Curtin University
Department of Petroleum Engineering
Fundamentals of Reservoir Engineering
PEEN6004Assignment 1
PEEN6004- Fundamentals of Reservoir Engineering Chapter 2 – Basic Concepts in Reservoir Engineering
Important note: · All the students are to answer ALL questions. Question 1.1
The vertical exploration well Genesis-1 was drilled to a total depth of 12,500 ft offshore in the Canning Basin. During drilling no gas was found to be present in the mud but oil florescence was seen in the drill cuttings.
Prior to running the 9 5/8 inch casing string it was decided to run the modular dynamic tester (MDT) in the open hole over the sand body to help confirm the fluids present in the reservoir identified earlier from well logs.
The data obtained from the MDT survey is provided in Table 1. The data was measured “Relative to Kelly Bushing” (RKB) which was 75 ft above the mean sea level (MSL).
You are required to carry out the following. Remember, your answers should be in Field Units.
1. Identify the fluid contacts present (if any) across the formation, with depths referenced to a sub-sea (SS) datum. 50%
2. Calculate the various fluid gradients and densities.40%
3. Comment on the hydrostatic pressure regime of the reservoir.10%
Depth
Formation
(RKB)
(metres)
Pressure
(psia)
3,523
4,973.0
3,528
4,974.3
3,529
4,974.6
3,530
4,974.8
3,531
4,975.1
3,532
4,975.4
3,536
4,978.3
3,540
4,982.9
3,543
4,986.3
3,546
4,989.8
3,549
4,993.2
3,556
5,002.8
3,560
5,008.5
3,570
5,023.0
3,572
5,025.9
3,586
5,046.1
Table 1. MDT survey data
Question 1.2
An offshore exploration well was drilled 100km North of Rottnest Island, in 100ft water depth, to a total depth of 3,200 ftSS. The well was logged, cased and perforated across the interval of 2,700 to 2,780 ftSS. The well produced quite steadily 1,000 barrels of oil at a water cut of 5% and a constant GOR of 300 scf/stb over a period of 8 hours.
From well logs it has been confirmed that the oil water contact is at 2,800 ftSS. An MDT survey was performed across the formation; however, only two pressure measurements were made due to tool problems.
Depth
(ftSS)
Pressure
(psia)
Temperature
(oF)
2,450
1,184
100
2,700
1,225
100
Specific gravity of the gas produced was 0.7 relative to air at 14.7psia and 60oF and the gas deviation factor is nearly constant at 0.825 across the pressure interval of 1,150 to 1,200psia. Reservoir water was tested at surface and the density was found to be 65.40lb/ft3 with a formation volume factor of 1.022. API gravity of stock tank oil is 25.
You are required to
1. Identify the gas oil contact. 70%
2. Estimate the height of the oil column. 30%Question 1.3
Analyse the reservoir production data in Table 1 and then:
· Calculate the Stock Tank Oil Initially in Place (STOIIP) from the geologist’s volumetric estimate given in Table 2. 20%
· Identify the drive mechanism(s) occurring during production. 45%
· Estimate the .
Curtin UniversityDepartment of Petroleum EngineeringFundam.docx
1. Curtin University
Department of Petroleum Engineering
Fundamentals of Reservoir Engineering
PEEN6004Assignment 1
PEEN6004- Fundamentals of Reservoir Engineering Chapter 2 –
Basic Concepts in Reservoir Engineering
Important note: · All the students are to answer ALL questions.
Question 1.1
The vertical exploration well Genesis-1 was drilled to a total
depth of 12,500 ft offshore in the Canning Basin. During
drilling no gas was found to be present in the mud but oil
florescence was seen in the drill cuttings.
Prior to running the 9 5/8 inch casing string it was decided to
run the modular dynamic tester (MDT) in the open hole over the
sand body to help confirm the fluids present in the reservoir
identified earlier from well logs.
The data obtained from the MDT survey is provided in Table 1.
The data was measured “Relative to Kelly Bushing” (RKB)
which was 75 ft above the mean sea level (MSL).
You are required to carry out the following. Remember, your
answers should be in Field Units.
