bpf16!06!10 sand control

8/9/2019 Bpf16!06!10 Sand Control

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6 Frontiers August 2006

Saving sandSand control has always played an important role in oilproduction, but now BP is going one step further. Nina Morgan

discovers what it means to move Beyond Sand Control


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Frontiers August 2006 7

A

s reservoir rocks go, porous

and permeable sand formations

filled with large volumes of

hydrocarbons that flow easily

into an oilwell are every petroleum

engineers dream. But when that sand

formation turns out to be so poorly

cemented together that sand grains flow

into the well along with the oil, that dream

can sometimes become a nightmare.

Sand can damage equipment such as

valves, pipelines and separators, it can

cause poor performance in injection wells,

and can lead to lost production.

Producing hydrocarbons from sand

prone reservoirs can present some

difficult challenges, says Chris Lockyear,

director of BPs Beyond Sand Control(BSC) programme within the companys

exploration and production business. And

these are challenges engineers will have to

tackle more and more often in the future.

Just a few years ago around a quarter

to a third of BPs reservoirs were affected

by sand. But by the end of the decade

nearly half of the companys reservoirs

are expected to be sand-prone. Adding to

this challenge, virtually all of these will be

offshore, and many will be in deeper water

an environment where intervention to solve

problems is more expensive and difficult.

And to complicate things further, many

of these reservoirs are stacked one on top

of the other and exist at different pressures.

The increase in sand is really down to

the regions where BP is looking for and

finding oil, notes Lockyear. Many of

the reservoirs in key BP assets, including

those in Azerbaijan, Angola, Trinidad,

Egypt, the deep water areas of the Gulf

of Mexico, the North Sea west of Shetland

and parts of Alaska, happen to be prone

to sand production.

The sand problem is not new and

affects the entire industry. In some cases

several tonnes of sand can emanate from

a reservoir in a single day. The traditional

methods of sand control, applied as part

of the well completion, include gravelpacking and sand screens (Frontiers,

December 2001), and all have the same

aim: to provide a barrier to keep sand

from entering the well along with the

hydrocarbons. Depending on the physical

characteristics of the reservoir and the

geographical setting, such preventative

techniques can and do work well but

they are not always reliable.

With more and more production coming

from sand-prone reservoirs, the ability to

be able to manage sand efficiently and

effectively all of the time has become

dollars


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even more important, says Lockyear.

Thats why BSC was designated as a

technology leadership area for BP in 2004. In

orderto maintainourcompetitiveadvantage, its

crucial for BP to develop a distinctive position

in sand control. This is what BSC aims to do.

Model management

BSC consists of a portfolio of projects and a

unique philosophy, explains Dave Rich, well

completions manager for BPs Azerbaijan

business unit, based in Baku, and a member

of the technical steering committee for BSC.

What makes BSC really distinctive is that it

brings all the different operations and

disciplines into the conversation to work

together towards a common goal. This

interface between different disciplines is

a key factor in BSC.

Some projects under the BSC umbrella

concentrate on improving or developing

hardware solutions. Others are exploring theuse of chemical treatments to consolidate

sand and hold it in place. Some target ways

to handle sand once it reaches the surface.

Still others draw on the expertise found in

universities in Europe, the USA, and Canada

to focus on fundamental science to get to

the root of the sand problem. And in some

projects, the aim is to assess whether sand

control is actually needed at all.

Theres no doubt that sand is an

important problem, says Hans Vaziri, sand

management advisor in BPs exploration

and production technology group (EPTG) in

Houston. But many engineers take this a bit

too much to heart and develop a fear of sand

that can lead them to take extra precautions,

whether they are needed or not.

Deciding when its necessary to take

precautions to deal with sand is a difficult

judgement call. On the one hand, putting

measures in place to actively control sand

can create complexities and lead to extra

costs in terms of skilled resources and

specialised equipment, extra drilling rig time

and potentially lower rates of production. On

the other hand, failing to control sand can lead

to damaged equipment and facilities, and loss

of production. By developing a computer

model to reveal how a reservoir ages during

production and what physical changes take

place as the well continues to produce, Vaziri

and his colleagues are working to develop a

tool that will help engineers predict the areas

where sand may cause problems and, where

necessary, determine optimal measures to

control sand in wells or to prevent it from

entering the well in the first place.

