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EAGE Workshop on Borehole Geology in Asia Pacific
- Conference date: March 30 - April 1, 2021
- Location: Online
- Published: 30 March 2021
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An Evolving Approach to Characterize Fractured Basement Reservoir Using Acoustic Image and Element logs, Bohai Bay Basin, Offshore North China
More LessSummaryThe Bohai Bay basin is located on the offshore North China, the target Bozhong19-6 buried hill trap is a typical condensate gas reservoir formed in the basement. However, the fractures are unevenly developed due to the multi tectonic movements. In addition, the minerals in the basement are complex and variable by the effect of metamorphism and alteration. Accurate petrophysical property estimation is a must to clarify the relation of DST and reservoir type with different lithology and fracture development. An evolving approach was proposed for the above challenges, firstly, acoustic image logs was used to identify different fracture types, dissoluted fracture and partially open fracture are firstly identified besides open and close fracture. Element logs was used to improve the accuracy of petrophysical property calculation. Then, the element logs and acoustic logs were involved deeply to characterize structural transition zone. Finally, the bridge linking the reservoir type, fracture type and lithology was built, which will maximize gas production by optimized well design in the future field development.
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A New Approach for Automatic Quantitative Resistivity Image Calibration in Water-based Mud
Authors S. Yang, T. Zhang, I. Le Nir and R.H. Al LawatiaSummaryWe provide a new automatic system and apparatus that generates quantitative resistivity image from the apparent electrical downhole acquired images. The analysis results from two case studies show that the new system is not only automatic, but also reducing the uncertainty to get more accurate fracture and vug evaluation parameters because of the processing steps take the hardware bedding response into consideration.
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Stretching Operating Envelop of New LWD High Resolution Resistivity Images in Oil Based Mud - First Application High Resolution Resistivity Images in Kuwait for Unconventional Reservoir.
SummaryNajmah formation in Kuwait is known having rich kerogen rock that has potential of the hydrocarbon gas. The formation contains the mixtures limestone – dolomitic – clay and kerogen and has low to medium porosity. The fracture is the most important to be identified as the driver of the rock permeability. Borehole images is required to understand the fractures development and geological features in Najmah formation. However, upcoming development strategy in the field is high deviated well construction which limits the acquisition of the image logs with conventional wireline. The strategy to ensure the acquisition of downhole images logging with LWD are critical to be investigated while operation efficiency is meet. This paper will discuss a comparison between conventional electromagnetic resistivity images conveyed by wireline with the new generation multi-measurement of LWD imager in synthetic oil base mud in unconventional reservoir Najmah Kerogen formation. The main objective for the study is to have lesson learnt and assessing the quality of the multi-measurement LWD image’s data with given stretch operating condition. The solution of the minimizing the effect high mud attenuation to the images acquired due to variable stand-off and heavy mud weight will be discussed.
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A Study of Drilling and Borehole Geophysics in The Geothermal Potential Area of The Mae Chan Hot Springs in Northern Thailand
Authors S. Siricharoensri, R. Onsibut, S. Siricharoensri and P. WatkrathokSummaryThe Mae Chan fault zone has been studied as one of the most potential development for geothermal resources in Northern Thailand. The hot springs have been seeped through traces of the active Mae Chan fault system ( Wood and Singharajwarapan, 2014 ). In this study, the surface geological mapping and geophysical surveys were employed to locate the five wellbores in the potential area at the site around the Mae Chan hot springs. The wells were logged as altered Biotite Granite and Cataclastic fault materials such as fault breccia and fault gouge. Furthermore, the electrical well logging was used to determine the physical properties of the rock formations and interpreted with the information of the boring logs. Consequently, the five wellbores were successfully completed, and the information of the interpretation shows the core logging matched well with the results of the E-logs.
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Wireline Resistivity Image Interpretation, and 1D Mechanical Earth Modelling, as Inputs for Deep Block Cave Mine Design and Hydraulic Fracture Planning
Authors D. Lewis, R. Puspitasari and D. TennantSummaryIn this study, an FMI image log interpretation, and a One-Dimensional Mechanical Earth Model (1DMEM), were used to provide key data for rock mass classification and critical information to understanding potential hydraulic fracture geometry in a deep block cave mine. The FMI image interpretation provided fracture type, size, orientation and density information valuable for rock mass classification used in the mine expansion; whereas, the 1DMEM provided valuable information on mechanical properties and insitu stresses for the hydraulic fracturing planning. As a result of the FMI interpretation and 1DMEM, Newcrest was able to accurately define and delineate geotechnical hazards. Poor rockmass quality associated with some faults was also identified, and mine design improvements and engineering critical controls such as hydraulic fracturing were successfully undertaken.
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Automated well log correlation: An approach using traditional and FMI logs
Authors J. Ali, M.Q. Nasim, T. Maiti and T. SinghSummaryIn general practise advanced image processing algorithms extract image characteristics and build a feature dataset. This dataset can be analyzed using different unsupervised and supervised machine learning techniques for interpretation. Interpretation of the dataset can range from identifying a cluster structure that represents sets of similar rock types and provides well interpretation. Chronostratigraphic (mapping out time surfaces) well log correlation (correlation means interpreting top in well A to well B) is a combination of lithostratigraphic correlation and application to conceptual models of how sediment is transported and deposited. Image logs such as FMI along with traditional well logs like Gamma ray, neutron porosity are used in such well correlation studies. We also present Well log correlation is the identification and connection of equivalent patterns/ geological units between log curves of adjacent wells . This helps us in understanding subsurface geology.
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Visualising blind zones in borehole image analysis: An open-source code for addressing the limitations of the Terzaghi correction
Authors I. Wallis, D. Dempsey and J. RowlandSummaryFracture data picked from borehole image logs suffer from geometric sample bias: Fracture planes that are perpendicular to a borehole are very likely to be intersected while those parallel with the borehole are rarely intersected. Isogenic contours depict the geometric sample bias on a stereonet and, therefore, enable us to quickly recognise the effect on the fracture dataset. Although this bias was recognised in the mid-60’s, we present the first open source software for plotting isogenic contours. The code is available in Fractoolbox (https://github.com/ICWallis/fractoolbox), which is a repository of Python tools for fracture analysis and geomechanics. Elements of the Fractoolbox were presented in the context of a geothermal case study in the November 2020 New Zealand Geothermal Workshop. However, this is the first detailed discussion of the isogenic contour plotting tool and how it supports fracture data interpretation.
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