma (GR) or spontaneous potential (SP) curve morphology, lithology during drilling, and core observation. By comparing the characteristics of well-drilled areas and low-exploration areas, the direction and extent of the source material extension can be determined.

[0051] The delta front is dominated by underwater distributary channels, mouth bars, and superimposed sediments of underwater distributary channels and mouth bars. Well logging GR or SP curves show "box", "bell" or "funnel" shapes. Underwater distributary channels mostly have "box" or "bell" positive cycle characteristics, while mouth bars mostly have "funnel" negative cycle characteristics. The superimposed underwater distributary channels and mouth bars mostly have "bell" and "funnel" positive and negative cycle superimposed characteristics.

[0052] like Figure 3 , Figure 4 , Figure 5 As shown, core observations from wells TX11 and YX6 reveal parallel bedding, wavy bedding, and cross-bedding. The lithology observed during drilling is light gray siltstone, with corresponding logging curves of "box-shaped," "bell-shaped," or "funnel-shaped," indicating that the sand bodies are primarily composed of underwater distributary channels and mouth bars. Figure 3 , Figure 6 , Figure 7 , Figure 8 As shown, wells F7X, F2, and S218 near the SG fault were not cored, but analysis of the logging curves reveals that they are mostly "box-shaped" or "bell-shaped," suggesting the development of thick underwater distributary channel sand bodies. Furthermore, the lithology identified during drilling is light gray siltstone, indicating that the delta front has advanced to the vicinity of the fault. Figure 3 , Figure 9 , Figure 10 As shown, the uplifted block of the SG fault is a well-explored area, while the downlifted block is a low-exploration area. Only two wells, BG1 and Q20X, were drilled, neither of which were cored. However, analysis of the logging curves reveals "box-shaped," "bell-shaped," "funnel-shaped," or a combination of both, indicating that the sand body type is also mainly composed of channels, mouth bars, and channel-mouth bar superpositions. The lithology recorded during drilling is sandstone, suggesting that the delta front has advanced into the downlifted block of the fault. Figure 2 , Figure 11 As shown, the logging curves in the central delta front-shallow lacustrine sedimentary area are flat, and the logging lithology is mainly mudstone, which is significantly different from the subfacies sediments of the eastern delta front, belonging to two different sedimentary facies zones.

[0053] The second step is to clarify the characteristics of faults and sand-controlling mechanisms during the depositional period in low-exploration areas. By analyzing the thickness differences between the uplift and downlift blocks of the faults corresponding to the strata during the depositional period, it can be determined whether the faults controlled deposition. If it is a syn-depositional fault, the strata thicknesses on both blocks will differ; if it is a fault from a different depositional period, the strata thicknesses on both blocks will be the same. A fault from a different depositional period is a location where the fault did not exist during the depositional period, and sand bodies can advance and deposit along this location. The ratio of downlift block strata thickness to uplift block strata thickness equals w. If w equals 1, it indicates a location where the fault did not exist during the depositional period; if w is greater than 1, it indicates a location where the fault existed during the depositional period.

[0054] like Figure 12 , Figure 13 As shown, the thickness differences of the hanging wall and footwall of the three members of the Funing Formation in the SG area of ​​the JH Depression during the depositional period were analyzed. The time of the uplift and downlift was read vertically from the seismic profile. At the A-line location, the profile showed that the uplift was 225 ms and the downlift was 270 ms. At the C-line location, the profile showed that the uplift was 240 ms and the downlift was 270 ms. The A-line and C-line profiles indicate the locations where the faults were developed during the depositional period of the third member of the Funing Formation. In the area where the B-line profile is located, the time of the uplift and downlift were similar, both 240 ms. w=1 indicates the location where the faults were not developed during the depositional period.

[0055] Along the dense tangent of the NE-trending SG fault, the depositional pattern of the SG fault zone during the E1f3 period is re-delineated. The ratio of the thickness of the downthrown block strata to the thickness of the upthrown block strata equals w, where w is 1. Locations where the thicknesses of the upthrown and downthrown blocks are roughly equal indicate areas where faults are not well-developed. Figure 13As shown, the SG fault developed 7 small fault-undeveloped zones during the depositional period, and overall it is considered to have developed 4 obvious fault-undeveloped zones ①-④.

