Borehole Image Logs Research Articles

Concurrent 1. Presentation for: Reservoir quality and diagenesis of the West Erregulla field, North Perth Basin, Western Australia

Presented on Tuesday 17 May: Session 1 The West Erregulla field is the deepest onshore gas discovery in Australia today, with three wells drilled to more than 5000 m vertical depth. The reservoir quality has been preserved at depth by clay coating, which shows a similar trend with core from other shallower fields in the northern Perth Basin such as Waitsia and Beharra Springs Deep. The primary reservoir in the West Erregulla field is the Permian Kingia Sandstone that was deposited in a tidal estuary environment, which allowed for mixing of meteoric and saline waters. This depositional setting has been inferred from core, image logs and seismic interpretation. This setting resulted in quartz grains coated in chlorite/illite that has limited quartz overgrowth cements and maintained intergranular porosity. This paper presents Strike’s interpretations of the depositional environment that resulted in the anomalous depth–porosity trend based on core analysis, high-resolution borehole image log interpretation and cuttings. To access the presentation click the link on the right. To read the full paper click here

Reservoir quality and diagenesis of the West Erregulla field, North Perth Basin, Western Australia

The West Erregulla field is the deepest onshore gas discovery in Australia today, with three wells drilled to more than 5000 m vertical depth. The reservoir quality has been preserved at depth by clay coating, which shows a similar trend with core from other shallower fields in the northern Perth Basin such as Waitsia and Beharra Springs Deep. The primary reservoir in the West Erregulla field is the Permian Kingia Sandstone that was deposited in a tidal estuary environment, which allowed for mixing of meteoric and saline waters. This depositional setting has been inferred from core, image logs and seismic interpretation. This setting resulted in quartz grains coated in chlorite/illite that has limited quartz overgrowth cements and maintained intergranular porosity. This paper presents Strike’s interpretations of the depositional environment that resulted in the anomalous depth–porosity trend based on core analysis, high-resolution borehole image log interpretation and cuttings.

Microseismic and Focal Mechanism Analyses for Structural Interpretation – Muara Laboh Geothermal Field

Microseismic monitoring has been used for gathering subsurface information in Geothermal field as part of reservoir monitoring and management plan. New micro earthquake (MEQ) stations were installed in the Muara Laboh geothermal field in the end of 2019, coinciding with the first operation of Unit-1. They have been continuously used to monitor the MEQ events until now. This paper discusses MEQ data analyses to support the subsurface structural interpretation in the Muara Laboh geothermal field. Geothermal production and injection activities create micro seismicity which is triggered by stress failure in fractures / fault planes due to percolation of fluid within fractures network. Distribution of hypocenter locations and magnitude are analyzed, considering highly operational activities, rock mechanic and slip orientation. There are two micro seismicity clusters observed, namely South and North clusters. The South cluster represents 80% of the total recorded micro seismicity events, having NE – SW trend direction; while the North cluster consists of 10% of the total events, correlated with the NNW – SSE structural trend direction. Focal mechanism analysis explains that micro seismicity observed on extended fault zone in the south is thought to be correlated with the distributed fractured network on the hanging wall of normal fault. It is shown by some micro seismicity swarms identified in the south basin-sidewall fault area. These orientations support the current kinematic model of the Muara Laboh geothermal field derived from the structural geology mapping and borehole image logs.

Looking into the Reservoir: Performance Evaluation of Fractured Long Horizontal Wells Using of Borehole Imaging Logs

Field G is a highly fractured and faulty field, this paper is seeking about the necessity to keep running Image logs in new oil wells and how the interpretation of the results would led the team to completing wells optimally and to design our well completion properly to prevent high initial water cut. Learnings are summarized from 40+ image logs ran in this field over the last few years. A cross field G seismic interpretation confirmed on lapping reservoirs and 3 major fault trends with different transmissibility. Also, sseismic and sub seismic Faults and fractures are confirmed from BHI with a NE-SW strike of field G and can be possibly related to production behavior of some wells. In 2015, field G Water Encroachment Study was conducted to identify the cause of high initial water cut of producers. It proposed that detecting fractures early via under-balanced drilling, Borehole Imaging Tools (BHI) and sealing the conduits with production packers would help reduce initial water-cuts [2]. BHI tools are open hole tools that measure either electrical conductivity of the borehole wall or the sonic travel time and amplitude. Micro-conductivity or amplitude and travel time measurements generate an image that shows bedding, fractures and many other fine-scale features. Acoustic tools are preferred in Oil Based Mud (OBM) system and hence they have not been used in field G to the extent that it required a dedicated discussion.