The quality of the output of any model

is strongly related to the quality of the input,

notes Vaziri.

The most important input when it comes

to modelling sand behaviour is reliable data

about the physical properties of the potential

sand-producing formations. One aspect of

EPTGs work in BSC focuses on collaborating

with researchers at the University of

Rhode Island in the USA to develop betteralgorithms for translating the data from

well logs to provide consistent and reliable

information about the strength of the

reservoir formation, particularly in weak or

unconsolidated sand. They are also working

with scientists at other institutions in the

USA and Canada to find more effective ways

of measuring the characteristics that directly

affect sand production.

The goal here, says Vaziri, is to develop

a consistent approach to data collection

so we can input the right parameters into

our computer models.

Rock/soil mechanics

Near wellbore forces

Material science

Interventions

Fluid mechanics

Reservoirfluids

Reservoir

fluids

Well

Sand can build up in pipework (top left) and vessels such as separators (bottom left). Installing

preventative measures in wells at the reservoir (above right) can help prevent sand ingress

In BPs Beyond Sand Control programme, detailed subsurface investigations are focused on understanding

the fundamental nature of sand in the reservoir and the wellbore. The above graphic highlights some of

the key areas under investigation


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Frontiers August 2006 9

The group is also developing numerical

models that can be applied to both

production and injection wells. These are

already being used successfully to mitigate

sand problems during start-up and

production of wells in various locations.

Although increases in computing

power have helped in the sand models

development, the more important

improvements, Vaziri believes, are linked

to gaining a better

understanding of

all aspects of the

problem and its

fundamental causes.

Over the past

three to four years

weve used this new

understanding to

make savings of

hundreds of millions

of dollars in existingwells by eliminating

redundant capital

expenditure, reducing sand-related

operational expenses, and improving

the overall production from shut-in and

choked-back wells, he notes. And the

multidisciplinary integration thats a key part

of BSC is helping us to add new features

that we hope will make the model even

more useful for managing the development

of some of BPs newer assets.

Expanding the options

One of BPs business assets that stands to

benefit from BSC is in Azerbaijan, where a

BP team recently won the companys Paul

Martins Production Excellence Award for its

achievements in the use of gravel packs to

control sand production (see

page 39). Azerbaijan is also

proving to be a fertile testing

ground in BSC for exploring

the use of sand control

hardware, such as

expandable sand control

completion systems. These

mechanical devices are

installed within a wellbore

and are expanded to make

contact with the wall of theborehole to support and

prevent any significant sand

movement, using a fine metal mesh to

prevent sand ingress into the well (Frontiers,

August 2003). Some of the systems BP

is working with Weatherford International

in one case also contain sealing elements

that allow different zones of the reservoir to

be closed or opened to the wellbore, to

achieve selective hydrocarbon production

or, conversely, water injection.

BP is working with leading equipment

suppliers to develop new designs for

expandable completions, and these are

already being used successfully by BP and

others in a number of areas. But, notes Rich:

Although we have a lot of data about how

expandable screens work in dry conditions

that is when you are producing oil alone

we need to know more about how they will

work once you start to enhance production

by flooding a reservoir with water, and begin

producing water with the oil.

As development in Azerbaijan ramps

up, Richs team expects to be carrying out

20-25 well completions a year in sand-prone

reservoirs. These will provide ample

opportunity to further develop and test

the use of expandable screens and other

new sand control technology. The teamis already working closely with service

contractors to carry out field trials of a

number of designs.

We are very meticulous about taking

a stepwise approach to trials, so that each

time we carry out a new trial we know what

we are gaining and what we are learning,

Rich reports. We are basically trying to

Cased holegravel pack

Cased holefrac pack

Open holegravel pack

Expandablesand screen

Stand-alone screenGravel

Gravel

Selectedand orientedperforation

BP expects to

complete 20-25

wells a year in

Azerbaijans sand-

prone reservoirs

Main graphic: Expandable sand screens are among the latest techniques to join the established methods of preventing sand from entering wells

Inset above right: Detail of an expandable sand screen from Weatherford International

Sand control completions


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well. As a result of this realisation, the BSC

programme expanded in 2006 to take in

research about how to best handle sand

topsides, that is, once it reaches the

surface facilities.

