Page 101 - Handbook Of Multiphase Flow Assurance

Frequency of blockage remediations 97

• Water injectivity loss
• Formation damage or compaction
• Hydrate
• Ice
• Wax and gels
• Scale
• Sulfur deposition
• Naphthenate
• Asphaltene
• Diamondoids
• Heavy oil
• Viscous oil
• Bacterial growth
• Corrosion products
• Sand
• Field layout with low spots

Choice of technology(ies) for managing each of these possible threats should be based on res-
ervoir rock type, reservoir fluids chemistry, regional environmental regulations, regional waste
handling availability, and technology commercial availability in the region. Various combina-
tions of available and permissible flow assurance technologies should be screened in prelimi-
nary concepts evaluation. Technologies may be changed or made complementary during the life
of field, for example, operations may choose to switch from AA to KHI as water cuts increase, or
from KHI to MEG as demand for system reliability increases. Details of addressing some of the
flow assurance risks below may serve for development of project-specific flow assurance.

Frequency of blockages

The sequence in Fig. 5.1 and in Table 5.1 below is based on the subjective survey from the
SPE Flow Assurance Forum held in USA in June 2015. Although the forum was attended by
flow assurance specialists from different continents, these values should be used as indicative
only as this survey represents a fairly small sample size for a proper statistical analysis.
Location and frequency of blockages were marked by the Forum participants based on
their knowledge of the industry.

Frequency of blockage remediations

Historically, the US Minerals Management Service had received and processed applications
for flowline remediation in deepwater. Between 1991 and 1998, 52 subsea flowlines were re-
ported blocked with wax and hydrates (Alvarado, 1999, 2003). Of these, all hydrate blockages
were remediated, and approximately half of the pipelines plugged with wax were abandoned.
Since then, several long-reach coiled tubing technologies have been commercialized to
clear out blockages from pipelines by hydraulic jetting. Similarly, technologies for subsea
hydrate and other blockage remediation by a subsea pump depressurization have matured
and became a common practice.
Some information about the global use of subsea blockage remediation with a commer-
cially available subsea pump equipment during the past decade from 2008 through 2017 was