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Multi-Tracer Analysis for Distributed Temperature Sensing

IP.com Disclosure Number: IPCOM000225722D
Publication Date: 2013-Feb-28
Document File: 5 page(s) / 390K

Publishing Venue

The IP.com Prior Art Database

Abstract

Thermal tracers have previously been shown to add information to a distributed temperature sensing (DTS) survey (Gerard et al. 2007). In this paper we look at the concept of using multiple tracers simultaneously in the wellbore. A multi-tracer shut-in monitoring program and analysis techniques are described using an inter-well communication scenario. It was demonstrated that multi-tracer analyses more clearly elucidate inter-well communications than single tracer analyses in the wellbore.

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Multi-Tracer Analysis for Distributed Temperature Sensing

Abstract

Thermal tracers have previously been shown to add information to a distributed temperature sensing (DTS) survey (Gerard et al. 2007). In this paper we look at the concept of using multiple tracers simultaneously in the wellbore. A multi-tracer shut-in monitoring program and analysis techniques are described using an inter-well communication scenario. It was demonstrated that multi-tracer analyses more clearly elucidate inter-well communications than single tracer analyses in the wellbore.

Introduction

Distributed temperature sensing (DTS) may be used as a tool for describing fluid movements in the wellbore. By analyzing the fluid movements, we may calculate the fluid leak-off rates in individual production zones and determine the leak-off profile (Gerard et al. 2009). In some wells and situations, especially in long horizontal wellbores, small temperature contrasts may be present and, hence there is then the difficulty tracking fluid movements by monitoring the distributed temperature in the wellbore. In such cases, thermal tracers may be used to produce sharp temperature signatures that are easy to track. Having multiple tracers in the wellbore at the same time may additionally increase the information we get out of a DTS survey. We describe herein a multi tracer shut-in analysis for an inter-well communication survey as an example. In evaluating communication between wells, it is important to find the communication points. In addition, the extent of the fluid transfer between the wells at the communication points may be important to quantify. The location of the communication points and the relative fluid transfer at these points may then be used to design an optimal shut-off treatment program.

Thermal Tracers

A thermal tracer is a certain volume of fluid designed to have a different temperature than the rest of the fluid in the wellbore. The temperature differentiation will make the fluid stand out on a distributed temperature profile and will be easy to track. We may produce a tracer by using a fluid with different thermodynamic properties (density and specific heat capacity) than the rest of the fluid column, or alternatively, inject a fluid that reacts in an exothermic or endothermic reaction.

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An example of a monitoring pumping program with four thermal tracers is as follows:


1. Thermal Tracer - 2 m3


2. Seawater - 5 m3


3. Thermal Tracer - 2 m3


4. Seawater - 5 m3


5. Thermal Tracer - 2 m3


6. Seawater - 5 m3


7. Thermal Tracer - 2 m3


8. Displacement

Multi-Tracer Shut-in Analysis

When the pumping program is finished, the well may be shut-in. A multi-tracer shut-in analysis may then be used to find direct communication points between wells. The flow pattern in a neighboring well may be altered by putting it on production, injection, or shutting it in. The thermo-hydraulic response on the fluid column in the first well that is shut-in is then analyze...