artificial lift methods

GAS LIFTSUCKER ROD PUMP

ELECTRIC SUBMERSIBLE PUMPOTHERS

Artificial Lift Methods

1

PENDAHULUAN (1)

Pwf

Pwh Psep

Pwf

PwhPsep

Pwf=Psep+dPf+dPt

Pwf<Psep+dPf+dPt

Flowing Well No - Flow Well

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PENDAHULUAN (2)

Untuk mengangkat fluida sumur:

Menurunkan gradien aliran dalam tubing

Memberikan energy tambahan di dalam sumur untuk mendorong fluida sumur ke permukaan

Pwf

PwhPsep

No - Flow Well

Energy ?

3

Gradien ?

PENDAHULUAN (3)

Figure 1

Gas Lift Well ESP Well Sucker Rod Pump Well

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PENDAHULUAN GAS LIFT (1)

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Persamaan Umum Pressure Loss

Pengurangan gradien aliran dengan menurunkan densitas fluida

dZ

L

dZ

dv

g

v

g

g

dZ

dp w

cc

dg2

vf)

dL

dp(

c

2

f

Pwf

PwhPsep


Densitas Campuran

Gradient Elevasi Gradient Friksi

Gradient Akselerasi

?

?

6

vd

N Re


Pwf

PwhPsepPwf<Psep+dPf+dPt

7

Pwf>Psep+(dPf+dPt)

Berkurang

GAS LIFT (1)

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Gas lift technology increases oil production rate by injection of compressed gas into the lower section of tubing through the casing–tubing annulus and an orifice installed in the tubing string.

Upon entering the tubing, the compressed gas affects liquid flow in two ways:

(a) the energy of expansion propels (pushes) the oil to the surface and

(b) the gas aerates the oil so that the effective density of the fluid is less and, thus, easier to get to the surface.

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SURFACE COMPONENTS

SUB-SURFACE COMPONENTS

RESERVOIR COMPONENTS

Detail Gas Lift Surface Operation

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InjectedGas

Res. Fluid +Inj. Gas

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Sistem Sumur Gas Lift

Gas Injection Line

Pt

Pc

Compressor Subsystem• intake system• outlet system• choke • pressure gauge• injection rate metering

Flow Line

Separator

Wellhead Subsystem :• Production subsystem

• wellhead• production choke• pressure gauge

• Injection subsystem• injection choke

ValveSubsystem

Wellbore Subsystem:• perforation interval• tubing shoe• packer

Separator Subsystem:• separator• manifold• pressure gauges• flow metering

Unloading Gas Lift Mandrells

Gas Injection Valve

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Compressor Sub-System

DPgas

Compressor

Wellhead

Separator

Pintake Pdischarge

Horse PowerCompressor

Pinjection@wellhead

Pinjection@wellhead=Pdischarge - DP

QgasQgas

Wellhead

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Wellhead Sub-System

ProductionChoke

InjectionChoke

Surface InjectionPressure

WellheadPressure

Gas Injection

Production Fluid

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Gas Lift Valve Sub-System

Pt

Pc

Pc

Pt

GasInjeksi

FluidaProduksi

Pc = Pt

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Gas Lift Valve

GasInjection

TubingPressure

Close condition Open condition

Kriteria Operasi Sumur Gas Lift

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There are four categories of wells in which a gas lift can be considered:

High productivity index (PI), high bottom-hole pressure wells

High PI, low bottom-hole pressure wells

Low PI, high bottom-hole pressure wells

Low PI, low bottom-hole pressure wells

• Wells having a PI of 0.50 or less are classified as low productivity wells.

• Wells having a PI greater than 0.50 are classified as high productivity wells.

• High bottom-hole pressures will support a fluid column equal to 70% of the well depth.

• Low bottom-hole pressures will support a fluid column less than 40% of the well depth.

Continuous Gas Lift Intermittent Gas Lift

• A continuous gas lift operation is a steady-state flow of the aerated fluid from the bottom (or near bottom) of the well to the surface.

• Continuous gas lift method is used in wells with a high PI (0:5 stb=day=psi) and a reasonably high reservoir pressure relative to well depth.

