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You have seen some great technologies and technological innovations here
today. Nail guns are also a great technological innovation. They can
significantly improve a carpenter’s efficiency. However, if you place a nail
gun on a table, nothing happens.
You need a carpenter to use the nail gun to build the house. The carpenter
could use a hammer, but the nail gun is more efficient
Workstations are great technological innovations, they can significantly
improve an interpreter's efficiency. However, if you place a workstation on
a table, nothing happens.
You need a geoscientist to use the workstation to define the subsurface
geology to find oil and gas. They could use paper sections and colored
pencils, but the workstation is more effective.
However, many geoscientists today rely solely on their workstation
to find oil and gas for them. They use the workstation to auto
correlate, to highlight amplitudes, AVO, and attribute anomalies, and
to make their maps and calculate their reserves.
Here is an example of a map made by a geoscientist who relied on the
workstation and not their understanding of geology.
The prospect, seen in this investor presentation found on the SEC
website, is for a fault propagation fold in the Malataya Basin of
Turkey. The map was constructed in the workstation from a grid of 2D
data. The mapped horizon is the blue event highlighted with the arrow.
Based on this map, would you invest in the prospect?
Before you decide to invest, lets look at the Windjammer discovery
in the Rovuma Basin of Mozambique. The Windjammer discovery
was drilled in a fault propagation fold, similar to that seen in our
The Windjammer well encountered three pay zones; one in the
Miocene, a second in the Oligocene, and a third in the Paleocene.
The Miocene and Paleocene pays are stratigraphically trapped. The
Oligocene pays are structurally trapped in the core of a fault
Coming back to our investment opportunity, we can see amplitudes in the
core of the fold in line 1, similar to the Oligocene pays seen in the
With Windjammer as an analog, would you invest?
Since the prospect consists of a fault propagation fold, perhaps we
should look at a fault propagation fold before we decide to invest. This is
a Google Earth image of the Sheep Mountain Anticline, a fault
propagation fold on the flank of the Big Horn Basin.
I have overlain some contours so we can see what the map pattern is for
a fault propagation fold.
Fault Propagation Folds are asymmetric folds. The back limb of the
fold will exhibit a relatively low dip rate that will be constant and
will have the same dip as the fault surface, which for Sheep
Mountain is between 30 and 45 degrees.
The front limb of the fold will exhibit much steeper dip, and may be
overturned . The front limb of the Sheep Mountain Anticline is
almost 80 degrees.
Coming back to our prospect in the Malatay Basin. Look again at the
map. Do you see any dip on the front limb of the fold?
Whatever contouring algorithm the interpreter used, it did not
contour the dip on the front limb of the fold. The map is wrong, and
you should not invest, at least until you have re-contoured the map
and re-calculated the reserves.
There is no question that technology has made our workflow more
efficient. Technology has also made it easier for us to see things in
the data that we could not see before. But has it really improved our
ability to make money?
Let s take a moment and go back in time to see how technology has
impacted our industries success.
We will go back to the early 1980s. In the early 1980 we were pre-
email and pre-internet. Computers were capable of running
spreadsheets but little else.
Workstations at this time consisted of a drafting table, colored pencils
Our number one exploration tool was our ability to think about the
geology we were interpreting.
In the early 1980s geoscientists hand-interpreted their seismic, hand-
correlated their wells and hand contoured their maps, forcing them to
fully understand the geology of their area and their prospect
During that time, the industry average exploration success rate was
just under 25%. In the Gulf of Mexico, it was ~22%.
But in the 1980s, industry began to increasingly use seismic bright
spots to define prospects. Now geoscientists need only to find and
delineate an anomalous amplitude and drill it.
With industry drilling bright spot defined prospects, our exploration
success rate jumped up to just over 25%, in other words, no real
What the industry came to learn is that by focusing on seismic bright
spots to define prospects, we got away from understanding the
geology of our prospects. We also came to learn that bright spots can
be caused by many things other than commercial accumulations of
oil and gas.
In the late 1990s, industry began using Amplitude Versus Offset to
define prospects. AVO is a fluid discriminator, so it can help
differentiate hydrocarbons from water. Now geoscientists need only
to find and delineate an AVO anomaly and drill it.
With industry drilling AVO defined prospects, our exploration
success rate jumped up to approximately 30%, a slight increase, but
hardly the “magic bullet” that many managers had hoped for.
We soon came to learn that AVO anomalies can be caused by many
things other than commercial accumulations of oil and gas. And,
again, by focusing on technology rather than the geology, we drilled
many avoidable dry holes, which is the same mistake we made with
Today, we have seismic inversion and attribute volumes. We have
incredibly robust software that allows interpreters to identify porosity
and anomalous areas and to map leads and prospects at the push of a
So with industry drilling prospects defined by the computer, our
exploration success rate has now jumped up to 30%, in other words,
there has been little to no change in our industry average success rate
I suspect that sooner or later we will come to realize yet again that
focusing on technology rather than the geology will cause us to drill
unnecessary dry holes.
