Method and system for surface filtering of solids from return fluids in well operations

A filter system for separating the debris from the fluid in a fluid stream coming from a well and for directing the filtrate to a flow back tank and the debris to a debris pit, the system comprising:

• an inlet line connectable to the well;
• a filter connected to the inlet, the filter comprising:
• an outer tube, and;
• an inner tube inside the outer tube, the inner tube having an inlet end and outlet end and a perforated sidewall therebetween, the inner tube being sized to provide an annulus between the inner tube and the outer tube, wherein the inlet end is connected to the inlet line so that the fluid stream passes from the well into the inner tube and so that the filtrate passes through the perforated sidewall and into the annulus and so that the debris collects inside the inner tube;
• a flow back line connected to the annulus of the filter for directing the filtrate to the flow back tank;
• a debris tube having an inlet and an outlet and adapted to receive debris purged from the inner tube of the filter;
• a debris transfer line connecting the outlet end of the inner tube and the inlet of the debris tube;
• a discharge line for passing debris from the debris tube into the debris pit;
• a downstream filter valve for controlling passage of debris through the debris transfer line;
• a purge line connecting the flow back line to the debris transfer tube;
• a debris choke for modulating flow of filtrate through the debris tube;
• and
• a purge choke for modulating flow of debris through the discharge line;
• whereby debris in the inner tube of the filter can be passed into the debris tube and out through the discharge line without interrupting flow of the fluid stream through the filter.