УДК 662.6.035.6
M.D.Ryssakova, J. Lee
Kazakh-British
Technical University, Almaty, Kazakhstan
madinarysakova@gmail.com
PROCESSING AND TRANSPORTATION DESIGN OPTIONS FOR
KALAMKAS-SEA OFFSHORE OILFIELD
Abstract: The
purpose of this paper is to review the main processing options available for
aKalamkas-Sea offshore oil field production facility, including comparisons,
availability of infrastructure, environmental and technical major factors
affecting safety.
Key words:
Offshore processing, multiphase pipeline, pipeline routing, offshore platform,
separation.
The
decision with respect to the split between field processing will be relatively
obvious and be driven by the type and proximity of existing infrastructure, eg.
pipeline systems and onshore oil/gas reception and processing facilities. In
newer/remote areas, where the designers effectively have a “clean sheet of
paper” to deal with, the offshore/onshore split decisions is much less clear.
The
North Caspian Sea region is currently in the center of economic and political
interests of Kazakhstan. On the threshold of the new century, over 70 oil and
gas fields were discovered within the North Caspian Sea including Kashagan, one
of the largest in the world and Kalamkas-Sea fields.
Kalamkas-Sea field is
located in the Northern Caspian Sea, about 130 km south-west of the Kashagan
field. The field is located at shallow depths (from 8 to 9 m). Hydrocarbon
deposit lay at an absolute depth of 1600-2100 meters from sea level, it
represented by reservoir of 40 km in length, which includes several areas of
structural uplift [1].
Figure 1 – Kalamkas-Sea
fieldlocation
Development
of the Kalamkas-Sea oil field requires decisions on fluid processing and
transportation system.
An
examination of the processing options implemented on Kalamkas-Sea offshore oil
field development indicates a range of possibilities:
Minimal
offshore processing or all produced fluid sent to the onshore terminal forfinal
processing.
According
the first option, there should be multiphase pipeline constructed and
infrastructure in onshore for processing. In multiphase pipeline when oil,
water and gas are flowing together, the three phases can distribute many
configurations due to the density difference among the fluids. Different fluid
interfaces result in different hydrodynamics of the flow as well as mechanisms
of the momentum, heat and mass transfer among the fluids. Since flow in
different flow regimes may include different pressure drops expose to a risk on
pipeline integrity and environmental safety, causing challenges such as
hydrates, liquid accumulation and slugging, wax deposition, sand accumulation.
Flow
assurance of multiphase pipeline is expected to be a major challenge in the
North Caspian region due to long distances, cold temperatures, and harsh
environment. The ability to accurately predict and manage multiphase flow of
well fluids from subsea wells to a platform or onshore facilities is critical
to the subsea production in the Kalamkas field, located 60 kilometers away from
the nearest shore [2].
This option considers offshore pipeline with length of about 215 km from
the Kalamkas-Sea to the Bay of Bautino with onshore crude oil tank farm or 60
km pipeline to the Buzachiisland with construction of new facility. The
potential pipeline routes are shown in the Fig. 2.
Figure 2 –
Pipelinerouting options.
Full
processing offshore to make specification product, with no further onshore
processing required and separate transportation of products to the shore.
In the second option, separation of crude oil and gas then is made
offshore to allow single-phase transmission of oil and gas through their
separate transportation systems. Separation is required offshore because of the
extremely large pressure drops experienced due to two phase flow of liquid
hydrocarbon and gas being shipped together by pipeline.
The
potential route of the export pipeline in this case will be to the Buzachi
half-island, located at 60 km south-east, tied in the existing main pipeline of
the transport company "KazTransOil" (KTO), located on the territory
of the Karazhanbas field (Fig 2). In order to connect to main pipeline system
product have to meet saleable specifications.
The
processing of the crude oil starts in the offshore oil-gas wellhead and passes
through complex processing steps before the outcoming oil and gas will called
qualified products. Processing unit operations arrange in the following way:
·
Separation of 3-phase well-fluid;
·
Gas compression and dehydration;
·
Produced water conditioning;
·
Oil desalting by electrostatic coalesce [4];
Offshore
production platforms are built to provide a working area to separate water,
liquid hydrocarbon and gas.
The
process flow diagram of the topside processing option in Kalamkas-Sea field is illustrated in Figure 3.
Figure 3 –
Offshoreprocessing flow diagram
Full
processing offshore to make specification product, with no further onshore
processing required and transportation of oil to the shore, injection gasfor
pressure maintenance system.
