Method and apparatus for injecting drilling waste into a well while drilling

A method for disposing of drill cuttings generated during the process of drilling oil and gas wells, by injection into the annulus of a well bore and into the earth formation, throughout the well bore operation through the use of secondary casings, injection tubes attached externally to the surface casing string and by injection into a special well bore directionally drill adjacent the primary well bore in a path leading away from the primary well.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the injection of drill cutting by 
deposition into the annulus around a well casing and more particularly to 
the injection of such cuttings in a well being drilled at a much earlier 
stage than is presently considered feasible. 
2. General Background 
In oil and gas well development operations, the handling and disposal of 
the waste material entrained in the fluid during the drilling process, 
commonly known as the drill cuttings, has become an increasingly difficult 
problem. Environmental regulations and considerations prohibit or make 
undesirable the surface disposal of so-called drilling muds and drill 
cutting. On the other hand certain categories of material produced in the 
drilling process may be reclaimable as useful construction materials such 
as various grades of sand or gravel. Such material may be used to 
back-fill reserve pits and to construct and maintain road beds etc. 
Moreover, although the disposal of drilling fluids and materials such as 
clay, shale or fine earth particles, brought to the surface in the 
drilling process, may be unwanted from an environmental impact 
perspective, the disposal of these materials into subterranean formations 
may be acceptable and possibly beneficial. 
To this end the present inventive process has been developed with a view 
towards providing a unique system and method for disposing of certain 
materials generated during the process of drilling oil and gas wells and 
the like. The injection of drill cuttings into the annulus of a well bore 
is not unique. However, the present injection process takes place only 
during the last phase of the drilling process, generally during the last 
20% of the well bore usually after the intermediate casing has been set. 
Since drill cutting are generated throughout the well drilling process, it 
is essential that the cutting be contained, stored or otherwise disposed 
of during the first 80% of the drilling operation, thereby incurring 
excessive high cost for collection and transportation. Therefore there is 
a need to utilize the cuttings injection process throughout the drilling 
process thus reducing cost and adverse environmental impact as a result of 
transport and disposal of the cuttings at a remote site. 
SUMMARY OF THE INVENTION 
The present invention is directed to a method for disposing of certain 
waste materials generated during the process of drilling oil or gas wells 
in a manner which allows for the injection of such materials as a slurry 
into a subterranean formation throughout most of the well boring 
operation. The present inventive concept discloses a process which allows 
for drill cutting to be injected at a much earlier stage of the drilling 
operation. One such method would provide a well head which includes a 
predrilled well bore adjacent the well being drilled. The predrilled well 
bore being directionally drilled in a path leading away from the oil or 
gas well being drilled. The cuttings from the oil or gas well currently 
being drilled would then simply be injected down the predrilled well bore 
and into the earth formation. A second method is to provide an injection 
tube which extends below well head and runs alongside and attached to the 
surface casing located between the drive casing and surface casing. The 
injection tube being extended with the length of the surface casing 
string. Therefore, as soon as the surface casing string is set and 
cemented, perforation of the injection tube permits injection to begin. A 
third method is to provide a secondary casing between the first drive 
casing and the surface casing string thereby providing an annulus which is 
plugged at its lower end when the surface casing string is set. The 
secondary casing and its setting cement is then perforated to allow for 
cuttings injection. Each of these three methods allows cuttings injection 
to take place in the well being drilled in the upper two thirds of the 
well bore rather than only in the last third.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As seen by viewing FIG. 1 the prior art is shown which demonstrates that at 
least in most cases 80-100% of the drilling operation must be completed 
before attempting to inject drill cuttings via the well head 1 into the 
annulus 3 located between the production or intermediate casing 5 and the 
surface casing string 7. As seen in this case the production string 5 and 
the surface casing string 7 must be set by cementing them into the earth 
formation prior to injection of the drill cutting slurry. Therefore, all 
waste materials must be contained or disposed of during most of the 
drilling operation. As cost soar for containing and transporting drilling 
waste material, it is therefore becoming imperative that new and improved 
methods for injecting cuttings back into the well being drilled. One such 
innovative method can be seen in FIG. 2 wherein a well head 12 is modified 
to accommodate an injection tube 28 and connection 26, in addition to a 
drive or conductor casing string 14 and a surface casing string 16, the 
drive casing 14 passing through a body of water 18 and into the seabed 
earth formation 20. A production or intermediate casing 22 is centrally 
located within the surface casing 16. By providing an injection tube 
connection 26 in the well head 12 for a tube 28 to be attached along the 
length of the surface casing 16 by straps 30, and protected by spacers 34, 
a path is thereby provided for injecting well cuttings slurry into the 
earth formation as soon as the surface casing string 16 has been cemented 
32 in place. This is usually done within the first 3000 ft of well bore. 
By perforating the lower extremity 35 of the tube 28 and its surrounding 
cement 32 the cuttings slurry can be forced into the earth formation 20 by 
high pressure injection. Yet another alternative is to simply drill a 
second small bore hole adjacent the planned well site as seen in FIG. 4. 
By modifying the drill head 50 so that it comprises a special casing head 
having a primary bore drive casing and an auxiliary but substantially 
smaller drive casing 52. In such cases the injection well bore 54 can be 
directionally drilled away from the production well site and into more 
acceptable earth formation for the injection of drill cuttings via high 
pressure injection. A tubing string 56 can then be inserted into injection 
bore 54 and set with cement 32. The extremity of the tubing string 56 can 
then be perforated thus allowing the cuttings injection process to begin. 
An alternative method 40 may be seen in FIG. 3 where the well casing head 
is modified to include a secondary casing 42 between the first drive 
casing 14 and the surface casing string 16, thus providing an annulus 
connected to the slurry injection connection 26. In this case when the 
surface casing is cemented in place the lower extremity 44 of the 
secondary casing 42 is plugged and can therefor be perforated in the same 
manner as the injection tube 28 as discussed above. 
Obviously the same processes can be used in sub sea operations where the 
cuttings slurry is fed to the well head 10 on the sea floor, as discussed 
above, via external tubing attached to riser casings connecting the 
surface vessel or platform to the well head 10 and connected to the 
injection tube 26. 
Because many varying and different embodiments may be made within the scope 
of the inventive concept herein taught, and because many modification may 
be made in the embodiments herein detailed in accordance with the 
descriptive requirement of the law, it is to be understood that the 
details herein are to be interpreted as illustrative and not in any 
limiting sense.