OIL WELL TESTING

1463374 Wells &c HALLIBURTON CO 18 Feb 1974 [26 Feb 1973] 7373/74 Heading E1F A fluid sampler for use in an oil well test string, has a member which is reciprocated by varying the pressure of fluid in the annulus about the string. The sampler which comprises power and sampling sections releasably connected is located in the string adjacent a packer. In use the string is supported by a sub aqueous wellhead and extends through a riser to a vessel, the power section being above the sampling section and the packer being below the sampling section. The power section is charged with low pressure nitrogen which together with a spring acts downwardly on a piston fixed to the member. As the string is lowered into the well the effect of buoyancy is counter balanced by annulus fluid acting downwardly on a further piston, the annulus fluid also passing through ports to act on the nitrogen to increase its pressure with depth. When the packer is just above the formation to be sampled the packer is set and the weight of the upper part of the string is allowed to telescope parts of the power section closing the ports. The piston which is biassed by the spring and nitrogen is also subjected to the pressure of the annulus fluid acting upwardly so that increase in annulus pressure moves the piston and member upwardly. The lower part of the casing of the power section is fixed to the casing of the sampling section and the member is attached to a pull mandrel of the sampling section. Increased annulus pressure moves the member together with the mandrel upwardly to open ports in the sample chamber of the sampling section to permit formation fluid to flow upwardly through the chamber and string. Release of the increased pressure moves the member and mandrel downwardly to trap a sample of formation fluid in the chamber. When the sample section is removed from the string formation fluid trapped in the sample section but not in the chamber is discharged through a spool valve, and parts of the casing are removed to give access to valves draining the sample from the chamber. Should the well be threatened with a blow out through the annulus the increased pressure moves the member with such force that a close and lock device in the sampling section is actuated.