In
this option considers separation and transportation of oil according to the
previous option,however removed gas from the 1st HP stage of separation train
is routed for further treatment. Treated gas then transported from Kalamkas-Sea
field to satellite Khazar field for gaslift operations.
Disposal
of gas from an offshore production site will depend on a combination of
reservoir and economic factors. If well production is primarily oil, the gas
may be handled as a byproduct and be disposed of in the most economical way.
Piping the gas to a land site for sale and use as a fuel is generally preferred
if it can be done economically. Injection back into the producing formation is
a common alternative. This helps maintain reservoir pressure and conserves the
gas for possible future sale. In some areas, gas flaring is still acceptable,
but for Kazakhstan now forbid it except for the short test periods and for the
disposal of small amounts of residual waste gas.
To
arrive at the desired gas disposal system, consideration is given to the total
platform. After the location and operation of the platform are worked out,
process development of the platform begins. Physical data from the field such
as gas to oil ratio, specific gravity, viscosity, water, sand, etc., are
studied. Heat and material balances are made for use in equipment selection.
Piping and instrument diagrams are prepared to show the complete process flow
scheme. Finally, process and mechanical specifications are written [5].
All
produced fluid sent to the onshore terminal by tankers.
In the case if an offshore
pipeline can be the single most expensive element of an offshore installation,
an offshore oil field is too remote, production rates are too low, or the field
is too short-lived to justify a pipeline economically, the alternative is to
transport the oil using tankers. This usually requires some type of loading
system installed, such as a moored buoy or articulated loading tower. A
seafloor pipeline connects the loading facility during the transfer of oil.
The two most important
drawbacks of tanker-loading operations are sensitivity to weather and the need
for separate oil storage. Tanker loading is best suited to mild weather areas
to minimize downtime from storms. Oil storage requirements will depend on total
field producing rates and reservoir characteristics (i.e., whether the wells
can be shut in for short periods without lost productivity) as well as tanker
downtime. This has led to the development of permanently moored storage
tankers[6].
Taking into account the
environmental, geographical and technical characteristics of the Klamkas-Sea
oilfield, piping is still the safest, most economical way to transport
crude-oil production from this field to a land site.
The
decision on which offshore processing and transportation option is more
suitable for an appropriate field has to been made with significant
implications, such as:
-
Offshore platform size and
complexity;
-
Availability of an onshore terminal
required for final processing and storage;
-
Offshore pipeline operation: single
phase or multiphase;
-
Project schedule and manning
requirement;
-
Impact on subsequent future
projects.
REFERENCES
1.
Environmental Impact Assessment Report. North Caspian Operating Company.
August 20, 2013. -5-7 p.
2.
I. Brandt, S. Nas, D. Gunasekera, Multiphase Flow Simulation – Optimizing
Field Productivity //Oifield Review 27, May 2015, no.1. -3 p.
3.
H.Fang, M. Duan Offshore Operation Facilities: Equipment and Procedures //
Offshore Oil/Gas Research Center, China University of Petroleum, Beijing,
China, 2009. -103 p.
4.
M. Bothamley, SPE, John M Campbell & Company. Offshore Processing
Options for Oil Platforms //SPE Annual Technical Conference and Exhibition held
in Houston, Texas, U.S.A., 26-29 September 2004. -10-12 p.
5.
Safety and
integrity of arctic marine pipelines. Contract Report for Minerals Management
Service//United States Department of the Interior, C-CORE Publication. June
1998.-47 p.
Рысакова М.Д., Ли Д.
Теңізде орналасқан Қаламкас кен орнынан мунайды дайындау және тасымалдау
нұсқаулықтары.
Түйіндеме. Зерттеуде
теңізде орналасқан
Қаламкас кен орнында мунайды дайындау және
тасымалдаудың нұсқаулары оның өндіру
ерекшеліктеріне, географиялық орнына, инфрақұрылымның
болуына, қауіпсіздікке әсер
ететін экологиялық және техникалық факторларды ескере отырып
қарастырылған.
Кілтті сөздер:
Теңіз кен орнында мұнайды өңдеу, көпфазалы
құбыр, құбыр жолы, теңіз платформасы,
сепарациялау.
Рысакова М.Д., Ли Д.
Варианты
подготовки и транспортировки нефти на морском месторождении Каламкас море.
Аннотация.Целью данной работы является рассмотрение
основных вариантов
подготовки и транспортировки нефти, доступные для морской
добычи на месторождении Каламкас море, учитывая наличие инфраструктуры,
географические особенности, основные экологические и технические факторы,
влияющие на безопасность.
Ключевые слова: Подготовка
нефти на море, многофазный трубопровод, маршрут
трубопровода, морская платформа, сепарация.