THE MULTIPLE COMPLETION CHOKE ASSEMBLY - A NEW PROFIT MAKING TOOL

by

J. W. Hodges Sun Oil Company Beaumont, Texas

__0—

For presentation at the 15th Annual Technical Meeting

PETROLEUM & NATURAL GAS DIVISION, C. I . M.

May 6-8, 1964 Calgary, Alberta

The Multiple Completion Choke Assembly -

A New Profit-Making Tool

Abstract

This paper describes the construction, method of operation,

and f i e l d performance of the Sun Oil Company-developed Multiple

Completion Choke Assembly.

This down-hole commingling tool has been i n operation since

March, I960. I t has been used i n approximately 75 wells located i n

Louisiana, Texas, Mississippi, Oklahoma, Mexico, Kuwait, and India.

Sun O i l Company's Gulf Coast Division, through the use of

this tool during the past four years, has saved approximately

$289,000 i n tubular goods, and produced approximately $282,750 worth

of hydrocarbons not otherwise recoverable.

The paper reports the results of Sun O i l Company's i n s t a l l a ­

tions and discusses the various applications and li m i t a t i o n s of the

t o o l .

The method of allocating production to each zone is

explained„

Advantages and disadvantages i n simultaneous production of

two separate reservoirs through a single tubing s t r i n g are enumerated.

Construction and Operation

Fig. 1 shows a well equipped to receive a multiple completion

choke assembly. A retainer type packer separates the two producing

zones. The upper packer is optional. A side-door choke landing

nipple hookup is located i n the tubing s t r i n g above the lower packer.

The multiple completion choke assembly w i l l be locked i n t h i s landing

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nipple. Normally located a j o i n t or two above the upper zone, the

position of the landing nipple hookup can be varied to sui t well

conditions. For example, where the two zones are widely separated,

i t might be placed just above the lower packer to f a c i l i t a t e bottom

hole pressure tests of the lower zone.

The tool consists of two separate assemblies, as shown in

Fig. 2. The outer assembly, which is run on a wire l i n e and locked

in the landing nipple, contains the check valves and packing seals

which prevent flow from one zone to the other.

The orifice-head assembly, which carries the tungsten-carbide

choke beans, is run separately and is seated and locked i n the outer

assembly. The method of running each section is i l l u s t r a t e d i n Fig. 3.

Fig. 4 is a schematic drawing which shows how the device

works. Production from the lower zone enters the assembly through

a slotted section, flows through a sleeve-type check valve, enters

and flows through the tube of the orifice-head assembly, is choked

and - now regulated - flows into the tubing. Produced f l u i d s from

the upper zone enter the casing opposite a blast j o i n t on the tubing,

flow through the ported collar of the side-door choke landing-nipple

hookup, through the upper slotted section, through the upper check

valve, into the annulus surrounding the tube, and through the upper-

zone choke bean into the tubing. Here the two controlled flow

streams, which have been segregated to t h i s point, combine and flow

to the surface.

Allocation of Production

Detailed instructions for testing and allocation of pro­

duction are available i n the manufacturer's "Service Manual fo r

-2-

Otis Type 'S' Multiple Completion Choke Assembly—Dual Flow"; i n

general, however, allocation i s based on the results of a stabilized

test of one of the zones while the other zone is blanked o f f . The

established rate from t h i s zone is then subtracted from the commingled

rate to calculate production from the second zone.

Test procedure w i l l depend on whether or not one of the

zones i s i n c r i t i c a l flow. A stream is i n c r i t i c a l flow when

alterations i n pressure downstream from an o r i f i c e do not affect the

rate of flow. The c r i t i c a l point i n a gas stream flowing through

an o r i f i c e occurs when the pressure downstream from the o r i f i c e i s

53$ of the upstream pressure; for gas-liquid mixtures, the c r i t i c a l

r a t i o is higher but should not exceed approximately 0.58.

I f one of the zones is i n c r i t i c a l flow, alterations i n

the tubing i n l e t pressure (the pressure immediately downstream from

the multiple completion tool) w i l l not change the predetermined

rate from that zone, and the allocation process i s si m p l i f i e d .

I f neither zone is i n c r i t i c a l flow, the zone with the

higher pressure is tested i n d i v i d u a l l y at several rates i n a range

of tubing i n l e t pressures expected to occur during commingled flow.

By p l o t t i n g the rate versus tubing i n l e t pressure, a graph i s

obtained from which the production from the zone can be determined

during commingled flow. Fig. 5 shows the results of such a test

i n the Kinder Field, Louisiana. This graph can be used to determine

the rate from the lower zone during commingled flow. I f the zone

is out of c r i t i c a l flow, i t s rate is a function of the tubing i n l e t

pressure.

