Deep well safety valve

#This invention relates generally to controlling the upward flow of production in a well, and more particularly concerns the fluid pressure control from the surface of sub-surface valves, particularly in deep wells, in such manner as to obviate the effects of excessive control pressure due to well depth.

#In the past, production flow controlling sleeve valves have been constructed to take advantages of the pressure of the production flow to urge the valve sleeve in one direction between open and closed positions. While this was in certain instances satisfactory, serious problems can arise when the pressure of the production flow varies, as for example can occur with the valve at a fixed installation depth, and also when the valve is moved up or down in the well. For example, if the production flow pressure increases greatly, then it requires much more control pressure to overcome the effect of increased production flow pressure on the valve sleeve, in order to shift the valve sleeve in the opposite direction, or to maintain the valve in open condition, for example. Also, excessive static control pressure tends to maintain the valves open is a problem, particularly in deep wells. These conditions in turn serve to limit the depths at which said sleeve type safety valves can be usefully installed, and also requires monitoring of such valves and adjustments of control pressure application to make sure that they remain in desired open or closed state.

#It is a major object of the invention to provide a surface controlled, sub-surface safety valve characterized in that the effects of excessive control pressure due to well depth are obviated. Basically, the invention is embodied in the combination that includes

#FIGS. 1a and 1b are vertical half sections showing one form of the invention;

#FIG. 2 is a vertical half section like FIG. 1b showing a shifted pilot valve condition;

#FIG. 3 is a vertical section like FIG. 1b but showing a modification;

#Referring first to FIGS. 1a and 1b, a tubing string 10 is located in a well 11 provided with casing 12. The annulus 13 between the string and casing is packed off at 14 below the level of a side passage 15 in a valve housing 16 connected in series with the string. In main valve open condition, the upward flow of production fluid in passage 15 is represented by arrows 17. That passage includes, in upward sequence, annularly spaced, vertical openings 15a drilled in housing or body section 16a, and annular passage extent 15b formed between housing inner wall 16b and the outer wall 19a of an insert tubular carrier 19 recessed into and landed in the housing at shoulder 20. Upper port 21 returns the upward flow from the upper end of the passage extent 15b into the housing interior at 22 and the upper tubing string interior at 23 for ultimate collections and distribution at the surface, via means indicated schematically at 24. Accordingly, the valve may be considered a tubing to tubing, sub-surface, surface controlled valve. Note that the housing has upper and lower threaded ends 25 and 26 connected with the tubing.

#In accordance with the invention, a main valve is carried for movement relative to the housing between open and closed positions to control production fluid flow between opposite ends of the housing, as via passage 15. The main valve may with unusual advantage comprise a sleeve 27 carried by the removable carrier 19 for movement between up position shown in solid lines, in which annular port 18 is open, and down position shown by broken lines 27a in FIG. 2, in which port 18 is then closed.

#The main sleeve valve 27 is slidably carried at 28 by the lower stem 19d of the carrier, and an annular seal 29 at the lower end of the sleeve valve packs off between that stem and the housing inner wall 29a, in up position of that valve. Note that shoulders 30 and 31 associated with stem 19a limit up and down stroking of the main valve 27. Also, the main valve is flow pressure balanced, as by exposing vertically opposite end surfaces to production fluid pressure. Thus, lower end surface or seal 29 is exposed to flow pressure, and the upper end surface at 27a is exposed to pressure communicated via ports 32, 33 and 34. For actuating the main valve, piston surface 35 thereon receives control fluid pressure communicated to chamber 36 to displace the valve upwardly, and piston surface 37 receives control fluid pressure communicated to chamber 38 to displace the valve downwardly. Surfaces 35 and 37 may be considered as an actuator for the main valve, whatever form the latter may take.