Liuhua 11-1/4-1 Oil Field Secondary Development Project

The Liuhua 11-1/4-1 secondary development project is a deepwater oil field redevelopment currently in progress in the South China Sea, China.

Chinese oil and gas firm CNOOC is the developer and operator of the Liuhua 11-1 and Liuhua 4-1 deepwater oil fields, which commenced production in 1996 and 2012, respectively.

The Liuhua 11-1/4-1 secondary project will involve the development of new horizontal wells, sidetracks, and existing wells at the two fields, with new drilling, production and subsea installations.

A new drilling and production platform, a cylindrical floating production, storage and offloading (FPSO) unit and two subsea pipelines will be installed to produce crude oil from the fields.

The Liuhua 11-1/4-1 secondary development project is expected to start operations in December 2023. The project will be the first to feature cylindrical FPSO in Asia.

Location and field details

The Liuhua 11-1 and Liuhua 4-1 oil fields are located in the Pearl River Mouth Basin of the South China Sea, China, approximately 220km southeast of Hong Kong.

The Liuhua 11-1 field currently comprises a subsea production system (SPS), the Nanhai Sheng Li FPSO and the Nanhai Tiao Zhan floating production system (FPS). The FPSO and the FPS will leave the Liuhua 11-1 field, following the completion of the secondary development project.

The Liuhua 4-1 oilfield consists of a subsea pipeline to transport the wellstream to Liuhua 11-1 for further transport to the FPSO.

Liuhua 11-1/4-1 oil field secondary development details

The Liuhua 11-1/4-1 secondary project will involve the development of 32 horizontal wells, including 24 new wells, two sidetracks and six existing wells at the two fields, with the construction and installation of a new drilling and production platform LH11-1 DPP.

A cylindrical FPSO to process and store crude oil, and a subsea pipeline connecting the Liuhua 11-1 DPP and the new FPSO will be laid as part of the project. A subsea pipeline will also be installed between the Liuhua 11-1 subsea manifold terminal and the LH11-1 DPP platform.

The redevelopment project will also include installing a subsea cable to supply power to the Liuhua 11-1 DPP. The Liuhua 4-1 oilfield development will involve the tieback of the existing SPS to the LH 11-1 DPP platform with the installation of an umbilical. It will also include the development of six existing wells and two new sidetracks in the existing wells.

LH 11-1 DPP platform details

The LH 11-1 DPP platform, currently under construction, is planned to develop the new wells in the Liuhua 11-1 field. The topsides of the platform will consist of drilling and production units and will sit on a jacket installed on the sea floor.

The platform will be installed at a water depth of 325m. The jacket will be 338m-high and weighs more than 37,000 tonnes.

The LH11-1 DPP platform will conduct initial processing of wellstream from both the Liuhua 11-1 and the Liuhua 4-1 oilfields, before it is transported to the new cylindrical FPSO. The platform will receive power from the FPSO.

Cylindrical FPSO details

The cylindrical FPSO will have a crude oil processing capacity of around 6,000m3 and a storage capacity of 60,000m3. The FPSO will weigh around 60,000 tonnes and operate in a water depth of approximately 324m. It will have a design service life of 30 years.

Crude oil processed by the FPSO will be stored in tanks and transported to the shore by shuttle tankers.

The associated gas produced will be partly utilised for power production on the FPSO and the remaining gas will be flared.

The water separated from the crude oil will be treated to the required standard before discharging to the sea.

Subsea pipelines and umbilical

The Liuhua 11-1/4-1 oil field secondary development will include the installation of a 15in-inner diameter, 3.5km-long subsea pipeline from the existing Liuhua 11-1 subsea manifold terminal to the LH11-1 DPP platform.

A new 10in-inner diameter, 2.5km-long subsea pipeline will be built to connect the LH11-1 DPP platform to the new FPSO.

A 2.5km-long subsea power cable will be installed from the new FPSO to the LH11-1 DPP platform and a 16km-long umbilical will be laid from the LH11-1 DPP platform to the existing LH4-1 SPS.

Contracts awarded

Offshore Oil Engineering (COOEC), a subsidiary of CNOOC, was selected as the main contractor for the construction of the cylindrical FPSO. Construction of the FPSO commenced at its Qingdao Yard, China, in March 2022.

The vessel is the first cylindrical FPSO to be designed and built by China independently. It is also claimed to be the seventh FPSO of its kind globally.

COOEC commenced the construction of the jacket of the Liuhua 11-1 DPP platform in December 2021.

MacGregor, part of Cargotec, was awarded a contract to deliver two FPSO offloading systems for the Liuhua 11-1/4-1 redevelopment project in February 2022. The offloading systems, which will enable oil exports from the FPSO to shuttle tankers, are expected to be supplied to the COOEC Qingdao Yard in January 2023.

OffshoreTech was contracted by CNOOC to perform third-party independent verification of all design conditions of the LH11-1 DPP platform jacket. The contract also involved the verification of design documents for the front end engineering design (FEED) of the jacket.