• Intermittent gas lift operation is characterized by a start-and-stop flow from the bottom (or near bottom) of the well to the surface. This is unsteady state flow.

• Intermittent gas lift method is suitable to wells with (1) high PI and low reservoir pressure or (2) low PI and low reservoir pressure.

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2 Types of Gas Lift Operation

Materi Perencanaan Sumur Gas Lift

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This chapter covers basic system engineering design fundamentals for gas lift operations. Relevant topics include the following:

1. Liquid flow analysis for evaluation of gas lift potential2. Gas flow analysis for determination of lift gas compression

requirements3. Unloading process analysis for spacing subsurface valves4. Valve characteristics analysis for subsurface valve selection5. Installation design for continuous and intermittent lift

systems.

Evaluation of Gas Lift Potential

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Evaluation of gas lift potential requires system analyses to determine well operating points for various lift gas availabilities.

The principle is based on the fact that there is only one pressure at a given point (node) in any system; no matter, the pressure is estimated based on the information from upstream (inflow) or downstream (outflow).

The node of analysis is usually chosen to be the gas injection point inside the tubing, although bottom hole is often used as a solution node.

Gas Injection Rates

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Four gas injection rates are significant in the operation of gas lift installations:

1. Injection rates of gas that result in no liquid (oil or water) flow up the tubing. The gas amount is insufficient to lift the liquid. If the gas enters the tubing at an extremely low rate, it will rise to the surface in small semi-spheres (bubbly flow).

2. Injection rates of maximum efficiency where a minimum volume of gas is required to lift a given amount of liquid.

3. Injection rate for maximum liquid flow rate at the ‘‘optimum GLR.’’4. Injection rate of no liquid flow because of excessive gas injection.

This occurs when the friction (pipe) produced by the gas prevents liquid from entering the tubing

THE GAS IS INJECTED CONTINUOUSLY TO ANNULUS

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CONTINUOUS GAS LIFT

Continuous Gas Lift Operation

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The tubing is filled with reservoir fluid below the injection point and with the mixture of reservoir fluid and injected gas above the injection point. The pressure relationship is shown in Fig. 13.4.

Gas Lift OperationPressure vs Depth

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Parameter Design

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• Jumlah gas injeksi yang tersedia• Jumlah gas injeksi yang dibutuhkan• Tekanan Gas Injeksi yang dibutuhkan di setiap

sumur• Tekanan Kompresor yang dibutuhkan

GAS LIFT PERFORMANCE CURVE

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GAS INJEKSI YANG DIPERLUKAN

Unlimited amount of liftgas Limited amount of gas

• In a field-scale valuation, if an unlimited amount of lift gas is available for a given gas lift project, the injection rate of gas to individual wells should be optimized to maximize oil production of each well.

• If only a limited amount of gas is available for the gas lift, the gas should be distributed to individual wells based on predicted well lifting performance, that is, the wells that will produce oil at higher rates at a given amount of lift gas are preferably chosen to receive more lift gas.

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Availability amount of Gas Injection

Kebutuhan Gas Injeksi (1)

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• Nodal Analysis:– IPR Curve– Tubing Performance

Curve– GLR formasi

• Variasi GLR– GLR-total (assume)– Qg-inj = Qtotal – Qq-f

• Plot Qg-inj vs Qliquid

0

500

1000

1500

2000

2500

0 200 400 600 800 1000

Laju Produksi, stb/d

Tek

anan

Alir

Das

ar S

umu

r, p

si

IPR

200 scf/stb

400 scf/stb

600 scf/stb

800 scf/stb

1000 scf/stb

1200 scf/stb

Kebutuhan Gas Injeksi (2)

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• Qg-inj >> maka Qliq >>

• Pertambahan Qliq makin kecil dengan makin meningkatnya Qg-inj

• Sampai suatu saat dengan pertambahan Qg-inj, Qliq berkurang

• Titik puncak dimana Qliq maksimum disebut sebagai Qoptimum

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200 1400

Perbandingan Gas-Cairan, scf/stb

Laj

u P

rodu

ksi,

stb

Unlimited Gas Injection Case

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If an unlimited amount of gas lift gas is available for a well, the well should receive a lift gas injection rate that yields the optimum GLR in the tubing so that the flowing bottom-hole pressure is minimized, and thus, oil production is maximized.

