(International Patent pending, PCT-IB-2004-003980)
Liner Hanger with ports for placing Gravel Pack around screens
1. Use of Stop-Sand Liner Hanger
This tool has been particularly designed for water wells where the aquifer is made up
by loose sediments.
The Gravel Pack is placed in the annulus between the borehole wall and the well
screens to prevent formation material (usually sand) from entering the screens.
2. Previous Liner Hangers used in water wells
Until now, the efficiency of Liner Hangers used in water wells for installation of gravel pack has been very often unsatisfactory, leading even, in extreme cases, to the loss of the well itself.
Amongst the most common reasons of this failure we could mention the difficulty of
a proper installation, the often complicated internal system to open and close the
gravel ports, the defective annulus sealing by the rubber Packer and the irregular Gravel Pack emplacement by which some sections of the screens may remain directly exposed to the formation.
The consequences are water/sand production and pump failure.
3. The installation of Stop-Sand Liner Hanger
The installation of the Liner Hanger is easy and trouble free.
Three steel elliptical balls are welded inside of the cemented casing in such a position that
they do not obstruct the passage of a tricone rock bit or other tools.
The function of the balls is to support and fix the Liner Hanger in place, so that the weight
of the screens and casing liners cause the automatic expansion of the rubber Packer.
4. Tool Description
The Tool appearance is that of a steel pipe of ranging diameter and length, depending on well geometrical requirements
A standard Liner Hanger for the use in water wells with cemented 13 3/8" (340 mm) casing
has, for example, a max. diameter of 313 mm and a total length of about 1,830 mm;
the two rubber Packers are located at the top, while the x-over to the screens/liners
is at the bottom.
By hanging the Tool on the three elliptical balls, an internal simple mechanism, acting
under the weight of underlying screens/liners, causes a mobile lower ring to move
upwards, thus compressing the above rubber Packer against the fixed upper ring.
This movement generates the expansion of rubber Packer against the cemented casing, thus
sealing off the annulus between the casing and the Liner Hanger itself.
The emplacement of Gravel Pack is then made by using a special setting tools lowered
inside the top of the Liner Hanger; the setting tool provides also enough pressure (weight)
to compress a spring and open three sliding gravel Ports, through which gravel and water
are pumped down into the Formation(Aquifer) - screens/liners annulus.
By completion of the Gravel Pack emplacement the setting tool is retrieved and the
upwards expansion of the spring closes the Gravel Ports. The work is done
5. Schematic Stop-Sand Liner Hanger and Gravel Pack installation sequence.
(see enclosed sketch)
6. Material used
Stop-Sand can be manufactured by using any type of Steel.
Packer is made with special expandable rubber.
7. Stop-Sand manufacturing
Stop-Sand components are manufactured and assembled in a specialized workshop
by using standard API equipment.
8. Innovative system: simple and efficient
New is the idea of the three supporting elliptical balls welded inside the cemented
casing. They allow a stable and secure Liner Hanger setting by eliminating the usual
hold-down slips and the need for a sufficient drilling string weight to release and set
in place a normal Liner Hanger.
New is also the automatic sealing system of the annulus by the rubber Packer
by only setting Stop-Sand Liner Hanger on the three supports.
Further, the Tool allows an unlimited and easy repetition of gravel emplacement
operations until the Gravel Pack is homogeneous and complete.
Finally, by Gravel Pack completion, the inside spring provides the automatic
closure of the gravel Ports, simply, by retrieving the gravel setting tool.