Oil and Gas Well Completions

Tubinghead and X-mas tree

Tubinghead

 

•Surface equipment from which the tubing is 

suspended

Xmas tree or valve array

•Used to control well during production

•Mounted above wellhead

•Typically sourced from same manufacturer

Wellhead & BOP during completion

 

Primary functions of tubinghead

•Suspend tubing with hanger

•Seal between tubing and annulus

•Provide access ports to annulus

–gaslift gas

–inhibitor injection

–circulating the well

•Provide mounting for adapter flange or Xmas tree

Tubing Hanger Types

•Threaded Hanger Flange

–used in low pressure wells (e.g. Pumping wells)

•Boll Weevil Type

•Ram Type Tubing Hanger

•Boll Weevil Type

Tubing Hanger for Bowl Type Tubing Head.

 

Less suitable to land tubing in tension 

Boll-Weevil type hanger and housing 

 Spool and Hanger

Hangers for Dual Completion

•Ram Type Tubing Hanger

–allows free tubing manipulation to latch tubing in

 tension

Tubing tension hanger Cameron SRT

Tubing Hanger with Extended Neck

Hanger may have extended neck

 

•Projects into base of X-mas tree or adapter 

flange

•Sealed flow path through wellhead

Xmas tree or adapter interface

 

 

Oil and Gas Well Completions cont 1

WELL CONTROL COURSE SECTION A cont

CAUSES OF KICKS

PRIMARY CONTROL

NORMALLY:

MUD HYDROSTATIC  =    FORMATION PRESSURE

WHAT CAUSES MUD HYDROSTATIC TO DROP?

PRESSURE  =  0.052 X MUD WT X TVD

HOW CAN HYDROSTATIC PRESSURE CHANGE?

CAUSES OF KICKS (REDUCTION IN MUD WEIGHT)

RUNNING INTO A BUBBLE

CIRCULATING HOLE CLEAN

ADDITIONAL CAUSES OF KICKS (SUBSEA)

Accidental Riser Disconnect (Riser Margin)

• Riser can be accidentally disconnected due to vessel drive off’s, hydraulic control problem, riser failure, etc.
• Bottomhole pressure will be reduced due to net loss of hydrostatic pressure.
• In this example, BHP would be reduced by:

Mud Loss      = 1770 x 10.8 x .052  = 994 psi

Seawater HP  = 1710 x 0.445 psi/ft  = 761 psi

Net Loss        = 994 – 761                = 233 psi

 

GAS IN THE WELLBORE

Effect Of Gas Expansion in Open Well

Gas in Subsea Riser