Jeff DaCunha - EBook.pdf

Decoding 7 Mysteries of
Downhole Pump Cards
Jeff DaCunha, PhD

Decoding 7 Mysteries of Downhole Pump Cards
Copyright © 2021 by Jeffrey J. DaCunha
All rights reserved. This book or parts thereof may not be reproduced in any form,
stored in any retrieval system, or transmitted in any form by any means- electronic,
mechanical, photocopy, recording, or otherwise- without prior written permission of
the publisher.

Contents
Contents 3
1 A Brief Historical Introduction 7
2 The Meat and Potatoes of Downhole
Pump Cards 12
2.1 The effect of combination fiberglass
and steel rod strings . . . . . . . . . . 14
2.2 Easily identifying a hole in tubing . . 17
2.3 Bottle opener card and rod dynamics
with pump leakage . . . . . . . . . . 19
3 38

jeff-dacunha.teachable.com Decoding Downhole Pump Cards
2.4 Race car surface card and the split
pump barrel . . . . . . . . . . . . . . 22
2.5 Surface cards with tails do not neces-
sarily mean the pump is tagging . . . 24
2.6 Identifying paraffin deposition . . . . 29
2.7 Severe pump leakage that looks like
full pump fillage – leaking your
pump full . . . . . . . . . . . . . . . . 31
3 Closing thoughts 37
4 38

Prologue
From eight to five, you make a living. From five to
midnight, you make progress.
–Ken Nolen, PE
I just did something simple-minded. If it works, it’ll
be a miracle!
–Sam Gibbs, PhD
Holy smokes! Just what, exactly, is this book
about? We’ve all seen surface or pump dynagraph
cards in our careers that puzzle us. The twelve basic
5 38

pump cards help us identify the conditions at the
downhole pump by providing a base set of differ-
ent introductory pump card shapes. But what about
when there is a new, complex, or uncategorized condi-
tion at the surface, along the rods, or at the pump... Or
better still, multiple issues occurring simultaneously
at the pump that creates a card that is a mystery?
This e-book will help to answer this question for 7
mysterious downhole cards that are encountered in
sucker rod pumping.
6 38

Chapter 1
A Brief Historical Introduction
Let’s take a step back and discuss what the down-
hole card is and where it comes from. The down-
hole pump dynagraph (or simply, the downhole card
or pump card), is defined to be the load and position
of the bottom of the last sucker rod. And what com-
ponent is connected to the bottom of the last sucker
rod? That’s right, the pump plunger. Attached to
this plunger, we have a traveling valve ball and seat
assembly... and sometimes two traveling valves in
series for redundancy in case one becomes fouled.
7 38

Figure 1.1: Overlaying the calculated pump dynagraph from Sam’s
algorithm with the measured pump dynagraph card from Glenn’s
downhole dynamometer shows the incredible accuracy of the wave
equation.
This plunger moves back and forth inside a pump
barrel, which has a hold-down to keep it in place in
the tubing and a standing valve ball and seat to allow
fluids to enter the pump... and yes, the standing valve
may also be double-valved for redundancy.
8 38

Back in 1936, Walton E. (Wally) Gilbert created
a downhole dynamometer to measure the load and
position at different points in the rod string1. In par-
ticular, he was very interested in the load and position
of the bottom of the last sucker rod, which is by defi-
nition, the load and position of the pump plunger. A
complete library of pump conditions was created by
running this tool in numerous wells and then pulling
the rods to inspect the tool.
Three decades later, Dr. Sam Gibbs, while working
at Shell in the 1960s, developed a patented method2
to determine the downhole pump card mathemati-
cally. Sam describes his eureka moment in a video
interview for SPE’s Oral History. Using only load
and position data gathered at the polished rod, along
with the information about the rod string, he was
1
W.E. Gilbert, An oil-well pump dynagraph, API Drilling and Pro-
duction Practice (1936), 94–115.
2
Method of determining sucker rod pump performance, US Patent
3343409.
9 38

able to compute the load and position at any point
in the rod string, in particular, at the pump. Now
the downhole pump condition could be illustrated on
every stroke of the pumping unit, instead of having
to pull the rods and inspect a tool, which is obviously
very expensive and inefficient.
For the next 30 years, Sam, partnering with Ken
Nolen, PE, taught the industry about the utility of the
downhole pump card. In 1996, Glenn Albert created
a digital downhole dynamometer that measured the
load and position along the rod string as well as at
the bottom of the last sucker rod. With this tool,
Sam was challenged to prove that his mathematics
were accurate. Rigging up both sets of equipment on
the same well at the same time, both Sam and Ken,
along with Glenn, measured the same strokes of the
pumping unit with their respective equipment. The
results speak for themselves in Figure 1.1. Sam would
later conjecture:
10 38

