Borehole images constitute a rich source of high-resolution geological data about various formations penetrated by oil and gas wells. Interpretation techniques of these images have progressively improved over the years and provide detailed information about formation dips, structure, rock fabric, fractures, and drilling-induced borehole damage. Wireline tools have the flexibility to be used in a wide variety of borehole sizes. In contrast, logging-while-drilling(LWD) tools are designed for particular borehole sizes. A new high-resolution LWD imaging tool has been built for 8.5-in. boreholes. This paper presents the results from two logging runs located in offshore United Arab Emiratescarbonate fields, including the first worldwide logging run of the tool. Measurements made by this new high-resolution imaging tool are based on laterolog principles for the measurement of resistivity. The tool performs two main types of measurements, including an array of focused resistivity measurements with an axial resolution near 1 in., and an ultrahigh-resolution resistivity imaging pad consisting of an array of eight buttons. This paper focuses on the LWD tool’s imaging section, designed to provide the same volume ofinvestigation as one of the focused resistivity measurements. This design featureresults in measurement calibration confidence with respect to the formation resistivity, allowing for quantifiable analysis of the formation properties using the image data. The data for this first run were acquired during a washdown through a carbonate-evaporite sequence. Borehole deviation was approximately 60° and the mud was a typical high-salinity water-base mud. A suite of wireline data, acquired after the LWD washdown run, includes a pad-based resistivity imaging tool, which allows comparison of thetwo sets of acquired data. Data from both the wireline and new high-resolution imaging LWD tools were processed and interpreted. Structural and cross-bedded layers were clearly visible on both imaging-type tools. Borehole crossing and layer-bound fractures were also observed and could be quantified from both tools. Examples show how identifying some featuresis made easier on the full borehole coverage of the LWD images; however, the higher resolution of the wireline tool is beneficial for identifying some textural features. Results from both types of logging tools are presented and the similarities and differences are summarized. Advances in borehole image visualization are also presented as 3D views in addition to cross-sectional views across the borehole, which make visualization of features more user friendly for those not familiar with borehole image interpretation.
ZADCO's new field development program calls for drilling extended reach wells from artificial islands with the borehole kicking off at shallow depths and holding high inclination angles through the overburden. Previously, the development plan relied entirely on short reach, horizontal development wells drilled from jackup rigs with shallow overburden borehole sail angles rarely exceeding 30°. For both types of wells, bentonite weighted sea water is the preferred drilling fluid for the 16″ or 17.5″ diameter holes. Drilling problems that were managed in low-inclination wells became exacerbated at higher angles causing significant rig non-productive time (NPT). To improve our understanding of the shallow overburden formations, a comprehensive logging program was conducted in a key well drilled with a potassium chloride (KCl) mud system. Wireline borehole image, dipole shear sonic, spectroscopy and neutron-density-resistivity triple-combo logs were used to characterize the formations. A successful logging program relies on maintaining the borehole in good condition. In this case, the KCl mud in conjunction with good drilling practices kept the hole near the 16″ bit gauge for 90% of the interval. Drilling mud losses were also minimized. The logging tools were successfully run to T.D. and the data acquired. The mineralogy of the penetrated formations was accurately quantified using spectroscopy tools. A high-resolution resistivity image log revealed that the entire interval was weakly fractured with a few zones of high secondary porosity and conductivity. These zones correlated well with zones of similar characteristics in offset wells. The key to drilling a high angle well lies is the geomechanical / geochemical characterization of the overburden formations to determine the wellbore failure mechanism(s). This paper highlights the benefits of a KCl mud in the top hole and the results of advanced logging covering the predominately shallow carbonate formations that exist above a large carbonate reservoir. It emphasizes the need for characterizing not only the reservoir but the overburden formations. This advances drilling engineers’ understanding of formation characteristics so that increased drilling sail angles could be achieved through the shallow overburden and thus successfully reach the reservoir targets.
