GB1407844A - Well tester apparatus and method of operating a well test valve - Google Patents

Abstract

1407844 Wells &c SCHLUMBERGER TECHNOLOGY CORP 17 Nov 1972 [17 Nov 1971] 53131/72 Heading E1F A test valve is opened by the difference in pressure between a control pressure in excess of the hydrostatic pressure at the depth of the test and the pressure of a body of compressible fluid, the pressure of the body being before use of the valve less than the hydrostatic pressure at the depth and being increased to the hydrostatic pressure before applying the control pressure. A test string is suspended from a wellhead 12, the string comprising a control valve 15, a pipe 17, a slip joint and safety valve 19, a reversing valve 20, a choke 21, the test valve 22, a flow control valve 23 operated by longitudinal movement of the string, a packer 24, a perforated nipple 27 and pressure recorders 28. The string may also include a safety joint 29 and jar 30. The test valve comprises a housing 36 having a sample chamber 50, and a valve mandrel 44 having a bore 54. A piston 57 on the mandrel is urged downwardly by annulus fluid passing through ducts 60 and upwardly by a spring 63. A chamber 67 in the housing has a floating piston 73 subjected on the lower side to the annulus pressure through ducts 79 and on the upper side to the pressure of the body of compressible fluid (nitrogen) in the chamber 67 which is connected by ducts 76 to the chamber containing the spring. The valve housing 36 is connected to the mandrel 84 of the valve 23, the mandrel being telescopic within the housing 85 of the valve 23. The piston and mandrel 44 are biased upwardly to close the valve 22 as the string is lowered into the well. At the test depth the joint 19 is closed so that weight sets the packer, the housing 36 and mandrel 84 moving downwardly to open the valve 23 to admit formation fluid to the valve 22 and to close ducts 79 trapping annulus fluid at pressure in the chamber 67. Pressure is applied to the annulus so that the control pressure acts downwardly on the piston 57 to move the mandrel 44 downwardly to the postion shown in Fig 3, formation fluids flowing through the valve 22. After a short time the pressure is removed from the annulus and the spring 63 moves the mandrel 44 to the closed position shown in Fig 2. The valve 22 is left closed, or alternately closed and opened, whilst pressures are taken by the recorders. To end the test the pressure on the annulus is reduced and the string is lifted, a sample of the formation fluid being trapped in the chamber 50. The chamber 67 is large compared with the displacement of the piston 57 so that the body of the fluid remains at a substantially constant pressure. Joints may be provided in the housing 36 and the mandrel 44 to give acccess to the chamber 50. During the test the well is controlled by blow-out preventers at the wellhead.