Downhole Gas Separator Selection - ALRDC - Home - 4... · Downhole Gas Separator Selection Feb. 17 – 20, ... Downhole Gas Separator ... Safety Valve Operation

Gas Well Deliquification Workshop

Sheraton Hotel, Denver, Colorado

February 17 – 20, 2013

Downhole Gas Separator Selection

James N. McCoy & Lynn Rowlan

Many operators with medium to high capacity

wells who have low production rates and low

pump fillage ask the question:

What kind of downhole separator should be used?

Downhole Gas Separator Selection

Feb. 17 – 20, 2013 2 2013 Gas Well Deliquification Workshop

Denver, Colorado

Gas Separator

Liquid Capacity

is Based on the

Following

Principle:

GAS BUBBLES FLOW UPWARD IN OIL OR WATER AT A RATE OF

APPROXIMATELY 6 INCHES PER SECOND. THUS, GAS BUBBLES WILL BE

RELEASED FROM A LIQUID COLUMN IF THE DOWNWARD LIQUID VELOCITY IS

LESS THAN 6 INCHES PER SECOND.

A LIQUID COLUMN HAVING AN AREA OF 1 SQUARE INCH TRAVELLING AT

6 INCHES PER SECOND IS A RATE OF 50 BPD.

Downhole Gas Separator

Principle of Operation

Feb. 17 – 20, 2013 3

2013 Gas Well Deliquification Workshop

Denver, Colorado

The outer pipe can be

the casing or the outer

barrel of a gas

separator. The inner

tube is the inlet to the

pump.

ESP Producing 5 MMCF/D of CO2 Gas

Free Gas flows in the annulus, if the casing

pressure builds up after the casing valve is closed.

What Kind of Separator is Needed?


Denver, Colorado


Denver, Colorado

Dynamometer and Acoustic Analysis of Seating

Nipple Type Gas Separator Performance

88.6” Effective Plunger Stroke

with 87% Pump Fillage

Feb. 17 – 20, 2013 5

Casing Pressure Buildup

4.13 psi/min ~ 298 MscfD

Annular Gas Flow Rate

Gas Separator with Seating Nipple

Natural Gas

Separator

The most efficient downhole gas separators locate the pump intake below the lowest gas entry point.

Gas is not pulled down to the pump perforations unless the liquid velocity is greater than 6 inches per second.

Maximum capacity is obtained using casing annulus.

6

Natural Gas Anchor


Denver, Colorado

liquid in

separator

pump

slip

gas in

separator

Tubing Conveyed Downhole Separator System

Gravity separation is

the governing principle

for downhole gas

separators.

Insert Separator has

less capacity than

using the casing ID.

Downward Liquid

velocity greater than 6

inches per second in

separator pulls gas into

pump.

Feb. 17 – 20, 2013 8


Denver, Colorado

Sorry “Poor Boy” Gas Separator

Seating Nipple

Collar

Perforated Sub

Collar

Joint of Tubing

Dip Tube

Tubing Collars

prevent

perforated sub

from laying

against casing

wall where

liquid

accumulates

Casing

Limited

Flow Area

and Small

Holes

Feb. 17 – 20, 2013 9

“Poor Boy” Gas Separator

Liquid Capacity


Denver, Colorado


Denver, Colorado

Many Modifications of

“Poor Boy” Gas Separator

Seating Nipple

Collar

Perforated Sub

Collar

Joint of Tubing

Dip Tube

Casing

Feb. 17 – 20, 2013 11


Denver, Colorado

Collar Size Separator

Eliminates Poor Boy

Deficiencies

A good separator must

balance annular flow area,

separator flow area, dip

tube diameter and pressure

drop.

Outer barrel OD same as

collar OD.

Thin short wall outer barrel

and short dip tube.

Large inlet ports distributed

around outer barrel

facilitate entry of liquid.

Feb. 17 – 20, 2013 12

Collar-Sized Gas Separator

Specifications Designed with thin-wall tubing, large ports and

minimum lengths to optimize gas separation

from the liquid that enters the pump.

Set 5.5 foot long separator 3 joints below tubing

anchor.

OD of outer barrel of gas separator is the same

OD as the tubing collar.

Collar at the top of separator attaches to

bottom of pump seating nipple.

Optimum size dip tube is permanently mounted

inside the outer barrel.

A bull plugged joint of tubing can be run below

the bottom half-collar for a solids collection

chamber if desired instead of the bull plug.

13 2013 Gas Well Deliquification Workshop

Denver, Colorado

To get gas capacity of a specific installation multiply the

table value by the Pressure at the Pump Intake (psi)

and divide by 14.7 14 2013 Gas Well Deliquification Workshop

Denver, Colorado

Collar Size Separator - Gas and Liquid Capacity


Denver, Colorado

Poor Boy Separator Franks #1

34.4” Effective Plunger Stroke

with 34% Pump Fillage

Feb. 17 – 20, 2013 15


.25 psi/min ~ 18 MscfD



Denver, Colorado

Collar Sized Gas Separator Franks #1

Feb. 17 – 20, 2013 16

Production of 100 BPD

with a Full Pump


1.8 psi/min ~ 161 MscfD


MIST

FLOW

Gas Velocity

should be less

than 10 ft/sec

in Annulus

Between ID of

Casing and

OD of Gas

Separator

GAS Should NOT Flow Too Fast

Past Outside Gas Separator

Feb. 17 – 20, 2013 17

Liquid Moves Slower in Separator

Than Inside Pump Chamber

4.17 sec

SV Closes

1.8 sec

SV Opens

Pump Plunger

Velocity

Liquid Velocity

Inside Separator


Denver, Colorado 18

Feb. 17 – 20, 2013

Bubble Size Impacts Rise Velocity

Clift, Grace and Webber (1978)

