Disclosed herein are various embodiments of methods and systems for drilling an oil or gas well safely and efficiently using underbalanced or near-balanced drilling techniques, wherein the primary means of pressure control is a Annular Pressure Control Diverter positioned below the BOP stack, with a return flow pattern where no drilling fluid returns up the (traditional) annulus between the drill pipe and the production casing and instead drilling fluid returns up the annulus between the production casing and intermediate casing. Drilling fluid returns flow through a wellhead, instead of a flow spool conventionally located below an upper RCD, and hence to the drilling choke. This drilling approach eliminates the need for hydraulic fracturing and preserves the natural fracture system of the producing formation while providing additional safety measures. It also prevents the accidental or deliberate discharge or flaring of methane during drilling and production.

Reducing the diameter of a well bore has many advantages. To achieve this a subsurface well bore is provided comprising one or more expandable sleeve components, preferably expandable liners, each expandable sleeve component being fully overlapped by one or more non expandable sleeve component, preferably conventional liners, such that the interior of the well bore is cased entirely by non expandable sleeve components. In addition the through holes for downhole lines can be provided within the well head rather than the tubing hanger. As the tubing hanger does not need to provide space for through holes and associated mounting couplings, its diameter can be reduced, thus reducing the internal diameter of the well bore by several inches.

Reducing the diameter of a well bore has many advantages. To achieve this a subsurface well bore is provided comprising one or more expandable sleeve components, preferably expandable liners, each expandable sleeve component being fully overlapped by one or more non expandable sleeve component, preferably conventional liners, such that the interior of the well bore is cased entirely by non expandable sleeve components. In addition the through holes for downhole lines can be provided within the well head rather than the tubing hanger. As the tubing hanger does not need to provide space for through holes and associated mounting couplings, its diameter can be reduced, thus reducing the internal diameter of the well bore by several inches.

A method of manufacturing a configurable pre-machined forging for use with a multiple bore tubing hanger or a mono bore tubing hanger includes providing a configurable common master valve block with a main bore along a main central axis. After providing the configurable common master valve block, a target subsea assembly is identified that has a mono bore subsea completion with a production bore along a central axis of a tubing hanger, or a multiple bore subsea completion with the production bore offset from the central axis of the tubing hanger. If the target subsea assembly has the mono bore subsea completion, the machining of a lower interface of the common master valve block is centered around the main central axis. If the target subsea assembly has the multiple bore subsea completion, the machining has an eccentric interface axis that is parallel to, and offset from, the main central axis.

A method of manufacturing a configurable pre-machined forging for use with a multiple bore tubing hanger or a mono bore tubing hanger includes providing a configurable common master valve block with a main bore along a main central axis. After providing the configurable common master valve block, a target subsea assembly is identified that has a mono bore subsea completion with a production bore along a central axis of a tubing hanger, or a multiple bore subsea completion with the production bore offset from the central axis of the tubing hanger. If the target subsea assembly has the mono bore subsea completion, the machining of a lower interface of the common master valve block is centered around the main central axis. If the target subsea assembly has the multiple bore subsea completion, the machining has an eccentric interface axis that is parallel to, and offset from, the main central axis.

A wellhead system includes a housing defining an axial bore, an outer pipe secured to the housing and extending axially from the housing, an inner pipe passing through the axial bore and through the outer pipe and having an outer diameter that is smaller than an inner diameter of the outer pipe, and a sealing device positioned along an inner surface of the housing and sealed to the inner pipe to seal an annular region defined between the inner and outer pipes.

An apparatus for hanging a production string and a coil tubing within a well, the apparatus comprising: a main body with a lower end defining an annular mounting flange; a production string tubing hanger bowl in the interior open area configured for accommodating the production tubing string suspended therein, the production string tubing hanger bowl having a center axis non-concentrically positioned relative to the annular mounting flange; and a coil tubing access port extending from the outer surface of the main body to an inner opening, the coil tubing access port configured for accommodating the coil tubing passing therethrough and having an angular orientation downwardly and being on an angle off vertical and directed away from a center point of the annular mounting flange.

An apparatus for hanging a production string and a coil tubing within a well, the apparatus comprising: a main body with a lower end defining an annular mounting flange; a production string tubing hanger bowl in the interior open area configured for accommodating the production tubing string suspended therein, the production string tubing hanger bowl having a center axis non-concentrically positioned relative to the annular mounting flange; and a coil tubing access port extending from the outer surface of the main body to an inner opening, the coil tubing access port configured for accommodating the coil tubing passing therethrough and having an angular orientation downwardly and being on an angle off vertical and directed away from a center point of the annular mounting flange.

Disclosed herein are various embodiments of a method for minimizing formation damage while drilling an oil or gas well. An Annular Pressure Control Diverter is designed to be positioned below the conventional blowout preventer stack, and is activated during near balanced drilling operations to seal the annulus between the drill pipe and the production casing. Returned drilling fluid and produced fluids are diverted up the annulus between the production casing and intermediate casing and through a well head located below an all-inclusive BOP stack. The seal elements within the Annular Pressure Control Diverter do not rotate. Doors are provided on each side of the Annular Pressure Control Diverter to permit changing of the seal elements. The Annular Pressure Control Diverter also is used to ensure the capture of methane while drilling in a hydrocarbon bearing reservoir.

Disclosed herein are various embodiments of a method for minimizing formation damage while drilling an oil or gas well. An Annular Pressure Control Diverter is designed to be positioned below the conventional blowout preventer stack, and is activated during near balanced drilling operations to seal the annulus between the drill pipe and the production casing. Returned drilling fluid and produced fluids are diverted up the annulus between the production casing and intermediate casing and through a well head located below an all-inclusive BOP stack. The seal elements within the Annular Pressure Control Diverter do not rotate. Doors are provided on each side of the Annular Pressure Control Diverter to permit changing of the seal elements. The Annular Pressure Control Diverter also is used to ensure the capture of methane while drilling in a hydrocarbon bearing reservoir.