Page 19 - Handbook Of Multiphase Flow Assurance

How flow assurance and production chemistry work together 13

– emulsions,
– foaming,
– scale formation,
– sand production,
– slugging,
– materials-related issues.
The API 17 TR4 list above captures most of the scope and is fairly comprehensive for a
typical oil or gas field development.
Flow assurance prevention methods are usually thermal (insulation or a cooling spool) or
chemical (inhibitors) whereas mitigation can be mechanical (pumps), chemical (solvents) or
thermal (active heating).
Production chemistry prevention is usually chemical (surfactants or inhibitors) or mechan-
ical (segregation of incompatible fluid streams). Mitigation is chemical (chelants, dispersants,
dissolvers) or mechanical (milling). Chemical injection dosages are, on average, 100 ppm with
typical range of 50–250 ppm, and can be much higher for hydrate inhibitors ranging from 10,000
to 500,000 ppm or much lower at 5–10 ppm for emulsion breakers and corrosion inhibitors.
In some sub-cases such as under-treated severe bacterial accumulation or foaming, flow
also gets affected.
Main focus of production chemistry is on product value including: oil quality (water con-
tent), water quality (organics content and total dissolved solids, oxygen content, souring and
corrosion potential).
Chemicals may be deployed in a variety of locations. Typical ranges of chemical dosages
are needed to design a chemical delivery system. Such ranges are shown below in Table 1.2.

TABLE 1.2 Initial estimates of chemical dosages and typical locations of chemical injection
Chemical Dosage, ppm mass basis Place of injection usually
Emulsion breaker 5–10 Downhole, tree, topsides
Reverse demulsifier (water clarifier) 15–50 Topsides
Corrosion inhibitor (liquid and multiphase) 30–200 Tree
Corrosion inhibitor (gas export) 5–10 Topsides, process plant
Wax inhibitors 50–800 Downhole, tree
Wax dispersant 50–1000 Downhole, tree
Asphaltene inhibitor/dispersant 50–800 Downhole
Drag (friction) reducers: oil 100–1000 Process plant
Drag (friction) reducers: water 20–100 Tree, topsides, process plant
Pour point depressant (PPD) 25–1000 Downhole, tree
Scale inhibitors 5–100 Donwhole, tree
Scale dissolvers Batch Downhole, topsides

Continued