[0056] The third step, as Figure 14 As shown, the thickness, distribution, and sedimentary microfacies characteristics of the sand bodies were determined. Stratigraphic division was performed on drilled wells in the area, using electrical properties, lithology, marker beds, and sedimentary cycles as criteria to divide the strata to the sub-member level. E1f3 exhibits three sets of reverse-cycle sediments, which can be divided from bottom to top into E1f3... 1 E1f3 2 E1f3 3 The three sub-sections are divided according to the differences in lithological and electrical characteristics of different zones, based on the following principles (Table 2). Figure 14 Establish a backbone profile; combine the drilled resistivity curves, spontaneous potential curves, natural gamma curves and well logging interpretation results to delineate sandstone layers, and count the sandstone thickness and sandstone percentage in each sub-section of E1f3 in the well-drilled area. Sandstone thickness maps and sandstone percentage maps can be compiled. The distribution characteristics of sand bodies are preliminarily analyzed, and the sedimentary microfacies characteristics are analyzed in combination with well logging curves and core observations. The sedimentary microfacies are mainly the underwater distributary channel sedimentary microfacies of the delta front and the estuary bar sedimentary microfacies.

[0057] Table 2. Stratigraphic principles of the Fusan Member in different areas of the eastern JH Depression

[0058] The fourth step is to predict the distribution characteristics of sand bodies using geophysical methods. This involves conducting multi-element seismic attribute predictions and reservoir inversion predictions, and selecting the prediction results that best match the actual drilled wells.

[0059] Multi-element seismic attribute reservoir prediction was conducted on the downthrown block of the SG fault. Among the results of instantaneous amplitude, instantaneous frequency, sweet spot attribute, and phase cosine attribute, the sand body with full-band amplitude attribute showed good correspondence with the amplitude, but the boundary clarity was not high. Further optimization of the 15Hz low-frequency seismic amplitude attribute resulted in clearer reservoir distribution boundaries, which best matched the development characteristics of the drilled sandstone. Figure 15 ).

[0060] like Figure 16 As shown, phase control high-precision inversion method is used for reservoir quantitative prediction. Well logging quality control is performed, and rock physical analysis is conducted using the well logging curves to clarify the sensitive parameters of the sand bodies. Based on this, the SMI (Seismic Waveform Indicative Inversion) waveform inversion method is used to quantitatively predict the thickness of each sub-member of E1f3 sand bodies. The inversion results are consistent with the attribute prediction results, and the profile shows E1f3... 1 Sand body thickness ratio E1f3 2 E1f3 3Thicker.

[0061] Fifth step, as Figure 17 , Figure 18 As shown, combining the provenance, sedimentary microfacies characteristics, fault-controlled sand control mechanisms, and geophysical prediction results, sandstone thickness maps and sandstone percentage content maps were compiled to clarify the sand body distribution characteristics, establish a sedimentary model for the exploration area, and identify favorable exploration areas. Figure 19 As shown, the source of the JH Depression comes from the northeast and southwest. The eastern SG area is mainly composed of delta front deposits, which advance from the northeast to the southwest to the vicinity of the SG fault. During the depositional period, the fault did not exist and could become a sandstone depositional channel. Therefore, the sand body could advance to the downthrown block of the SG fault and establish a depositional model. The sandstone development area is the favorable exploration area or target area.

[0062] The sixth step involves evaluating drilling targets across multiple favorable areas, including assessing trap confirmation (data quality, reliability, and trap characteristics), hydrocarbon accumulation conditions (oil and gas injection conditions, reservoir conditions, and preservation conditions), resource size, engineering difficulty, drilling significance, and risk analysis, to select the optimal target. Figure 20 The displayed trap target is further used to establish an hydrocarbon accumulation model for the trap target. Figure 21 The final well location deployment plan was determined.

[0063] (1) Evaluation of the degree of implementation of the enclosure The target block is located on the downthrown block of the SG fault zone in the JH depression. The 3D seismic data has a high signal-to-noise ratio and resolution. (T3) 1 The seismic reflection layer (bottom of the Fusan section) shows clear wave group characteristics and good continuity. Fault points and fault planes are clear and reliable, fault characteristics are obvious, and the overall data is good. Well-seismic correlation is well-matched, allowing for accurate identification of the target layer. Well data in the study area can be used for stratigraphic identification and well-to-well correlation, with reliable stratigraphic correlation. Random surveying, layer velocity extrapolation, and well-interrupted stratum thickness investigation methods ensure reliable stratigraphic tracking. Seismic slicing technology, coherence parameter optimization technology, seismic attribute fusion technology, fault plane consistency, and fault attitude consistency techniques are used to identify fault points on the profile and to rationally combine faults on the plane, confirming trap comparisons. Figure 20 ).

