2. PILE DRIVEABILITY ANALYSIS REPORT
TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................................. 4
1.1 GENERAL PROJECT DESCRIPTION ................................................................... 4
1.2 LOCATION ............................................................................................................. 4
1.3 FIELD DEVELOPMENT ........................................................................................ 5
1.4 SCOPE OF WORK .................................................................................................. 5
1.5 SYSTEM OF UNITS ............................................................................................... 6
1.6 SOFTWARES .......................................................................................................... 6
1.7 ANALYSIS PROCEDURE ...................................................................................... 6
1.8 ANALYSIS RESULTS ............................................................................................ 7
2.0 REFERENCES ....................................................................................................... 8
2.1 PROJECT SPECIFICATIONS AND REPORTS ...................................................... 8
2.2 CODES AND STANDARDS ................................................................................... 8
3.0 PILE DRIVEABILITY ANALYSIS...................................................................... 9
3.1 DESCRIPTION OF DRIVEABILITY ANALYSIS .................................................. 9
3.2 LIMITATION OF PILE STRESS ............................................................................ 9
3.3 SOIL RESISTANCE TO DRIVING......................................................................... 9
3.4 HAMMER DATA.................................................................................................. 10
3.5 WAVE AND CURRENT LOAD ........................................................................... 11
3.6 SOIL PROPERTIES .............................................................................................. 11
3.7 RESULTS OF DRIVEABILITY ANALYSIS ........................................................ 12
4.0 PILE MAKE-UP DESIGN................................................................................... 14
4.1 PILE UP-ENDING................................................................................................. 14
4.2 PILE STICK-UP .................................................................................................... 14
APPENDIX A: TL PLEM PILE DRIVEABILITY ANALYSIS RESULTS…………..…....16
APPENDIX B: DD PLEM PILE DRIVEABILITY ANALYSIS RESULTS………….……33
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3. PILE DRIVEABILITY ANALYSIS REPORT
TABLE OF FIGURES
Figure 1.1: Thang Long – Dong Do Field…………………………………………………………..….4
Figure 1.2: Development Schematic…………………………………………………………………..5
Figure 1.3: Pile and Soil Model for Stress Wave Analysis …………………………………...……….6
TABLE OF TABLES
Table 1.1: Summary of TL Pile Driveability and Stick-up Analysis ………………….……………….7
Table 1.2: Summary of DD Pile Driveability and Stick-up Analysis ………………………………….7
Table 3.1: Hammer data used in the analysis .……………………………………………...…………11
Table 3.2: Wave and Current Parameters ……………………………………………………………..11
Table 3.3: Soil profile input for Wave equation analysis ………………………………………...…...11
Table 3.4: Soil dynamic properties for wave equation analysis ………………………..…………..…12
Table 3.5: Pile Drivability Result Summary for TL PLEM …………………………….……………..12
Table 3.6: Pile Drivability Result Summary for DD PLEM …………………………………….…….13
Table 3.7: Pile Self-penetration ………………………………………………………………………..13
Table 4.1: Pile Stress Unity Check ………………………………………….………………………....14
Table 4.2: TP PLEM Pile Stick Up Length & Combined Static and Dynamic UC …………………...15
Table 4.3: DD PLEM Pile Stick Up Length & Combined Static and Dynamic UC ………..…………15
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4. PILE DRIVEABILITY ANALYSIS REPORT
1.0 INTRODUCTION
1.1 GENERAL PROJECT DESCRIPTION
Lam Son JOC was established following a Petroleum Contract being signed between
Petro Vietnam (50%) and Petronas Carigali Overseas Sdn. Bhd. (50%) on 7th January
2003, providing for Lam Son JOC to conduct petroleum exploration within Blocks
01/97 & 02/97 which are the relinquishments of a Petroleum Sharing Contract (PSC)
for Blocks 01 & 02 signed in September 1991 between Petronas Carigali Overseas
Sdn. Bhd. (85%) and Petro Vietnam (15%).
