Produced Water De-Oiling Membrane Package

INTRODUCTION

Three main production fluids emerging from reservoir upon produced are gas, crude and produced water. While gas and crude are further process and export to onshore, the produced water is normally separated, treated and dump to overboard. In early years of oil and gas operation, to minimize offshore facilities, produced water is normally export together with crude to onshore for further separation process. With well maturity, crude and gas production will depletes but this pattern is not applicable to produced water resulting a bottleneck to onshore crude separation system. That said, it is vital to remove produced water at upstream prior to export for optimising export pressure, offshore power consumption and chemical injection cocktail consumption.  A produced water treatment package is typically introduced at aging offshore facilities to separate produced water but restricted space and weight tend to arise as a challenge. The conventional produced water treatment package – consist of produced water hydro cyclone and compact flotation unit (CFU) with chemical injection cocktails – however is prone to disrupt upstream system upon upset.

Our study has suggested that using ceramic membrane in removing oil from produce water, it can reduced to lower than 10ppm, allowing treated water to be used as water injection for reservoir’s pressure maintenance. As produced water has no oxygen content, its water is well suited for water injection system as compared to seawater.

DESCRIPTION

A produced water de-oiling package as minimum will consist of the following, which illustrated in green in figure 1.

  • Produced Water De-oiling Hydro Cyclone
  • Produced Water De-oiling Hydro Cyclone Reject Oil Return Pump
  • Produced Water Booster Pump
  • Produced Water De-oiling Membrane
  • De-oiling Membrane CIP Package
Simplified Flow Diagram of Produced Water Deoiling Membrane Package
Figure 1.0 Simplified Flow Diagram of Produced Water De- oiling Membrane Package

Produced water ceramic membrane is suitable for produced water treatment in view of the following:

  • High design temperature: Ceramic membrane can withstand incoming fluid with reservoir temperature without cooling temperature.
  • Erosion resistance:  Ceramic membrane can withstand erosions of fine sand particles without risking surface area
  • High design pressure: Potential elimination of water injection booster pump
  • Lower oil in water content at battery limit: Treated produced water with oil in water content less than 10 ppm.

The membrane uses ultrafine filtration philosophy where only particles smaller than 0.03 micron is able to pass through wall of membrane.

Membrane Filtration Level
Figure 2: Membrane Filtration Level

While a conventional produced water treatment package offers smaller footprint for treating limited oil in water content, it is limited to oil water content of 30ppm at battery limit. A produced water membrane de-oiling package can however further reduced the water content to lower than 10 ppm, enabling treated produced water to be used for water injection operation. As the produced water is ready with zero (0) oxygen content, less chemical cocktail will be required compared to seawater deaeration package. As a result, there wouldn’t be a need for deaeration tower for water injection which makes produced water de-oiling membrane package a comparatively feasible option to conventional seawater deaeration package.

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