Formation Testers

The formation tester, as the name implies, is a tool built for testing thecontents of sands encountered in drilling wells without actually cementingcasing on the sand. The tester was developed in the Mid-Continent and has been in use commerciallythere since about 1926. However, some two dozen patents have been issued onformation testers dating back to the seventies. The method apparently was anoutgrowth of the old Mother Hubbard grain or bean packer, used around casingbefore the days of cementing casing. These packers were also seated in atapered hole and if the formation tested was not satisfactory the casing waspulled loose and the hole taken down to another formation. A great deal ofexperimental work has been done in its development, and as a result of thiswork the formation tester became an accepted integral part of the petroleumdevelopment in California. The formation tester was introduced into California some three years ago by M.O. Johnston. Months of discouraging and expensive work followed itsintroduction into this state, but one organization after another tried the tooland its use is now fairly general. Shortly after Johnston began testing inCalifornia, the Halliburton tester was also introduced into the state and nowanother too) is being introduced, the Shaffer-Boles tester. Princaple and Operation of Testers The principle employed in all formation testers is that of packing off thefluid in the hole above the formation to be tested and thereby preventing itfrom having access to the testing tool. This permits the fluid contained in thegiven formation to have unrestricted access to the tool. It is accomplished byrunning the tool and packer on the bottom of the drill pipe; the valves in thetool being closed while going into the hole to prevent fluid from entering thedrill pipe. The packer is then seated at the desired point, trapping thedrilling fluid above it. When this has been done, the valves in the tool areopened and the fluid from the formation is allowed to enter the empty pipethrough the tool.