A PRESENTATION ONHORIZONTAL AND VERTICAL CHRISTMAS TREE

Submitted by"Mr . AMAR M.GAIKWAD"

Under the guidance of" Prof. S.A. Joshi "

DEPARTMENT OF PETROLEUM ENGINEERINGMAEER'S

MAHARASTRA INSTITUTE OF TECHNOLOGY,PUNEUNIVERSITY OF PUNE

2015-2016

What is Christmas tree?

The set of valves, spools & fittings connected to the top of the well to isolate, direct and control the flow wellbore fluids.

The control valves, pressure gauges and chokes assembled at the top of the well to control the flow of oil and gas after the well has been drilled and completed.

The purpose of a production Christmas Tree:

The purpose of an injection Christmas Tree:

Christmas Tree System

Fig. Schematic of Wellhead & Christmas Tree

Tubing Hanger   Tubing Head Spool   Tree piping   Flow line connector   Wellhead connector   Valves and fittings   Choke

Main Components of Christmas Tree:

Safety barrier Safely stop produced or injected fluid Injection of chemicals to well or flow line Allow for control of down hole valves Allow for electrical signals to down hole gauges To bleed of excessive pressure from annulus Regulate fluid flow through a choke Allow for well intervention

Christmas Tree Functions

API 6A: Specification for Wellhead and Christmas Tree Equipment.

API 17D: Design and Operation of Subsea Production Systems-Subsea Wellhead and Tree Equipment.

ISO 13628-4: Petroleum and natural gas industries – Design and operation of subsea production systems.

ISO 10423:2009: Petroleum and natural gas industries - Drilling and production equipment - Wellhead and Christmas tree equipment.

Applicable standards for the Christmas tree

1. Vertical Christmas Tree2. Horizontal Christmas Tree

l Christmas Tree

Types Of Christmas Trees

Vertical Christmas Tree Horizontal Christmas Tree

Christmas Tree -Main Types

Horizontal tree Vertical tree Production master valve (PMV) in horizontal

bore Single, concentric bore

Must pull the production tubing to retrieve the tree

Both barriers fail if the tree is accidentally removed

Designed to take the load from a BOP (increased weight)

Batch-wise completion possible

Tubing hanger is installed in the tree body instead of the wellhead.

The Horizontal tree concept can be further defined as –

1.“Partial Drilling HT” 2.“Full Drilling HT”

Production master valve (PMV) in vertical bore Dual bore (production + annulus)

Must pull the tree to retrieve the production tubing

Requires landing string to secure well before work over

Primary barrier is maintained if the tree is accidentally removed

Not designed to take the load from a BOP

The vertical tree concept can be further defined as –

1.“Eccentric” production flow is routed eccentrically (dual bore configuration)

2.“Concentric” concentrically (single bore configuration) through the tubing hanger.

The valves are mounted on the lateral sides, allowing for simple well intervention and tubing recovery.

This concept is especially beneficial for wells that need a high number of interventions.

Swab valves are not used in the HXT since they have electrical submersible pumps applications.

The key feature of the HXT is that the tubing hanger is installed in the tree body instead of the wellhead.

This arrangement requires the tree to be installed onto the wellhead before completion of the well.

Horizontal Tree

Schematic of Partial & Full Horizontal Tree

Fig. Partial Drilling HT Fig. Full Drilling HT

Partial Drilling HT: Diana, Marshall, Madison

(ExxonMobil GOM) Mica (ExxonMobil GOM) Kizomba (ExxonMobil

Angola)

Full Drilling HT: Dalia (Total Fina Elf –

Block 17 Offshore Angola) Ross (Talisman Energy –

North Sea UK)

Partial & Full HT concept was used for the following projects:

The master valves are configured above the tubing hanger in the vertical Xmas tree (VXT).

VXT are applied commonly and widely in subsea fields due to their flexibility of installation and operation.

The vertical tree concept can be further defined as –

“Eccentric” production flow is routed eccentrically (dual bore configuration)

“Concentric” concentrically (single bore configuration) through the tubing hanger.

Vertical Tree

Schematic of Eccentric & Concentric VT

Fig. Concentric Mono-bore VTFig. Eccentric Dual Bore VT

Eccentric VT:- Zinc (ExxonMobil – GOM) Girossol (Total Fina Elf -

Block 17 Offshore Angola) Balder (ExxonMobil –

North Sea Norway) Blackback (ExxonMobil –

Austraila)

Concentric VT:- Bongo (Shell – Nigeria) Mensa (BP – GOM) Crazy Horse (BP – GOM) Macaroni (Shell – GOM)

Eccentric & Concentric VT concept was used for the following projects:

The cost of an HXT is much higher than that of a VXT; typically the purchase price of an HXT is five to seven times more.

A VXT is larger and heavier, which should be considered if the installation area of the rig is limited.

Completion of the well is another factor in selecting an HXT or VXT. If the well is completed but the tree has not yet been prepared, a VXT is needed. Or if an HXT is desired, then the well must be completed after installation of the tree.

An HXT is not recommended for use in a gas field because interventions are rarely needed.

Tree Selection

For the last 20 years the Horizontal Christmas tree has been the preferred design for deepwater fields, while in recent years the focus in the industry is returning to the conventional Vertical Christmas tree system.

An HXT is applied in complex reservoirs or those needing frequent workovers that require tubing retrieval, whereas a VXT is often chosen for simple reservoirs or when the frequency of tubing retrieval workovers is low.

A tree often provides numerous additional functions including chemical injection points, well intervention means, pressure relief means, monitoring points such as pressure, temperature, corrosion, erosion, sand detection, flow rate, flow composition, valve and choke position feedback, and connection points for devices such as down hole pressure and temperature transducers.

Conclusion

 1.Towns, T. K., Deeken, D. G., Derby, L. M., Exxon Mobil Development Company, “Diana Subsea Tree Selection and Installation Results in 4,653 Feet of Water” Deep Offshore Technology held in Rio de Janeiro, Brazil, October 17-19, 2001.

2. Moyer, M.C., Barry, M.D., Tears, N.C., "Hoover-Diana Deepwater Drilling and Completions", OTC 13081, Offshore Technology Conference, Houston,, May 2001.

3. Havard Devold," Oil And Gas Production Handbook", An Introduction to Oil And Production, ABB Oil And Gas, May (2009), Edition 2.0 Oslo,29-32.

4. Oda Ingeborg Stendebakken, NTNU Trondheim, "A reliability study of a Deepwater Vertical Christmas Tree with attention to XT retrieval rate", June (2014),11-32.

5. Randy J. Wester and Eric P. Ringle / FMC Energy Systems," Installation and Work over Time Savings: Key Drivers for Deepwater Tree Selection" ,OCT 12943, Offshore Technology Conference, May (2001).

References

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