Horizontal wells in ChevronTexaco's Captain Field in the North Sea typically exhibit low temperature and pressure in the produced intervals with highly viscous heavy oil production in 2 and 3-phase flow. The highly viscous oil (88 to 135 cp) has historically presented difficult conditions for most horizontal production logging instrumentation due to the tendency for plugging and coating of sensors. The wells are also screened completions which makes logging and interpretation more complex. Production profiles in three of the Captain Field screened horizontal wells were recently determined utilising an advanced horizontal production logging system. The system combines 2-dimensional parallel-plate capacitance array measurements of 3-phase holdup and velocity profiles, pulsed neutron measurements of 3-phase holdup and water velocity, and conventional production logging measurements to determine the production profile.This paper presents the results of the logging campaign, including several interesting observations relating to production and measurement in the profiles under flowing conditions (and shut-in, with cross-flow).Atypical velocity profiles due to the presence of heavy, highly-viscous oil.Observation of annular flow regime, or "core flow", where oil flow is surrounded by an annular layer of water.Effects due to flow through the gravel pack and the need for both capacitance and pulsed neutron measurements.The importance of simultaneous measurement of holdups and velocities across-the-wellbore for accurate flow rate determination. Introduction In simplest terms, flow profiling in a horizontal well bore requires identifying the cross-sectional area fraction of each phase present, or holdup, and quantifying the velocity associated with each phase. Flowrates are then obtained based on the velocities, hold-ups, and associated flow path geometry. In practice the situation is invariably more complicated than this simple ideal. Obtaining an accurate holdup for each phase in "normal" light oils is generally a challenge, but one which has been addressed. Various technologies have been developed that can provide reasonable holdup data in favourable conditions. Phase velocity determination on the other hand has been rather less well provided for than holdup determination. Various instruments are available which can provide partial answers that are then augmented by modelling to generate a velocity profile. Historically, however, none of these have been capable of generating a result over a sufficiently wide range of flow regimes. To circumvent this limitation various combinations of instruments have been generally operated such that data coverage along the well bore can be maximised. A tough challenge, but one which has historically been met under some of the simpler flow conditions which exist. In the case of the Captain Field this task is further complicated by the high viscosity of the oil (88–135 cp) and the low reservoir temperature. In addition the pressure in some wells is below the bubble point resulting in the presence of three phase flow conditions. This combination of conditions presents a difficult challenge for earlier-generation horizontal logging instruments and has historically resulted in coating and subsequent blinding of some types of holdup sensors, in particular, probe-type measurements. The perforamance of the standard spinner flowmeter measurement can likewise be severely degraded in this environment.

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