That is because technology does not find oil and gas, interpreters do.
Just as nail guns do not build houses, carpenters do.
For a geoscientist to be successful, we must make accurate reserve
estimates. If we underestimate reserves, then we can cause our
company or investor to not drill potentially economic wells. If we
overestimate reserves, we can cause our company or investor to drill
Less than 15% of the worlds geoscientists are highly successful, that
is, achieve a drilling success rate above the industry average.
Those geoscientists that do have above average drilling success rates
shared 10 habits which are geologic best practices.
In a 2005 talk to the Houston Geologic Society Cindy Yeilding (BP)
posed the question “Are Workstations Killing Geology?” She noted
that our mapping packages allow us to make good looking maps but
they are often inaccurate, and that we make bad maps faster than
ever. She then pointed out that those inaccurate maps cause us to drill
“dumb” wells or unnecessary and avoidable dry holes.
She posed several additional questions including regarding our over-
reliance on the workstation:
Are all geologic views best displayed on a 20” monitor? (NO)
Do we spend too much time displaying our interpretation than
thinking about it? (YES)
Is the philosophy of seismic to simulator flawed? (Absolutely)
Moreover, many geoscientists are relying more on the workstation
that their own skills and geologic knowledge. Many interpreters
today have never hand-contoured a map or made a cross section, nor
are they aware of the proper methods or structural models necessary
to make valid interpretations. Increased reliance on auto-picking for
interpretations delegates the interpretation to the computer.
The reason workstations cause dry holes is that as interpreters
become more dependent on the technology they are losing their
geologic skills. We are observing that the workstations are doing to
geologic skills what the calculator has done to math skills
So just how bad are our math skills?
Just how bad was demonstrated when a group of high school students
were given calculators programmed to give wrong answers for use in
a simple math test.
Almost all of the students turned in tests with all wrong answers,
mostly quite obviously wrong. The students were asked if they
noticed anything wrong? There answer was yes, but since the
calculator said this was the answer, that it must be, even though they
‘felt’ that the answer was wrong.
Our comfort with the workstation has made us complacent, and we
now tend to accept what comes out of the workstation without
question, even when it is wrong.
So it is important for interpreters to use the workstations as a tool to
interpret the data. For those of you who rely on the workstation to interpret
the data, you need to be aware of how the computer sees the data
When geoscientists look at this line, they should see a rift basin with
some minor inversion. As a geoscientist, you can develop a
familiarity with rift basins which you can use to predict where the
source rocks were deposited, where the reservoirs were deposited,
and where hydrocarbons will migrate
When a computer looks at this line, it sees digits, So a computer can
not make geologic interpretations, it makes statistical correlations. A
computer cannot develop a familiarity with rift basins nor can it
Before a carpenter builds a house with a nail gun, he needs to know what a house
looks like and he should know how to build it if he only had a hammer
Likewise, before a geoscientist uses a workstations to interpret a prospect,
they should know the geology of the area that they are interpreting. They
should also know all of the methods and techniques needed to fully
evaluate the subsurface and to make accurate maps.
Lets look at a case study where reserves were added to a field simply
by the construction of a geologic cross section.
The 9300 Foot Sand in a field producing from multiple reservoirs was an
under-producing reservoir. The 9300 Foot Sand was completed in well #10
and produced about 12,000 BO. The well was estimated to have been able to
produce over 500,000 BO. Well #4 produced gas and rapidly pressure
The 9300 Foot Sand was abandoned for several years until a new study of the
field has done. It was recognized that based on this map that there was a
material balance problem for the 9300 Foot Sand.
It was also recognized by the young geologist doing the study that no cross
section had been constructed for this reservoir.
In doing the new study the geologist constructed a correlation cross
section to study the reservoir in greater detail. You can see that wells 3
and 4 encounter a thick channel sand. Wells 7 and 10 encounter overbank
or crevasse splay deposits The low production from well 10 was from the
crevasse splay sands.
The gas production was from the transgressive sand capping the
sequences. The main channel sand had not been produced.
Now that the review team had a new depositional model, they constructed a Log
Facies map from the regional wells. We can see from that map that the field was
situated in one branch of the channel system
The review team then constructed a net pay isochore for the channel sand and
recognized two possible channels in the field, one in the central portion of the field, and
another on the western margin of the field.
The team then constructed a net pay isochore for the channel sand. The volume potential
in the western branch of the channel were too small to develop.
The central channel was determined to have approximately 4 million barrels of
recoverable reserves remaining. Well 4 was re-completed in the channel sand and found
That example is not the only example of finding additional
reserves by constructing a cross section.