The method of allocating production with the multiple

completion tool is basically the same as that used i n conventional

-3-

practice; i.e., determining the rate from each zone by testing,

commingling the production downstream from the choke beans, and

allocating the interim production between test periods on the

basis of the individual tests. In either case, accurate allocation

depends upon the consistency with which each zone continues to

produce at i t s tested rate, and t h i s i s i n large measure dependent

upon accurate flow rate control. The tungsten carbide choke beans

in the multiple completion choke assembly, being highly resistant

to erosion and located below the zone of p a r a f f i n deposition

(precluding plugged chokes) w i l l provide better flow rate control

than w i l l conventional surface chokes. In Sun's wells, the o r i f i c e

head has been pulled approximately 450 times, and i n each instance

the chokes have remained true to gauge.

Applications

The multiple completion choke assembly is not a specialty

t o o l . I t is applicable i n almost any type of multiple completion.

Sun Oil Company has made nineteen i n s t a l l a t i o n s i n wells ranging

i n depth from 3790' to 15,576' and i n bottom hole pressure from

814 psi to 8173 p s i .

I t is applicable i n multiple o i l , multiple gas, and

combination oil-gas wells.

I t can be run on i n i t i a l completion, or i n the conversion

of a concentric or twin s t r i n g dual completion. In the l a t t e r case,

when either zone becomes defi c i e n t , the tool can be i n s t a l l e d with

wire-line tools, preferably i n a Type nS M side-door choke landing

nipple; a hook-wall tool i s available, however, i f a side-door

nipple has not been run.

-4-

A l i s t of i t s applications follows.

1. In wells where one or "both zones require a r t i f i c i a l

l i f t , one set of gas l i f t valves can be used to produce the two

zones through the tool at reduced cost and greater efficiency than

is possible i n other types of dual completions.

2. As a means of using gas-cap gas to l i f t liquids from

the lower part of the same sand.

3. Two multiple completion tools can be used with dual

strings of tubing to produce either three, four, or f i v e zones

simultaneously.

4. The tool Is compatible with slim hole multiple com­

pletions .

5. Applicable to tubingless completions and permanent

type completions.

6. Can be used to produce selective completions dually.

7. Can be modified and used to i n j e c t salt water or

gas into separate reservoirs with reasonably accurate allocation

to each reservoir.

There are two limi t a t i o n s to the use of the t o o l : l )

where there is excessive sand production and 2) where there is

i n s u f f i c i e n t reservoir energy for required production and external

gas is not available for gas l i f t .

Table No. 1 describes the wells i n which Sun has used

the multiple completion choke assembly.

Advantages

The advantages i n using the multiple completion choke

assembly are as follows:

-5-

lo Reduction in well equipment costs. In Sun Oi l

Company's Belle Is l e Unit #1-56, Belle Is l e Field, Louisiana,

approximately $42,000 was saved on equipment alone as compared

to a twin st r i n g dual.

2. Increased ultimate recovery. The economy of the

method has resulted i n production from reservoirs which would not

have been tested otherwise. For example, i n Sun's Belle I s l e Unit

#3-5, over $97,000 worth of hydrocarbons were produced i n the f i r s t

year of operation from a questionable zone that would have been

writ t e n o f f i f t h i s tool had not been available.

3. Increased daily production. The income from Sun's

Vicksburg Unit #3, Kinder Field, Louisiana (the lower zone i n a

dual completion), has increased from $2770 per month to $8500/month

since i n s t a l l a t i o n of the tool i n March, I960. The gas-oil r a t i o

has decreased from 54,000 c.f. per bbl to 19,600 c.f. per bbl. See

Fig. 6.

4. Reduction i n workover costs (compared to multiple-

s t r i n g completions.)

5. Reduction i n surface equipment costs. This includes

heaters, separators, compressors, high pressure g a s - l i f t l i n e s ,

meters, etc.

6. Maximum use of reservoir gas. By bottom hole choking

and commingling production immediately above the tool, gas breaking

out of solution at this point results in the lowest possible

gradient in tbe tubing. When a strong well i s combined with a

weak well in this way, the weak well can be produced at i t s

maximum potential. This not only prevents waste; i t Is also quite

economical to the operator, as i t postpones or eliminates the need

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to provide a r t i f i c i a l l i f t f or the weaker zone. Conventional

completions, by maintaining separation of production to the surface,

i n t h i s respect act contrary to the principles of conservation.

The multiple completion choke assembly i s i n effect a

single-point i n j e c t i o n , retrievable flow valve, u t i l i z i n g gas

supplied d i r e c t l y from the formation at maximum efficiency. To

i l l u s t r a t e the degree of efficiency, i n Sun Oil Company's Dishman-

Lucas #1, Sour Lake Field, Texas, a comparison was made between

this method and a conventional gas l i f t system. This study showed

that the multiple completion tool used one-sixteenth as much gas

and produced twice as much l i q u i d .

7. Reduction i n corrosion i n h i b i t o r and p a r a f f i n t r e a t ­

ment costs.

Disadvantages

1. Cost of testing. The periodic testing required

results i n wire-line costs otherwise not incurred; however, there

are two important considerations that should not be overlooked:

(a) the future value of the money saved by virtue of using the

t o o l . In Belle I s l e Unit #1-56, the $42,000 saved i n i n i t i a l cost

is worth $44,520 at 6$ compound interest after one year, $56,205

afte r f i v e years, and $75,215 at the end of ten years. Obviously,

th i s gain in value w i l l absorb wire-line costs (which have run

from $50 per month to $150 per month i n Sun's nineteen wells);

(b) the use of the tool w i l l result i n an increase i n production i n

most wells. The income from just one additional barrel of o i l per

day w i l l i n most instances pay the wire-line costs.