Solutions of the wave equation that match measured time
histories of surface load and position will produce the
exact downhole pump card if the friction law in the wave
equation is correct. In computing the pump card, no
knowledge of the pump conditions is required. Any error
in the friction law will cause error in the pump card.
In the paper that Sam and I coauthored, Modeling a
finite-length sucker rod using the semi-infinite wave
equation and a proof to Gibbs’ conjecture, SPE 108762
PA-P, I wrote a proof for his conjecture and it was
raised to theorem status. Gibbs’ conjecture is now
formally known as Gibbs’ Theorem.
11 38

Chapter 2
The Meat and Potatoes of Downhole
Pump Cards
What I want to touch on in this ebook are the cards
that you cannot find using Google. These are the
cards that, without a doubt, you will encounter dur-
ing your career working with sucker rod pumps. As
always, if you want to know what is happening at the
pump, you have to think like the pump. Put yourself
at the bottom of the rod string. Think as if you are
the pump. Think downhole.
12 38

The 12 Basic Pump Cards
The twelve basic pump cards that we have all been
taught are:
1. full pump
2. tubing movement
3. incomplete fillage/fluid pound
4. gas interference/gas expansion
5. rod part/flowing well/inoperative pump/fouled
traveling valve
6. pump hitting (tagging) up or down
7. bent barrel/trash in pump/sticking pump
8. worn traveling valve and/or plunger
9. worn standing valve
10. worn or split pump barrel
11. fluid (viscous damping) friction
12. drag (Coulomb) friction
Often we can deconstruct a downhole pump card
and determine which of the 12 basic shapes have
occurred simultaneously. We have to play detective.
13 38

Figure 2.1: An inward load spike on the top of the pump card about
50 inches into the upstroke.
In the following sections, I will go a little bit further
than the 12 basic pump card shapes. I will help you
decode and explain 7 mysteries of downhole pump
cards... enjoy!
2.1 The effect of combination fiberglass and
steel rod strings
When we speak of the perfect downhole pump card,
we typically mean a full pump with minimal fric-
14 38

Figure 2.2: Inward load spikes appearing as horns on the left and
right hand sides of the pump card during load transfers.
tion and minimal leakage. What many people do not
realize is the rod string is a fixed-free vibrating sys-
tem, which means that the pump does not operate in
unison with the polished rod. Tension and compres-
sion waves are traveling back and forth along the rod
string, which cause the pump to sometimes move at
a different speed or in a different direction than the
polished rod is moving. As a result, the pump can
“hiccup” for lack of a better term.
15 38

Inward load spikes and pump card horns are two
common occurrences that can sometimes cause un-
warranted concern. The first of these two hiccups,
the inward load spike, is seen on the top of the pump
card in Figure 2.1.
The second hiccup appears when pump loads
change during the upstroke, downstroke, or during
the load transfer (the left and right hand side of the
pump card). They become more noticeable when
the pump is showing traveling valve leakage and/or
slippage around the plunger.
Now, these inward load spikes during load trans-
fers are not easily seen when we have full pump
fillage with minimal to no leakage, as in Figure 2.1.
However, when traveling valve leakage is significant,
the result looks like small horns on the left and right
side of the pump card, as in Figure 2.2. This shape
anomaly often causes concern when it is observed
on the downhole card.
16 38

I am here to tell you that this is one of the accept-
able anomalies that is just part of the dynamics that
occur in the rod pumping system. There is no prob-
lem, it is simply the result of a rod string being driven
from the surface, along with tapers that have differ-
ent diameters and different materials (which means
different moduli of elasticity and thus different wave
propagation speeds) which cause wave reflections at
each point where the taper changes in the rod string.
2.2 Easily identifying a hole in tubing
The area of a dynamometer card is an indication of
the amount of work that is being done by the system.
When a pump has a valve that is fouled, either the
standing valve or the traveling valve, we observe a
flat line pump card every time. Just think about it, if
you woke up in the hospital and looked over at the
screen and saw a flat line, what would you think?
You’re dead, right? Right! Your pump is not working!
However, the location of the flat line downhole
relative to a properly working pump with full liquid
17 38

Figure 2.3: An overlay of corresponding surface and downhole
cards with a full pump and a HIT.
fillage (for a particular well) is extremely important.
We will refer to the downhole card of a properly
working pump with full liquid fillage as the reference
card. As we all know, if the flat line card is along the
top of the reference card, it means that the traveling
valve is closed for the entire stroke, which implies
that the standing is open for the entire stroke. If the
standing valve is open for the entire stroke, then it is
18 38

not operating properly and it is fouled. We also know
that if the flat line card is along the bottom of the ref-
erence card, then the standing valve is closed for the
entire stroke, which implies that the traveling valve
is open for the entire stroke. If the traveling valve
is open for the entire stroke, then it is not operating
properly and it is fouled.
But what if a flat line pump card is observed not on
the top or the bottom of the reference pump card, but
somewhere between? This is puzzling because we
immediately start trying to guess which one of the
two valves, the traveling or the standing valve, is not
working. However, this is not the correct analysis.
By in large, the downhole condition that is causing a
flat line to appear along the middle of the reference
card is a hole in the tubing.
2.3 Bottle opener card and rod dynamics with
pump leakage
One of the most problematic/confusing cards that
people come across is the so-called bottle opener card.
19 38

