The main advantage of sidetracking over other means of well- workover operations is its opening big possibilities for increasing production. You receive a new bottom-hole instead of working with the old one.

       Owing to the technology of sidetracking you don’t have to close old wells that have a poorly cemented flow string or water or gas breakthrough in the perforation zone, for example; you can also avoid many cementing under pressure operations that may be successful or not.  Using the sidetracking method you will be able to run a new liner above the bottom-hole, evaluate the current state of the deposit and perform the perforation, knowing the actual location of different formation fluids.

       Cutting a window includes the installment of a whipstock and its positioning in the direction where the new hole is to be drilled. The positioning takes place using the UBHO (Universal BoreHole Orientator). The UBHO consists of a drilling tool sub and a stinger trap. The trap has a guide in accordance with which the positioning is realized. This guide is put into a position that corresponds to the direction of the whipstock bevel with the help of a special handling unit.

        The whipstock is designed to provide the required inclination of the cut section from the the main hole axis when cutting a “window” in the flow string and directing the bottom-hole assembly when drilling a new hole.

        The gyroscopic inclinometric navigation system IGMC 44-100/80 is used to position the whipstock. A stinger which has a special groove for a guaranteed connection with the trap guide and owing to which it is placed in the same position in the trap as that determined by the position of the guide is attached to the tool at the bottom.

 

1. Trap 

2. Stinger 

3. IGMC 44-100/80.

       Owing to the use of the technology of inertial determination of position in the geographic reference system the tool is insensitive to magnetic disturbances caused by the presence of ferromagnetic substances in the wellbore (works in cased wells).

Sidetracking stages:  

- descent and positioning of the whipstock   

- milling out of the sidetracking window  

- drilling a second hole

       When sidetracking is performed in the casing column, cutting a window using the whipstock is preferable to milling a casing column section for the following reasons: 

1. High-quality cementing of the casing column in the window cutting area is not necessary, whereas during complete milling of the column with the sonic cement bond log indicators below 70% additional cementing under pressure is recommended.

 2. From the point of view of the geological section windows may be cut in any rock, whereas when milling a section arenaceous rock is preferable.

 3. When milling a casing column section in order to provide the removal of chips special requirements are put to drilling mud properties and the washing regime.  When cutting a window no special requirements are put to drilling mud properties and the washing regime. 

4. When cutting a window you don’t have the problem of metal chips removal as when cutting a window filings are formed and the volume of milled metal is 4-6 smaller than when milling a column section. 

5. Sidetracking with the use of the whipstock is a 100% successful operation as it is performed at the same time with cutting a window. When milling a casing column section sidetracking is performed separately and its success is not always guaranteed as it depends on a number of factors: 

- the length of the section milled; 

- the quality of the cement plug;  

- type and strength of rock in the sidetracking area; 

- type of bottom-hole assembly, sidetracking regime etc. 

6. The origin of the second hole formed with the help of a trough-shaped metal whipstock is more reliable than that formed in cement rock as in the future this area will be effected by bottom-hole assembly elements and tool joints during round trip operations and drill pipe rotation.  The destruction of the cement in the second hole area may bring to unforeseen problems. 

7. In vertical wells owing to the use of the gyroscopic inclinometer the whipstock is positioned and a new hole is cut in the right direction. When milling a section the second hole is usually drilled at random and only after that it is run in the right direction.  

8. Cutting a window is, as a rule, cheaper than milling a casing column section.

 Ground tool design features: computer processing of data, display of data at the driller’s control panel, display and printer, setting and well tool power control. 

Communication design features: a single core cable.