Miscellaneous Subsurface Methods 737 



damage caused when releasing the packer from the seat is relieved by this 

 unit. (figs. 392 and 394) . 



Since the area of contact is greatest at the packer seat, a safety joint 

 is usually run immediately above. This permits the removal of all equip- 

 ment above that point should a fishing job occur. Several types of safety 

 joints are available which may be run at any desired point in the string. 

 It is a suggested practice to run safety joints on formation tests; however, 

 it is optional with the well operator. One type is shown in figure 395. 



Because of varied drilling programs that have incorporated forma- 

 tion testing, it has been necessary to develop testing packers for all well 

 conditions, some of which, although infrequently used, nevertheless re- 

 main available. 



(1) The cone packer, so named because of its conical shape, was 

 designed to effect a seal on the shoulder created when coring 

 at reduced size below the drill hole. This type of packer is now 

 very seldom used . 



(2) The wall packer has almost completely replaced the cone type 

 of packer. This packer was developed to be used in wells where 

 a core shoulder was not available or where testing zones had 

 been penetrated with the drill bit before coring. Its results are 

 more effective because of its ability to be used in the regular 

 drill hole as well as in the smaller core holes, (fig. 392) . 



(3) The practice of running a wall-over-cone packer combination 

 has been eliminated. Although it was popular several years ago, 

 improved testing techniques and packer construction has made 

 possible the completion of open-hole tests more satisfactorily 

 without the added cone packer. 



(4) Double-wall packer testing utilizing two wall packers, one above 

 the other, is effective many times when a single packer has failed. 

 This is especially true when attempting to set the packer opposite 

 a thin lens or in a broken-sand and shale formation. 



(5) Testing between two packers is common in many areas. This 

 procedure is usually conducted by setting one packer at the top 

 of a given sand and one at the bottom with a perforated section 

 of pipe between the packers. This setup provides a means of 

 testing a zone that has known productive horizons above and be- 

 low. Although this procedure is practical in many areas, it is 

 not a suggested practice for an area such as the Gulf Coast or 

 upper Gulf Coast regions where very soft and cavy formations 

 are found. 



(6) That the casing has been set and cemented does not necessarily 

 mean the well is ready for production. Certain information is 

 frequently desired before final completion. These data can only 

 be obtained by formation testing or production testing. Forma- 

 tion testing frequently offers as much information in much less 