Figure 2.4: Pump cards displaying incomplete fillage can often
have an appearance of a bottle opener.
The hook shape on the right-hand side of the card in
Figure 2.4 looks like a bottle opener on its side in Fig-
ure 2.5. This is another example of a combination of
the twelve basic cards and the rod dynamics (tension
and compression waves discussed in 1 above) that
has to be dissected into the basic shapes that make
up the card.
20 38

Figure 2.5: Pump cards displaying incomplete fillage can often
have an appearance of a bottle opener.
Notice in Figure 2.4 that the conditions of the pump
are incomplete fillage, traveling valve leakage and/or
slippage, and rod dynamics happening during the
load transfers between the standing valve to traveling
valve on the left side of the card and the traveling
valve to standing valve on the right side of the card.
The explanations for the aforementioned phenomena
are discussed in detail in my classes.
21 38

2.4 Race car surface card and the split pump
barrel
When the pump barrel is split, the resulting down-
hole card is one of the most unique shapes that exists.
Once this shape is understood, we can also go a little
further in identifying where in the barrel the split is
occurring... toward the bottom of the barrel, in the
middle, or toward the top. However, in this section,
we are discussing one of the surface cards that sur-
faces (ha!) with split pump barrels. It looks like the
outline of a race car without the wheels.
This example is just one of the many that shows
the importance and utility of the downhole pump
card. When we have a split pump barrel, we are
going to see a pump card with a basic shape found
in Figures 2.6 and 2.7. However, there is an infinite
number of surface card shapes that can be associated
with a given downhole pump card. One of the surface
card shapes that is found relatively frequently with
22 38

Figure 2.6: A split pump barrel, midway through the plunger’s
stroke, with the race car surface card.
split pump barrels is the race car surface card, seen
here in Figure 2.6.
But just because you have a split pump barrel does
not mean you will have race car surface card. Other
surface cards can be associated with split pump bar-
rels, as in Figure 2.7.
23 38

Figure 2.7: A split pump barrel, low in the plunger’s stroke, without
a race car surface card.
2.5 Surface cards with tails do not necessarily
mean the pump is tagging
Just because a surface card has a tail at the end of
the card, it does not mean that the pump is tagging.
A tagging pump can actually manifest well into the
upstroke on a surface card. When a tail or even a loop
is observed at the left or right end of a surface card,
a common assumption is that the pump is tagging.
I am here to tell you that that is NOT the case. Just
look at Figure 2.8, which shows a tail on the left hand
24 38

Figure 2.8: A tail on the left hand side of the surface card, but
no pump tag identified on pump card. However, there is a small
inward load spike at the end of the downstroke on the bottom left
corner of pump card. Inward load spikes are harmless artifacts of
rod dynamics throughout the stroke.
side of the surface card, but no tag at the pump. To
be good at diagnosing rod pump conditions, as stated
above, you have to think like the pump. Think as if
you were the pump. If you are interested in what is
happening at the pump, look at the pump card!
25 38

Figure 2.9: A (seemingly) sublte tag is observed on the pump
card. The tag does not manifest itself on the pump card until
approximately 18 inches into the upstroke.
Now, wait, am I saying that a surface card showing
a tail or loop cannot be the result of a tagging pump?
No... the answer is no. A tagging pump can certainly
show a loop or tail on the end of a surface card. But
we must confirm the tag by observing the pump card.
And sometimes the tag on the pump card is subtle,
as in Figure 2.9, while other times it is quite obvious,
as in Figure 2.10. Notice that the surface card in
Figure 2.9 does not have a tail on the left hand side,
26 38

Figure 2.10: A more abrupt tag is observed on the pump card. In
this case, there is a discernible tail on the left hand side of the
surface card.
but the surface card in Figure 2.10 does have a tail at
the end of the downstroke.
One of the most interesting phenomena that I have
encountered is when the pump tag signal reaches the
surface after the pumping unit is already on the up-
stroke. Remember I said above that the rod string is
a fixed-free vibrating system, where the pump and
27 38

the polished rod do not have to be moving in uni-
son. Well, in the case of Figure 2.9, imagine that the
pumping unit at the surface has come to the bottom
of the stroke and is now beginning the upstroke. But,
downhole, the bottom of the rod string is still travel-
ing downward due to overtravel and the elasticity of
the rod string. In this example, when the pump does
tag downhole, the signal from this tag travels up the
rod string to the surface where it becomes evident
on the surface card– this happens at approximately
20 inches into the upstroke. So, in this case the tag
does not look like a tail or a loop at either end of the
surface card. Instead, it looks like an indent at the be-
ginning of the upstroke. And if you look closely, you
can see it again at about 35 inches into the upstroke.
Remember, this vibration signal that was intro-
duced into the rod string from the pump tagging
travels up and down the rod string until it finally
damps out or decays and loses its energy. This typi-
cally happens during a single stroke. But if the pump
is tagging stroke after stroke, then it will reappear in
28 38

