This invention relates generally to a valve for use in a tubing disposed in a bore hole and more particularly, but not by way of limitation, to a retrievable fluid control valve for controlling the flow of a column of fluid through a tubing and into the bore hole of an oil or gas well.
It is well known in the petroleum industry that there is a need for pumping fluids into a well and on into the formation into which the well is drilled. Such fluids are used for a variety of purposes, such as for scale removal, chemical treatments, and acidizing with jet tools on long open hole intervals or multiple sets of perforations. It is also known that such fluids are conducted into the formation through an open bore hole of the well into which a tubing has been placed for conducting the fluids.
Although many formations require the introduction of fluids for facilitating the drilling, completing or producing of a well, some formations cannot receive a continuous flow of fluids. Rather, such formations must intermittently receive the fluids. Therefore, there is the need for some type of device which can intermittently, rather than continuously, flow the fluids.
This need has been previously recognized as shown in U.S. Pat. No. 3,847,223, entitled "Retrievable Fluid Control Valve and Method" and issued Nov. 12, 1974. This patent discloses a valve, disposed in a tubing, which opens in response to the pressure of a column of fluid held by the valve reaching a predetermined magnitude. More particularly, this valve includes a single spring which provides a preset pressure threshold in response to the compression of a piston which is actuated in the bore hole by the hydrostatic head of the fluid column supported by the normally closed valve.
It is to be noted that the valve disclosed in U.S. Pat. No. 3,847,223 is not completely presettable at the surface, although a degree of surface presetting is achieved by means of the type of spring and the nature of the piston-retaining collar or external spacer rings used. Furthermore, this patent does not disclose a mechanism by which pressure on both sides of a seating nipple can be equalized for facilitating extraction of the valve from the tubing when the valve is closed. Additionally, this patent does not show a valve having a relatively wide range of different pressure threshold settings which are fully presettable at the surface. Because these features would enhance the utility of such a valve, there is the need for an improved retrievable fluid control valve which combines each of these features into a single device.