Optimizing the Downhole Safety Valve Design

Specialists of Cosmos-Neft-Gas (Voronezh) and Astrakhan Gazprom (Astrakhan) designed and successfully tested a downhole safety valve (Fig.1, 2) which enables it to be used as either an automatic mechanical unit or hydraulically operted by gas flow coming from the well.
Supporting elements of the structure, which take the stem spring force and interact with the mating thrust faces of the body and stem, are fabricated with identical seats and can be repositioned from one end of the stem to the other depending on the valve operating mode.
For well operation, the valve is installed in the tubing nipple and is fixed in it with the help of lock 1, installed in adapter 2. Pressurized working fluid is supplied through channels 4 in body 3 of the actuating mechanism, and channels 9 in inner body 8 to the pilot cavity 5, formed by the inner surface of body 3 and outer surface of hollow cylinder 6, which form a spring-loaded system with a shaped inlet section in which a replaceable shaped sleeve 7 is installed. This fluid effects the collar on the shaped outer surface of hollow cylinder 6, acting as a piston. Under working fluid pressure, the spring-loaded stem including shaped hollow cylinder 6 shifts towards butterfly gate 14 and opens it compressing at the same time retracting spring 10. One of its end faces bears against support washers 11, and the other one against the mating thrust surface of the valve body 12 through the replaceable sleeve 13. A butterfly gate 14 revolves around its pivot axis compressing spring 15.
In off-design or emergency operating conditions, a command from the control panel decreases the pressure of liquid in pilot cavity 5 and retracts spring 10 moving the hollow cylinder 6 with replaceable shaped sleeve 7 from butterfly gate 14 which then is closed under the action of spring 15 and oncoming gas flow.
If necessary, when the hydraulically operated valve is converted to a mechanically operated one, replaceable shaped sleeve 7 of hollow cylinder 6 is changed, and on the inner surface of body 3 of the actuating mechanism a groove is made for communication of this cavity with the valve cavity. In such a case, channels 4 are excluded from operation by their simultaneous shutoff, for example by means of screwing plugs into them, or by replacement of the channeled body with a body having no channels and, with simultaneous adjustment of the spring force, support washers 11 of retracting spring 10 and replaceable intermediate sleeve 13 are rearranged.
The flow area of replaceable shaped sleeve 7 of hollow cylinder 6 is determined based on conditions, when the elastic force of retracting spring 10, which effects the actuating mechanism at one side, will be larger or equal to the pressure of the oncoming gas flow, effecting the replaceable shaped sleeve 7 at the other side. When design parameters of the flow, and in particular, of the flow rate are increased, hollow cylinder 6 of the actuating mechanism, by overcoming the elastic force of  retracting spring 10, moves upwards and butterfly gate 14 closes the flow area of the valve and shuts off the flow.
The application of design solutions enabled unification of the safety valve design, allowing the creation of a universal valve by completing, as necessary, either a hydraulically operated or automated mechanical valve with virtually the same components. This considerably extended its functional capabilities, which enabled a significant reduction of both time and cost of well servicing.
The valve design is protected by a RF patent.

Source: www.kng.ru

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