Abstract: A hydraulic system has a filter that filters only when the fluid is flowing in one direction. The filter is located in a flow passage between a hydraulic fluid source and a valve in a well. The source supplies hydraulic fluid pressure in a forward direction to keep the valve open. A bypass passage allows hydraulic fluid to bypass the filter. A check valve located in the bypass passage prevents forward flowing fluid from flowing through the bypass passage. If hydraulic pressure is lost, hydraulic fluid will return through the bypass passage, rather than flowing through the filter, to allow the valve to quickly close.

Abstract: A through the tubing perforating gun assembly having means for separating the upper head from the gun carrier upon firing. This allows the gun carrier to fall to the bottom of the well and eliminates the need to retrieve the carrier. Special charges are used to separate the carrier from the head with the charges being fired simultaneously with the gun charges.