A subsurface safety valve includes a one piece pressure housing having a flow passage provided therethrough and a recess formed in a side wall of the flow passage. A flapper member having first and second, respectively open and closed positions, is mounted to the housing in the recess. A control mechanism controls movement of the flapper member between its first and second positions. The control mechanism may include at least one piston substantially longitudinally aligned with flow passage wall, the at least one piston being positioned in longitudinal relation to a portion of a surface of the wall, the surface of the wall being provided with a longitudinal groove and the at least one piston being provided with a protrusion which is received within the longitudinal groove.

A hydraulically actuated subsurface safety valve for controlling fluid flow through a well tubing by actuating a first piston and cylinder assembly through a fluid passageway. A positive valve seat and valve element closes the flow of fluid to the assembly when the safety valve is opened. An equalizing valve is provided in an equalizing line and is actuated by a second piston and cylinder assembly through a fluid communication line downstream of the positive valve seat and element. A fluid bypass bypasses the second piston and cylinder assembly for bleeding off the opening pressure to the equalizing valve for allowing the equalizing valve to be biased to the closed position.

A release mechanism for use in a well tool that requires a hydraulic piston area to be equalized with a minimum force. A valve seat and valve element are positioned in a fluid passageway for actuating the assembly. A rod having a first and second section is connected to the assembly and movable for moving the second section into the valve seat. The second section has a smaller cross-sectional area and smaller length than the first section. The area of the valve seat is less than the cross-sectional area of first section but larger than the second section. The release mechanism allows the sealing area to be reduced without reducing the strength of the rod.

A subsurface well safety valve having an equalizing line between a point below the safety valve and a point above the safety valve and an equalizing valve in the line. A sleeve valve is releasably locked in a first position opening the equalizing line and in a second position closing the equalizing line for protecting the equalizing valve or closing the equalizing line in the event the equalizing valve develops a leak.

A drainage pipe section for a horizontal subterranean well has a base pipe coaxially circumscribed by a tubular structure having a longitudinally intermediate portion defined by a sand screen assembly. An annular flow passage is formed between the base pipe and the tubular structure and communicates with the interior of the base pipe via base pipe sidewall openings positioned inwardly adjacent opposite end portions of the tubular structure. Annular adjustable flow control members having variable length labyrinth passages recessed into their outer sides are coaxially interposed in the annular flow passage between the opposite ends of the sand screen assembly and the base pipe sidewall openings. The flow control members are sealed within the annular flow passage by means of a rubber coating adhered to their outer side surfaces, and an adhesive type sealant material injected into annular spaces between the flow control members and facing portions of the base pipe. Specially designed plugs having resilient portions are used to selectively seal off portions of the labyrinth passage to selectively vary its effective length and thus the resistance to flow therethrough and the fluid flow into the base pipe interior through the annular flow passage. Additional seal structures are provided at the opposite ends of the tubular structure, each including a quantity of adhesive type resilient sealant material injected between the tubular structure end portion and the base pipe, and two annular resilient elastomeric backup seals.