Miscellaneous Subsurface Methods 739 



set at any desired point in the casing by means of slips that, 

 when released, bind between the slip body and casing and act 

 as an anchor on which to set the packer and to operate the tool 

 mechanism. 

 There are several applications for which this type can be used: 



(A) Productivity through perforations in the casing. 



(B) Productivity from the open hole below a cemented casing. 



(C) Testing for water shut-off after cementing. 



(D) Testing for holes in casing. 



Figure 396 shows examples of various packer combinations. 



Debris in the drilling fluid, at the time of testing, should be removed 

 and the mud properly strained before entrance is made into the choke 

 area of the testing assembly. Two sets of strainers are provided for this 

 purpose. The anchor, as used for open-hole tests, serves as one strainer, 

 and built within the anchor and mounted over the choke is a secondary 

 strainer. This strainer is smaller in diameter and length, but contains 

 many more holes of smaller diameter to catch debris that has passed 

 through the outer screen. In like manner, double screens are used in 

 casing or hook-wall packer testing (figs. 392, 393B, 394, and 396). 



Great strength is required in the anchor pipe for open-hole testing 

 to withstand the weight of the mud column in the annulus above, plus the 

 limited weight of the drill pipe used in collapsing the packer. Flush 

 pipe with tool joints has replaced collared pipe as an anchor. In many 

 areas, drill collars are used to withstand the severe loads, especially when 

 testing thick zones at great depth. 



A safety precaution employed during a test is the running of a cir- 

 culating valve. This valve is usually placed in the string several joints 

 above the tester assembly. Provision is made for free flow of the recovery 

 upward through the valve during the test, yet permitting circulation down- 

 ward through the running-in string and upward in the annulus between 

 pipe and well bore if necessary. This is made possible by a back-pressure 

 valve opposing fluid entry from outside the drill pipe. This device has 

 proved invaluable in preventing blowouts, controlling wells, and con- 

 ditioning drilling mud after the test. 



For testing in cased wells, a reverse circulating valve has been de- 

 veloped. This unit permits the pumping of fluids, either down the run- 

 ning-in string or down the annulus between the casing and running-in 

 string. This arrangement facilitates the removal of the test recovery 

 while the running-in pipe is still in the well and the recovery of a dry 

 string when coming out of the hole with the tools. Its use is quite popular 

 when drilling town-site leases or on wells over water where the recovery 

 must be controlled at all times, (figs. 392 and 394). 



Surface control is an essential phase of a test during the operational 

 procedure. Although it is known that in some areas surface control is of 

 no importance, it is necessary in many others to place special emphasis 



