PNG 491
December 11, 2013
Fall 2013 Final Report
Mitchell Joseph
TABLE OF CONTENTS
Summary.………………………………………………..…………………..2
Objectives ……………………………………………......………………….3
Materials/Programs.………………………………………………………....3
Procedure.………………………………………..……….………………….4
Economic Analysis.………………….…………..……….………………….6
Results & Analysis ………………………………………………………….7
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Summary
To begin this project, possible drilling locations in the Piceance Basin
was analyzed during the previous semester. Using the log data we were
given, we were able to calculate the porosity, saturations, oil and gas in
place, and many other parameters needed to determine the best locations to
drill. Once we found these locations, we were then able to begin working on
the drilling portion of the project. Our team worked together over the 16
weeks of the semester to determine exactly how we should design and build
our wells in the areas we choose.
Objectives
The objectives for our team were to first establish ourselves and
assign positions to each team member. Once we were organized, we began
to look at our problem and determine the best possible solution to solve it.
Our objectives were to calculate the pore pressure and fracture gradient,
design the drilling fluid to be used, design the casing and cement for the
well, and to determine the proper drilling bit and perform a cost analysis on
the well. All of these objectives have been completed and are explained in
detail below.
Materials / Programs
-Microsoft Excel
-Microsoft Word
-MATLAB
-Well Data (Provided by Noble Energy)
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Procedure
First, the pore pressure was calculated using the following equation, along
with data about the stress found online about the Piceance Basin.
Pff = 0.33 x [(σOB / d) + 2 x (σpore / d)]
This was found to be approximately 0.42 psi/ft. The fracture gradient was
also found in this information for the basin and is approximately 0.73 psi/ft.
Next the drilling fluid was calculated using our depths, using the following
equation:
Mud Weight = Pressure x (0.052 x TVD)
Our pressures were also taken at the depths that we determined best. Once
we had the depths, we were able to calculate the casing for each depth and
it’s own casing.
Next, the casing was designed based off of the depths that we calculated for
our wells. These depths were determined using the log data and finding
where the water tables were located. Once these values were obtained, we
were able to use the Drilling Design book to locate the proper diameters for
our well.
After designing the casing we were able to design the cement. First we chose
class G for the cement type, since this class is used for high early strength
properties, which allows cement to be used at high water levels. After that,
the density of the cement was calculated through the upcoming equation:
𝒑= 𝞺∗𝒈∗𝒉
Were 𝒑 is the pore pressure gradient.
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The next step was determining the cement volume that is going to be used in
the design.The cement was designed based off the diameter that were used to
design the casing. First we had to calculate the annular capacity for each
casing section through the following equation:
Ac = (dout2 – din2) / 1029.4 (bbl/ft)
After that and using this equation:
Volume = Ac (bbl/ft) * Depth (ft)
The volume of the cement was determined for each casing individually. And
to get the total cement volume using in this design we added all the casings
volumes together.
The selection of drill bit is extremely important for our analysis. The drill bit
is an important part of the drilling process, because this is what is actually
drilling the hole. Choosing the wrong drill bit can result in setbacks while
drilling. It is important to choose a drill bit based on the rock formations that
you are going to be drilling through. For softer formations it may be
acceptable to use cheaper less durable drill bits. However, in this section of
the Piceance Basin we will be drilling through shale as well as tight
sandstones. Additionally the portion or western Colorado experiences
extreme weather variations. In the winter there can be snow and bitter
temperatures, while in the summer the temperatures and rise above 100
degrees Fahrenheit. This makes it extremely important to choose the right
drill bit that can handle these though conditions. We have chosen to drill
using a Poly Diamond crystal bit. Even through this type of drill bit is much
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more costly than other types of bits, we believe the advantages of this bit
would be worthwhile to justify the added expenses. Poly diamond crystal bit
tend to drill much faster than other types of bits. Additionally this bit works
very well drilling through the type of rocks, which we will encounter.
Furthermore Poly diamond crystal bits tend not to break as often as other
types of bits; this will reduce total operating expenses by reducing the total
time needed to drill to our target depth. Through research we have also
determined that the poly diamond crystal bit has been very effective in
drilling in this portion of western Colorado.
We will be drilling using multi pad drilling, which uses 75% less land.
Multi pad drilling will allow this to be a more economical play to develop.
Additionally, since we will be working in mountainous terrain multi pad
drilling will be much more efficient. Therefore there are limited areas which
a suitable for pad development in this terrain. By using multi pad drilling we
would be able to fully maximize the limited amount of suitable terrain,
which does exist.
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Economic Analysis
The penetration rate will vary throughout the drilling processes,
however we have estimated that throughout the processes we would average
34.4 ft./hr. This was determined based on the averages penetration rates of
Poly diamond crystal bits as well using additional information about drilling
rates from the Piceance Basin. Since we would be drilling 12,000 feet we
have estimated that it will take approximately a total of 14.5 days to drill to
the pay zone. This is assuming everything goes relatively smoothly, and
there are no major complications. If there is technical trouble the total
amount of time to drill to the pay zone can certainly increase.
We have used the following equation to estimate the cost of drilling:
 C= [(R=$916.67)( (t=12 hrs) +(td=350hrs)+Cb]/F
 C= [(R=$1125)( (t=12 hrs) +(td=350hrs)+Cb $25,000]/(F=12,000ft) =
$36.02/ft
Therefore we estimate that the cost to drill one foot is $36.02.
Additionally we believe it will cost approximately $29,652.35 each day,
which we are drilling. This will give a total cost of around $432,331.27 to
drill to our pay zone. Overall this price seems reasonable, although it may be
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on the low side. Unforeseen troubles will certainly caused this cost to
increase while the drilling is actually taking place
Results and Analysis
 Gradients
Pressure Gradient = 0.42 psi/ft.
Fracture Gradient = 0.73 psi/ft.
 Drilling Fluid
Conductor =
13.4 ppg
Surface =
8.76 ppg
Intermediate =
7.58 ppg
Production =
6.16 ppg
 Casing Design
Casing
Diameter
Casing
Pressure
Conductor
23.125 in
20 in
35 psi
Surface
19.2 in
14 in
1100 psi
Intermediate1
3.5 in
11.25 in
2460 psi
Production
9.4 in
8.4 in
4850 psi
 Cement design
Density of the cement = 11.53 ppg
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Casing
cement volume (bbl)
cement volume (ft3)
Conductor
6.5
36.498
Surface
368.9
2071.37
Intermediate1
324.58
1822.52
Production
207.49
1165.07
Total cement volume
907.47
5095.44
 Drilling Bit
Poly-Diamond Crystal Bit