734 Subsurface Geologic Methods 



releasing of the formation pressure of a selected zone to atmospheric 

 pressure under full control before expending time and money to case 

 and complete the well. This is accomplished by setting a packer on drill 

 pipe or tubing to effect a seal against the wall of the bore hole, a pro- 

 cedure which eliminates communication of the drilling fluid from the 

 annulus above to the isolated section below. After the packer is properly 

 sealed, torque is taken on the pipe and added weight released upon the 

 assembly forces which open the valves of the tools and permit the forma- 

 tion pressure of the isolated section to enter the empty drill pipe above. 

 The drilling fluid trapped below the collapsed packer necessarily passes 

 through the tester valves before liquids or gases from the formation may 

 enter. After the test has progressed a desired length of time, the valve is 

 closed and the running-in string removed from the well, at which time 

 samples of the fluids may be taken as the recovery is raised to the surface 

 (fig. 392). 



Constant research and development have provided improved equip-, 

 ment and methods of testing to keep pace with the fast changes in drilling 

 procedures. New mechanical adaptations have been added which have in- 

 creased the safety of the process. Knowledge gained by practical exper- 

 ience indicates that the time element has been extended without hazard, 

 an extension which provides more time for increased recovery. The 

 clearance between the packer and the wall of the bore hole has been re- 

 duced so that there is a more eff"ective packer seal. This experience has 

 also indicated that shales erode more quickly than sand formations under 

 bit action, a fact which renders them less suitable for a packer seat. 



The portion of the testing tool assembly that is lowered to the selected 

 testing point of the well consists of several individual units. Each unit 

 has a special duty to perform, yet all combined are operated as one unit 

 during the testing procedure. The valve assembly usually consists of three 

 valves held safely in position by a / arrangement that protects the empty 

 drill pipe against premature fluid entry and which may be opened when 

 desired for securing the test, then automatically closed when the test is 

 completed. The size of these valves may be adjusted according to the 

 type of test to be made. Figure 393A shows in section one popular type of 

 testing device. 



A choke bean is usually placed immediately below the valve assembly 

 for a dual purpose: (1) to control high-formation pressures and decrease 

 the shock load at the opening of the tool, and (2) to determine better 

 the potential value of the zone being tested. Very few wells are tested 

 without the assistance of choke beans. Figure 393B shows this unit. 



The closed-in pressure valve, figure 393C, was designed to close off 

 posivitely the testing zone below the packer to obtain static-formation pres- 

 sure in the tested zone. This pressure is recorded on a subsurface-pres- 

 sure, recording-device chart. 



The by-pass, or equalizing valve, is usually assembled below the 



