A successful Reinforced Thermoplastic Pipe (RTP) Candidate for Upstream Oil Fields Development
______________________________________________________________________________________
A successful Reinforced Thermoplastic Pipe (RTP) Candidate for Upstream Oil
Fields Development
Abstract
New upstream oil fields developments require fast materials delivery, ease and quick
installation. Upstream Corrosion Control Cost is very prohibitive. Therefore, the need for
corrosion resistant material adding reliability to deliver production fluids is critical.
Moreover, the reliability of flowlines transporting disposed water and oil at Saudi
Aramco requires improvement due to corrosive transported fluids and sever operating
environment. The non-metallic flexible RTP pipe is believed to be a feasible alternative
to the carbon steel (CS) pipe. The CS pipe experiences frequent leakages, coating failures
and high maintenance costs resulting in loss of production and eventually, high
operational costs. Saudi Aramco has successfully field trial tested three non- metallic
flexible Re-enforced Thermoplastic Pipe (RTP) flowlines in upstream oil field of the
Arabian Desert transporting disposed corrosive water to injection wells for more than six
years in service. These operational flexible RTP flowlines showed very reliable and
superior field performance with zero leakages. The life cycle of such operational RTP
Flexible Thermoplastic pipes to date is zero dollars being a cost effective and reliable
candidate. It has been concluded that RTP non-metallic pipe is a potential candidate for
new field development due to its low installation cost, low life cycle cost and reliability.
Consequently, the RTP pipe is a viable replacement to the Carbon steel pipes.
1. RTP Pipe Technology
Reinforced Thermoplastic Pipe (RTP) comprises composite system combining
the flexibility, ease of use, and chemical resistance. The RTP pipe composite
structure shown in figure 1 consists the following: 1) fluid-tight, corrosion resistant
HDPE liner; 2) Fibre reinforcement for strength; and 3) Ambient resistant white
HDPE cover, fully desert climate proof, to protect from UV, abrasion and solar
heating.
Figure 1: RTP Pipe composite structure
1
2- Introduction
Pipe inspection activities detect significant corrosion damage and coating
deterioration exhibited on carbon steel pipes transporting disposed water and
hydrocarbon fluids jeopardising the pipe integrity leading to various failure modes
result in shutdowns with production associated with safety and environmental
effects. Periodic steel pipe inspection and repair work consume considerable
budget and labour intensive. This shortcoming supports the requirement for an
alternative pipe candidate that is corrosion resistant such as the flexible non-
metallic thermoplastic pipe. The introduction of the non-metallic RTP Flexible
pipe in Saudi Aramco upstream oil fields came as a result of the cost of corrosion
associated with the CS pipe and frequent CS pipe leakages. Upstream fields
flowlines leakages and metal loss occur as a result of internal and external
corrosion, coating damage and poor or failure the CP system. Current producing
oil wells experience increasing water cut causing accelerated corrosion damage
to steel pipes leading to frequent CS pipe replacement and high pipe repair
costs. The Hawtah oil producing wells all are artificially lifted using Electric
Submersible Pumps. Hawtah producing wells produce oil with increasingly high
water cuts transported through flow lines with pipe size range from 6” to 12” with
underground and above ground installations. The flowlines transporting the water
required for injection maintaining reservoir pressure are rated class 300# made
from carbon steel API 5LX42 NACE certified. The water injection flowlines are
currently operating at 1450 psig @ 120 F. Pipe leakages occur in the region
between the 3 and 9 o’clock positions after a distance of 40 meters downstream
the GOSPs prevailing throughout the entire pipe length to the injection well. All
the upstream oil transporting flowlines are flowing to a Gas Oil Separation Plant
(GOSP) to separate water and gas from the oil. A typical Saudi Aramco GOSP
facility is shown in figure 2. The separated water is transported through flowlines
to the water injection wells.
Figure 2: Typical Gas Oil Separation Facility (GOSP)
2
Background
Cost of Corrosion Studies in Saudi Aramco operational facilities reported
increasing corrosion costs expenditures resulting from frequent corroded steel
pipe replacements, coating repairs, loss of production due to steel pipe leakages
developed during corrosion process. CS flowlines experience accelerated
corrosion with life cycle replacement after 6 to 8 months of installation and
operation. The study resulted in several recommendations targeting reducing the
upstream flowlines corrosion influence emphasizing on the introduction of the
non-metallic materials due to its superior performance and very low installation
costs assessing fast field development.
Approach of Eliminating Corrosion
Saudi Aramco has acknowledged that implementation of no-corrosion
occurrence is a vital commitment for safe and low cost operations. Consequently,
a non-metallic materials campaign has been formed progressing rapidly. Saudi
Aramco has developed in-house standards and procedures governing
qualifications of installing non-metallic pipelines and fittings, standards and
procedures for repair of non-metallic and standards qualifying operating
conditions.
Water Injection Wells Data
The entire Hawtah field water injection flowlines network represents a total of
length of 192 kilometres with CS pipe sizes of 6”, 8”, 10” and 12” transporting
disposed water from the GOSP to the injection wells. Desert terrain type includes
sand dunes, solid ground and rocky areas. Sand storms and strong winds are
prevailing.
Hawtah Oil Filed RTP Pipe Installation
The field installation started in year 2001 to date with demonstrated superior field
performance of the reinforced thermoplastic pipe (RTP) being a potential
replacement for carbon steel pipes due to their excellent characteristics such as
light weight, ease of installation with no welds required and corrosion free. The
RTP Pipe can be installed/laid down on the ground with no supports
requirements. Figure 3 shows current RTP flowline installations in Hawtah Oil
field transporting high pressure water streams used for injections to maintain
reservoir pressure. The illustrations show that the RTP flowline can be supported
above ground and laid down on the ground with no supports. This is an added
advantage that RTP pipe does not need structural supports except if ground
topography elevation requires. The RTP pipe can be laid down on the ground
with no RTP pipe external corrosion fear contrary to the CS pipe.
