Interpreting Spinner Response in Multiphase Bubble Flow

Abstract

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.

A Successful Introduction of a New Tools Configuration and Analysis Method for Production Logging in Horizontal Wells

“…A mini-spinner in the high side of the borehole would behave similar to a vertical bubble flow regime. The oil bubbles impinging the small impeller vanes immersed predominately in water will create an impeller response that would not accurately represent the velocity of the oil bubbles (Wang et al 2000). A distributed fluid-ID sensor tool will respond only to water in the lower sensors and alternate water and oil in the sensors located in the high side of the borehole.…”