Sand filters

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EQUIPMENT DESCRIPTION

  • Wire filter element design, installed within a pressure vessel.
  • A Sandfilter is utilised on installations where sand producing wells and Proppant clean-up programmes are to be performed.
  • Where produced sand requires filtering prior to the main production or temporary well test process.
  • It has a non- intrusive flushing system to remove solids.
  • Each unit comes complete with a lifting arrangement to ease the removal of and re-insertion of the screen element.

PURPOSE OF SAND FILTER

  • Removal of solids prior to production process limiting erosion.
  • Filtered fluids can flow from choke assembly direct to main process limiting erosion.
  • All solids captured by the filter element are collected in Sandfilter vessel.
  • All contaminated solids returns are directed from filter units to collection for disposal either overboard or designated container.

EQUIPMENT HOOK-UP

  • Air winch should be fitted and gantry raised.
  • Filters with an appropriate mesh size suitable to the sand size expected should be installed in each filter pot prior to start-up.
  • Hook-up differential meter.
  • Ensure pressure tappings to differential pressure unit to each filter pot are open and all vents/drains on each filter pot are closed.
  • Fit gauges of suitable range to each pot for observing pressure in pot. Ensure gauges are protected by suitable isolating valves.
  • Check operation of valves by cycling from fully closed to fully open position. Close bypass valve. Close inlet valve and outlet valve on one pot (standby pot), leaving the other pot ready for service (duty pot), if required, else open bypass and close all pot valves.
  • Sand hopper should be fitted and drain hose run to a dedicated tank or to the mud pits. NO liquids should be dumped overboard without prior consent.
  • A water line should be hooked up to enable filters to be flushed.
  • Rig up flexible vent lines as applicable.
  • Filters should be earthed to rig structure using appropriate earthing strap.

EQUALISING POTS

  • Assumptions
  • A flexible hose has been run from the top of the sand filter pot to the appropriate safe area for venting purposes while flowing via the dedicated clean-up line. This hose should be isolated when not in use.
  • When Flow is diverted via the test system then this hose must be rigged down and if required to vent the sandfilters then this should be done by means of a vent hose taken from the top of the pot.
  • Open equalising line valves in the order, valve nearest the vessel first followed by sacrificial valve.
  • Pressurise pot up to +/- 200 psi.
  • Close equalising line valves in reverse order, i.e. sacrificial valve first
  • Vent down standby filter pot to zero.
  • Open equalising line valves as step 1.
  • Pressurise standby vessel slowly to full well pressure.
  • When pressure gauge confirms balanced pressure, close the equalising valves in reverse order.

DIVERTING FLOW VIA DUTY POT

  • Slowly pressurise one filter pot to line pressure.
  • Open filter pot upstream inlet valve.
  • Open filter pot downstream inlet valve.
  • Open filter pot downstream outlet valve.
  • Open filter pot upstream outlet valve.
  • Slowly close bypass valve. It is not recommended to reopen this valve during clean up due to the risk of sanding up.
  • Note differential pressure on DP gauges (if any) - this is initial clean up and will be dependant on gas flow rate and liquid content.
  • An increasing differential pressure is indicative of the filter element filling with sand and it may be necessary to switch to the standby filter pot.
  • NOTE: Excessive sand and fluid production will result in high D.P.'s and present a risk of filter damage. Under these conditions time is at an essence.

SAFETY CONSIDERATIONS

  • Monitor all changes in flow through choke changes or pump rates.
  • Constant monitoring of differential pressure across filter element.
  • If electronic sand monitoring is installed check for solids production downstream of filter units.
  • Check solids production downstream of filter units through BS&W and choke inspection made by well test company.
  • If differential pressure across element rises above 1000 psi then it is recommended that the filter element should be pulled for damage inspection.