A program to forward model the failure pattern around the wellbore in elastic and strength anisotropic rock formations

A wellbore drilled in pre-stressed formations concentrates the far-field stresses. These concentrations often lead to borehole instability producing breakouts, drilling-induced fractures, or complete failure. In isotropic rock masses this problem has been extensively studied. However, fewer studies attempt to understand borehole failure in more realistic rocks characterized by both elastic and strength anisotropy. A program to calculate the failure pattern in elastic and strength anisotropic rocks is developed. The program combines a recent algorithm for calculating stress concentrations around a borehole within an anisotropic rock mass with anisotropic rock strength as applied through differing failure criteria. Shear failure in the rock matrix and the weak plane are examined based on Jaeger’s single plane of weakness theory. Results from test models clearly indicate that failure in the weak plane complicates the failure pattern around the wellbore, resulting in that the breakout orientation cannot correctly represent the minimum horizontal stress orientation as commonly suggested for a vertical wellbore aligned with the principal stresses. The complexity of failure patterns due to formation anisotropy suggests that additional care must be taken when borehole image logs are interpreted for stress direction indication and stress magnitude constraint.

Multiscale spatial analysis of fracture arrangement and pattern reconstruction using Ripley's K-function

This work presents novel multiscale spatial data analytics using Ripley's K-function, as a measure of spatial interaction, to study one-dimensional arrangement of fractures. Fracture spatial arrangements are classified into clustered, anticlustered, or indistinguishable from random by testing statistical significance of the calculated Ripley's K-function. Characterizations of fracture arrangements are performed as a function of length scale and position. Analysis of the K-function along the study interval identifies where fracture clustering and anticlustering occur. A simulation technique is also introduced here to statistically reconstruct spatial arrangements and to generate fracture realizations that are spatially similar to the fractures observed in the field. With this simulation technique, one can also fill spatial gaps in fracture measurements where data are absent, unreliable, or unused. Synthetic as well as field-measured 1D fracture datasets are used for testing and demonstration. Methods introduced in this work can be readily applied to fracture datasets observed in outcrops, borehole image logs, and cores.

Fault and fracture study by incorporating borehole image logs and supervised neural network applied to the 3D seismic attributes: a case study of pre-salt carbonate reservoir, Santos Basin, Brazil

Fractures play a significant role in the development and production phases of carbonate reservoirs. Quantitative interpretation of fractures not only enhances reservoir models but also reduces the drilling risk and optimizes well design. In this study, we attempt to predict the fracture density map by integrating well and seismic data along with maximum horizontal stress identification. To this end, we propose a workflow with a set of machine learning approaches. First, 3D seismic data is conditioned after the migration processing sequence and the main faults and horizons are interpreted. Next, a number of curvature and coherence attributes are created for a supervised neural network technique to generate new seismic-based discontinuity attribute. Using a geostatistical method to incorporate the interpreted dip and azimuth attributes from well image logs and 3D seismic discontinuity attribute, the fracture density map is predicted and the results validated with a blind well. Finally, we evaluate the strike azimuth of possible open fractures based on the stress regime analysis, from which two distinctive zones are identified. There are, however, some limitations in this study. The predicted fracture density map can be employed to build a discrete fracture network, update dual porosity and permeability estimation, and identify sweet spots.

Intelligent Classification of Carbonate Reservoir Quality Using Multisource Geophysical Logging and Seismic Data

Reservoir quality evaluation is an integral part of oil–gas exploration and development in fracture-vug carbonate formations. Varieties of geophysical data with different advantages are used in reservoir evaluation. These multisource data include conventional logs (CLs), borehole imaging logs (BILs), borehole acoustic reflection imaging logs (BARILs), and even seismic data. Obviously, combining these data can get richer formation information, which is more reliable than single-source data. In this work, the fusion dataset was constructed by calculating the principal components of CLs, BILs, and BARILs. The fusion dataset describes the fracture-vug information in different depths of investigation. Then, the agglomerative hierarchical clustering was used to analyze the fusion data and evaluate the reservoir quality in the borehole. Finally, taking the borehole-side seismic data and borehole evaluation results as training data, an intelligent model was trained based on the random forest algorithm. Also, the intelligent model can be used for reservoir quality classification in a 3-D space. In the case study, the evaluation results of reservoir quality are consistent with the validation data, and the accuracy of the final intelligent model is 85.15%.