The key sand issues at the surface arise

in the flowlines between the well and the

production facility the systems used to

separate hydrocarbons from water and

the produced water re-injection system.

Separators are designed to work efficiently

at a certain production rate, but if they

start to fill up with sand the effective

volume of the separator is reduced and

separation efficiency can be greatly

impaired. If this happens, production must

be slowed down, or even halted, while

the sand is removed.

To explore the potential solutions for

handling sand at the surface, Campbell-

Brown and his colleagues are involved in

a significant programme of technologybrokerage. This involves taking a wide

view of the problems in-house, gaining an

understanding of where the best solutions

will come from, then linking up with the

relevant suppliers, consultants or

researchers to seek a solution. We have

three main goals, explains Campbell-Brown.

To better understand the known technology;

to look at the fundamental science; and to

examine innovative solutions.

To achieve these goals, the team spends

around half of its budget externally, working

together with university researchers and

consultants. For example, they are

collaborating with researchers at the

University of Nottingham, UK, to explore the

potential use of microwaves to preferentially

heat layers where sand is mixed with

hydrocarbons to make it easier to separate

out the sand. In addition, the group is

teaming up with engineers at another UK

university to use a test flow loop to study

the behaviour of sand in multiphase flow, a

topic of importance for transporting sand in

pipelines. And a three-year programme has

been initiated at the University of Cambridge

where researchers will be exploring thefundamental science and theory of sand

flow to gain a better understanding of how

sand behaves in separators.

With around a dozen field trials ongoing

or planned in 2006, these are busy and

exciting times for BSC, concludes Lockyear.

Although theres still much work to do, BSC

is already showing real benefits in terms of

cost savings and enhanced production, and

most importantly, it is allowing BP to access

additional value that would have previously

been eroded literally and metaphorically

by sand problems.

of BSC is that it is treating all the different

aspects of sand control in a holistic way,

he says. Sand control started as a downhole

issue, but in BSC we now take a view that

encompasses the full sand chain, ranging

from the reservoir face to the ultimate

disposal of sand at the surface. Instead of

focusing in on a single aspect or area of sand

control, in BSC were now thinking in terms

of where and how best to manage sand.

In some cases the right answer may be

to deal with sand on the surface, rather than

finding a way to control sand down in the

build confidence in the use of new

techniques, while at the same time

minimising risk. Were learning about

expandables because we need them here.

But the reality is that the learning we gain

in Azerbaijan will be shared throughout the

rest of BP. This is one of the great

achievements of BSC.

Surface solutions

Donald Campbell-Brown, team leader for

facilities excellence in EPTG based in

Sunbury, agrees. One of the great benefits


Gas

Gamma-ray

ProfilerGas out

Weir

Oil out

Cross-section

through separator

Water out

Inlet oil/water/gas/sand

Foam

Oil

Emulsion

Sand

Water

Seeing inside separators

Sand drops out from reservoir wellstreams into surface facilities. In a three-phase separator the sand

can take up valuable separation volume, thereby reducing residence time, and can also help to stabilise

unwanted emulsions formed by the oil and water. In order to understand these effects better, BP has

initiated a research programme with the University of Cambridge, and is also working with suppliers on

equipment development. The separator in the graphic above features a proprietary Profiler device developedby Tracerco in the UK. The Profiler consists of titanium dip-pipes holding low-energy gamma-ray emitters

and gamma-ray detectors (Geiger-Mller tubes). As the oil, water, sand, emulsion and foam in the vessel

have different densities, the gamma ray signals are attenuated by different amounts as they pass through

the fluids. The resulting signals can be used to create an accurate real-time graphical profile of the fluid

levels and interfaces in the vessel (shown below) effectively seeing inside the separator.

bpf16!06!10 sand control

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