This paper focuses on the first applications of an improved, second-generation multiple sensor production logging system designed for use in horizontal and highly deviated multiphase producers. The system integrates several key measurements to provide a comprehensive analysis of well performance under a variety of conditions and flow rates. An expanded and improved 2-dimensional capacitance array is used to define flow regime and measure 3-phase holdup, velocities and flow rates. A new 3-detector pulsed neutron instrument provides an independent measurement of water velocity, 3-phase holdups, and formation water saturation. Auxiliary sensors include an acoustic transducer and distributed temperature sensors useful for gas entry, liquid entry, and behind-casing channel identification. A quartz-pressure gauge measurement is recorded which is also useful in mechanistic models of multiphase flow. While a brief description of the system components will be provided in order to familiarize readers with the measurement concepts, this paper will concentrate on field examples from the Middle East that demonstrate the first use of the improved logging system in horizontal openhole multiphase producing wells. Determination of multiphase holdups, cross-wellbore velocity profiling, and production inflow profiling is demonstrated. Openhole logs are also shown, including resistivity image data, which clearly differentiate the inflow points as producing bed layers or conductive fractures.

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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.

This paper was prepared for presentation at the 1999 SPE Middle East Oil Show held in Bahrain, 20-23 February 1999.

The conventional production logging spinner is widely used to log both single and multiphase flows in producing wells, and it is well known that the spinner response in multiphase flow is complicated and difficult to interpret. A brief literature survey finds few models for interpreting the spinner response in multiphase flow. The general conclusions from previously published works are that the response is still more or less linear with the total volume flow rates, but still very difficult to interpret with any confidence. In this paper, a mechanistic model based on angular momentum balance of the spinner rotor in bubble flow is introduced. The model is composed of two parts. In the first part, it is assumed thatthe fluids passing through the spinner blades are well mixed,there is slip between phases,the flow does not swirl. Therefore, an idealized spinner response under idealized bubble flow is developed. The results show that the spinner response in multiphase bubble flow is not a linear univariable function of the total fluid volume passing through the spinner, but rather a multivariable function of slip velocity, volume fraction, continuous phase velocity, and fluid properties. The second part of the analysis introduces the concept of bubble travel length to consider the effect of the spinner cage or centralizer on bubble flow trajectory. Introduction A conventional production logging tool string is composed of temperature sensors, pressure sensors, fluid density sensor, fluid capacitance sensor, caliper, gamma ray, and spinner flow meter. Among the measurements from these sensors, the temperature measurement, the pressure measurement, and the spinner readings are related to fluid flow velocities. The spinner reading is most directly related to fluid flow velocities. Therefore, the accurate interpretation of spinner response in multiphase flow is critical in the determination of production profiles. There are three types of spinner logging instruments usually used in production logging, the continuous spinner flow meter (small diameter centerline spinner), the folding impeller/caliper flow meter (fullbore spinner), and the basket (diverting) flow meter. The model in this paper is mainly developed for the continuous spinner flow meter and the folding impeller/caliper flow meter. A spinner flow meter is composed of blades, bearings, cage or protective centralizer cage, and rotation pickup device1,2. Usually, the spinner flow meter response is interpreted according to the calibration conducted by logging down and up at known instrument speeds relative to the wellbore. The interpreted apparent fluid velocity is assumed to be the mixture centerline velocity, and a correction factor is applied to obtain the averaged mixture velocity. The details of spinner flow meter, its calibration, and interpretation can be found in the following documents2,3. A brief literature survey found that there are few models developed for interpreting spinner response in multiphase flows. According to Hill3, the conclusions from single phase flow can still be used in multiphase flow provided that the flow is homogeneous enough. These flow regimes are dispersed bubble flow, annular-mist flow, and emulsion flow. There are four well-recognized flow regimes in vertical wells (Brill and Mukherjee4.) These flow regimes are bubble flow (bubbly flow and dispersed bubble flow,) slug flow, churn flow and annular flow (annular flow and annular mist flow.) The bubbly flow and the dispersed bubble flow differ in the mechanism of the flow. The bubbly flow occurs at the relatively low continuous phase flow rates, and is characterized by slippage between the two phases. The dispersed bubble flow, on the other hand, is well mixed and there is no slippage. The slug flow is characterized by the flow of successive Taylor bubble and liquid slugs. The flow patterns that are most frequently encountered in production logging interpretation of vertical and deviated wells are bubbly flow and slug flow. This paper addresses the spinner interpretation in bubbly flow.