| 摘要 |
<p>The present invention is directed to an apparatus and method for providing a tubing drain valve suitable for use in a borehole. The present invention is particularly useful in connection with production strings employed in wells producing heavy, sand-bearing oils. The invention comprises a tubing drain valve operable independently of any action or condition on the interior of the pipe string. The tubing drain valve of the present invention is opened in response to the pulling of the pipe string from the borehole. A plurality of dogs carried by a sleeve biased to an initial position about a tubular member suitable for incorporation in a pipe string and including a valved passage through the side wall thereof are designed to engage the casing and temporarily prevent movement of the sleeve as the pipe string is being pulled from the borehole. Continued pulling of the string produces relative movement of the sleeve and tubular member along the longitudinal axis of the tubular member. The valve passage is opened only after relative movement through a predetermined distance. After the fluid passage has opened, the dogs at least partially retract within the opened passage to free the sleeve and permit the pulling of a "dry string," including the drain valve apparatus.</p> |
