Subsurface Safety Valves Minor Project Report

Submitted By:

Akhilesh Kumar Maury

Under Guidance of:

Dr. Surya Prakash Rao

HOD, Earth Sciences

College of engineering Studies

University of Petroleum & Energy Studies,

Bidholi, via Prem Nagar, Dehradun

CERTIFICATE

This is to certify that the project work on “SUBSURFACE SAFETY VALVE” submitted to the

University of Petroleum and Energy Studies, Dehradun, by AKHILESH KUMAR MAURY

(R040307003), BHAWUK LUTHRA (R040307007) and RESHMA RAMAN (R040307043) in

partial fulfillment of the requirement for the award of degree of B.Tech in Applied Petroleum

Engg. (2007-2011) is a bonafide work carried out by them under my supervision and guidance.

Place: DEHRADUN Signature of Mentor

Date: 15-12-2009 (Dr.Surya Prakash Rao)

ACKNOWLEDGEMENT

With completion of minor project on “Subsurface safety valves” we would like to

express my gratitude to all of people who helped me and guided.

Firstly I would like to express my thanks to Dr. S.P. Rao sir, HOD, Earth sciences,

University of Petroleum and Energy studies, Dehradun, for being mentor for our

minor project.

We would like to extend my gratitude to Mr. A. Arvind Kumar Sir, for providing

such opportunity to work as team in one direction for submission of minor project.

We would also like to extend my thanks to all those friends who helped us

throughout.

We would like to thank all once again.

Akhilesh Kr. Maury (R040307003)

Bhawuk Luthra (R040307007)

Reshma Raman (R040307043)

Btech (Applied Petroleum Engg-II)

CONTENTS

Abstract

Objective

Methodology

Introduction

History of the safety valve

Safety valve operation

Types of subsurface safety valve

List of components

Conclusions

Bibliography

ABSTRACT

Subsurface safety valves is an integral part of well completions, that provides the ultimate

protection against uncontrolled flow from producing oil and gas wells in case of catastrophic

damage to wellhead equipment. It is incorporated in the tubing and comprises of a tubular body

adapted for placement within a wellbore and defining a fluid passageway. Their use offshore is

legislated in many parts of the world to protect people and the environment. Safety valves have

evolved from the relatively simple downhole devices of the 1940s to complex systems that are

integral components in offshore well completions worldwide.

Closing mechanism is either by Ball type valve or Flapper type valve. Safety valves are of two

types: surface operated and subsurface operated safety valves. Surface operated valves are

further classified into pressure differential and pressure operated safety valves while surface

operated safety valves are classified into wireline retrievable and tubing mounted safety valves.

An SCSSV is operated remotely through a control line that hydraulically connects the safety

valve, up and through the wellhead, to an emergency shutdown system with hydraulic-pressure

supply. The design is fail-safe: through the control line, hydraulic pressure is applied to keep the

valve open during production. Aspects of the safety valve are employed by a related method and

system.

Date:

Signature

Dr. Surya Prakash Rao

(Mentor)

Objective

The objective of this project is to develop a clear understanding of the working and applications

of one of the most widely used artificial lift methods in the industry, the subsurface safety valve.

The project involves studying the various parameters that affect both in terms of enhancing and

reducing the performance, efficiency of subsurface safety valve.

However, apart from above, the main intent of this project has been to push our technical skills

to the extreme so that we can come up with an innovative design which would help demonstrate

future research and development into more efficient models for subsurface safety valve.

Methodology

To complete the present study the following methodology will be adopted:-

Collection of literature

Explore the available theoretical data

Generate mathematical expression over its working principle

Compilation the published data.

All above methods have been scheduled within time framework given bellow table:

WORKING SCHEDULE TIME

(DAYS)

Literature Review 3

Preparation for synopsis 2

Data collection & Work done 4

Presentation 2

Completion of Project Report 5

Introduction

A term subsurface safety valve has very clear meaning: a safety valve installed beneath the

surface. It is completion tool installed in well to shut in oil/gas production in case of a

catastrophic surface or at subsurface level and to control the fluid flow producing formation to

surface of the well. Fluids like water, brine, oil & gas which are readily available are used in

control line to control the safety valve. It is incorporated in the tubing and is located approx 30 to

50 m below the ground level (onshore) or below seabed (offshore). It provides emergency, fail-

safe closure to stop fluid flow from a well- bore if surface valves or the wellhead valves are

damaged or inoperable (not being operated).

