Wellhead Design Slideshow

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Wellhead Design

Lunch & Learn

06-Feb-07

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Presented by:

Gerry Bryant, P.Eng.

Integrated Services Mgr.

Dril-Quip Beijing RO

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Agenda

• Wellhead Equipment for Exploration and

Development

• Conventional Wellhead Systems, Unitized Wellhead

Systems, and Horizontal Wellhead Systems

• Engineering Design Requirements for Surface

Wellhead Equipment

• Bohai Phase 2 Development Wellhead Design

• Subsea Wellhead Equipment

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Wellhead Design, Lunch & Learn, 06-Feb-07

• Typical Land

Based Oilwell

Reprinted from:

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• Typical Land

Based

Drilling Rig

Reprinted from:

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• Typical

Offshore

Platform

Reprinted from:

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Wellhead Equipment for Exploration and

Development

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• Conventional Wellheads

used for Exploration

and Development Wells

• Unitized Wellheads

used for Development

Wells

• Mudline Equipment

used for Development

Wells, but generally run in Exploration Wells

as contingency

• Production Equipment

used for Development

Wells

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• Exploration wells use

Conventional Wellheads almost exclusively because they can be stacked to

accommodate multiple casing strings

• ConocoPhillips used a

Cameron conventional

wellhead for the exploration well PL25-8-1 in October 2006

• Drilling depth is a major

criteria in determining casing program because casing is used to stabilize the up-hole formations, so conventional wellheads can accommodate from one to five casing

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• Conventional Wellheads

require nippling-up and nippling-down the BOP

stack to install each section, which requires a lot of rig-time; rig-time is very

expensive

• Typically low technology

design options • After use, Convention –al Wellhead spools can be easily separated, repaired, inspected, and re-used

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• Development wells can be

completed with the

conventional wellhead system

discussed earlier or using the

Unitized Wellhead System

shown here

• Designed in the 1950’s, the

major benefit of the Unitized

Wellhead System is reduced

rig-time removing the BOP

stack after running each

casing string, then having to

re-install it.

• This is accomplished as the

Unitized Wellhead System

suspends multiple strings of

casing within the one

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• CoPC Bohai Phase 2

Unitized Wellhead will

receive the 9-5/8”

casing hanger and the

4-1/2” tubing hanger

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• Mudline Systems are used in

both exploration and

development wells and are

designed for temporary

abandonment and reconnect

at a later time

• Used if exploration

campaigns are expected to

yield good shows of oil or if

development of the oilfield

may take several more

months or years

• With the improved design of

today’s Mudline Systems,

they are almost universally

used during exploratory

drilling

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• Mudline

Hangers are

designed to nest

one inside the

other

• Each Hanger

except the last

includes internal

profile to

suspend the

casing hanger

for the next

casing string

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• Temporary Abandonment

(TA) Caps are installed

after drilling to isolate the

annuli and hole bore for

months or years until the

platform is installed

above

• The upper-most TA Cap is

spaced out during drilling

to be a couple metres

above the mudline

• Tie-back hangers have

seals to re-establish

integrity with each casing

string back to the

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• Once the drilling has reached its total depth and

production casing is in place, the operations that

prepare the well for production is referred to as

Completion.

• Completion includes displacement of drilling mud

with completion fluid, perforating the casing, and

installation of the production tubing.

• Finally, the Surface Production Equipment is

installed which will control the flow of oil from the

well during production.

• This flow control equipment is an assembly of valves

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• The christmas tree

can include

actuated valves (air

or hydraulic),

manual valves, and

production chokes

in order to the

control flow of oil.

Pneumatic Actuated Master Valve Manual Master Valve

Production Choke

CoPC Bohai Wellhead and Tree Assembly

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There are numerous designs

and arrangements for the

production equipment.

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Engineering Design

Requirements for

Surface Wellhead

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American Petroleum Institute (API)

• established in 1919 when American oil companies worked

together to standardize oil field equipment in order to provide more reliable supply to the country

• maintain more than 500 standards and recommended practices

covering all segments of the oil and gas industry to promote use of interchangeable equipment and sound engineering practices

• license facilities that produce products that meet API

standards, to monogram those products with the API logo

• API Specification 6A covers the standardization of valves and

wellhead equipment and first appeared in 1961. The Nineteenth Edition is the current reference for manufacture and use of

surface wellhead equipment.

• Scope of API 6A includes criteria for performance, design,

material selection, testing, inspection, welding, marking,

handling, storage, shipping, and documentation of the wellhead equipment.

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API Design.

Design Methodology for pressure containing equipment is as described in ASME, Section VIII, Division 2, Appendix 4.

Design allowable stresses are limited by the following criteria: St = 0.83 * Sy and Sm = 2/3 * Sy

where,

Sm = design stress intensity at W.P.

St = maximum allowable general primary membrane stress intensity at T.P. Sy = the mat’l specified min. yield strength

The theory of constant energy of distortion can also be used for design calculations for pressure containing equipment. Discontinuities and stress concentrations must be considered where applicable.

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Equipment Specifications are detailed in the title block.

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Equipment Specifications are detailed in the title block.

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Temperature Ratings – equipment

must be designed to operate in one or more of the specified

temperature ratings per API 6A. The design must consider the effects of differential thermal expansion from temperature gradients which the equipment experiences in service.

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Material Requirements – are determined by considering factors such as H2S

concentration, CO2 partial pressure, erosion effects, etc. The numerical value refers to maximum

allowable partial pressure of H2S, in this case 1.5%.

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Product Specification Level (PSL) – defines five different levels of technical quality requirements. PSL1, PSL2, PSL3, PSL3G,

PSL4.

The selection of PSL should be based on a quantitative risk analysis of potential hazardous events if the equipment fails. H2S concentration, radius of exposure to the public,

corrosivity of retained fluid are important factors to consider. In general, the higher the Product Specification Level the more inspection and testing will be required for the equipment.

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Performance Requirement (PR) – is specific and unique to the product in the as-shipped condition. Two PR levels exist, PR1 and PR2.

These performance requirements must be verified by a testing procedure performed on a prototype of a specific design, or by a means which verifies the test requirements defined in API 6A, Section 10.

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Bohai Phase 2

Development

Wellhead

Equipment

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Design Objectives:

‘ Standardize the wellhead and tree components to the greatest extent practical considering the following factors:

a. interchangeability of components, b. minimizing spare part inventory, c. maintenance, and

d. cost effectiveness.

• Minimize the aerial envelope of the wellhead and tree assembly

in order to maximize the working clearance between wellheads and to ensure safe ingress/egress of the wellhead area.

(see 3D image of Wellhead decks)

• Use a basic design philosophy in order to choose reliable and

well-proven equipment to reduce maintenance and workover costs.

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• The CoPC Bohai Wellhead System was designed

with a unique horizontal production tree.

• A horizontal production tree allows complete access

to the well bore without removing the tree. The well

is produced from the side of the tubing hanger and

flows horizontally through the master valve.

• Horizontal production trees are ideal on wells where

frequent workovers are anticipated, such as Electric

Submersible Pump (ESP) applications.

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Conventional Wellhead and Tree

Assembly

Horizontal Wellhead and Tree Assembly