1 in/sec

3 in/sec

6 in/sec

Feb. 17 – 20, 2013 2013 Gas Well Deliquification Workshop

Denver, Colorado

During 5th Stroke 1 in/sec Bubble is

Pulled into Bottom of the Dip Tube Plunger Dia. 1.25 Inch

Plunger Area 1.227 sq.in.

Pump Depth 10,540 feet

Begin 0 - SV Opens 1.8 - SV Closes 4.17 – End 8.633 sec.

6.95 SPM

2 3/8" Collar Sized Gas Separator

Area between Dip Tube and Barrel

ID - OD 4.581 sq.in.

Collar Sized Gas Separator

Results of Early Field Tests

Installed in over 300 wells

Increased production by an average of 25% in those wells with additional production capacity.

Reduced pumping time by an average 50% in wells with Pump-Off controllers.


Denver, Colorado

Packer Gas Separator

Inner tube can hold a pump or

simply be a long small dip tube to

a pump landed above.

Uses gravity separation like the

“Poor Boy” except more

separation area and capacity.

Higher cost and higher risk of

mechanical and sand problems.

Page Oil Tools 1957

Feb. 17 – 20, 2013 22


Denver, Colorado

Gas Separator Design Top

Collar

Bottom

Collar Formation

Fluids

Formation Fluid

Outlet

Pump

Seating Nipple

Pump Inlets

Fluids from the formation flow

upward to the gas separator and

then flow through a concentric

annulus to an outlet at the top of

the separator which discharges on

one side into the casing annulus.

The gas rises and the liquid falls in

the casing annulus.

The pump inlet is located at the

bottom of the gas separator

causing the pressure drop from the

liquid at the bottom of the separator

to the pump inlet to be negligible.

Diverter Cups or a packer or tail

pipe with packer is located below

the Separator to force formation

fluids into the separator.

Casing

Diverter cups or

Packer or Stinger 23

Gas Separator Selection Criteria

Use Packer Type when dP/dT >2

Use Collar Type when dP/dT <2

24 Feb. 17 – 20, 2013

Average

of all data


Denver, Colorado

Determine

Gaseous

Liquid

Column

Gradient

Below

Liquid Level

Adjusted Liquid Level

Transition from

Collar Sized to

Packer Type

Gas Separator

25

If Liquid Rate is

Low, Poor Boy

Gas Separator

May be OK

Downhole Gas Separator Selection Criteria

Feb. 17 – 20, 2013 26


Denver, Colorado

Conclusions

Feb. 17 – 20, 2013 27


Denver, Colorado

• Best gas separation performance is obtained by locating

the pump intake below the gas entry point.

• Proper gas separator selection when pump intake is

above the formation must take into account casing

annulus gas production rate and well liquid production

rate.

• Use casing pressure buildup rate to help select Gas

Separator Type.

• Use % Liquid Surrounding Separator with % Pump Fillage

to Determine Separator Performance


Denver, Colorado 28

Copyright

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– Display the presentation at the Workshop.

– Place it on the www.alrdc.com web site, with access to the site to be as directed by the Workshop Steering Committee.

– Place it on a CD for distribution and/or sale as directed by the Workshop Steering Committee.

Other use of this presentation is prohibited without the expressed written permission of the author(s). The owner company(ies) and/or author(s) may publish this material in other journals or magazines if they refer to the Gas Well Deliquification Workshop where it was first presented.


Denver, Colorado

29

Disclaimer

The following disclaimer shall be included as the last page of a Technical Presentation or Continuing Education Course. A similar disclaimer is included on the front page of the Gas Well Deliquification Web Site.

The Artificial Lift Research and Development Council and its officers and trustees, and the Gas Well Deliquification Workshop Steering Committee members, and their supporting organizations and companies (here-in-after referred to as the Sponsoring Organizations), and the author(s) of this Technical Presentation or Continuing Education Training Course and their company(ies), provide this presentation and/or training material at the Gas Well Deliquification Workshop "as is" without any warranty of any kind, express or implied, as to the accuracy of the information or the products or services referred to by any presenter (in so far as such warranties may be excluded under any relevant law) and these members and their companies will not be liable for unlawful actions and any losses or damage that may result from use of any presentation as a consequence of any inaccuracies in, or any omission from, the information which therein may be contained.

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5 Seconds

10 Seconds

15 Seconds

20 Seconds

Start

The problem of separating the gas from the liquid before

the liquid enters the pump may be related to the creation

of small gas bubbles from the drop in pressure of liquid in

the dip tube as the oil travels to the pump inlet.

30 2013 Gas Well Deliquification Workshop

Denver, Colorado

Feb. 17 – 20, 2013

Documents

Downhole Gas Separator Selection - ALRDC - Home - 4... · Downhole Gas Separator Selection Feb. 17 – 20, ... Downhole Gas Separator ... Safety Valve Operation