Cementing tool and method

Details Cementing tool and method Cementing tool and method

2002-01-22

2004-11-23

Dang, Hoang (Department: 3672)

Wells

Processes

Cementing, plugging or consolidating

C166S050000, C166S177400, C166S313000

Reexamination Certificate

active

06820691

ABSTRACT:

TECHNICAL FIELD
The invention relates generally to cementing operations for wellbores. More specifically, the invention relates to a method and apparatus for cementing casing in a wellbore.
BACKGROUND
In the petroleum industry, wells are drilled in selected formations in an effort to produce hydrocarbons in commercially feasible quantities. During drilling operations for a typical oil or gas well, various earth formations are penetrated. To complete the well, casing is installed into the drilled wellbore.
Referring to
FIG. 1
, an example casing assembly
20
used in some oil and gas wells is shown. The casing assembly
20
for a given well is typically selected with an outer diameter that is small enough to go into the hole and still leave room for a cement layer
22
around the casing assembly
20
, and an inner diameter that is large enough for the passage of downhole tools. Typically, as joints of the casing assembly
20
are connected to form a conventional casing string, the casing string is gradually moved downhole into the well. Once the desired length of a casing assembly
20
is connected, the casing assembly
20
is suspended or “hung” in the well, either from the surface or from the end of a previously cemented casing.
A casing assembly
20
may include a guide shoe (not shown) at the bottom of the casing assembly
20
to guide the casing assembly
20
as it is lowered into the well. A guide shoe prevents the casing assembly
20
from snagging on the wall of the wellbore
14
as it is lowered into the well. A fluid passage is typically formed through the center of the guide shoe to allow drilling fluid to flow up into the guide shoe as the casing assembly
20
is lowered into the wellbore
14
. The fluid passage also allows cement pumped down the casing assembly
20
to flow downhole and out of the casing assembly
20
during cementing operations.
Cementing of the casing assembly
20
in the well is typically done by pumping a volume of cement into the casing assembly
20
sufficient to fill the annulus between the casing assembly
20
and the wellbore
14
, followed by pumping displacement fluid on top of the cement to displace the cement down the casing assembly
20
and up the annulus between the casing assembly
20
and wellbore
14
. The volume of cement required to fill the annulus between the casing assembly
20
and the wellbore
14
can be calculated from the geometry of the wellbore
14
and the geometry of the casing assembly
20
inserted in the wellbore
14
.
Cementing techniques are well developed for single-bore wells. However, multilateral wells are becoming increasingly more desirable to improve production. A bore leading from the surface is referred to as a primary or main wellbore. Each of directional wellbores extending from the primary wellbore is referred to as a lateral wellbore. The junction between a primary wellbore and one or more lateral wellbores is referred to as a wellbore junction.
Casing and cementing in a multilateral well presents a greater challenge than for uni-bore wells, especially in providing support and pressure integrity at the wellbore junction between the primary wellbore and a lateral wellbore. Existing cementing technology for multilateral wells makes use of hardware components, such as cement retainers, packers, and diverters, which are permanently set in the casing assembly during cementing operations that must be milled to clear the path for subsequent drilling operations. At a wellbore junction, the milling of the hardware components and cement in the internal volume of the wellbore may cause damage at the wellbore junction. This milling operation can also be time consuming and costly because of the number of downhole trips required.
SUMMARY
In general, an improved cementing tool for cementing a casing assembly at a junction of plural wellbores is provided. For example, the cementing tool includes a body, an anchoring mechanism adapted to anchor the body within the casing assembly, and a flow conduit adapted to channel cement flow to an annular region outside the casing assembly. The anchoring mechanism is adapted to be released to enable retrieval of the cementing tool from the casing assembly.
Other or alternative features will be apparent from the following description, the drawings, and the claims.


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