The optimum GLR is liquid flow rate dependent and can be found from traditional gradient curves such as those generated by Gilbert (Gilbert, 1954).

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200 1400


Laj

u P

rodu

ksi,

stb

Unlimited Gas Injection Case

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• After the system analysis is completed with the optimum GLRs in the tubing above the injection point, the expected liquid production rate (well potential) is known.

• The required injection GLR to the well can be calculated by

Limited amount of gas injection

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• If a limited amount of gas lift gas is available for a well, the well potential should be estimated based on GLR expressed as

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200 1400


Laj

u P

rodu

ksi,

stb

Gas Flow Rate Requirement

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• The total gas flow rate of the compression station should be designed on the basis of gas lift at peak operating condition for all the wells with a safety factor for system leak consideration, that is,

whereqg = total output gas flow rate of the compression station, scf/daySf = safety factor, 1.05 or higherNw = number of wells

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POINT OF INJECTION

Output Gas Pressure Requirement (1)

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Kickoff of a dead well (non-natural flowing) requires much higher compressor output pressures than the ultimate goal of steady production (either by continuous gas lift or by intermittent gas lift operations).Mobil compressor trailers are used for the kickoff operations.


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• The output pressure of the compression station should be designed on the basis of the gas distribution pressure under normal flow conditions, not the kickoff conditions. It can be expressed as

L

fout P

SP

DPgas

Compressor

Wellhead

Separator

Pintake Pdischarge

Horse PowerCompressor

Pinjection@wellhead

Pinjection@wellhead=Pdischarge - DP

QgasQgas

Wellhead

COMPRESSOR

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• The injection pressure at valve depth in the casing side can be expressed as:

• It is a common practice to use Dpv = 100 psi. The required size of the orifice can be determined using the choke-flow equations presented in Subsection 13.4.2.3

vvtvc PPP ,,

Pt

Pc

Pc

Pt

GasInjeksi

FluidaProduksi

Pc = Pt

Tekanan Tubing @ Valve Gas Lift

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Pwf

Dp @ tubing


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• Accurate determination of the surface injection pressure pc,s requires rigorous methods such as the Cullender and Smith method (Katz et al., 1959).

• However, because of the large cross-sectional area of the annular space, the frictional pressure losses are often negligible.

• Then the average temperature and compressibility factor model degenerates to (Economides et al., 1994)

ProductionChoke

InjectionChoke


WellheadPressure

Gas Injection

Production Fluid

Up-Stream Choke / Injection Choke

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• The pressure upstream of the injection choke depends on flow condition at the choke, that is, sonic or subsonic flow.

• Whether a sonic flow exists depends on a downstream-toupstream pressure ratio. If this pressure ratio is less than a critical pressure ratio, sonic (critical) flow exists.

• If this pressure ratio is greater than or equal to the critical pressure ratio, subsonic (subcritical) flow exists. The critical pressure ratio through chokes is expressed as

ProductionChoke

InjectionChoke


WellheadPressure

Gas Injection

Production Fluid

Gas Lift Injection Parameters

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Compressor Pressure

Pwf

Point of Injection

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vvfvc PPP ,

Point of Balanced

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vvfvc PPP ,

Unloading ProcessGas Lift Wells

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UNLOADING VALVES DESIGN

Persiapan Operasi Sumur Gas Lift

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• Katup Unloading sudah dipasang.

• Sumur masih diisi killing fluid

• Fluida produksi masih belum mengalir ke dalam tubing

Valve 1 : Terbuka

Valve 2 : Terbuka

Valve 3 : Terbuka

Valve 4 : Terbuka

PermukaanKilling fluid

No flowChokeTutup

TAHAP O

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Tahap I

• Pada Gambar 1 ditunjukkan penampang sumur yang siap dilakukan proses pengosongan (unloading). Pada tubing telah dipasang empat katup, yang terdiri dari 3 katup, yaitu katup (1), (2) dan (3), yang akan berfungsi sebagai katup unloading. Sedangkan katup (4) akan berfungsi sebagai katup operasi. Sebelum dilakukan injeksi semua katup dalam keadaan terbuka.