2. Somewhat more complicated (technical) method of

-7-

production accounting. The engineer i n charge must practice more

of his production technology than is normally required i n routine

production accounting. This may or may not be a disadvantage, and

the bulk of the work can s t i l l be handled by the production clerk.

Attitude of the Conservation Agencies

Co-operation of the various State agencies has come about

through recognition that l ) commingling down hole with the choke

assembly is no d i f f e r e n t from commingling at the surface; 2) the

tool i s mechanically sound; 3) the tool w i l l prevent waste and

increase ultimate recovery; and 4) most of the people i n the o i l

industry are honest. Those that aren't w i l l f i n d a cheaper way

to produce multiple completions dishonestly.

Conclusions

Simultaneous production of two reservoirs through a single

s t r i n g of tubing w i l l i n many wells result i n a si g n i f i c a n t reduc­

t i o n i n completion and l i f t i n g costs and increase i n current income

and ultimate recovery. The Multiple Completion Choke Assembly w i l l

maintain separation of reservoirs and control the rate of production

from each. Test procedures have been developed which provide an

acceptable method of determining the production from each zone. A l l

requirements imposed by the State regulatory agencies can be

s a t i s f i e d .

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CASING

TUBING

UPPER PACKER (OPTIONAL)

FLOW COUPLING

LANDING NIPPLE

PORTED COLLAR

- POLISH NIPPLE

UPPER ZONE

X x--BLAST JOINT

PACKER

PERFORATED NIPPLE (OPTIONAL)

LOWER ZONE

, t , k « < , d a « .

Fig. 1—Well Properly Equipped for Multiple Completion Choke Assembly

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Fig. 2—Multiple Completion Assembly for 2-3/8-in. Tubing. Check valves and choke beans are shown opposite position occu­pied within t o o l .

UPPER-ZONE CHOKE BEAN

UPPER-ZONE FLOW PATH -

LOWER-ZONE FLOW PATH

FLUIDS COMBINED HERE LOWER-ZONE CHOKE BEAN

ORIFICE-HEAO ASSEMBLY

OUTER ASSEMBLY

UPPER CHECH VALVE PORTED COLLAR

UPPER PERFORATIONS

LOWER CHECK VALVE

EQUALIZING DISC

PRODUCTION PACKER

LOWER PERFORATIONS

Fig. ^--Schematic Drawing Showing Operation of Multiple Completion Choke Assembly

GAS PRODUCTION mcf/day (Ji tk (J\

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R A Y C. JONES Chai rman

H A R O L D F R E E M A N V i c e - c h a i r m a n

W I L B U R N C A R T W R I G H T Member

C A R L B. M I T C H E L L Secretary

OKLAHOMA

Corporation Commission

DAN R. D U N N E T T D i rec to r Of Conse rva t i on

F E R R I L L H. ROGERS Conse rva t i on A t t o rney

O K L A H O M A CITY O K L A H O M A

D. L . JONES A s s i s t a n t D i rec to r

S T A N L E Y ROGERS A s s i s t a n t D i rec to r

W. J . M A R S H A L L A s s i s t a n t D i rec to r

W. H. S O L L E R S Trial Examiner

R A L P H L . W A M P L E R A s s t . Conse rva t i on A t t y .

N E L L RHODES F ISHER A s s t . Conse rva t i on A t t y .

O I L A N O GAS C O N S E R V A T I O N

DEPARTMENT

4, 1963

Mr. Russell Thompson Attorney at Law 1719 First National Building Oklahoma City 2, Oklahoma

Miehaal B. Sllva, Attorney Phillip* Patrol am Company Oklahoma Mortgaga Building Oklahoma City 2, Oklahc

Mr. Joa A. Owens Sun Oil Coopany P. 0. Box 2831 Beaumont, Texas

Mr. William a. Dow Citlas Service Oil company Box 4577 Oklahoma City 2, Oklahoma

Mr. Jamas R. Marty Amarada Petroleum Corp ora tl< Liberty Bank Building Oklahoma City 2. Oklahoma

Hr. Karl Tunscell Otis Engineering Corp. 301 S. S. 29 Oklahoma City. Oklahoma

Mr. A. J. McCraady Socony Mobil Oil Company 120 Northwest 2 Oklahoma City 2, Oklahoma

Centl Rat Cauaa CD No. 19034

Enclosed find copy of Report of Trial Examiner in tha above canoe, which will ba filed on tha 9th day of Decenber, 1363, and you have until Decembar 12v 1963, ia which to file exceptions thereto* i f you so desire.

Yours vary truly.

CORPORATION COMMISSION OF QKLAHOKA

Raloh L. Wamnler I Ralph I*. Wampler Trial Bxamiaer

RLW/b 1.