Abstract

Studies of the fluid- and flow properties of reservoir fluids is important to ensure an effective and safe production and transport of oil and gas. Among the many areas where it is important to gain further knowledge is the formation and deposition of hydrates and wax in pipes transporting reservoir fluids or crude oil. On this background, Christian Michelsen Research A/S (CMR) has studied various measuring techniques over the past few years, and instrumentation for deposit monitoring has, and is in the process of being developed. Recently, CMR has developed ultrasonic laboratory instrumentation for on-line monitoring of solid deposition in pipes.

The system consists of two ultrasonic "clamp-on" transducers operating inpulse-echo mode, two compact electronics units and a PC "control unit" handling all data acquisition, signal processing and presentation of results. The system has been installed on a multiphase flow "loop" at Statoil's Research Centre in Trondheim, and is designed to :

  1. detect the deposition of hydrate on the pipe wall, or

  2. measure the thickness of a possible wax layer.

In this paper, the system, its detection principles, and the results from initial tests are described and presented. The critical factors influencing the operation and robustness of the system are discussed, as well as the conditions which must be satisfied and the challenges to be met for a successful industrial application.

Introduction

Studies of the fluid- and flow properties of reservoir fluids is important to ensure an effective and safe production and transport of oil and gas. Among the many areas where it is important to gain further knowledge is the formation and deposit of hydrates, wax and asphaltenes in pipes transporting reservoir fluids or crude oil. On this background, Christian Michelsen Research A/S (CMR)has over the past few years studied various techniques for measuring soliddeposit, and instrumentation has, and is in the process of being developed. Ina collaboration with Statoil Research Centre, CMR has recently developed ultrasonic laboratory instrumentation for on-line monitoring of solid deposition in pipes. The system is presently installed on a rotating multiphase flow wheel at Statoil's Research Centre in Trondheim simulating multiphase transportation. In this paper, the system, its detection principles, and the results from initial tests are described and presented. Furthermore, the critical factors influencing the operation and robustness of the system are discussed.

Clamp-on deposition monitoring system based on ultrasonic pulse echo technique

The system consists of two ultrasonic "clamp-on" transducers operating inpulse-echo mode, two compact electronics units and a PC control unit handling all data acquisition, signal processing and presentation of results. The system is presently installed on a 2" multiphase flow "loop" at Statoil's Research Centre in Trondheim, and is designed to :

  1. detect the deposition of hydrate on the pipe wall, or

  2. measure the thickness of a possible wax layer.

Asketch of the system, as installed at Statoil, is given in Figure 1.

Both ultrasonic transducers operate in pulse-echo mode. The detection of hydrate deposit and thickness measurement of a possible wax layer are, however, based on largely different principles.

Wax deposit measurement

Wax measurements are based on a standard pulse-echo technique, where thickness is estimated from the time-of-flight of echoes from the steel/wax-(inner pipe wall) and wax/gas interface, respectively.

Wax deposit measurement

Wax measurements are based on a standard pulse-echo technique, where thickness is estimated from the time-of-flight of echoes from the steel/wax-(inner pipe wall) and wax/gas interface, respectively.

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