1. Field of the Invention
Embodiments of the present invention generally relate to a composite downhole tool for hydrocarbon production and method for using same. More particularly, embodiments of the present invention generally relate to a composite cement retainer and method for using same.
2. Description of the Related Art
A wellbore is drilled to some depth below the surface to recover hydrocarbons from subterranean formations. The wellbore can be lined with tubulars or casing to strengthen the walls of the borehole. To further strengthen the walls of the borehole, the annular area formed between the casing and the borehole can be filled with cement to permanently set the casing in the wellbore.
Cement is typically pumped from the surface through the casing and forced out from the bottom of the casing and upwardly into the annulus between the casing and the bore hole. To facilitate the cementing process, a float shoe and/or a float collar is inserted in or adjacent the bottom of the casing. The float shoe and/or float collar are essentially check vales which allow the flow of cement from inside of the casing to the annular space between the casing and the borehole and prevent opposite flow therethrough.
Once the float shoe and/or float collar are located at the bottom of the casing, a bottom plug is then pumped through the casing by the cement. After a sufficient amount of cement has been introduced into the casing, a top plug is places on top of the column of cement. The cement that is bound between the top plug and the bottom plug is pumped down the casing, e.g. by drilling mud, until the bottom plug lands on the float shoe and/or float collar. When the bottom plug lands on the float shoe and/or float collar, the pressure on the top plug is increased until a diaphragm in the bottom plug ruptures thereby allowing the cement to pass through the float shoe and/or float collar and flow around the bottom of the casing and upwardly through the annular space between the casing and the wellbore. After the cement has set, the top plug, bottom plug and any cement set in the casing are drilled out to form a clear path through the wellbore.
The valves and cement in the casing are typically destroyed with a rotating milling or drilling device. As the mill contacts the valves and cement, the valves and cement are “drilled up” or reduced to small pieces that are either washed out or simply left at the bottom of the wellbore. The more metal parts making up the valves, the longer the milling operation takes. Metallic components also require numerous trips in and out of the wellbore to replace worn out mills or drill bits. Depending on the types (i.e. hardness) of the metals in the valves, the drilling removal operation can be extremely timely and expensive for a well operator.
Once the casing is set in the wellbore and the float shoe and float collar have been removed from the wellbore, the casing is then perforated to allow production fluid to enter the wellbore and be retrieved at the surface of the well.
During production, tools with sealing capability are typically placed within the wellbore to isolate the production fluid or to manage production fluid flow through the wellbore. The tools, such as plugs or packers for example, typically have external gripping members and sealing members disposed about a body. Such body and gripping members are typically made of metallic components that difficult to drill or mill. The sealing member is typically made of a composite or synthetic rubber material which seals off an annulus within the wellbore to prevent the passage of fluids. The sealing member is compressed, thereby expanding radially outward from the tool to sealingly engage the surrounding casing or tubular. For example, bridge plugs and frac-plugs are placed within the wellbore to isolate upper and lower sections of production zones, and packers are used to seal-off an annulus between two tubulars within the wellbore.
In workover operations, cement retainers or cement retainer plugs are typically used to close leaks or perforated casing. Certain cement retainers have similar external gripping and sealing members to seal and grip the surrounding well bore or casing, and a valve which can be used to open and close off cementing ports. The retainer is run on either a wireline or a tubing string, and the gripping and sealing members are actuated to seal off the annular space within the wellbore between the retainer and the surrounding casing. Cement is then pumped through the tubing string, through the interior of the retainer, and out the cementing ports to repair the surrounding casing. Such retainers are also constructed of metallic components which must be milled or drilled up to remove the retainer from the wellbore once the cementing job is complete.
There is a need, therefore, for a non-metallic plug that can effectively seal off an annulus within a wellbore and is easier and faster to mill. There is also a need for a non-metallic cement retainer that can effectively seal off an annulus for cementing operations and is easier and faster to mill.