Produced Water Handling and

Treatment

PAB 3073

Learning Outcome

Explain basic concept of water treatment operation

Introduction

Necessary to handle waste water that include

Crude oil

Rain water

Washdown water

Offshore :HC that can be discharge

15mg/l to 50mg/l

Onshore : water cannot be disposed on surface ~ possible salt contamination

Water Handling and Distribution

Over time, water may be produced along with oil

This produced water has no commercial value therefore treat to remove oil and dispose to sea

Oil remains in water in 2 forms:

Emulsion

Oil droplets in water

Emulsion between oil and water

Main phase is water

Inject emulsion breaking chemicals upstream water treatment tank

Oil droplets in water

Oil droplets float freely in water

Settle out given enough time or use equipment/methods to assist removal of oil droplets – water treatment tank

Water Handling and Distribution

Oil floats to top of water treatment tank and skimmed off into the drain system

Water then disposed to sea through Closed Drain Caisson

Water sampling – Effluent Discharge Quality must be < 100ppm

Water Handling and Distribution

Produced water treatment equipment

Initial separation of oil and water

Gravity separators

Primary separation can be enhanced via

Heating of crude oil – separate water via reduced viscosity

Demulsification chemicals – break emulsions and let water droplets to settle

Electrostatic separation – reduce water content of dense, dry crude oil

Types of water treatment equipment

Corrugated Plate Interceptor (CPI)

Dissolved Gas Floatation Unit (DGF)/Dispersed Gas Floatation

Hydrocyclones

Produced water treatment equipment

Corrugated Plate Interceptor

Plate interceptors reduced distance required for oil droplet to migrate before it comes into contact with other oil droplets and coalesces

Interceptor packs consists of a series of closely spaced, parallel plates mounted at angle 45 degree

Plates have corrugated profile – allows large oil droplets to move upwards and collect at the high point

CPI works off because of short separation distance between the plates

Oil moves upwards through the water phase as the size increases

Oil layer formed then skimmed off by oil outlet weir

Configuration of water inlet and outlet arranged to minimise turbulence that causes re-mixing of small oil droplets

Remove up to 60micron

Dissolved/Dispersed Gas Floatation

Uses gas floatation to accelerate separation of oil from water

Via buoyancy effect caused by rising gas bubbles attached to oil droplets

Oil carried to surface coalesce and separate using oil weir

Gas injected in 2 manners

Inject into water and dispersed by rapidly rotating impeller

Dissolved in water under high pressure

Travels via pressure vessel and limited residence time causes gas to dissolve

Then reduce pressure rapidly, gas comes out in form of bubbles

Hydrocyclone

Use centrifugal force to increase effect of gravity

Oil-water feed flows tangentially into the upper, swirl section

Swirls around in circular path, then accelerate as flows enters taper section (reduced diamater)

Lighter oil moves up, heavier water exits out

http://www.plateseparator.com/