3
__________________________________________________________________________________
4
A successful Reinforced Thermoplastic Pipe (RTP) Candidate for Upstream Oil Fields Development
______________________________________________________________________________________
Figure 3: RTP flowline transporting water injection
The RTP flexible pipe operating in Hawtah oil field is very amendable to be
coupled with CS/SS fittings such as flanges, couplers and to CS pipes using
electro-fusion welding process. Figure 4 shows two RTP flexible pipe joints
coupled to each other using CS flanges.
Figure 4: RTP Pipe flange coupling
Figure 5 also shows an RTP pipe coupled to a metal valve via steel flange
coupling indicating the flexibility of coupling the RTP pipe to all kinds of metallic
structures such as valves, flanges and steel pipes.
5
A successful Reinforced Thermoplastic Pipe (RTP) Candidate for Upstream Oil Fields Development
______________________________________________________________________________________
Figure 5: RTP pipe coupled to metal valve through metal flange coupling
Figure 6 shows another metallic flange coupling of the RTP pipe to a CS pipe
indicating the fact that RTP pipe can also be used as a repair section for
corroded CS pipes.
Figure 6: RTP pipe coupling to CS pipe using metallic flange connection
The Hawtah RTP pipe installations are very flexible and include buried pipe
sections and aboveground lay downs sections as shown in figure 7. This
advantage permits easy and negligible cost in performing visual inspection.
Figure 7: RTP Pipe complete joint buried and above ground lay down
Figure 8 shows Hawtah RTP pipe field installation coupling to a CS flange using
electro-fusion welding process where the flange is bolted to a CS flowline ends.
__________________________________________________________________________________
6
A successful Reinforced Thermoplastic Pipe (RTP) Candidate for Upstream Oil Fields Development
______________________________________________________________________________________
Figure 8: RTP Pipe coupled to a CS pipe via flange connection
Figure 9 demonstrates Hawtah RTP pipe field installation with pressure gauge
inline installed indicating flowline operating pressure. The gauge is also hocked
up to a steel fitting coupled through the RTP pipe using electro-fusion process
concluding that the RTP pipe is very attractive to be used in field applications
combining the advantages of CS pipe and non-metallic benefits being corrosion
free equipment.
Figure 9: Pressure gauge in-line installed on a RTP pipe
7
RTP Flowlines Test Results in Hawotah Filed
Table 1 demonstrates RTP flowlines operational in the upstream oil filed of
Hawtah transporting the water injection with flowline data and inspection
background.
Table 1: Hawtah Field RTP Water Injection Flowlines
Pipe Designation A B C
Pipeline Diameter 4 Inches 4 Inches 4 Inches
Pipeline Length 295 meters 1393 meters 270 meters
RTP MAOP Pressure 1305 psi 1305 psi 1305 psi
Operating Pressure 1350 psi 1054 to 1157 psi 1240 psi
Operating Temperature 120 F 120 F 120 F
Liquid Specific Gravity 0.995 0.995 0.995
Pipeline through
3072 BPD 8500 BPD 8500 BPD
Capacity
Installation Date June 2003 June 2003 April 2003
Inspection Date August, 2008 August, 2008 August, 2008
The up-to-date RTP flowlines inspection reports indicated no corrosion or pipe
deterioration after several years of service transporting corrosive oil water.
Corrosion Prevention Technologies
Carbon steel pipes require corrosion protection for continued safe service. Saudi
Aramco invests high cost figures in protecting its CS flowlines from corrosion
attack. Figure 10 shows percentages of various corrosion prevention
technologies employed to all the CS flwolines. These technologies represent
ongoing operational costs and could be avoided of the RTP non-metallic flexible
pipe is used as an alternative to the CS pipe.
Figure 10: Corrosion Prevention Technologies
Life Cycle Costing (LCC)
8
The annual average LCC comparison between CS pipe in oil service and the
flexible RTP pipe is demonstrated in figure 11. The CS pipe has much higher
LCC than the RTP non-metallic pipe.
Comparison of Annual Average Life Cycle Cost for CS & Low
Pressure RTP 6" size Pipes for Oil Service
40
35
30 CS Pipes
25
Cost ( M$ )
20
15
RTP
Pipes
10
0
Above ground with pipe Underground
supports
Figure 11: LCC comparison between CS oil service and RTP pipe
The annual average LCC comparison between CS pipe in water injection and the
flexible RTP pipe is demonstrated in figure 12. The CS pipe has much higher
LCC than the RTP pipe.
9
Figure 12: LCC comparison between CS water injection service and RTP pipe
Comparison of Annual Average Life Cycle Cost for CS & Low
Pressure RTP 6" size Pipes for Water Injection Service
60
50
40 CS Pipes
Cost ( M$ )
30
RTP Pipes
20
10
0
Underground Above ground with pipe
supports
10
Conclusion and Recommendations
Field experience showed that the RTP flexible pipe is has superior performance
and very reliable equipment compared the CS pipe. The three installed
operational RTP pipes flowlines have been in service for at eight years with no
history of failures or ruptures. RTP has a very low operational and life cycle cost
compared to the CS pipe. The RTP pipe is a potential candidate for new field
development due to its superior benefits in terms of low installation cost,
corrosion free, re-usable, easy to transport and extended working life. Saudi
Aramco has been pursuing aggressive efforts and launched a campaign
attracting non-metallic materials, particularly, pipes to Saudi Aramco operational
facilities in order to reduce the increasing cost of corrosion, elevating safety and
operational reliability as a potential alternative to the CS pipes susceptible to
corrosion
11
12