In this case, the operator had produced this field for a number of
years, recovering ~ 1.5 MMBO from the oil rim. They were now
ready to blow down the gas cap.
Before granting the operator approval to blow down the gas cap, the
regulatory agency wanted proof that the oil rim had been fully
In compliance with the regulatory agency's request, the operator
conducted a complete geological study of the reservoir, including
construction of a correlation cross section
The correlation Cross section showed that there was a thick incised valley sand
in wells 12, 17, and 3. Wells 12 and 17 were in the gas cap and well 3 was
below the water level
Incised valley sequences are rarely in communication with the sequence they
incise so it was considered unlikely that this incised valley sequence had been
The review team developed 2 different incised valley interpretations. With interpretation
1, the incised valley crossed the field from northeast to southwest and had a volume
potential of 3.5 MMBO
Two locations were proposed for testing this interpretation. If the first well
encountered the incised valley, they would drill the second proposed well.
In the second interpretation, the incised valley missed the oil rim. However, the re-
mapping showed that there was an additional volume potential of 1.5 MMBO remaining
in the oil rim. If the first well did not encounter the incised valley sequence then they
would not drill the second of the two proposed wells.
The first of the two proposed wells encountered the incised valley sand as
predicted in interpretation 1, so the second proposed well was drilled The
incised valley sequence was found to be thicker than originally thought such
that the final reserve add was 4.5MMBO
If you are not constructing cross sections you do not understand the
distribution of the fluids or the nature of the reservoir. If you do not
understand those, you are most likely leaving reserves behind.
Looking at this cross section, one can see that in the uppermost sand
of the eastern fault block the perforations (purple rectangles near the
depth track) are near the water level, leaving significant attic
The time to construct a cross section and interpret varies from a few hours to
a few days, depending on how complex the geology is. Finding additional
reserves with that cross section is priceless.
We will look at another best practice, constructing a fault surface
map and integrating that map with the horizon map to define the fault
traces in their proper position
This field has been producing for several years, at which time the
company sold the field along with several other assets. The field,
mapped with 3D seismic and well control, consists of a three-way
fault closure against a large growth fault. In addition to the producing
fault block, a prospective fault block had been identified and mapped
to the north of the producing fault block.
The original interpreters had not made a fault surface map. They had
simply picked faults on the seismic and posted a fault polygon.
Since the original operator had never made a fault surface map, one
of the first things the new operator did following the purchase of the
field was to construct a fault surface map and integrate it with the
The fault surface map was constructed from the 3D data as well as
the fault picks in the wells. The data posted by the wells is the
amount of missing section (Vertical Separation) observed in the wells
and the depth of the fault.
When the producing horizon was integrated with the fault surface
map, the position of the fault traces shifted to the east, opening up
approximately 400 acres of additional closure; adding almost 20
BCF of recoverable reserves.
In addition to finding additional reserves by constructing fault
surface maps, we can also use them to avoid drilling dry holes.
Here is a structure contour map generated with 2D seismic. Is it geometrically valid?
Since we are dealing with a 2 dimensional map that is portraying a 3 dimensional
surface, it takes more understanding, investigation, and analysis to identify geometric
The prospect was drilled and the result was a dry hole Let’s examine the trapping fault:
The amount of offset along the trapping fault decreases from east to west. The offset
then increases again but the sense of throw is to the north, or up-thrown direction. There
is almost no offset at the well location
This is a screw fault. Screw faults CANNOT occur in compressional or extensional
faults (Scissors fault can occur with strike-slip faults). Therefore, the map portrays a
structure that is geometrically, and geologically, impossible.
We call fault interpretations like this “Screw Faults” since the change in the
direction of the direction of offset of the fault makes it appear as if the fault is
screwing itself through the section. We also call the screw faults because if you drill
a well in a prospect set up by a screw fault, you are screwed.
Screw Faults indicate 2 faults have been mapped as 1 fault. This is a result of the
interpreters picking fault sticks and using them to post a fault polygon as opposed
to mapping the fault.
The failure to map the fault surface results in the company drilling an unnecessary
and avoidable dry hole.
Screw fault interpretations are very common in our industry. So common
that we can see a screw fault in the Petrel User Manual.
If the interpreter had constructed a fault surface map it would have
been immediately apparent that the interpretation of the fault as a
single fault was geometrically and geologically impossible.
A fault surface map takes only a few hours to construct. The failure
to map the fault surface cost this company $5.5 million dollars.
Technology makes our workflow much more efficient. And, it can
help us to find and better develop oil and gas.
But ONLY, if we use it as a tool to help us understand the geology of
our prospects and fields.
If we use technology to replace our thinking and our knowledge of
the petroleum system, we will continue to drill unnecessary and
avoidable dry holes.
For no matter how robust technology becomes, oil is first found in
the mind. Technology is nothing more than a tool to help the mind
And nail guns are just a tool to help carpenters build houses