The diagnostic criteria of borehole electrical imaging log for volcanic reservoir interpretation: An example from the Yingcheng Formation in the Xujiaweizi Depression, Songliao Basin, China

Electrical image log can be used to establish volcanic facies sequences, and thus used for reservoir interpretation, while the key is to set up available diagnostic criteria to guide lithology, structure and facies interpretation. A total of 50 datasets of borehole image logs, combined with wireline logs and cores, have been collected in the Yingcheng volcanic reservoir in the Xujiaweizi Depression, Songliao Basin, providing an opportunity for repeated image interpretation in the volcanic strata. The interpreted lithology includes rhyolite, dacite, andesite, basalt, welded ignimbrite, tuff, volcanic breccia and agglomerate, sedimentary tuff, sedimentary volcanic breccia and agglomerate. The volcanic structures are calibrated in terms of fluidal and deformed fluidal structure, vesicular and amygdaloidal structure, and massive structure. Based on the lithology and structures, volcanic facies including volcanic sedimentary facies, effusive facies, explosive facies and volcanic conduit facies, have been further determined. Layered structures of the weathered volcanic crusts are shown in borehole images and mainly developed at the top of the Yingcheng Formation. Borehole images indicate that SHmax direction in the area is consistent with the regional SHmax direction, with a preferable trending of 88°. Four sets of filled/open tectonic fractures are developed with approximately north, south, NNE and NW dipping. It infers that different volcanic facies can be well correlated between wells, and tectonic movements have a slight influence on the Yingcheng volcanic strata. The proposed diagnostic criteria and the workflow can be referred for a direct image interpretation in volcanic reservoirs or ocean drilling programs when cores are unavailable.

Cretaceous–Cenozoic regional stress field evolution from borehole imaging in the southern Jinzhou area, western Liaoning, North China Craton

The Mesozoic Yanshanian Movement affected the tectonic evolution of the North China Craton (NCC). It is proposed that Mesozoic cratonic destruction peaked ~125 Ma, possibly influenced by subduction of the western Pacific Plate beneath the Euro-Asian Plate in the Early Cretaceous. The southern Jinzhou area in the eastern block of the NCC preserves clues about the tectonic events and related geological resources. Studies of the regional stress field evolution from the Cretaceous to the Cenozoic can enhance our understanding of the tectonics and dynamics of the NCC. Borehole image logging technology was used to identify and collect attitudes of tensile fractures from 11 boreholes; these were subdivided into four groups according to dip direction, i.e., NNW-SSE, NWW-SEE, W-E and NE-SW. The development of these fractures was controlled primarily by the regional tectonic stress field; temperature, lithology, and depth contributed to some extent. In 136–125 Ma in the Early Cretaceous, the area was characterized by extension that was oriented NNW-SSE and NWW-SEE; from 125–101 Ma the extension was oriented W-E; after 101 Ma it was NE-SW. This counterclockwise trend has persisted to the present, probably related to oblique subduction of the Pacific Plate, and is characterized by ongoing extension that is nearly N-S-oriented and NEE-SWW-oriented compression.

An integrated high-resolution image log, sequence stratigraphy and palynofacies analysis to reconstruct the Albian – Cenomanian basin depositional setting and cyclicity: Insights from the southern Tethys

Borehole image logs are used to overcome the lack of core samples and other conventional open-hole logs in many subsurface reservoirs around the world, significantly reducing the likelihood of petroleum resource exploration. These image logs can provide high-resolution data to visualize sedimentary structures, facies types, lithofacies, geomechanical characteristics, and depositional trends. Sedimentologists recognize the Bahariya Formation of the North-Western Desert of Egypt as the typical coastal -shallow marine depositional model that emphasizes a typical heterogeneous sandstone reservoir with many obstacles in production profile. One of the most significant issues related to the heterogeneous Bahariya reservoir that confronts hydrocarbon producers is the loss of productive target zones due to spatial facies changes. This research aims to overcome the exploration and development challenges of the complex and heterogeneous sandstone reservoir of the Albian – Cenomanian Bahariya Formation that lies in the Abu Gharadig Basin, Southern Tyths, Egypt. In this work, we used integrated image logging in conjunction with palynofacies, core samples, and sequence stratigraphy to provide high resolution information that can aid in better resource exploitation. Furthermore, we utilized the integrated work in the definition of the high-resolution para-sequences, sequences boundaries, lithofacies characteristics and paleocurrent analysis of each facies association. The interpretation of coastal shallow marine facies from four BHI-logs was established and calibrated with two core sets in order to define the best hydrocarbon reservoir intervals and focus on improving the development plan of the study area. Our findings show that the Bahariya Formation is characterized by eleven facies associations which have been interpreted based on the integrating of the twenty-seven electrofacies extracted from the FMI images, wireline logs, and core photographs. The identified facies associations were classified into five depositional sequences and their boundaries were determined using dipmeter patterns and extracted lithofacies from BHI. The LST and MFS deposits in both the fourth and fifth depositional cycles, respectively, whereas the HST deposits are found only in the third depositional cycle. According to our findings, the development of the shoreface sandy facies of cycles three and five represents the maximum rate of sea-level rise, as well as the development of the offshore sand bar system, which represents high-quality sandstone reservoirs. This case study demonstrates how image logs can be used to better understand the spatial distribution and geometries of sandstone bodies in the Bahariya Formation. Furthermore, it provides a reference imaging fingerprint of high-resolution coastal shallow marine, high-frequency sequences analysis, sedimentary structures, and extracted electrofacies analogues that can be used in the basin and elsewhere.

