The present invention relates generally to operations performed and equipment utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a system of measuring properties and transmitting measurements in wells.
It is very beneficial to be able to measure properties, such as pressure, in a well and then transmit those measurements to a remote location, such as the earth""s surface or another location in the well. For example, a valve system described in U.S. Pat. No. 6,152,232, the entire disclosure of which is incorporated herein by this reference, permits a drill string to be conveyed through a casing string in an underbalanced condition. The system includes a valve which is opened when the drill string is run into the casing string, and the valve is closed when the drill string is retrieved from the casing string.
In order to open the valve, it is desirable for there to be no pressure differential across a flapper of the valve, or at least for the pressure differential to be known before opening the valve. Unfortunately, however, there presently exists no satisfactory means for measuring this pressure differential at the time the drill string is run into the casing string, or for transmitting the pressure differential measurements to a remote location. Therefore, an operator must estimate the pressure differential by making certain assumptions, calculating hydrostatic pressure at the valve, etc., which leads to errors in the pressure differential estimate.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a system and method are provided which solve the above problems in the art, and which are useful in other situations, as well. In an example described below, at least one sensor is used to sense a pressure differential across a closure member of a valve. An indication of the pressure differential is transmitted from the valve to a tool positioned in a flow passage of the valve for transmission to a remote location.
In one aspect of the invention, a method of measuring a pressure differential across a closure member of a valve in a well is provided. The method includes the steps of: positioning the valve in the well, a flow passage extending longitudinally through the valve, and the closure member blocking flow through the flow passage; sensing the pressure differential in the flow passage across the closure member using at least one sensor positioned in the valve; conveying a tool into the flow passage; and transmitting an indication of the sensed pressure differential from the valve to the tool.
In another aspect of the invention, a valve for use in a well is provided. The valve includes: a flow passage formed through the valve; a closure member operative to selectively permit and prevent flow through the flow passage; and at least one sensor operative to sense a pressure differential in the flow passage across the closure member.
In yet another aspect of the invention, a valve system for use in a well is provided. The valve system includes: a valve positioned in the well, the valve including a closure member selectively permitting and preventing flow through a flow passage formed through the valve, and at least one sensor operative to sense a pressure differential in the flow passage across the closure member; and a tool positioned in the flow passage, the tool transmitting power to the valve to operate the sensor, and the valve transmitting an indication of the sensed pressure differential to the tool.