Apparatus and method for treating injection fluid

Abstract

An apparatus for treating a fluid to be injected into a subterranean hydrocarbon-bearing formation includes a filtration unit having one or more filtration membranes including either or both ultra-filtration membranes and microfiltration membranes, and an ionic species removal plant, wherein fluid to be injected is first treated by the filtration unit and then treated by the ionic species removal plant. In a preferred embodiment, the ionic species removal plant is a sulfate removal plant which incorporates nano-filtration membranes. A method of treating fluid to be injected into a subterranean formation is also disclosed. A cleaning system and method for use in an apparatus for treating injection fluid is also disclosed.

1 . A method of treating fluid to be injected into a subterranean hydrocarbon-bearing formation, said method comprising the steps of:
 flowing injection fluid through a filtration unit comprising at least one filtration membrane including at least one of an ultra-filtration membrane and a micro-filtration membrane; and then   driving said injection fluid through an ionic species removal plant.   
   
   
       2 . A method as claimed in  claim 1 , wherein the ionic species removal plant is a sulfate removal plant for removing divalent sulfate ions from the injection fluid. 
   
   
       3 . A method as claimed in  claim 1 , wherein the ionic species removal plant comprises at least one nano-filtration membrane. 
   
   
       4 . A method as claimed in  claim 1 , further comprising the step of flowing the injection fluid through a pre-filtration unit prior to flowing the fluid through the filtration unit. 
   
   
       5 . A method as claimed in  claim 1 , further comprising the step of flowing the fluid through a deaerator. 
   
   
       6 . A method of cleaning a fluid treatment apparatus incorporating a plurality of filtration units each comprising at least one filtration membrane including at least one of an ultra-filtration membrane and a micro-filtration membrane, and an ionic species removal plant coupled to and located downstream of the filtration unit, said method comprising the steps of:
 providing a cleaning fluid supply taken from the fluid treatment apparatus at a location downstream of the filtration unit; and   directly diverting at least a portion of the cleaning fluid supply from the fluid treatment apparatus through the at least one filtration membrane.