[0064] (2) Conditions for hydrocarbon accumulation ① Oil and gas injection conditions The target block is located in the mature source rock development zone of E1f2 in the SH sub-depression of the SG fault zone. The hydrocarbons generated by the mature source rocks of E1f2 are adjusted vertically along the SG fault zone and accumulate in the E1f3 of the downthrown block. Figure 21 ).

[0065] ② Reservoir conditions E1f3 is a deltaic front subfacies deposit, mainly composed of interbedded sandstone and mudstone. The sandstone thickness ranges from 30 to 70 m, with a sandstone content of 10% to 30%, indicating a relatively well-developed reservoir. Analysis of core data from well TX11 at depths of 2301–2307 m shows that the porosity of the E1f3 reservoir in the uplift plate of the target area is 13.3%–25.2%, with an average porosity of 18.3%, and permeability ranging from 0.441 to 75.7 mD, with an average permeability of 15.511 mD. This indicates a medium-porosity, low-permeability reservoir with favorable physical properties. Analysis of data from well BG1 in the downlift plate shows that E1f3 at depths of 3190–3440 m has an oil layer porosity of 9.4%–24.3%, with an average porosity of 15.8%, and permeability ranging from 1.6 to 105.8 mD, with an average permeability of 25.7 mD. This also indicates a medium-porosity, low-permeability reservoir. The Q21X well has a burial depth of 2890–3360 m, which is shallower than that of the BG1 well. It is speculated that the E1f3 reservoir has better physical properties than the BG1 well.

[0066] ③ Storage conditions like Figure 20 , Figure 21 As shown, the E1f4 mudstone in this area is a regional caprock with a thickness of 350-500m, providing good sealing conditions. The northeast-to-west dipping SG fault has a displacement of 730-870m. The target block E1f3 mainly aligns with the E1f1 sandstone and mudstone development section of the uplifted plate, exhibiting some randomness in lateral sealing. However, the SG fault is a long-term active large fault, suggesting that it inherently possesses good sealing conditions. The near-east-west dipping north fault to the north has a displacement of approximately 200m and does not deviate from the E1f4 mudstone caprock, indicating good lateral sealing conditions. The near-east-west dipping north fault to the south has a stable displacement of 30-40m. The target block E1f3 aligns with the E1f3 of the uplifted plate, exhibiting random sealing.

[0067] (3) Resource scale The target block has a containment area of ​​2.3 km². 2 The effective thickness of the E1f3 oil layer is taken as 28m, referencing the drilling data of wells BG1 and Q20X; the single-reservoir coefficient of E1f3 is taken as 8.5×10 based on the reported reserve data of blocks BG1 and Q6. 4 t / km 2 •m; The filling coefficient or oil (gas) area coefficient is weighted to 1 based on the comprehensive evaluation of the trap, and the resource volume of the trap is 348×10 4 t.

[0068] (4) Engineering difficulty The JH Depression has undergone multiple stages of exploration and development. The various engineering and technological processes for exploration and development in this area are relatively mature. However, considering the relatively large burial depth of the target block, the comprehensive evaluation suggests that the engineering and technical control coefficient is around 0.9.

[0069] (5) The strategic significance of trap drilling for resources Through detailed structural interpretation and fault analysis, a number of traps were identified in several favorable exploration areas along the uplift and downlift sides of the SG fault in E1f3. The Q21 block trap was selected as the preferred trap due to its well-defined structure, developed reservoir, and favorable oil source conditions. It is of great significance for exploring new formations in the Fusan Member of the SG fault and possesses significant exploration potential. A breakthrough in this area would have substantial strategic value and significance.

[0070] (6) Risk Analysis On the one hand, there is a certain risk in lateral sealing of target block E1f3. On the other hand, there are uncertainties regarding the effective reservoir thickness and reservoir properties of target block E1f3.

[0071] Existing technologies for the exploration and research of deep, low-permeability oil reservoirs are mostly concentrated in areas with high exploration levels. For areas with low exploration levels, there are often no effective means and methods to evaluate favorable targets for oil and gas exploration. This application comprehensively utilizes key technologies to establish sedimentary models by analyzing provenance, sedimentary facies, fault characteristics, and sand body distribution characteristics. Favorable areas are then selected, and drilling targets are evaluated within these favorable areas to establish reservoir formation models and determine well location deployment plans. This technical solution eliminates interference from complex analytical methods, focusing on the analysis of key issues, thus improving the accuracy and efficiency of the evaluation. The accuracy is increased by 50 percentage points, reaching 95%. It also improves work efficiency, avoiding ineffective work, reducing the workload of 5 people for 60 days to 4 people for 30 days. This facilitates the deployment of deep, low-permeability wells, opening up new exploration ideas and methods. The deployment of the Q21X well is expected to achieve a major breakthrough in the exploration of new areas and new layers in deep, low-permeability fields. It comprehensively, efficiently, and accurately solves the problem of selecting favorable targets in low-exploration areas, providing important support for increasing reserves and production in old oilfields in the east and securing energy resources.

