Tool for inspecting the upper end of a string of casing set in the bottom of a body of water

An inspection tool for detecting any flaws or defects in the upper end of a string of casing set in the bottom of a body of water. The tool has a cylindrical housing carrying a radiographic-sensitive film which fits over the open end of the string of casing and a radiographic source supported in the axis of the cylindrical housing. Means are provided for raising and lowering the tool.

BACKGROUND OF THE INVENTION 
This invention relates to the inspection of the upper end of casing set in 
the bottom of a body of water to which riser pipes can be connected which 
extend to a floating structure. 
In recent years there has been attention directed toward many different 
kinds of floating structures. One system receiving attention for mooring 
is the so-called Vertically Moored Platform (VMP). A Vertically Moored 
Platform can be described as a floating marine structure for drilling 
wells and/or producing hydrocarbons from an underwater formation and 
anchored by essentially parallel, vertical, and elongated members such as 
riser pipe. Riser pipes are usually considered to be heavywalled, 18-inch 
steel pipe. In the preferred form of a Vertically Moored Platform, the 
riser pipes are without slip joints and provide the only anchoring means 
for the Vertically Moored Platform. Such a platform is described in 
several patents, including U.S. Pat. No. 3,648,638, issued Mar. 14, 1972, 
Kenneth A. Blenkarn, inventor. 
In these instances of the Vertically Moored Platform, a plurality of casing 
is set in a selected pattern in the bottom of the body of water so as to 
resist any upward force. The upper end of these set casings are provided 
with connectors which mate with connectors on the lower end of riser pipes 
which are supported by and lowered from the floating structure. Once the 
connection is made between the riser pipes and the said casing, the 
structure is anchored. 
Perhaps the closest known prior art is the well-known systems of using 
x-ray to inspect welds in pipelines. 
BRIEF DESCRIPTION OF THE INVENTION 
This concerns an inspection of a submerged upper end of a casing set in the 
bottom of a body of water which has a connector to which the lower end of 
a riser pipe having a suitable mating connector can be lowered to and 
attached. This inspection tool includes a cylindrical housing having one 
end open and larger than the casing, a radiographic source carried within 
the housing, radiographic film carried on the interior of said housing, 
and means to energize the radiographic source from a location remote from 
said inspection tool. 
The inspection tool is normally attached to the lower end of a string of 
drill pipe and is lowered until the inspection tool surrounds the 
connector on the said casing string. The radiographic source is then 
activated to expose the radiographic film so that any defects in the 
connector will be shown on the film when developed.

DETAILED DESCRIPTION 
Attention is first directed to FIG. 1 which shows a riser pipe 12 
connecting a leg 10 of a floating vessel or structure not shown with a set 
casing 34. This system is shown in U.S. Pat. No. 4,062,313, issued Dec. 
13, 1977, for installation of Vertically Moored Platforms. This invention 
is not limited to any particular form of floating structure or particular 
riser pipe configuration, and FIG. 1 is shown to illustrate what is 
believed to be a particularly important application of this invention. 
Shown is a buoyant leg 10 floating on a body of water 11 connected by 
riser pipe 12 through various connectives to a conductor casing 42 
cemented in a hole in bottom 46. There are typically four buoyant members 
10. Although only one riser pipe 12 is shown, there would normally be 
eight for each buoyant member 10. Included in the riser pipe system are an 
upper terminator section 16 and a lower terminator section 14. The nature 
of these terminators and connectors are shown clearly in said U.S. Pat. 
No. 4,062,313. The lower end of riser terminator 14 is connected through a 
connector 40 to a conductor 42, which is set in the hole and secured there 
by cement 44. Conductor 42 is typically a 20-inch string of steel pipe or 
casing which is set in the bottom 46 below the body of water 11. Vertical 
bearing 48 and horizontal bearings 50 are indicated and a wellhead 52 is 
shown at the top of an upper riser terminator 16. Vertical bearings are 
shown in U.S. Pat. No. 4,127,005 and horizontal bearings are shown in U.S. 
Pat. No. 4,130,995. 
Attention is next directed to FIG. 2 which shows an enlarged view of the 
connector. Shown thereon is a "J" slot connector having a slot 52 on the 
upper exterior end of conductor casing 42 and a "J" lug 54 on the lower 
interior of riser pipe 12. It is to be noted, however, that the connector 
between riser pipe 12 and conductor 42 can be of many and varied types. It 
is also shown that conductor casing 42 is latched into a mudline 
suspension system 56. Such suspension systems are well known and will not 
be described herein. Most of the various components of a Vertically Moored 
Platform can be retrieved and fully nondestructively tested on the deck of 
the VMP or onshore or inspected in-place. One notable exception is the 
inspection of the connector secured to the upper part of conductor 42 such 
as "J" slot 52. The riser pipe 12 can be released from the connector and 
raised to the surface and its connector 54 can be visibly inspected. 
However, it is impossible to pull the conductor casing 42 inasmuch as it 
has been set in cement to perform as an anchor. The present invention 
discloses a new radiographic inspection tool which can be utilized for 
examining this connection for any cracks due to fatigue or overstressing. 
This radiographic inspection tool is diagrammatically shown on FIG. 3. 
This involves a film cowl 62 which can be a cylindrical housing having a 
means for carrying a radioactive sensitive film 64 on the interior 
thereof. Alignment bracket 66 is provided at the lower end of cowl 62. The 
upper end of cowl 62 is provided with a plate 68 or frame to which is 
connected a drill pipe 70 which is used for lowering and raising the 
inspection tool. The tool will be lowered through water, therefore, it 
might be desirable to protect the film 64 with a thin cylindrical sheet 72 
of plastic or some other similar material. A point radiographic source 74 
is suspended within the cowl 62 and is supported by control cable 76 which 
permits source 74 to be activated from the surface. Point sources of 
radiographic tools are well known. 
When it is desired to inspect the connector 52, the riser pipe 12, as shown 
in FIG. 2, is disconnected therefrom and raised to the surface in a known 
manner. Thereafter the inspection tool is connected to drill pipe 70 and 
is lowered until the alignment bracket 66 directs the cowl 62 over the 
upper end of the conductor 42 to be in the position shown in FIG. 3. 
When it is determined that the inspection tool is in the position shown, 
radiographic source 74 is energized and an image is then imposed upon 
radiographic film 64, which when developed, will indicate whether there 
are any cracks in the connector due to fatigue or overstressing or other 
reasons. One method of insuring that the inspection tool is in the proper 
location would be by lowering it until plate 68 rests on the top of the 
"J" slot 52 as shown in FIG. 3. 
The inspection tool is now ready to be raised to the surface. This is done 
by raising drill pipe 70 in the normal manner and also reeling in control 
cable 76. When the inspection tool reaches the surface, the film 64 is 
then processed and inspected to determine if there are any cracks in the 
connector 52. 
While the above invention has been described in detail, it is possible to 
make various modifications therein without departing from the spirit or 
scope of the invention.