Soultz-sous-Forêts Geothermal Reservoir: Structural Model Update and Thermo-Hydraulic Numerical Simulations Based on Three Years of Operation Data

The geothermal powerplant of Soultz-sous-Forêts (France) is investigating the possibility of producing more energy with the same infrastructure by reinjecting the geothermal fluid at lower temperatures. Indeed, during the operation of the powerplant, the geothermal fluid is currently reinjected at 60–70 °C in a deep fractured granite reservoir, and the MEET project aims to test its reinjection at 40 °C. A 3D hydrothermal study was performed in order to evaluate the spreading of the thermal front during colder reinjection and its impact on the production temperature. In the first step, a 3D structural model at fault scale was created, integrating pre-existing models from 2D vintage seismic profiles, vertical seismic profiles, seismic cloud structure and borehole image logs calibrated with well data. This geometrical model was then adapted to be able to run hydrothermal simulation. In the third step, a 3D hydrothermal model was built based on the structural model. After calibration, the effect of colder reinjection on the production temperature was calculated. The results show that a decrease of 10 °C in the injection temperature leads to a drop in the production temperature of 2 °C after 2 years, reaching 3 °C after 25 years of operation. Lastly, the accuracy of the structural model on which the simulations are based is discussed and an update of the structural model is proposed in order to better reproduce the observations.

Taming the Thunder Horse With Axes and Vectors

The Thunder Horse Field targets Middle Miocene deepwater turbiditic reservoirs. Despite being prolific, the mapping of the ~180 m thick, partly amalgamated reservoir sandstones is challenging. Seismic quality is reduced by the presence of salt structures. The salt overburden and high formation pressure require the use of heavy mud weights and oil-based drilling fluids, which limit the resolution and interpretation potential of borehole image logs (BHI). Halokinetic movements caused significant post-depositional deformation of the already complex gravity-driven sediment stack, and the reservoir beds drape against an E-W oriented salt wall. Consequently, the assessment and removal of the structural dip component are not trivial, and the evaluation of paleo-transport directions is considerably more complicated compared to undisturbed deepwater reservoirs. This paper illustrates the potential of eigenvector methods to BHI from Ruehlicke et al. (2019) for reconstructing the depositional slope and the architecture of mass transport complexes in the case of chaotic depositional settings and uncertain structural dip. Figures from Henry et al. (2018) are used wherein part axial analysis was performed on data from a group of Thunder Horse wells and presented in more detail.

Fault-related fracture modeling in a pre-salt lacustrine carbonate reservoir from Santos Basin, offshore Brazil: Predicting preferential fluid flow paths using 3D geological and flow simulation models

The authors propose an integrated workflow from seismic to flow simulation to predict sub seismic and inter-well fracture distribution. This methodology provides insights in order to fulfill a knowledge gap in reservoir 3D modeling of naturally fractured carbonates applied in the industry. The workflow includes interpretation of borehole image logs, 3D seismic, geophysical and geomechanical attributes, and calibration with dynamic data. The main natural fracture parameters analyzed for the case study are direction, dip, and fracture intensity. The studied area is a naturally fractured Aptian lacustrine carbonate reservoir within the Santos Basin, offshore Brazil. The isolated platform developed over a series of elongated NE-SW horsts structures. The main seismic scale structures in the reservoir are NE-SW trending faults that show normal displacement, defining en échelon relay ramps that contain NW-SE sub seismic faults and diffuse fracture swarms. The damage zones that surround these main faults define continuous fracture corridors intercepted by oblique sub-seismic faults in relay-ramp zones. Structural analysis showed that fracture intensities are higher at the north domain in the Barra Velha Formation. The fractures were simulated stochastically using a discrete fracture network (DFN), generating a dual porosity and dual permeability model (DPDK) for the flow simulation resulting in a suitable model configuration for the history match.