1.2 LOCATION
Thang Long is geographically located in the south-western part of Block 01/97 &
02/97 in the Cuu Long basin (see Figure 1.1) approximately 120 km east of Vung
Tau, 26 km south of Ruby field and 35 km northeast of Su Tu Vang Field. The oil
was discovered by 02/97-TL-1X well (June, 2004) in the Lower Miocene and Lower
Oligocene sandstones. Dong Do is approximately located 5 km southeast of Thang
Long. The oil was discovered by 02/97-DD-1X (May, 2007). Water depths across the
block range from 60m to 70m. There were total 06 wells drilled in Thang Long -
Dong Do field.
Figure 1.1: Thang Long - Dong Do Field
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5. PILE DRIVEABILITY ANALYSIS REPORT
1.3 FIELD DEVELOPMENT
The development plan calls for a central processing facility located on an FPSO with
production from the two fields via dry trees only. As such two wellhead platforms will
be tied back; one located on Thang Long the other on Dong Do delivering full well
stream transfer to the FPSO as shown in Figure 1.2.
Figure 1.2: Development Schematic
The FPSO will be located 2.84 km from the Thang Long WHP and 2.0 km from Dong
Do WHP.
Unprocessed fluids from the wellhead platforms will be transferred to the FPSO where
the crude will be dewatered and stabilized to meet a tanker loading specification.
Associated gas will be used to provide fuel for the FPSO and lift gas for Thang Long
and Dong Do wells with the balance exported to a near-by gas export pipeline.
Produced water will be treated prior to discharge overboard.
1.4 SCOPE OF WORK
This report documents the results of the TL PLEM and DD PLEM pile drivability and
pile stick-up analyses. The scope covers the followings:
• Skirt pile installation feasibility study.
• Perform pile driveability study based on lower bound and upper bound SRD values
extracted from final Geotechnical report.
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6. PILE DRIVEABILITY ANALYSIS REPORT
• Asses the performance viability of hydraulic hammers IHC S-400 for piling.
• Perform pile stick-up analysis to check the pile stresses during hammer placement.
• Recommend piling sequence to the target depth
1.5 SYSTEM OF UNITS
The System International of Units (SI units) shall be used in all design, engineering
document and drawings. Where standard equipment is supplied with Imperial Units,
the Imperial Units shall be shown on the drawings with Metric equivalent in brackets.
1.6 SOFTWARES
The Pile driveability analyses for TL PLEM and DD PLEM are performed with GRL-
WEAP and SACs computer programs.
1.7 ANALYSIS PROCEDURE
1. Performing the pile driveability analysis base on the stress wave equation model as
the figure bellow:
Figure 1.3: Pile and Soil Model for Stress Wave Analysis
2. Determining the parameters are follow:
- Blow count versus depth of penetration for the given soil properties and
particular hammer type.
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7. PILE DRIVEABILITY ANALYSIS REPORT
- SRD versus blow count relationship for the given soil properties and particular
hammer type.
- Self-weight penetration and any incremental penetration upon placement of
hammer.
- Maximum dynamic stresses during continuous driving.
3. Pile strength code checking for pile stick-up and pile driving condition in
accordance with API RP 2A.
1.8 ANALYSIS RESULTS
1.8.1 Summary of Analysis results
The summary of pile driveability and stick-up analysis results for TL and DD PLEM
are shown in the table 1.1 and 1.2 bellow:
Table 1.1: Summary of TL Pile Driveability and Stick-up Analysis
Pile Stick-up Maximum Max
Hammer
Case length length Blown Combine Conclusion
Type
(m) (m) count/m UC
TL
PLEM 19 14 IHC S-500 6.7 0.44 Acceptable
Pile
Table 1.2: Summary of DD Pile Driveability and Stick-up Analysis
Pile Stick-up Maximum Max
length Hammer
Case length Blown Combine Conclusion
Type
(m) (m) count/m UC
DD
PLEM 21 16 IHC S-500 7.9 0.45 Acceptable
Pile
1.8.2 Conclusion
1. The hammer IHC S-500 is satisfied the driving capacity for TL PLEM pile and DD
PLEM pile.