• Sumur berisi cairan work-over, ditunjukkan dengan warna biru, dan puncak cairan berada diatas katup unloading (1).

• Gas mulai diinjeksikan, maka gas akan menekan permukaan cairan work over kebawah, dan penurunan permukaan cairan ini akan mencapai katup unloading (1). Pada saat ini gas akan mengalir dalam tubing melalui katup (1) yang terbuka.

Valve 1 : Terbuka

Valve 2 : Terbuka

Valve 3 : Terbuka

Valve 4 : Terbuka


No flow

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Tahap II

• Pada Gambar 2 gas injeksi mendorong permukaan cairan work-over, dan telah me-lampaui katup unloading (1) dan mencapai katup unloading (2). Pada saat ini katup unloading (1) tertutup dan gas injeksi mendorong permukaan cairan kebawah.

• Bagian bawah tubing yang semula berisi cairan work-over ditempati oleh fluida for-masi.

• Pada saat ini gas akan masuk kedalam tubing, melalui katup unloading (2) yang terbuka. Dengan masuknya gas injeksi tersebut kedalam tubing maka kolom cairan dalam tubing akan lebih ringan dan aliran cairan work over ke permukaan akan berlanjut.

Valve 2 : Terbuka

Valve 3 : Terbuka

Valve 4 : Terbuka

Valve 1 : Tertutup


PermukaanFluida Res.

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Tahap III

• Pada Gambar 3 gas injeksi mendorong permukaan cairan work-over, sampai me-lampaui katup unloading (1), (2) dan (3). Setiap saat permukaan kolom cairan work-over mencapai katup unloading, maka gas injeksi akan mengalir masuk kedalam tubing dan aliran cairan work-over dalam tubing akan tetap berlangsung. Jika per-mukaan kolom cairan work-over mencapai katup unlaoding (3), maka katup unloading (2) akan tertutup, dan gas injeksi akan masuk melalui katup unloading (3).

• Selama ini pula permukaan cairan formasi akan bergerak ke permukaan. Pada saat cairan work-over mencapai katup terakhir, yaitu katup operasi (4), maka katup unloading (3) akan tertutup dan seluruh cairan work-over telah terangkat semua ke permukaan, dan hanya katup operasi yang terbuka.


PermukaanFluida Res.

Valve 1 : Tertutup

Valve 2 : Tertutup

Valve 3 : Tertutup

Valve 4 : Terbuka

TAHAP IV

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• Pada Gambar 4 ditunjukkan bahwa semua cairan work-over telah terangkat dan sumur berproduksi secara sembur buatan.

• Katup operasi (4) akan tetap terbuka, sebagai jalan masuk gas injeksi kedalam tubing. Katup ini diharapkan dapat bekerja dalam waktu yang lama. Dimasa mendatang akan terjadi perubahan perbandingan gas-cairan dari formasi, yang cenderung menurun serta peningkatan produksi air, maka jumlah gas injeksi dapat ditingkatkan dan diharapkan katup injeksi dapat menampung peningkatan laju injeksi gas tersebut. Dengan demikian pemilihan ukuran katup injeksi perlu direncanakan dengan baik.

FluidaProduksi

Valve 1 : Tertutup

Valve 2 : Tertutup

Valve 3 : Tertutup

Valve 4 : Terbuka

gas lift Valve

gas lift Valve Mechanics

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UNLOADING VALVES DESIGN

Gas Lift Valve

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Gas Lift Valve

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Contoh Penampang Sumur Gas Lift

}Gas Lift MandrellGas Lift Valves

Gas Lift Valves:• Mandrell + Dummy Valves• Mandrell + Valves

Valves Operating Conditions:• Casing pressure• Test Rack Opening Pressure• Port Size• Temperature @ Lab.• Jenis Valves

Gas Lift Valve

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Pt

Pc

Pc

Pt

GasInjeksi

FluidaProduksi

Pc = Pt

Penampang Gas Lift Valve

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Jenis Gas Lift Valves

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Gas Lift Valve

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GasInjection

TubingPressure

Close condition Open condition

artificial lift methods

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