Facies analysis of the Middle Cretaceous Mishrif Formation in southern Iraq borehole image logs and core thin-sections as a tool

The Middle Cretaceous Mishrif Formation is one of the most important oil reservoirs in central and southern Iraq. The major goal of this study is to calibrate the FMI imaging log in front of the depth intervals where core data is available (thin sections), and then utilize the calibrated FMI behavior to predict the types of microfacies in the wells where core data is not available. Hence, this study focuses on distinguishing and correlating carbonate facies in four wells from the Mishrif Formation in the West Qurna and North Rumalia oilfields, southern Iraq, using borehole image logs and thin sections. Thin-section data from the cored wells were used to identify six carbonate environments based on their constituent carbonate microfacies and grain types. A succession of carbonate-environment-facies units was determined in the cores relative to already established members (mB2, mB1, CRII, mA, CRI) and used to discern how the borehole image logs respond to respective carbonate facies. These borehole image responses to changing carbonate-facies units were then used to identify similar behaviors in the wells without core and for correlation across the two oilfields. Thin-section analysis of microfacies and grain types led to the interpretation of six carbonate-environment facies in the Mishrif Formation, including mid-ramp, shoal, back-shoal, lagoonal and intertidal facies; a rudist-bioherm subfacies also occurred locally in shoal, back-shoal, and lagoonal facie units. The organization of the carbonate-environmental-facies units and their correlation across the two oilfields confirms that the Mishrif Formation in southern Iraq comprises two progradational depositional cycles, separated by a major transgressive flooding surface. Clearly, the combined analyses of thin sections from cored wells and borehole image responses from the same wells provide a powerful tool in understanding and correlating facies and sequences across nearby oilfields.

Evaluation of deep geothermal exploration drillings in the crystalline basement of the Fennoscandian Shield Border Zone in south Sweden

The 3.1- and 3.7-km-deep FFC-1 and DGE-1 geothermal explorations wells drilled into the Precambrian crystalline basement on the southern margin of the Fennoscandian Shield are evaluated regarding experiences from drilling, geological conditions, and thermal properties. Both wells penetrate an approximately 2-km-thick succession of sedimentary strata before entering the crystalline basement, dominated by orthogneiss, metabasite and amphibolite of the (1.1–0.9 Ga) Eastern Interior Sveconorwegian Province. The upper c. 400 m of the basement is in FFC-1 severely fractured and water-bearing which disqualified the use of percussion air drilling and conventional rotary drilling was, therefore, performed for the rest of the borehole. The evaluation of the rotary drillings in FFC-1 and DGE-1 showed that the average bit life was very similar, 62 m and 68 m, respectively. Similarly, the average ROP varied between 2 and 4 m/h without any preferences regarding bit-type (PDC or TCI) or geology. A bottomhole temperature of 84.1 °C was measured in FFC-1 borehole with gradients varying between 17.4 and 23.5 °C/km for the main part of the borehole. The calculated heat flow varies between 51 and 66 mW/m2 and the average heat production is 3.0 µW/m3. The basement in FFC-1 is, overall, depleted in uranium and thorium in comparison to DGE-1 where the heat productivity is overall higher with an average of 5.8 µW/m3. The spatial distribution of fractures was successfully mapped using borehole imaging logs in FFC-1 and shows a dominance of N–S oriented open fractures, a fracture frequency varying between 0.85 and 2.49 frac/m and a fracture volumetric density between 1.68 and 3.39 m2/m3. The evaluation of the two boreholes provides insight and new empirical data on the thermal properties and fracturing of the concealed crystalline basement in the Fennoscandian Shield Border Zone that, previously, had only been assessed by assumptions and modelling. The outcome of the drilling operation has also provided insight regarding the drilling performance in the basement and statistical data on various drill bits used. The knowledge gained is important in feasibility studies of deep geothermal projects in the crystalline basement in south Sweden.

