Abstract

We have developed a new on line water cut meter using low field Nuclear Magnetic Resonance (NMR) technology. This instrument is designed for use on heavy oil systems where conventional instruments experience difficulties.

We present laboratory and field data for application of low field NMR to water cut measurements of bitumen/water mixtures. Data from successful field tests near Cold Lake, Alberta, Canada, shows that the instrument is capable of making water cut measurements over a wide range of fluid types and temperatures. We have successfully measured fluid streams with temperatures ranging from 60 to 150 degrees Centigrade and with water cut ranging from 40 to 95 percent. The instrument is capable of functioning accurately over a wide range of emulsions and/or foams and through significant variations of water salinity.

The current application is for water cut measurements on a well site. However, the instrument can be applied in any system where heavy oil, bitumen, water, gas and solid systems may be encountered. It can be used for water cut and/or for three phase (oil/water/gas) volume fraction measurements. The instrument is equally capable of performing well site monitoring for regulatory/reconciliation purposes, for characterizing produced fluids, in separation, pipelining and upgrading processes for process control and for quality testing.

Introduction

One of the most challenging problems in the production and processing of heavy oil and bitumen is the task of measuring the flow of oil and water. Most instruments have been designed for conventional crude oils and perform poorly when applied to heavy and viscous hydrocarbons. We have developed a new water cut measurement tool specifically for use on heavy oil and bitumen streams. This tool is based on low field Nuclear Magnetic Resonance (NMR) and has shown great promise1 as an on line tool in use at a field in northern Alberta, Canada where bitumen in being produced using cyclic steam injection. This project is an extension of considerable experience in the lab with core analysis2–7.

The initial stages in this particular project have been discussed elsewhere1,7. In brief initial experiments consisted of measuring both known and unknown discrete samples of oil/bitumen and water mixtures in a lab NMR instrument similar to what was used here. Some measurements were also made using unknown samples collected at the wellhead and placed in the instrument with no further preparation. Excellent correlations between NMR measurements and Dean-Stark analysis (approximately 99%) have been reported from this work.1,7 The next step was to build an on line tool based on this technology. The field results are reported elsewhere1, but the results have generally been viewed as excellent with this technology being in general at least as accurate as other tools typically used on these types of oil fields. This paper attempts to explain the technology and how it works.

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