Applied Production Logging

And Reservoir Monitoring

1- Production Logging:

We would need to address the following topics:

• Water, oil and gas production from every zone.

• Productivity index and pressure for each zone

• Detection of leaks behind and inside casings

• Estimation of cross-flow between zones caused by uneven depletion.

• Three phase production in horizontal wells.

2- Reservoir Monitoring:

We would also need to address the following topics:

• Estimating fluid saturations of water, oil and gas behind conductive and non-conductive casings

• Applications of Pulsed neutron logging: capture mode (Σ) and Carbon/Oxygen mode.

• Resistivity (Rt) measurements behind conductive and non-conductive casings.

• Evaluating stand-alone PNL logs in old wells.

• Cross –well electromagnetic imaging to monitor water flood.

The course deals in details with evaluating these topics in production logging and reservoir monitoring. Practical applications of all those topics will be the foundation for this course.

Overview

Production Logging Basics:

To estimate the production of water, oil and gas (Qw, Qo, and Qg)

from every zone and subzone. Also to estimate the productivity

index (PI) and the pressure for each zone.

Uneven Depletion:

Most reservoirs have a large heterogeneity in permeability, hence

flow profiles resulting in uneven depletion and variations in zone-by-

zone pressure. This will result in cross-flow when the well is shut-in

and at small chokes.

Horizontal Well Production:

Flow regimes in horizontal wells tend to be more complex with

large variations in velocities and hold up. A new generation of

logging equipment (micro-spinners, micro hold up probes) are

deployed.

Leak Detection:

Most wells will develop leaks at some stage in their operational life.

Logging Tools and applications:

Spinner calibrations

Direct velocity measurements of the 3 phases

Hold up measurement of the 3 phases.

Estimating the effects of water coning.

Production Logging Challenge

Reservoir Monitoring Objectives:

To monitor Fluid saturations of water, oil and gas (Sw, So and Sg)

behind conductive and non-conductive casings.

Pulsed Neutron Logging:

Theory of PNL logging to obtain both Σ and C/O.

Interpretations of Σ and C/O logs to obtain Sw, So and Sg.

Estimating flood-water salinity.

Stand-alone PNL interpretations in old wells with limited open hole

log data.

Reservoir Monitoring Tools:

Pulsed Neutron Logging Tools: This have dual applications for

capture mode (Σ)and carbon/oxygen (C/O) mode.

Resistivity measurements behind conductive (Steel) casings.

Resistivity measurements behind non-conductive (Plastic, fibre-

glass) casings and in open hole completions.

X-well electromagnetic imaging for flood water sweep.

Monitoring using Resistivity logs:

In conductive casings: stationary readings of current leak is used to

obtain Rt behind casing

In open hole and non-conductive casings the induction log can be

used to obtain Rt- the same as in a standard open hole logging.

Reservoir Monitoring Challenge

This course addresses two very important aspects of well performance:

Production Logging and Reservoir Monitoring

Production Logging:

The course focuses on outlining the process of production data

acquisition and interpretations in vertical, deviated and horizontal wells.

The objectives are aimed at:

Estimating productivity index (PI) and reservoir pressure for each

selected interval.

Estimating inter-zone cross flow without shutting the well

Evaluating the water production intervals caused by coning and

behind the casing leaks.

20 field examples are used. The interpretations steps are simplified

so the most complicated data set should be completed within 10

minutes.

Reservoir Monitoring:

This is important for production, reservoir and petrophysics domains.

This covers the following:

The physics of Pulsed Neutron Logging (PNL), for both capture mode

(Σ) and inelastic mode (C/O).

Estimating Sw using (Σ) and (C/O) modes.

Stand-alone PNL interpretations in old wells with no open hole logs.

Combining (Σ) and (C/O) modes to obtain the average water salinity

Monitoring gas saturation (Sg).

Measurement of formation resistivity behind the casing (leakage

current) .

The use of slim hole induction logs in non-conductive casing

Cross-well deep electromagnetic mapping.

12 field examples will be used. The process is simplified whereby

each interpretation is done within 10 minutes.

This course is a must for anybody involved in field development to

optimise field recovery factor and minimise water production

Spinner Calibrations

Running the spinner at different velocities, in the opposite direction to the flow, provides the basis for spinner calibrations at any desired station, above perforations (B and C above) and at any station within the perforations (e.g. X). The slope of the straight line plot is the spinner sensitivity (velocity/rps which for a given spinner depends on the fluid type) and the intercept on the y-axis which is the raps due to the flow.