Rock joint detection from borehole imaging logs based on grey-level co-occurrence matrix and Canny edge detector

Rock joints play an important role in characterizing the rock mass quality for geomechanical design and stability analysis. An approach was developed to detect and characterize rock joints from images collected by a borehole imaging system. A grey-level co-occurrence matrix was employed to locate the joint regions, allowing more focused and effective detection processing, followed by extractions of the upper and lower edges of rock joints using the Canny algorithm. Four basic geometric parameters of rock joints (orientation, depth, aperture and core length) were determined based on the fitting of sinusoids to joint edges. Furthermore, the joint density was determined based on the geometric parameters. To calibrate the proposed approach, a borehole on the site of the planned Rumei hydropower station at Lantsang River was selected as a case study. Orientation of rock joints with gentle dip angles, which was determined from borehole imaging logs, corresponded to the measurements in three horizontal tunnels. Additionally, both joint density and pressure-wave velocity revealed that jointed rock mass was observed at depths from 100 to 120 m, and intact rock mass was present at depths of 150–170 m, indicating the good performance of the proposed method.

An Integrated Approach for Formation Micro-Image Rock Typing Based on Petrography Data: A Case Study in Shallow Marine Carbonates

Core rock-typing (RT) is commonly used for creating geologically reliable models of porous media in carbonate reservoirs. This approach is more advanced than the traditional porosity–permeability relationship and is based on the division of carbonate rocks into groups, using common classifications (lithofacies, FZI, Winland–Pittman, etc.). These clustering methods can provide either geological or petrophysical descriptions of the identified rock types. Besides, the connection of identified core rock types with standard logs could be challenging due to the different scales of measurement. This paper considers the creation of a new approach, named “integrated rock-typing,” which connects geologically and petrophysically driven rock types using borehole image logs. The methodology was applied to an Upper Devonian–Lower Carboniferous carbonate field. The workflow comprises borehole image structural/textural analysis with vug fraction identification, quantitative geological descriptions from thin sections, and petrophysical measurements. The geological section is divided into six rock types, which were controlled by sedimentary and diagenetic processes. The created Rock Type Catalogue provides clear links between rock types and log data, including wells with standard suites of logs. The results will be useful for geological modelling and validation of the future drilling strategy for the studied field.

Open fractures in pre-salt silicified carbonate reservoirs in block BM-C-33, the Outer Campos Basin, offshore Brazil

Natural open fractures are present in sidewall cores and in whole-core samples from pre-salt reservoirs in the licence block BM-C-33 in the Campos Basin, Brazil. Open fractures are also observed in borehole image logs, and fracture densities are in general high. The highest density of open fractures is seen in the damage zones above and below larger cavities (amalgamated cavern damage zones (ACDZs)). Outside the ACDZs the fracture density is high in silicified carbonates, where it tends to increase with decreasing porosity. Clean dolomites are less fractured than the silicified interval, while the less brittle argillaceous dolomites have the lowest fracture density. Some fractures appear vuggy on borehole image logs, and fracture densities are high close to vugs and larger cavities. The positive correlation between fractures and vugs is caused by flow of dissolving fluids through open fractures, and fracturing at stress concentrations around vugs. Two major fault zones have been interpreted from borehole image logs that have damage zones with very high fracture density. The well-test permeability is much greater than the matrix permeability estimated from sidewall core and log measurements. This excess permeability is attributed to fractures, in combination with caverns and intervals with frequent vugs.

Geometry of layer-bound fractures based on fracture density and aperture-depth plots from resistivity image logs of deviated wells

High resolution borehole resistivity image logs provide valuable bedding and fracture data from subsurface rocks including fracture type, orientation and aperture. The present study shows that common average shape and aperture geometry of uniformly located layer-bound fractures can be inferred from scan-line density and aperture-depth plots using image log data from a deviated well.The proposed method extends the use of borehole image logs and allows 3-dimensional (3D) modeling of fractures and fractured layers from subsurface data. So far, such 3D fracture studies could only be conducted using outcrop data. The approach is quite robust because correspondence between fracture geometry and image log plots is independent of fracture length and orientation, and applies to any fracture shape and aperture geometry.Joint interpretation of fracture scan-line density and aperture-depth plots, and bedding picks from borehole images also helps differentiate isolated/dispersed, unbound and multilayer fractures. Abundance of fractures that breach bed boundaries gives an idea about the cohesive bonding strength of bedding contacts and pave the way to construct fracture stratigraphy with several fractured layers that are separated by interfaces of varying bonding strength or by ductile beds. 3D fracture geometry may also provide some information on the type and mode of fractures and geo-mechanical conditions under which the fractures were generated.