Sanjack Group has designed and manufactured single-column, dual-well thermal wellheads for onshore thermal recovery.  The wellhead is 3.6m high and weighs 7.8t.  We assembled two sets of wellheads in one well slot.  These two sets of wellheads can operate independently, saving space on the platform and improving oil recovery efficiency.  This type of wellhead has obtained the national utility model patent.
The Oil Well Structure

Single-column and dual-well thermal recovery wellhead structure

1) Design of Sector Flange
In order to meet the requirement of 444mm center distance, casing head, casing head inverted slips, tubing head and adapter are designed into sector flange structure.

2) Design of adjust flange design
An adjustment flange is designed on the side of the throttle valve on the wing of the tree to ensure that the flow stroke of oil does not change during hot and cold recovery. The adjustment flange will be installed when steam is injected and removed during cold production, so that the crude oil flow will not change.

3) Design of large ring plate and compensate core
The large ring plate shall be mounted on a 30 “riser to ensure that the large ring plate will not deform while hanging two 300 m of 9 5/8” casing.  When two sets of 9 5/8 “casing are suspended from the large ring plate by compensating core, the core does not deform.  The core also serves as a positioning device to ensure that the center distance between the two sleeves is 444mm.

4) Design of wellhead stability
Support bolts were designed below the casing head adjustment plate to ensure wellhead stability.  Both casing heads are designed with a blow ring to prevent tilting.

5) Design of casing head positioning pins
We designed four positioning pins on the large ring plate and matching guide holes on the small ring plate.  When the casing head is installed, the guide hole of the small ring plate matches the positioning pin on the large ring plate to ensure the accuracy of the installation of both wellheads.

6) Oilfield application
Sanjack’s single-column and dual-well thermal recovery wellhead were approved by CNOOC’s auditors and installed on the offshore oil recovery platform in May 2012. At present, the effect is good.