Safety valves are essential in offshore wells and in many land wells located in sensitive

environments, or in wells that produce hazardous gases. They are installed to protect people, the

environment petroleum reserves and surface facilities. Successful installation, dependable

operation and reliability of safety-valve systems are crucial to efficient and safe well

performance.

Manufacturers have to apply for a level of diligence and testing beyond of related well

completion and flow control equipment, it shows the crucial role of subsurface safety valves.

These valves meet the specification of American petroleum Institue (API) and ISO standards. As

part of the safety system subsurface safety valves serve a relatively unglamorous but critical role.

By working properly when other systems fail, these valves are a final defense against the disaster

of uncontrolled flow from a well.

In principle, a safety valve is a simple device. Most of the time it is open to allow flow of

produced fluids, but in an emergency situation it automatically closes and stops that flow. To

affect this task, sophisticated engineering designs and state-of-the-art materials have been

developed. The valve’s closure mechanism must close and seal after months of sitting in the

open position and years after its installation. Special procedures and technologies applied to

reopening the valve after closure ensure its continued reliability.

Wells are drilled and completed under diverse conditions, so before an appropriate subsurface

safety valve is selected and installed, a thorough review of the reservoir, wellbore and

environmental conditions must be conducted.

In September and October 2002, Hurricane Lili impacted about 800 offshore facilities, including

platforms and drilling rigs, Category 4 storm passed through the oil-producing region (offshore)

in Louisiana, USA. Despite sustained winds of 145 miles/hr (233 km/hr), the US Minerals

Management Service (MMS) reported that the storm caused no fatalities or injuries to offshore

workers, no tires and no major pollution. Six platforms and four exploration rigs were damaged

by the storm. There were nine reported leaks of oil; only two exceeded one barrel. None of these

spills was associated with the six severely damaged platforms.

Subsurface safety valves are integral part of well completion and a no of oil and gas companies

have come up with their innovative idea to develop the technology and to reduce the

complexities in operational mechanism. Big players like Schlumberger, Halliburton, Otis

Engineering, and Baker Hugs are leaders in safety valve technology. They are manufacturing

safety valves for around 40 years from now. Schlumberger surface-controlled subsurface safety

valves use the innovative rod piston hydraulic actuation system. It offers six main safety valve

styles, ranging from basic to the most high-tech design available in the industry.

History of safety valves

The first safety device to control subsurface flow was used in US inland waters during the mid

1940s. Otis Engineering valve was dropped into the wellbore when a storm was imminent and

acted as a check valve to shut off flow if the rate exceeded a predetermined value. A slick line

unit had to be deployed to retrieve the valve.

Those first valves were deployed only as needed, when a storm was expected. The use of

subsurface safety valves was minimal until the state of Louisiana passed a law in 1949 requiring

an automatic shutoff device below the wellhead in every producing well in its inland waters.

Safety valve operation

Key features of ball

and flapper valves

A ball valve has a sphere

with a hole through it,

allowing flow through

the valve when the hole

is aligned with the

tubing. Rotating the boll

900 places the solid part

of the ball in the flow

stream, stopping flow.

The more common

flapper valve works like a

hinge with a spring.

When the flow tube is

down, the flapper is open,

and when it is pulled up

the flapper closes

Early subsurface safety valves

were actuated by change in

production flow rate. A flow

tube in such valves is equipped

with a choke bean, which is a

short, hard tube that restricts

flow, creating a differential

pressure between the top and

bottom of the tube. Production

fluid flowing through this choke

creates a differential pressure

across the bean—the pressure

on the lower face of the choke

bean is higher than the pressure

on the upper face. When the

force on the lower face exceeds

the combination of pressure on

the upper face and the force of

the power spring holding the

valve open, the flow tube

moves up and allows the

flapper to hinge into the flow

stream and close against a seat,

sealing off flow. The flow rate

to close the valve can be set

during manufacture by spring

and spring-spacer selection and

by adjusting the hole size

through the bean.