1. Identify the fluid contacts present (if any) across the
formation, with depths referenced to a sub-sea (SS) datum. 50%
2. Calculate the various fluid gradients and densities.40%
3. Comment on the hydrostatic pressure regime of the
3. 5,025.9
3,586
5,046.1
Table 1. MDT survey data
Question 1.2
An offshore exploration well was drilled 100km North of
Rottnest Island, in 100ft water depth, to a total depth of 3,200
ftSS. The well was logged, cased and perforated across the
interval of 2,700 to 2,780 ftSS. The well produced quite steadily
1,000 barrels of oil at a water cut of 5% and a constant GOR of
300 scf/stb over a period of 8 hours.
From well logs it has been confirmed that the oil water contact
is at 2,800 ftSS. An MDT survey was performed across the
formation; however, only two pressure measurements were
made due to tool problems.
Depth
(ftSS)
Pressure
(psia)
Temperature
(oF)
2,450
1,184
100
2,700
1,225
100
Specific gravity of the gas produced was 0.7 relative to air at
14.7psia and 60oF and the gas deviation factor is nearly
constant at 0.825 across the pressure interval of 1,150 to
1,200psia. Reservoir water was tested at surface and the density
4. was found to be 65.40lb/ft3 with a formation volume factor of
1.022. API gravity of stock tank oil is 25.
You are required to
1. Identify the gas oil contact. 70%
2. Estimate the height of the oil column. 30%Question 1.3
Analyse the reservoir production data in Table 1 and then:
· Calculate the Stock Tank Oil Initially in Place (STOIIP) from
the geologist’s volumetric estimate given in Table 2. 20%
· Identify the drive mechanism(s) occurring during production.
45%
· Estimate the bubble point pressure and Rsi and determine
whether the reservoir is saturated or undersaturated. 25
· Calculate the recovery factor and comment on whether this
value is typical of the drive mechanism interpreted from the
production data. 10%
Time
Average Reservoir Pressure
Oil Rate
Water Rate
Gas Rate
Cumulative
Oil Production
Water Production
Gas Production
(days)
(psia)
(stb/d)
(bbl/d)
9. Table 2. Volumetric Data
Question 1.4
Emerald oil field has been discovered 50 km off the shoreline in
the North-West Shelf of Western Australia in a water depth of
100 meters. Initial seismic interpretations have revealed that the
reservoir is divided into two sections by a fault (Figure 1). In
the first month of discovery Well A was drilled into the western
flank of the structure but no traces of hydrocarbon were found.
After further seismic data analysis it was decided to drill a
second well (Well B) into the other side of the fault (eastern
flank). From the mud-log analysis and well log interpretations it
has been revealed the structure on the east side of fault contains
commercially producible volumes of oil and gas. Therefore it is
believed that the fault running through the structure is a sealing
fault.
Figure 1 (figures are for illustration purposes only and not to
scale)
While drilling Well A, a single pressure measurement was
performed. At depth of 5,500 ftss the pressure was measured to
be 2,534.7 psia. From the well logs run in Well B, OWC has
been detected to be at 5,700 ftss. Two further pressure data
were also recorded in Well B (Table 1)
Depth (ftss)
Pressure (psia)
4,575.00
2,330.27
4,675.00
2,336.95
Table 1
From the PVT analysis performed on the fluid samples taken
from both wells the following data were obtained:
10. Bo
1.25
rb/stb
Rs
1,000
scf/stb
Bw
1.02
rb/stb
Gas expansion factor (E)
180
scf/rcf
Gas specific gravity (surface conditions)
0.7
Oil specific gravity (surface conditions)
0.8
Water surface density
64.63
lb/ft3
Table 2
a. Identify the gas-oil contact (GOC)? 80%
b. A well test program performed on Well B produced oil with a
constant flowrate of 7,000 stb/d and a corresponding gas
flowrate of 10 MMscf/d. Calculate the production GOR? Then
based on the GOR value you just calculated and with the
knowledge that the aquifer support for the reservoir is
considered to be weak, what advice you would have for the
production engineer to help him/her to prevent fast decline in
reservoir pressure? 20%
Notes:
· Assume there is perfect regional aquifer connectivity.
· Both drilled wells were vertical.
11. Top view of the structure
Cross section A-A
Fault
N
Well B
Well A
A
A
Well B
