Patent GB-851096-A (GB)
Title: Improvements in or relating to production of fluids from a plurality of well formations
IPC: E21B43/14
Filed: 1959-06-10
Abstract: 851,096. Oil wells. SUN OIL CO. June 10, 1959 [June 13, 1958], No. 19921/59. Class 85. A flow control device is positioned retrievably in a landing nipple 15 in a tubing string 14 and is designed to pass fluids from two production zones A, B the fluids being mixed in the tubing string 14 from which the mixture is discharged. One of the zones may have insufficient pressure to bring the oil to the surface, in which case the greater pressure of the other zone is used to effect the lift. In Fig. 1, the casing 10 has perforations 12, 13 at the zone levels, and a packer 9 prevents oil from the bottom zone from passing up the annulus. The flow control device comprises a cylindrical body 18 spaced at 19 from the wall of the landing nipple, and having ports 20 communicating with ports 17 in the nipple so that oil from zone A may pass a resilient non-return valve 25 and flow into the string 14 through a port 23. The flow from the lower zone B is up through the open end of the string 14, past a non-return valve 33 and into the string 14 through a port 27. The ports 23, 27 or either may receive a choke nozzle 28, according to the relative pressures in the zones A, B. As shown in Fig. 1, it is assumed that zone B is a high pressure zone, the choke 28 producing a sharp pressure reduction which causes solution gas to be released which aids the lifting of the mingled flows from the two zones. If zone B is a high pressure gas zone, lifting of oil from the low pressure zone A is likewise effected. If zone A has enough pressure only to bring oil into the annulus without forcing it through the flow control device, an intermittent extraneous gas pressure is applied to the top of the oil in the annulus, to force the oil through the ports 23, and then to allow further oil to collect. A modified flow control device is described wherein the upwardly flow from the lower zone is through an axial choke to a passage which is displaced from the axis to make room for a passage from the ports by communicating With the upper zone, the streams for the side-by-side passages co-mingling before admission to the string 14. In Figs. 7, 8, flow control devices 64 are retrievably positioned in side pockets 62 in the tubing string 61, and a packer is arranged between the zones A, B. The pockets are perforated at 65 to admit fluid to the ports 67, the flow being downwards past the non-return valve 72 to the choke nozzle 74. The rate of oil flow from the lower zone can be controlled by selection. of a choke for the lower device 64, or by controlling the back pressure by a valve 76. More than two zones may be served by a corresponding number of side pockets and flow-control devices and the devices may be lowered into or retrieved from the well without disturbing the other devices. The devices may be used for selectively acidizing, chemically treating or fracturing any one of the zones, the non-return valves preventing the acid &c. from reaching other zones. The tubing string may include a flow control device, as in Fig. 8, in a side pocket, and, at the level of zone A, a flow-control device as in Fig. 1, the zone B being in communication with the open end of the string. A packer is arranged between zones A and B, and a packer above zone A, but below the side pocket. With this arrangement, extraneous gas pressure is applied to the annulus above the upper packer and passes through the side pocket control device to stimulate production flow from zones A and B neither of which has sufficient pressure to flow unassisted. The side pocket flow-control device may be replaced by a conventional gas injection valve.