Several challenges are associated with the characterization of organic rich unconventional plays, most significantly with the identification of sweet spots for optimum placement of horizontal wells, estimation of producible hydrocarbons and subsequent stimulation design. This paper presents the petrophysics and geomechanics integration approach from the X Formation and the important factors for the identification of sweet spots. The case study concentrates on the X Formation that consists of a succession of argillaceous limestone, mostly fine grained packstones and wackestones together with subordinate calcareous shales in the lower part. The complex carbonate lithology and fabric combined with low porosity and the requirement to evaluate total organic carbon presents a challenge to conventional logs and evaluation of them. Amid all the rock properties, the low permeability and productivity dictate the requirement to stimulate the wells effectively. Detailed integration of advanced and conventional log data, core data, mud logs and geomechanical analysis plays a critical role in the evaluation and development of these organic rich unconventional reservoirs. Extensive data gathering was done with wireline logging suite, which covered Resistivitiy/Density/Neutron/Spectral GR- Acoustic logs – Resistivity & Acoustic Images – Dielectric- NMR - Advanced Elemental Spectroscopy technologies and microfrac tests to characterize the hydrocarbon potential, sweet spots and in-situ stress contrast within the organic rich X Formation. The azimuthal and transverse acoustic anisotropies were obtained from X-dipole data to fully characterize the elastic properties of the formation. The static elastic properties were obtained using empirical core correlations as triaxial core tests were not available at the time of the study. The stress profile was calibrated against straddle packer microfrac tests to identify intervals with stress contrast for proper hydraulic fracturing interval selection. The integration of conventional and advanced logs enabled the accurate evaluation of total organic carbon (TOC), petrophysical volumes, and sweet spot selection. The advanced elemental spectroscopy data provided the mineralogy, amount of carbon presence in the rock, and consequently the associated organic carbon within the X Formation. The NMR reservoir characterization provided lithology independent total porosity. The difference between the NMR and density porosities provides additional information about organic matter. NMR data was utilized in this case study to identify and differentiate the organic matter and hydrocarbon presence within the X Formation. Acoustic and image logs provided the geomechanical properties that enable selection of the best intervals for microfrac stress measurement and proper fracture containment modeling. Geomechanical workflow allowed identification of intervals with a good stress contrast in X formation. The core data and stress measurements are recommended for the accurate calibration of the stress profiles and hydraulic fracture propagation modeling. The extensive data integration work presented in this single-well study within X Fomation, is a key factor for any organic rich unconventional reservoir characterization that integrated geology, petrophysics, mineralogy, and geomechanics for sweet spot identification within tight oil carbonate reservoirs.
TX 75083-3836, U.S.A., fax ϩ1-972-952-9435understand not only the geological characteristics, but also the variations in reservoir properties within seemingly similar facies.This work presents the first account of interpretation based on a new technology for OBM formation imaging, with innovative inversion techniques. This also serves as a roadmap for carbonate reservoir characterization in Middle East in the wells drilled with OBM. Also, the encouraging results provide a trendsetting example of applications of this new technology.
Objectives/Scope: Comprehensive records retention schedules, which are based on records classification structures, are established to reduce costs associated with records growth and duplication, improve access to valuable information, and ensure compliance with applicable laws and regulations. All digital technical data, including Geology and Geophysics, Reservoir Engineering, Drilling, etc. need to be preserved forever. Data can be re-used, re-interpreted, re-analyzed for many Years later. If data is "well organized", no need to dispose-off anything. Similarly each electronic copy of non-technical data should be preserved. Methods, Procedures, Process: Before implementation of the mentioned workflow for Data Archival and Retention of documents, physical copies were kept forever and there was no mechanism for end user to easily access the required files. As policy was formalized at Group level, each assigned focal point was assigned with task of converting physical copies to electronic version (by scanning and uploading onto Network drives and Electronic Document Management Systems (EDMS). On completion of scanning activity below retention policy was applied to preserve the physical data for a defined timeframe (mentioned in below table). As files such as Final Well reports, drilling reports etc. are available online and accessible using Network drives / EDMS system, end user can easily access the required files in a matter of seconds which save the tremendous amount of end user time and increase productivity as an organization. Since policy is implemented tremendous efforts are placed by focal points to reduce the physical files by coordinating with different physical files sources (internal or external of organization) to provide with Digital copy which is much easier to maintain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.