Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Calculation method of wellhead bearing capacity of deepwater Suction Bucket Foundation
Chao Fu 1, Jin Yang1, Lei Li1, Xinyue He1, Qingfeng Wei1, Minghe Zhang1, Xiangji Kong2, Feng Qian2,Haibing Pan2
1 China University of Petroleum，Beijing, China
2 China National Oil and Gas Exploration and Development Company Ltd，Beijing, China

D,1991). The suction underwater pile wellhead adopted in the second
hydrate production test in the South China Sea was 67.5m in diameter,
12m in length, 96t in weight, guaranteeing the horizontal deflecting
capacity in shallow soil and preventing the wellhead from sinking or
overturning throughout the operation process (Philippe Jeanjean, 2002).
There have been some analyses about the bearing characteristics andinfluencing factors of the main cylindrical foundations, but the studies
about the bearing capacity of suction underwater pile wellhead undercomplicated geological conditions and wellhead dynamic loads in deepwater are few and far between.

ABSTRACT
Underwater wellheads are the basis for deepwater oil and gas fielddevelopment and carry the weight of various pipe strings and tools in thewell. The suction pile wellhead designed by combining a cylindricalfoundation with the underwater wellhead can greatly improve thebearing capacity of the wellhead, and ensure stability and operationalsafety. Based on pile foundation bearing theory and the ultimate
foundation reaction method, the wellhead bearing capacity of the suction
pile was analyzed, and the calculation model of the suction pile wellheadbearing capacity under different soil conditions was established, and theon-site operation suction pile wellhead bearing capacity chart wasobtained. The finite element method was used to analyze and verify thechange in bearing capacity of the suction pile under the action of seepage.
The results show that considering the undrained shear strength of theshallow soil in the South China Sea, a 6-m diameter suction pile at apenetration depth of 12 m, can reach a bearing capacity of up to 6000 kN.
The results of this study can provide a theoretical basis for deepwater oiland gas wellhead design.

This paper analyses the bearing capacity of suction underwater pile
wellheads basing on the pile foundation bearing capacity theory and theultimate foundation reaction method, reveals the stress-strain changing
rule relying on the finite element software ABAQUS, summarize thefailure mode, and build the bearing capacity calculation model undervirous soil textures in deep water. The bearing capacity chart of suction
pile wellhead in field operation is obtained, and can be used for reference
for the design and application of suction underwater pile wellheads.

Analysis of suction pile wellhead structure

KEY WORDS: Underwater wellheads ； suction pile wellhead ；bearing capacity

The cylindrical foundation with large diameter used by the suction
underwater pile technology has characteristics of shallow setting depth
and high bearing capacity. This innovative well building technology canovercome the problem of inadequate bearing capacity and improve thestability of subsea wellheads. The suction pile applied in deep-water
surface well construction technology is a suction cylindrical foundation
with special structure as Fig 1 shows.

INTRODUCTION
Deepwater oil and gas exploration and development is an important partof the world oil and gas exploration and development. There are many
issues still need further study. During deep-water operations, thepenetration of surface casing brings great disturbance to shallow layer
soft soil, which can lead to the shock and subsidence of the wellhead.
Insufficient load bearing capacity of the wellhead negatively affects thestability and safety of deep-water operations (Yunjin Xu et al, 2017). Thesuction underwater pile wellhead technology uses the cylindricalfoundation as a load bearing structure (Yanbin Wang, 2014). Comparedwith penetrating into shallow soil for well construction, the suction
underwater pile wellhead technology has smaller requirements ofshallow layer soft soil and enables marine conductors to be mass
installed into the sea. The strong bearing capacity of the suction
underwater pile improves wellhead stability and shortens wellconstruction period. For hydrate production tests, the suction underwater
pile wellhead technology is able to conquer the difficulties of building along horizontal interval of horizontal wells and putting completion
casings in place (Guan Zhichuan, 2009; Vaitkunaite E, 2016; Beck R.

Fig 1. Basic structure of suction pile wellhead858