2. The piles are satisfied the strength of material for the stick-up condition and the
driving condition.
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8. PILE DRIVEABILITY ANALYSIS REPORT
2.0 REFERENCES
2.1 PROJECT SPECIFICATIONS AND REPORTS
1. TLDD-0003-4JAW-A01-0001, “PLEM Design Basis”
2. TLDD-0003-4JAW-A07-0001, “PLEM Foundation Design”.
3. TLDD-0003-4JAW-A07-0003, “PLEM In-place Analysis Report”.
4. Metocean Criterial Study, Block 01/97 and 02/97, Viet Nam – Fugro Global
Environmental and Ocean Sciences, October, Number C50631/5751/R1, February,
17th, 2010.
5. Geotechnical Investigation report for BH-DD WHP, DONG DO LOCATION
OFFSHORE VIET NAM” – No AGSB/116/SI/09/SGN(B) – Asiangeos, October,
23rd, 2009
2.2 CODES AND STANDARDS
2.2.1. American Institute of Steel Construction (AISC)
• “Specification for Structural Steel Buildings - Allowable Stress Design and Plastic
Design”.
2.2.2. American Petroleum Institute (API)
• RP 2A-WSD, "Recommended Practice for Planning, Designing and Constructing
Fixed Offshore Platforms - Working Stress Design”. Errata and Supplement 3
October 2007.
• RP 17 A, “Recommended Practice for Design and Operation of Subsea Production
System”, second edition, December 1996.
2.2.3. Des Norske Veritas (DNV)
• RP – C204, “Design Against Accidental Loads”, October 2010.
• OS – C101, “Design of Steel structures general (LRFD method)”, October 2008.
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9. PILE DRIVEABILITY ANALYSIS REPORT
3.0 PILE DRIVEABILITY ANALYSIS
Pile drivability analysis has been carried out using the GRLWEAP program based on
the wave equation analysis concept with the soil data of the geo-technical report
“Geotechnical Investigation report for BH-DD WHP, DONG DO LOCATION
OFFSHORE VIET NAM” – No AGSB/116/SI/09/SGN(B).
3.1 DESCRIPTION OF DRIVEABILITY ANALYSIS
Pile drivability analysis employing wave equation is used to compute the pile driving
stresses and to predict blow counts based on soil resistance to driving, quake, soil
damping, pile section and segment length, hammer properties (driving rated energy,
hammer efficiency).
In wave equation analysis, pile is subdivided into segments of approximately 1.0m in
length. In order to cover the variety of soil resistances, various Soil Resistance to
Driving (SRD) is input for investigation of anticipated driving (dynamic) stresses
acting throughout the entire pile length.
3.2 LIMITATION OF PILE STRESS
Limitation of pile stresses during pile driving of a free standing pile is in accordance
with API RP 2A WSD:
• The combination of stresses due to the dynamic impact of hammer and dead load
of hammer and pile shall not exceed the yield stress of the material.
• The maximum dynamic stresses shall not exceed 90 percent of the yield stresses.
• Pile refusal is considered when blow count exceeds 300 blows/ft (1000 blows/m)
for consecutive five feet (1.5m) as per API RP2A clause 12.5.6.
3.3 SOIL RESISTANCE TO DRIVING
Skirt Pile drivability analysis is carried out to ensure the pile drivability
performance, despite for pile make up verifications and as guidelines for pile
installation. The analysis is not intentionally aimed to predict the blow counts
accurately.
In this one dimensional wave equation analysis, the driving stresses and predicted
blow counts are governed by the input SRD values taken from the geotechnical
report.