Typical subsurface-

controlled safety valve

Early safety valves were

relatively simple in

operation and created a

significant restriction to

production. The force of

the valve spring F5, acts

on the flow tube to keep

the flapper valve in a

normally open position.

The pressure below the

restriction is P1 and that

above is P2. These

pressures act on the

exposed faces of the

piston, creating a force F1

— F2 to close the valve.

When fluid flows upward,

the constriction creates a

pressure differential that

increases closure force.

The spring force is preset

for a specific flow rate, so

when the flow rate reaches

that critical rate, the piston

moves up, releasing the

flapper to close and shut

off fluid flow

Surface-controlled

subsurface safety valve

(SCSSV)

The more recent SCSSV

design is a normally closed

valve, with the spring

force, F5, acting to push

the piston upward and

release the flapper to close

the valve. Control pressure

transmitted from surface

through hydraulic-control

line acts against the spring

to keep the flapper valve

open during production.

This concentric-piston

design, which has been

replaced in many modem

valves by a rod-piston

design, has a ring-shaped

area between the piston

and the valve body that the

hydraulic pressure acts

upon to generate the

opening force F The small

difference in the piston-

wall cross sections

between the upper (U) and

lower (Ii faces of the

piston adds a small

additional upward force,

FL — Fu.

Types of Subsurface safety valves

1. Subsurface controlled subsurface safety valves.

2. Surface controlled subsurface safety valves.

Subsurface controlled subsurface safety valves (SSCSV)

Those valves which are installed beneath the surface are called SSCSV. They are also termed as

storm choke. They are set and retrieved by wire line. They closes the well whenever there is

change in flow conditions like either when there is increase in ambient flow rate i.e. (There is a

pressure loss across the valves) or when there is pressure drop opposite the valve. SSCSV’s

constitute:

(i) Pressure differential safety valve and

(ii) Pressure operated safety valves.

Pressure differential safety valves are designated as “pressure differential valves” or “velocity

safety valves”. Pressure loss in valve leads to close the valve. A return spring is fitted to keep

valve open, but if flow rate increases excessively, pressure loss occur creating a closing force

greater than that of return spring thus the valve closes.

The spring compression is set in such order that it can work at predetermined conditions, ie. it

shuts the well when there is any increase in velocity or flow rate beyond a suitable condition.

Closing and sealing mechanism is either a ball valve, a check valve or a poppet valve.

It can’t tolerate a high variation in flow rate. It suits to well being produced at relatively low flow

rate and thus it is confined to wells with high potential or wells whose reduced flow rate is

economically justified.

Pressure operated safety valves are also known as “ambient safety valves”. The closing

mechanism is controlled by a return spring and a gas chamber. It is normally closed and pressure

in the well keeps it open.

Pressure equal or greater than the specified operating pressure is exerted from above to open the

valve. As long as pressure remains greater than the value of set point, valves remain opened.

Moment the ambient pressure drops, valve is no longer open now and it closes abruptly.

The closing and sealing mechanism is either a ball valve, a check valve or a poppet valve and

these valves suits to well whose flow rate is very much sensitive to pressure variation.

Schlumberger has developed pressure differential valves naming “A-series velocity valves”. It’s

a flapper type valve and it can work with 10,000 psi (69,850 kPa). It is sweet to moderately

corrosive environment and in a temperature range of 40 F to 300

0 F (4

0 C to 149

0 C). It has so

many added advantages over other safety valves

Surface controlled subsurface safety valve (SCSSV)

These valves are controlled by hydraulic pressure in control line from surface. Valves are

normally closed. Control pressure applied on jack attacked to valve pushes the sleeve which

compresses the spring attached to it causing the valve to open. As long as control pressure equals

the set pressure the valve remains open. Failure of pressure leads to closing of valve.

