Patent GB-1067651-A (GB)
Title: Fluid-confined underground storage reservoirs
IPC: E21B41/00
Filed: 1964-08-24
Abstract: 1,067,651. Storing gases; gasholders of variable capacity. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ, N.V. Aug. 24, 1964 [Aug. 26, 1963], No. 34552/64. Headings F4P and F4X [Also in Division E1] A fluid storage reservoir in a permeable formation 12, Figs. 1-3, bounded by a horizontally extensive impermeable layer 11 is formed by displacing a barrier fluid 20 through the permeable formation 12 around a well borehole 10 traversing at least a portion of the permeable formation, establishing the barrier fluid 20 as a continuous vertically extensive wall of closed periphery 9 located around the borehole, in a position contacting the impermeable layer and spaced from the borehole, and the wall. is maintained in that position. The barrier fluid 20 is a gel solution capable of delayed rigidifying within the formation 12 and, simultaneously with its injection from the entire length of the perforated section of the casing string 13, an aqueous fluid such as formation brine is injected through the tubing string 15 into the area 21 of the formation below the casing string. This brine solution maintains the area 21 of the permeable formation beneath the casing storing 13 void of the gel solution 20. The gel solution is then displaced laterally from the borehole, to form an annular wall 9 by terminating the initial injection of gel solution and following it by the injection of an aqueous fluid 22 through the perforations 14 of the casing string 13, Fig. 2. The injection of aqueous fluid into portion 21 of the formation 12 beneath the casing string is continued to maintain this part of the formation void of the gel solution. The displacement of the gel solution with respect to the borehole is continued until it reaches a position which can be determined by logging devices or observation wells and on being established in position the annular wall 9 of the gel solution reacts to form a rigid and impermeable mass. The aqueous fluid within the formation 12 is confined within the annular wall 9 and exerts a static pressure on fluids injected into the formation 12 through the well borehole 10, which is now equipped for the introduction of any fluid lighter than the aqueous fluid previously injected through the borehole. In Fig. 3 natural gas is shown as displacing the aqueous fluid within the annular wall 9 downwardly to the level of line 25. In other embodiments of the reservoir, not shown, the impermeable layer may be below rather than above the permeable formation or an impermeable layer may be created by the same method within a permeable formation, Fig. 5, not shown, where impermeable formations are not naturally present. The arrangement shown in Fig. 6 utilizes a series of juxtaposed storage reservoirs to establish a vast underground central storage area 47 and the surrounding reservoirs 45, 46 can also be used. In a further embodiment, Figs. 7 and 8, not shown, the wall of the reservoir is a series of connected curtains rigidly formed by the same gel solution method between the various members of a ring of wall bores. Figs. 9 and 10 illustrate another embodiment intended for the storage of fluid such as natural gas having a relatively low specific gravity in a permeable formation 67 beneath a relatively impermeable layer 71. A controlled fluid cone 75 of brine solution is maintained within the permeable formation 67 around the stored fluid. Central production well 65, provided with casing string 72, production string 74, and conduit 73, has a plurality of injection walls 66 comprising only a string section 70, spaced around it for the injection of barrier fluid into the permeable formation 67. The walls of the fluid cone 75 vary with variation of volume of fluid being stored. In a further embodiment the dynamic fluid cone is initially established by using a rigidifying gel solution which then produces a fixed wall reservoir which can also be used for the storage of a heavy fluid. In yet a further embodiment an inverted dynamic fluid cone established in a permeable formation between two impermeable layers may be adapted for storage of fluids of relatively high specific gravity.