A new method for the rapid measurement of the fat content in live (or slaughtered) Atlantic salmon, based on a mobile low-field NMR analyser, has been developed and tested. The instrument, calibrated against a set of reference samples (fish oil in agarose), was used for non-destructive fat determination of the Norwegian quality cut (NQC) of anaesthetized fish. The total analysis time per fish was about 20 s. The fat content (range 90-182 g kg −1 ) showed significant correlation (r = 0.92) with chemical extraction data obtained after slaughtering the same fish. The spatial distribution of fat in the NQC was obtained and visualized as a 'fat image' using novel software. It was concluded that the mobile NMR spectrometer has potential for implementation in connection with on-line quality control.
fax 01-972-952-9435. AbstractDrilling in subsurface formations requires control of downhole pressures. Weighting materials are typically added to the drilling fluid and provide, ideally, a homogeneous fluid column with an even density to control these pressures. However, experience has shown that keeping the weighting material in suspension can be challenging. Especially when drilling with synthetic or oil-based drilling fluids the nature of the fluids prevents the generation of sufficient gel structures to keep high density particles in suspension. On one offshore operation the rig had to be evacuated. Because barite was sagging out of the drilling fluid and left a residual fluid phase with too low density, gas was entering the well during drilling.This paper provides a review of the sag studies performed to date, describes various testing techniques for sag evaluation as well as giving description several field cases where weighting material sag occurred. It also shows how the efficiency of operations was affected. The cases are analyzed and suggestions are made concerning the operational elements that may have provoked the incidents. The analyses use timebased drilling data to provide detailed information of the operational sequences prior to the sag incidents and how the incident was handled at the site.Several previous studies have shown no correlation between weighting material sag and standard measurements of drilling fluid properties. The present study, however, focuses on other fluid properties essential to hinder weighting material sag.
This paper describes the development of a low-solids mineral oil-based fluid and its successful application as a drill-in and completion fluid in a multilateral (MLT) well on Statoil's Aasgard field, off Mid-Norway. The introduction of highly complex technology, such as multilateral well design with long horizontal reservoir sections, demands a strong focus on the drilling fluid characteristics. Recent field experience showed that conventional oil-based mud (OBM) systems had limitations, when used in a demanding downhole environment influenced by elevated temperatures and ambitious drilling and completion objectives. This resulted in lower than expected drilling efficiency and well productivity. Accordingly, a development program was instituted to qualify a new high temperature OBM that possessed reduced formation damage potential and superior bridging characteristics while remaining thermally stable. The candidate fluids investigated were OBM of three different types:standard OBM with a mineral base oil,OBM with a linear paraffinic base oil anda low-solids (LS) OBM. The latter was based on an emulsion with a heavy calcium bromide brine as the internal phase and a mineral base oil as the external phase. Bridging materials and organoclay for viscosity were added as the only solids materials. The results of the qualification programme showed that the LS OBM exhibited superior sag stability and much higher return permeability values as compared to the two other oilbased alternatives. The field application of the fluid was very successful. And the Aasgard subsurface team managed to drill and complete a total well path length of about 4900 m. The well was drilled and completed 37 days ahead of plan and produces with a productivity index as expected. Introduction The Aasgard field development is located in the Haltenbanken area off mid-Norway and comprises three fields - Smørbukk, Smørbukk South and Midgard. The field was developed in the late 1990s with a subsea production system with two production facilities, Aasgard A (FPSO) and Aasgard B (semi submersible gas processing platform). In addition a storage and offloading vessel (Aasgard C) receives the liquid production from Aasgard B (Fig. 1). The three different fields have widely different fluids and reservoir quality, and accordingly, wells are completed differently. The Smørbukk reservoir is the most challenging with a reservoir temperature of 165°C in the deepest zones. Smørbukk South is somewhat shallower than Smørbukk and the reservoir temperature is 150°C in the deepest zones. The Midgard field is different again from both Smørbukk fields-the reservoir temperature is lower at 90°C and a different approach to drill and complete the reservoir has been adopted. This paper concentrates on the two Smørbukk fields. Additional information on geology, reservoir engineering aspects and early production strategies of the Aasgard field and field-specific technology challenges was reported by Haaland et al. (1996)1. Well constructions in the early development phase followed a rather straightforward design. In general, the Smørbukk wells were drilled vertical or deviated and the Smørbukk South wells were drilled horizontal. Completions consisted either of cased and perforated reservoir sections (Smørbukk) or openhole completions with pre-drilled liners (Smørbukk South). All Smørbukk wells are commingled wells, the Smørbukk South wells targeted the Garn formation only. Although experience with multilaterals (MLT) was limited in the mid-90s, multilateral wells with long horizontal sections were part of the long-term field development plan for production of the Ile and Tilje formations on Smørbukk South 1. MLTs were considered essential to maximize drainage from a reservoir with rather poor quality. With increasingly demanding well construction plans, work processes and system components for drilling and completion operations need to be continuously revised. Under high-temperature conditions all elements in the well construction process must be highly redundant and compatible.
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