[0072] This application also provides a method for selecting favorable targets in areas with low exploration levels, including any of the above-mentioned methods for well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 well location deployment in deep, low-permeability oil reservoirs in areas with low exploration levels, characterized in that, include: S101, analyze the source, sedimentary facies, fault characteristics and sand body distribution characteristics of the target area; S103. Based on the analysis results of provenance, sedimentary facies, fault characteristics and sand body distribution characteristics, a sedimentary model for the exploration area was established to identify favorable exploration areas. S105 involves evaluating drilling targets in favorable exploration areas, establishing reservoir formation models, and determining well location deployment plans.

2. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1, characterized in that, In step S101, heavy mineral analysis is used to clarify the provenance system of the study area. Different regions have the same heavy mineral types, but the proportion of different types of heavy minerals is different. The representative heavy minerals of the same provenance are the same. Well logging curves and core observation characteristics are used to determine the sedimentary microfacies characteristics. By comparing the characteristics of well-drilled areas and low-exploration areas, the provenance extension range is determined.

3. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1 or 2, characterized in that, In step S101, the characteristics of faults and sand-controlling mechanisms during the depositional period in the low-exploration area are clarified. By analyzing the thickness difference between the uplift and downlift sides of the faults corresponding to the strata during the depositional period, it is determined whether the faults during the depositional period controlled the deposition. If it is a syn-depositional fault, the thickness of the strata on the uplifted and downlifted sides will differ; if it is a non-syn-depositional fault, the thickness of the strata on the uplifted and downlifted sides will be the same; a non-syn-depositional fault is a location where the syn-depositional fault does not exist, and sand bodies can advance and deposit along this location. The thickness of the downthrown strata / the thickness of the upthrown strata = w. If w is 1, it indicates the location where the fault did not exist during the depositional period. If w is greater than 1, it indicates the location where the fault existed during the depositional period.

4. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1 or 2, characterized in that, In step S101, the thickness, distribution, and sedimentary microfacies characteristics of the sand bodies are determined. The drilled strata in the area are divided into sub-sections based on electrical properties, lithology, marker beds, and sedimentary cycles. The division principles are established to form a backbone profile for stratigraphic division. The location of sandstone layer development is determined by combining the resistivity curves, spontaneous potential curves, natural gamma curves, and well logging interpretation results of the drilled wells. The thickness and percentage of sandstone in the sub-sections in the vertical direction of a single well are statistically analyzed. Sandstone thickness maps and sandstone percentage maps are compiled. The distribution characteristics of the sand bodies are preliminarily determined. The sedimentary microfacies characteristics are analyzed by combining well logging curves and core observations.

5. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1 or 2, characterized in that, In step S101, geophysical prediction of sand body distribution characteristics is performed, multivariate seismic attribute prediction and reservoir inversion prediction are carried out, and the prediction result with the highest agreement with the actual drilling is selected.

6. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 5, characterized in that, In step S101, the phase control high-precision inversion method is used to carry out quantitative reservoir prediction, well logging curve quality control is carried out, rock physical analysis is performed using well logging curves to clarify the sensitive parameters of sand bodies, and then the seismic waveform indication inversion method is used to quantitatively predict the thickness of sand bodies in each sub-section.

7. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1 or 2, characterized in that, In step S103, based on the source material, sedimentary microfacies characteristics, fault-controlled sand control mechanism, and geophysical prediction results, a planar sandstone thickness map and a sandstone percentage content map are compiled to clarify the sand body distribution characteristics, establish a sedimentary model for the exploration area, and identify favorable exploration areas.

8. The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas according to claim 1 or 2, characterized in that, In step S105, the drilling target evaluation for the exploration favorable area includes: trap confirmation degree evaluation, hydrocarbon accumulation condition evaluation, resource scale, engineering difficulty, drilling significance and risk analysis. The trap confirmation degree evaluation includes data quality, reliability and trap characteristics. The hydrocarbon accumulation condition evaluation includes oil and gas injection conditions, reservoir conditions and preservation conditions. Based on the drilling target evaluation results, a hydrocarbon accumulation model is established, and finally the well location deployment plan is determined.

9. A method for selecting favorable targets in areas with low exploration levels, characterized in that, The method for well location deployment in deep, low-permeability oil reservoirs in low-exploration areas, as described in any one of claims 1-8.

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