Production logging is essential for assessing fluid movement in wells and ensuring proper completion efficiency. Key tools include temperature logs, flowmeters, and various sensors that help diagnose production issues, monitor cement placement, and assess corrosion. These tools aid in optimizing production by allocating resources efficiently and understanding reservoir dynamics.

1. Production logging tools
Sajjad Ahmad
Naeem Siddiqui

2. Production logging
 Production logging is one of a number of cased hole services that
includes cement monitoring, corrosion monitoring, formation fluid
contacts monitoring, perforating and plug and packer setting.
 The subsurface measurements in production wells which yield
information on the nature and movement of fluids within the well are
referred to as production logging.

3. They are run after the production casing string cemented and
well placed on production. Production logs are used for several purposes
evaluation of completion efficiency for production as well as injection
wells, mechanical condition of the well, detection of anomalous fluid
movements, and reservoir management. The most widely used through-
tubing production logging tools are high resolution thermometer,
gradiomanometer, continuous flowmeter, inflatable packer flowmeter,
and caliper..

4. Temperature surveys are carried out using the high resolution
thermometer under static as well as dynamic conditions. The
subsurface temperatures can be recorded downhole in the wellbore or
at the surface. Subsurface recording requires only a wireline to lower
the instrument to the desired depth, whereas surface recording
necessitates an additional conductor cable to transmit the data from
the measuring device to the recorder at the surface.

5. Applications of production logs
 Production logs are used to allocate production on a zone by zone basis
and also to diagnose production problems such as leaks or cross flow.
 The various tasks can be split between those where the target production
is into or out of the well and those where the flow never enters the well,
typically behind the flow.

6. Working principle of logs
Is any gas coming from the formation?
Yes….
How will you locate it?
In case if the reservoir has a gas cap, after oil production for sometimes the gas
expand and come into the wellbore(gas conning). When the gas expands it lowers the
surrounding temperature..
Why the temperature decreases?
How we will know that gas is coming into wellbore?

7. We will use a tool that measure the temperature inside the wellbore and
location where we find out a decrease in temperature, we will know from
where the gas is coming from.
1. Here we will use joule-Thomson effect Which states that
“ At ordinary temperature and pressure all real gases expands, except
helium and hydrogen.”
But why???
The cooling occurs while work must be done to held the gas molecules to
stop them moving further apart.

8. As the gas molecules expands it needs more space and moves with high
velocity. For velocity the molecules get the energy from the surrounding,
and the surrounding has to cool down because it gives its energy to the
molecules.
For that we will design a temperature log. In the wellbore where we found
the decrease in the temperature. It indicates the gas is coming into
wellbore at that position.
2. What will happen to resistance when you heat up a
conductor?

9. If we heat up a conductor, the movement of electrons slow
down. No current coming, if there is no current then it
means the resistance is high.
Higher the temperature , the higher is resistance and vice versa.
Electrons don’t move

10. From where the water is coming from?
If we connect two plates to a battery with water as medium between
them, the +ve charges will stay on plate A, and the –ve charges will
deposit on plate B. the capacitance can be found by the formula;
C= ɛ̥ ɛᵣ A/d
A= area of plate
d= distance between plates

11. Flowrate of fluid:
The flowrate of fluid within the wellbore (cased hole) can be defined as
by formula;
C is conversion factor to convert Q unit into bbls.
The flowrate of the fluid can be found by measuring its velocity. The
velocity and flowrate are correlate, the radius of wellbore is known.
The induced current is produced
Because of the rotation of the
spinner due to the flow of fluid
And we get signals on the surface,
and it’s the velocity.

12. Categories of Applications
Production logging tools find many applications from the time a well is drilled until
abandonment
1) Diagnose production problems and allocate production
2) Monitor cement placement
3) Monitor corrosion
4) Monitor reservoir fluid contacts
5) Select zones for recompletion

13. Category One
Includes tools used to track movement of fluid either inside or immediately outside
the casing of a well. The logs frequently used for such flow diagnosis and allocations
include :
.Temperature surveys
.Mechanical flowmeter surveys
.Borehole fluid-density or fluid-capacitance surveys
Each of these tools responds to fluid velocity or fluid type.The logs are run to
determine if a production problem; such as excessive water or gas production, is the
result of a completion problem or a reservior problem.
Also belonging in category One are;
.Evaluation of the placement of acids or hydraulic-fracturing material
.Diagnoses of premature flow or lost circulation in a drilling well

14. Category Two
There are two different objectives of cement-placement monitoring :
1) To determine where the cement went(cement top)
2) To determine whether the cement provides zonal isolation
The logs used to locate the cement top include:
• Temperature Log, which responds to hydration heating.
• Unfocused Gamma Ray Log, which responds to behind pip density.
• Regular bond log, which measures the acoustical deadening of pip.

15. Category Three
Zonal isolation should be addressed when pressure imbalance causes cross flow through poorly
cemented sections, leading to excessive production of unwanted fluids. The tools most often
used for this purpose include:
• Cement bond logs
• Temperature
• Noise
• Radio active tracer
• Neutron activation logs
The temperature log detects alteration caused by flow, the noise log measures turbulent sound
caused by flow, and the tracer log tracks tagged fluid behind casing. The neutron activation log
creates tracer in behind pipe water. Corrosion monitoring are specialized in nature and include
mechanical caliper tools and electromagnetic casing inspection tools. The mechanical caliper
tools are used to assess corrosion internal to the casing and to measure the shape of casing as
well as the amount of rod and drill pipe where inside tubing or casing.

16. Category Four & Five
The last two categories, monitoring of fluid contacts in formations and selection
of recompletion zones, use the cased whole nuclear logs such as:
• Neutron
• Pulsed Neutron
• Various spectral logs