Filter assembly having a bypass passageway and method

A filter assembly comprising:

• a housing having a longitudinal axis;
• a primary flow passageway through the housing, the primary flow passageway including at least one primary filter deployed therein;
• a bypass second flow passageway including a bypass filter;
• and
• a bypass valve assembly deployed in the housing, the bypass valve assembly disposed to selectively open the bypass flow passageway when a fluid pressure reaches a predetermined threshold pressure.

A filter assembly comprising:

• a substantially tubular housing having a longitudinal axis;
• a bypass flow tube deployed substantially coaxially in the housing, the bypass flow tube having upstream and downstream ends;
• a substantially annular primary flow passageway through the housing provided between an outer surface of the bypass flow tube and an inner surface of the housing;
• a secondary flow passageway through the housing provided internal to an inner surface of the bypass flow tube;
• at least one primary filter deployed in the primary flow passageway;
• a bypass filter screen coupled to the upstream end of the bypass flow tube;
• and
• a bypass valve assembly deployed in the housing proximate to the downstream end of the bypass flow tube, the bypass valve assembly disposed to selectively open the secondary flow passageway when a fluid pressure reaches a predetermined threshold pressure.

A downhole filleting sub for filtering a drilling fluid, the filtering sub comprising:

• a downhole tool body including a through bore and a longitudinal axis, the tool body further including first and second threaded ends, the tool body configured to be coupled to a drill string;
• the through bore providing a primary flow passageway through the tool body in a direction substantially parallel with the longitudinal axis;
• a bypass flow tube deployed in the through bore, the bypass flow tube providing a secondary flow passageway through the tool body;
• at least one primary filter deployed in the primary flow passageway about the bypass flow tube;
• a bypass filter coupled In the bypass flow tube, the bypass filter disposed to filter fluid flow through the secondary flow passageway;
• and
• a bypass valve assembly deployed in the housing, the bypass valve assembly disposed to selectively open the secondary flow passageway when a fluid pressure reaches a predetermined threshold pressure.

A method for filtering a drilling fluid in a borehole, the method comprising:

• (a) deploying a filtering sub in a borehole, the filtering sub coupled to a drill string, the filtering sub including:
• a downhole tool body including a through bore and a longitudinal axis, the tool body further including first and second threaded ends, the tool body configured to be coupled to a drill string;
• the through bore providing a primary flow passageway through the tool body in a direction substantially parallel with the longitudinal axis;
• a bypass flow tube deployed in the through bore, the bypass flow tube providing a secondary flow passageway through the tool body;
• at least one filter deployed in the primary flow passageway;
• a bypass filter coupled to the bypass flow tube, the bypass filter disposed to filter fluid flow through the secondary flow passageway;
• and
• a bypass valve assembly deployed in the housing, the bypass valve assembly disposed to selectively open the secondary flow passageway when a fluid pressure reaches a predetermined threshold pressure;
• and
• (b) pumping drilling fluid through the drill string.

A method for fabricating a filter assembly, the filter assembly configured for filtering a drilling fluid, the method comprising:

• (a) providing a drill collar, the drill collar having a through bore that provides a primary flow passageway through the drill collar, the drill collar configured for coupling with a drill string;
• (b) deploying a bypass flow tube in the through bore, the bypass flow tube including longitudinally opposed first and second ends;
• the bypass flow tube providing a secondary flow passageway through the drill collar;
• (c) deploying at least one filter in the primary flow passageway about the bypass flow tube;
• (d) deploying a bypass filter to the first end of the bypass flow tube, the bypass filter disposed to filter fluid flow through the secondary flow passageway;
• (e) deploying a bypass valve assembly in the drill collar proximate the second end of the bypass flow tube, the bypass valve assembly disposed to selectively open the secondary flow passageway when a fluid pressure reaches a predetermined threshold pressure.