Page 34 - Handbook Of Multiphase Flow Assurance

28 1. Introduction

Monitoring and data mining

A consistent set of metrics allows for lasting risk mitigation, and for the ability to extract
value from technology. If we can measure, we can improve.
Integrated analysis based on monitoring and modeling would allow near-term forecast-
ing of flow assurance issues with automated response. Realtime monitoring of production
allows operator to know downhole parameters, plan the deployment of chemicals and to
perform integrated analysis of production & near-term issues forecasting. All fields are
equipped with some instrumentation for measurements and automation. Many fields ana-
lyze these collected data to forecast the production. Some fields rely on automation to mon-
itor and analyze the data in real time to alert the operator to changes in flow. Few fields
actually can automatically predict and alert of an imminent flow assurance restriction or
plug so the operator could deploy the mitigation measures such as chemical injection or
heating.
With time the integrated analysis based on flow monitoring and modeling would allow
near-term forecasting of flow assurance issues with automated response in more fields.

Flow assurance in operations

Onshore production

Common problems encountered in onshore operations are: reservoir souring, liquids
loading and slugging in wells, hydrate, scale and paraffin blockages in wells and gather-
ing flowlines, slugging in in-field gathering lines, hydrate blockages in process plant lines
and equipment. Asphaltenes can occur in undersaturated reservoirs without gas cap and in
wells.
Gas fields can experience deposition of diamondoids and elemental sulfur in well tubing.
Sour fluids have elevated content of CO 2 or H 2 S or both. Mercury is not uncommon in gas
fields near continental rifts such as Asia-Pacific region.
Overpressured reservoirs contain fluids at pressure higher than hydrostatic. This is rare
but can happen in consolidated reservoirs, fractured reservoirs and in weakly consolidated
reservoirs both onshore and offshore. High pressure high temperature reservoirs bring addi-
tional constraints on material selection.

Offshore production

Shallow water production encounters the same problems as onshore with addition of se-
vere slugging caused by a significant elevation difference between a subsea flowline and
the platform topsides. Similar to liquid loading in an onshore well, liquids accumulate at
the riser base and get periodically produced by gas backpressure to the topsides separator.
Severe slugging affects stability of production in two ways: periodic movement of liquid
slugs causes regular impacts at flow path elbows and fatigue of both flexible and rigid risers,
and also surge of liquid can overfill the separator volume if the transfer pumps or the separa-
tor size or both are undersized.