SCSSV were developed around 40 years back taking well safety into consideration. It adhere to

American institute of Petroleum’s specification (API 14-A) and ISO 10432:1999. It depends on

parameters measured at wellhead rather depending on ambient flow condition. It allows

interference of surface facilities in controlling mechanism. The greatest advantage is that well’s

safety can be achieved manually and automatically in both the conditions whether the problem

occurred is directly related to well or not. In case of fire, explosion, process problems etc we can

directly access the valves. Depending on complexities of problem occurred we can take suitable

decisions to close the valves installed on wellhead or to close the valve installed subsurface.

Due to limited value of return spring force, depth at which valve need not be much. The spring

must be sufficiently compressed to overcome the opposing force (acting on jack directly) due to

weight of hydrostatic column of the fluid in the control line.

The valve can’t be opened when pressure difference between above and below exceeds 100psi

(0.7MPa). So in order to open the valve either we need to increase the pressure in control line or

to recompress the tubing above the vale by means of pump.

The surface controlled subsurface safety valve closing and sealing mechanism is either a flapper

valve or a ball valve. Earlier the ball valve was in fashion due to its sealing quality but nowadays

check valves are preferred over the ball valve because of its simplicity, roughness and robust

property. Lots of changes have been made in reliability and tightness of flappers and it’s in its

eleventh edition.

There are two types of surface controlled subsurface safety valves:

(i) Wire Line retrievable valve(WLR)

(ii) Tubing retrievable valve(TR) or “Tubing mounted”

(iii) Combination safety valves.

Wire Line retrievable valve (WLR)

It is set in a special landing nipple and retrieved by wire line. The valve is attached to a mandrel

that has been modified in order o transmit the control fluid pressure to valve’s jack. Some special

tools are like control shear pin, locking dogs are set in, in order to enhance the safety. In spite of

all these facts most oil wells are equipped with WLR valve because it makes well maintenance

easier.

Tubing retrievable safety valve (TR)

Generally gas wells are preferably equipped with tubing retrievable safety valve that provide an

inside diameter same as the tubing diameter. The production string must be pulled out to change

the valve. It is usually associated with tubing anchor and a disconnection system and thus it can

be pulled out by pulling the upper part of tubing. Gulf of Mexico wells are primarily equipped

with Tubing Retrievable and followed by Wire Line retrievable as secondary valve to avoid

hazardous conditions in malfunctioning of primary valves.

Combination safety valves

A sleeve, a flapper and a return spring are installed, integrated in tubing. Approximately it has

same advantages as both of wire line retrievable and tubing retrievable valve.

Comparison of slick line- and tubing-retrievable safety valve systems

The slick line-retrievable system typically locks into a landing nipple in the

completion string and seals on either side of the control-line port to isolate the

control fluid from wellbore fluids. The tubing-retrievable system is an integral

part of the completion string. The inside diameter of the valve is similar to the

inside diameter of the production tubing.

Conclusion

The trend toward more complex reservoir development continues to present challenges for

designers of safety-valve systems. Petroleum reserves today are exploited from deeper water and

in harsher producing and operating conditions than ever before.

An essentially unlimited setting depth could be achieved by developing subsurface safety valves

that incorporate solenoids to activate the valve. This would alleviate the problem of pressure

contributions from the weight of fluid in the control line or leaks in that line.

The success and reliability of features developed in the past are keys to the development of

innovative safety valves for the future.

Bibliography

http://www.slb.com/media/services/completion/safetyvalves/subsurface_

sv.pdf

http://www.halliburton.com/ps/Default.aspx?navid=114&pageid=201&f

olderid=MSE%3A%3A1045229747050391

http://www.glossary.oilfield.slb.com/Display.cfm?Term=subsurface%20

safety%20valve%20(SSSV)

http://www.bakerhughesdirect.com/cgi/bot/resources/ExternalFileHand

ler.jsp?bookmarkable=Yes&channelId=-

546906667&programId=546999579&path=/private/BOT/public/complet

ions/subsurface/cementsafe.html

Well completion and servicing By Dennis Perin