TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractPlacing a maximum reservoir contact well in a thinly layered reservoir has always been a challenge. Experiences showed that the well trajectory could easily be steered out of the target, necessitating expensive plug-back and redrilling operations to ensure that the well is drilled as planned. With the deployment of advanced LWD technologies, such as density image (DI), resistivity image (RI) and directional deep resistivity (DDR) logging tools, and high speed real time satellite data transmission, well paths can be geosteered from anywhere and kept in a thinly layered reservoir.The first Saudi Aramco field examples of utilizing RI and DDR are shown to demonstrate the added values of new technologies in geosteering difficult-to-drill wells. In some of the examples, images of density and resistivity are consistent and all could be used for geosteering. In other examples, wrong geosteering decisions would have been made had the DI been the only available tool. With the help of RI, reservoir contact of multi-lateral wells is increased. Examples also show that using DDR can prevent the well trajectory from being too close to the zero porosity rock layer or the underlying water.
Formation evaluation (FE) of horizontal injectors drilled in water swept reservoirs involves different physical understanding of log responses to fluid flow and distribution than that FE of oil producers drilled in dry oil intervals. In reservoirs swept with water, effects of rock electrical anisotropy on logging-while-drilling (LWD) apparent resistivity measurements (attenuation and phase shift) could be significant. These effects need to be considered in resistivity log interpretation. In this study, LWD resistivity modeling work was conducted to study relationships between true formation resistivity and LWD tool responses. In situations where the time-consuming resistivity modeling/inversion is not available, LWD apparent attenuation is found to be more representative to true formation resistivity than the apparent phase shift resistivity, thus can be used in formation water saturation estimation. An alternative measurement of formation fluid saturation is by pulse neutron (PN) after well completion. New technologies have been developed to characterize formation saturation through casing, i.e., behind-casing-analysis (BCA) which includes PN and casedhole resistivity. Logging long horizontal intervals of BCA services is different from logging vertical wells. First of all, the issue of vertical resolution in horizontal wells is not as critical. Secondly, the gravity effect on the tool orientation is different. Data quality could also be different when logging long intervals of the casedhole resistivity because the tool requires physical contact between the measurement pads and the casing. In this paper, all these issues are summarized. The BCA logs are integrated with results of the LWD modeling and production data while underbalanced drilling to provide more accurate formation evaluation.
Geosteering is the interactive placement of a wellbore using real-time geological criteria; its use allows increasingly more complex geologic targets for horizontal producers and injectors. This paper presents a case study of Geosteering horizontal wells in an onshore field of the western Niger Delta. The results demonstrate how an integrated team uses modern LWD tools to make real-time well path corrections in a challenging environment. The objective of geosteering is to direct the well using real-time logging and interpretation to a specific target within the reservoir. Various best practices are discussed in which geologic and structural data are combined with LWD measurements to lower the risk of " landing" and subsequently maintain the horizontal portion of the well in the desired location. Real-time dip estimation is a tool in the geosteering arsenal that can assist with geosteering decisions both during landing and while maintaining the lateral portion of the wellbore in the target window. Field examples illustrate the use of azimuthal density measurements to enhance real-time evaluation and decision-making processes. Quadrant density measurements and density images are used to calculate dips and enhance steering decisions made by an asset team of geologists, petrophysicists, and geosteering engineers for a field development project in Nigeria. Present methods in geosteering for real- time dip estimation include interpretation of resistivity and density images, estimation from the quadrant density log, and detailed stratigraphic correlation during approach hole drilling. Associated with each estimation method is an inherent uncertainty with the dip calculation; these uncertainties can lead to geosteering decisions of low confidence. To reduce the total uncertainty, more than one method for calculating dip can be used to assist with well plan adjustments. The thinner the sand is, the tighter the steering tolerance becomes, requiring the well to be drilled closer to bed or target boundaries. The most accurate possible dip estimation is needed for these cases. Introduction The " Swamp" Field is located onshore in the western Niger Delta, and is operated by Chevron Nigeria Limited (CNL) in a joint venture with Nigerian National Petroleum Company (NNPC). There are presently 35 horizontal development wells and 6 horizontal water injectors in this development. Production in March 2003 was 39,800 BOPD, with 47,200 BWPD being injected. The reservoirs comprised 10 to 60 ft thick shoreface sands with occasional tidal channel facies. Lateral variability in reservoir thickness and quality demand that all horizontal wells in the " Swamp" Field be geosteered.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWithin the Saudi Aramco organization, complex reservoir formation evaluation is regarded as a key discipline -fulfilling a critical role in maximizing production and facilitating accurate estimation of reserves. The timely acquisition of high quality and detailed petrophysical properties of the various reservoirs in Saudi Arabia is central to this role. Towards this end, Saudi Aramco Reservoir Description Division (RDD) introduced a new-generation multi-functional LWD (Logging-While-Drilling) technology into Saudi Arabia, has been directed to evaluation of on-shore complex carbonate reservoirs.The traditional LWD measurements of propagation resistivity, gamma ray, density and neutron porosity along with advanced gamma ray capture spectroscopy measurements into a single compact collar. The electronic pulsed neutron source required for the spectroscopy measurements also provides a much improved neutron porosity measurement 1 . This technology has been used in a number of Saudi Aramco horizontal wells in carbonate and clastic reservoirs. The data from these wells has been comprehensively evaluated. The results of the evaluation of the data acquired by the new tool and conclusions about the tool's introduction into Saudi Arabia are summarized in this paper.
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.