The static soil resistances can be estimated based on the followings:
• API static soil capacity for unplugged condition = ∑ (Fsr A0 ) + ∑ (Fsr Ai ) + q c Aup
• API static soil capacity for plugged condition = ∑ (Fsr A0 ) + q c A p
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10. PILE DRIVEABILITY ANALYSIS REPORT
Where,
Fsr = Unit skin friction calculated based on remolded shear strength
qc = Toe resistance at the pile tip
Ao = Outer pile shaft area
Ai = Inner pile shaft area
Ap = Plugged pile end bearing area
Aup = Unplugged pile end bearing area
The estimated SRD for continuous driving and soil set-up cases for either plugged or
unplugged pile can be taken as per PLEM Design Basis, Document No.: TLDD-
0003-4JAW-A01-0001.
Three (3) pile driving cases are considered in the analysis described as follows,
a) Continues driving case
Estimated SRD equals to 0.6 API static capacity.
b) Soil set up case - Lower Bound case
Assuming restart condition up to 12 hour delay, the estimated SRD is 0.9 API static
capacity.
c) Soil set up case - Upper Bound case
Assuming the delays of few days, the estimated SRD is taken equal to API static
capacity.
The skin friction on the inside wall of the piles is considered for the continuous
driving condition as per point a) above. The end bearing component of driving
resistance is assumed to be less than static end bearing as recommended in PLEM
Design Basis and assumed to be acting on the annular tip area.
After delays depending on the delay duration, the internal friction is assumed to
result in plugged driving, hence plugged condition is considered for the restart
condition. The end bearing component of driving resistance is assumed to be equal
to or less than static end bearing and assumed to be acting on the gross tip area in
accordance PLEM Design Basis..
3.4 HAMMER DATA
The list of hammers and their properties have been tabulated in the below table 3.1:
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11. PILE DRIVEABILITY ANALYSIS REPORT
Table 3.1: Hammer Data used in the Analysis
Rated Ram Strole Hammer
Hammer length Efficiency
Energy weight
Type
(kJ) (kN) (m) (%)
IHC S-500 496.544 246.085 2.018 95
3.5 WAVE AND CURRENT LOAD
Wave and current forces act on the pile have been considered as per PLEM Design
Basis [Ref.1]. No reduction due to wave kinematics and current blockage is
considered. The installation sea state considered for the analysis is:
Table 3.2: Wave and Current Parameters
Wave height Wave period Current Velocity
(m) (s) (m/s)
3 6 0.5
3.6 SOIL PROPERTIES
Soil properties used for the wave equation analysis in the GRLWEAP program are
tabulated in the table 3.3 and 3.4 bellow:
Table 3.3: Soil Profile Input for Wave Equation Analysis
Unit Skin Unit End
Soil depth (m)
Layer Soil type Friction (kPa) Bearing (kPa)
From To Top Bottom Top Bottom
Loose to medium
1 0 2.6 0 4.7 0 180
dense silty sand
2 2.6 4.6 Stiff Clayey silt 23.4 27.5 540 540
Medium dense sandy
3 4.6 6.6 12.3 18.1 510 750
silt
4 6.6 11.6 Stiff Clayey silt 37.5 47.1 720 720
5 11.6 30 Stiff Silty Clay 47.1 75.1 720 720
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12. PILE DRIVEABILITY ANALYSIS REPORT
Table 3.4: Soil Dynamic Properties for Wave Equation Analysis
Parameters Clay Sand
Side Quake (mm) 2.5 2.5
Point Quake (mm) 2.5 2.5
Side Damping (m/s) 0.33 0.16
Point Damping (m/s) 0.5 0.5
3.7 RESULTS OF DRIVEABILITY ANALYSIS
For the driveability assessment, two criteria are evaluated to determine the selection
of the hammer for the pile installation as below:
• Maximum pile dynamic stress during driving
• Pile refusal
3.7.1 Pile Driveability Analysis Results
The wave equation analysis for the PLEM Pile - Combination Lower Bound, Upper
Bound Condition and Continuous Condition for the selected hammer IHC S-400
performed.
