This paper presents an overview of the events leading to the establishment of a joint industry project (JIP) to address blockages in hydraulic control and chemical injection fluid conduits in subsea production systems (SPSs) and details its findings and outputs. The JIP has established that blockages are a major issue for the subsea production industry, and very limited information is currently published as to the causes, frequency and their avoidance. Additionally, it has determined that system designers and operating companies should have a detailed awareness of the potential causes of blockages and how they can be avoided.
Blockages invariably have very significant financial implications for the operator of an SPS; addressing the potential causes from project inception, through design, installation and commissioning, and to operational life should very significantly reduce, or eliminate, the risk of such events.
Umbilicals are a critical link in the recovery of hydrocarbons involving SPSs. Not only do they provide hydraulic power and electrical signals to operate and control the production centres, but they also are used to convey fluids (production chemicals, gas lift, annulus bleed) to assist in the recovery process and to maintain the life and operability of the trees and flowlines. Production chemical fluids (PCFs) are both diverse in nature and formulation, and to date many hundreds of such fluids have been considered or utilised by the subsea production industry.
What is noticeable about many of these fluids is that outside of the fluid manufacturers, little is known about their actual compositions or stability, and what relevant tests, if any, are performed to confirm their suitability for transportation through relatively small bore fluid conduits over long distances.
In using such fluids for umbilical service, there have been, over the years, reports of umbilical fluid conduits becoming blocked and in many cases for no obvious reason. Due to secrecy within the industry, such blockages have rarely been made public.
All of this changed with an initiative led by the Umbilical Manufacturer"s Federation (UMF) to hold a workshop to address the subject. With the assistance of the Society for Underwater Technology (SUT), which organised the workshop on behalf of the UMF, this was duly held in Aberdeen in January 2005. It comprised a morning session, whereby operators and fluid manufacturers provided examples of blockages or events which could lead to blockages, and an afternoon session involving working groups that discussed the morning"s presentations and how to prevent blockages occurring.
The workshop culminated in a distillation of the outputs from the working groups and was followed by a report on the findings and suggestions as to the way forward. To utilise the very useful information from the workshop for the benefit of the subsea production industry, the UMF decided that the best way forward would be to undertake a JIP with the aim of developing two documents: a recommended practice (RP) document, addressing how to avoid blockages in umbilical systems, and a design verification (DV) document