Two chokes to obtain PI and Pr for each zone Calibrations

Two chokes are used to

obtain PI and Pr for

each layer

Having Pr and PI for each layer will allow the shut in pressure to be

computed and hence the volume of cross-flow when the well is shut-in, or

the cross –flow at low chokes and flow rates.

Water Production

Water production is a serious

production limiter in most fields.

One common reason in high

producers is water coning.

Example shows how the water

production drops by 80% without

reducing (and often increasing)

the oil production when the choke

is decreased . A change in the

choke from 2 1/8 to 1 7/8 reduced

the top of the water entry level by

25 ft and increased the oil

production by 700 bl/d.

Coke: 2 1/8 Coke: 1 7/8

Production Logging in Horizontal Wells

Horizontal wells provide more challenges

to production logging. Variations of

velocities and hold-ups will span a wide

range for little variations in flow volumes.

This is caused mainly by small variations in

the well trajectory around 90 degrees.

New technology, like the FlowScanner

Imager (FSI) are effective in evaluating

multi-phase flow in horizontal wells.

Reservoir Monitoring

Pulsed Neutron Logging

Pulsed Neutron Logging (PNL) is the main tool that is used for

reservoir monitoring. This involves two data acquisition types:

Neutron Capture Mode (Σ). This is very effective where the water

salinity is known. .

Inelastic mode (Carbon/Oxygen). This relies .on spectroscopy

and used mainly in where water salinity is unknown or the water

salinity is very low.

Capture Mode Inelastic Mode

Reservoir Monitoring

PNL Life Cycle

The minitron source fires around 20 million neutrons at speeds of 17

MeV. They interact (bump) into the various atoms, slow down, then they

get captured. The whole life cycle of the neutron is approximately 200 m-

sec (200 thousands of a second).

• The first 50 m-sec when the neutron are travelling fast is when

spectroscopy takes place and C/O is obtained.

• The last 50 m-sec of the neutron cycle is when the capture mode

slope is obtained.

C/O Σ

Reservoir Monitoring

PNL Capture Mode

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The Neutron Capture Mode (Σ) is the most practiced form of reservoir

monitoring. It is very effective where the water salinity is high (>50 kppm).

It is most applied form is time-lapse as shown above. The measured

capture mode equation is the law of superposition as shown above where

the measured Σ for is the integral sum of the fractional volume of each

component multiplied by its unique Σ value.

Reservoir Monitoring

PNL C/O Mode

The Neutron High energy interaction can be used to obtain elemental

evaluation of Carbon and Oxygen. Empirically derived trapeziums for C/O

ratios of different detectors spaced at different distances can be used to

obtain both values of Sw when the salinity is low or unknown and when

combined with the capture Σ is also used to evaluate the fraction of the

two waters sweeping across.

Reservoir Monitoring

Resistivity (Rt) Measurement behind Casing

Formation Resistivity (Rt) measurement behind steel casing can be

made. This is based on measuring the small leakage current from the

casing to the formation when an axial current is induced in the casing.

The advantage of this is to provide a good correlation with the original Rt

that was made in open hole. This will highlight areas of poor injection

water sweep.

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Reservoir Monitoring

Field Wide Applications

Water saturation data obtained across the field, both open hole data and

cased hole reservoir monitoring data, obtain over a specific time span can

be used to map the water flood across the field.. This will highlight areas

of the field where there is a poor sweep. These maps can be made for

selected zones within the reservoir interval.

Day-1

• PL Overview

• Inflow Performance

• Slippage Velocities

• Fluid Velocities

• Spinner Calibrations

• Hold Ups

Day-2

• Equations

• Single Phase Flow Rate

• Two Phase Flow Rate

• 3 Phase Flow Rate

• Uneven Depletion and Cross flowDay-3

• Production Log Interpretations in Horizontal Wells

• Reservoir Monitoring Introduction

• Nuclear Physics of Neutron Interaction

• Pulsed Neutron Logging Tools

• Reservoir Monitoring Capture (Sigma) Mode

Day-4

• Reservoir Monitoring Inelastic Mode

• Log-Inject-Log

• Reservoir Monitoring Field Wide applications

Day-5

• Resistivity measurements behind conductive casing

• Resistivity measurements behind non-conductive casing

• Deep Reading Electro-Magnetic Imaging

There will be daily practical workshops on each of the topics covered using field examples

Agenda