Figure 2.11: Paraffin causes the surface cards to take an extreme
up and to the right orientation, with corresponding distorted pump
cards with an extremely stretched out, down and to the right orien-
tation.
a virtually identical fashion, stroke after stroke after
stroke.
2.6 Identifying paraffin deposition
Now this is cool. Not paraffin, no, not paraffin at all.
What is cool is the fact that once we identify paraffin
from the surface and downhole dynamometer cards,
we can quickly mitigate the problem by hot oiling
29 38

or hot watering the well and then getting the well
treated with the appropriated paraffin inhibitor.
The wave equation is used to translate the surface
dynagraph card into the downhole pump card. When
there is excessive friction anywhere along the rod
string, that distorts the computation of the downhole
card because the signals that reach the surface are
distorted from the friction. The wave equation itself
does not have the ability to remove this friction. In
fact, no rod pump controller nor oilfield SCADA sys-
tem has the ability to properly remove drag friction
along the rod string to yield a meaningful pump card.
But I do. I demonstrate it in my courses and I make
it available to my clients by analyzing data that they
send to me or by gathering the data myself at the well
site and taking it back to the office to fully analyze it
and provide a report and associated dashboard that
is accessible by my clients to view current and past
analysis as well as trend the performance of the rod
pumping systems over its lifetime.
30 38

2.7 Severe pump leakage that looks like full
pump fillage – leaking your pump full
Leakage can be so bad that it may appear that your
downhole card is filling completely. Figures 2.12–2.17
show the progression of traveling valve leakage, with
all other parameters staying the same.
Notice how the pump begins with 60% pump fillage
with 0 BPD leakage. As we progress through increas-
ing leakage rates of 0 BPD to 20 BPD to 40 BPD to 60
BPD to 80 BPD to 100 BPD, we see subtle differences
in the surface and downhole cards. Notice that the
surface card shows longer and longer initial stretch
on the rods during the upstroke with the correspond-
ing peak load during the upstroke being achieved
later into the upstroke.
Also notice on the downstroke that the pump fil-
lage appears to be increasing from 60% at 0 BPD pump
leakage all the way to 100% at 100 BPD pump leak-
age. Observe that the overall stroke length decreases
as the leakage rate increases from 0 BPD to 60 BPD,
31 38

but then from 60 BPD to 100 BPD leakage, the pump
stroke length begins to increase.
Figure 2.17 shows the pump leakage at a rate of 100
BPD, but the pump was only filling 60% from the well.
It appears as if the pump is filling completely, but
in fact, we can compare this with Figure 2.18 which
shows the pump with full fillage and 100 BPD leakage.
Subtle differences can be seen when comparing a
pump card that leaks itself full versus when it truly
has full fillage with excessive (100 BPD) leakage.
This particular issue can only be properly deter-
mined by incorporating knowledge about pump ca-
pacity, current test results, and valve checks at the
pumping unit to quantify the leakage at the pump
plunger, both standing valve and traveling valve. My
well analysis reports include valve checks and con-
firmation of production tests versus the computed
pump capacity.
32 38

Figure 2.12: 0 BPD traveling valve leakage/plunger slippage.
33 38

34 38

35 38

Figure 2.18: 100 BPD traveling valve leakage/plunger slippage and
full fillage.
36 38

Chapter 3
Closing thoughts
I hope that you enjoyed this brief discussion on dy-
nagraph interpretation, and in particular, how to de-
code 7 perplexing downhole cards. I am certain that
during your career as a lease operator, artifical lift
technician, well weigher, or engineer, you will come
across a number of pump cards that will require some
investigation and thought to determine the existing
conditions at the pump. In fact, you will most likely
come across pump cards that will certainly exceed the
37 38

7 aforementioned cards in complexity and difficultly
in diagnosing.
I want you to remember, in order to understand
what is happening at the pump, you have to think
like the pump.
Think downhole.
If you liked what you read here, please visit my web-
site jeff-dacunha.teachable.com. There you will find
more information on sucker rod pumping design,
analysis, optimization, and training. Also on my web-
site there are additional articles that I have written
about artificial lift, sample well analysis reports, and
a schedule of the different classes that I teach.
–Jeff DaCunha
38 38

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