The material used for piles in this project is the high tensile steel (type II) with a
minimum yield stress (Fy) of 345 MPa. The dynamic axial stress due to the driving
is limited to 0.9Fy according to the API RP 2A.
The results is tabulated in Table 3.5 and Table 3.6. For detailed results, refer to the
GRLWEAP output files.
Table 3.5: Pile Drivability Result Summary for TL PLEM
Maximum
Maximum
Target blow count/m Allowable
Dynamic Unity
Condition penetration to target Stress
Stress check
depth (m) penetration (Mpa)
depth (Mpa)
Continuous Plug 13 3.9 118.7 310.5 0.382
Driving Unplug 13 2.5 120.4 310.5 0.388
Set up Plug 13 6.7 111.4 310.5 0.359
Lower
bound Unplug 13 3.4 122 310.5 0.393
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13. PILE DRIVEABILITY ANALYSIS REPORT
Maximum
Maximum
Target blow count/m Allowable
Dynamic Unity
Condition penetration to target Stress
Stress check
depth (m) penetration (Mpa)
(Mpa)
depth
Set up Plug 13 6.4 119.4 310.5 0.385
Upper
bound Unplug 13 3.7 121.4 310.5 0.39
Table 3.6: Pile Drivability Result Summary for DD PLEM
Maximum
Maximum
Target blow count/m Allowable
Dynamic Unity
Condition penetration to target Stress
Stress check
depth (m) penetration (Mpa)
depth (Mpa)
Continuous Plug 15 8.2 122.1 310.5 0.393
Driving Unplug 15 5 121.4 310.5 0.391
Set up Lower Plug 15 7.9 120 310.5 0.386
bound Unplug 15 4.2 124.6 310.5 0.4
Set up Upper Plug 15 8.6 125.3 310.5 0.41
bound Unplug 15 4.7 124.6 310.5 0.4
3.7.2 Estimate Self-penetration
From the soil properties provided, the estimated self penetration of the piles with
respective pile self weight and hammer weight are calculated. The calculation for the
pile self weight and the self penetration estimation is present in Appendix A1 and
B1. The summary of the self penetration calculation results are tabulated in table 3.7
bellow:
Table 3.7: Pile Self-penetration
Minimum
Description Hammer
Self-penetration (m)
TL PLEM Pile IHC S-500 5.5
DD PLEM Pile IHC S-500 5.2
Note: The estimated self weight includes the pile weight, hammer and pile helmet.
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14. PILE DRIVEABILITY ANALYSIS REPORT
4.0 PILE MAKE-UP DESIGN
4.1 PILE UP-ENDING
The calculation results are shown in the report TLDD-0003-4JAW-A07-0001
“PLEM Foundation Design” – Section 4.5.
4.2 PILE STICK-UP
The maximum pile stick up length at different installation stages is calculated to
ensure that the acting stresses are within the allowable stress limit during stick-up
above the pile guide. The maximum permissible stick-up length along with pile self-
penetration with and without the hammer system is used to predict stickup length
from the skirt pile guide.
During pile driving operation, the following stress check applies for pile stickup
section:
• Static stresses are compared with allowable stresses as per API-RP-2A.
• Combined stresses = (Static Stresses + Dynamic Stresses)
Table 4.1: Pile Stress Unity Check
Stress Unity Allowable Stress
Stress
check
Static
Dynamic fd/0.9Fy 0.9Fy
Static +
Dynamic Fy
The pile stick up static analysis subject to installation wave and current using SACS
package program provides member stress unity check. The analysis results are
attached in Appendix A2 and B2.
The pile stick up dynamic analysis due to hammer impact energy is calculated using
GLRWEAP to obtain pile dynamic stress. The analysis results are attached in
Appendix A3 and B3.
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