Analysis of Gas-Lift Wells in Unconventional Reservoirs A ...

2019 Artificial Lift Strategies for

Unconventional Wells Workshop Cox Convention Center, Oklahoma City, OK

February 11 - 14, 2019

Analysis of Gas-Lift Wells in

Unconventional Reservoirs –

A Case Study based on SPE-190950-MS

Luis E. Gonzalez

Rajan Chokshi

Introduction

2 Feb. 11 - 14, 2019 2019 Artificial Lift Strategies for Unconventional Wells Workshop

Oklahoma City, OK

Gas lift has become a predominant, intermediate term, artificial lift system in majority of basins.

For over 3 years, most operators have been moving to gas lift after experiencing the high failure rates and significant downtime associated with other artificial lift systems.

The major cause of high failure rates and expenses can be attributed to the dynamic nature of these wells, specifically, the rapid decline of pressure and production rates in combination with slugging.

Source: Gas-Lift Workshop Key Note, Noonan, 2017

Gas Lift Equipment


Oklahoma City, OK

• Use of conventional

mandrels is the most

common in unconventional

• Restrictions to use side

pocket mandrels:

• Use of plunger lift in future

• Size of casing (5 1/2”) and

tubing (2 7/8”).

• Losing the ability to

optimize the well.

Gas Lift Design

Shows a sample gas lift

design.

Number of mandrels : 10-18.

Dome-charged valves are

used as operating valves.

Dummy valves are active

valves.

4 2019 Artificial Lift Strategies for Unconventional Wells Workshop

Oklahoma City, OK Feb. 11 - 14, 2019


Oklahoma City, OK

Reservoir – Pressure & PI – Behavior

is not well understood

SPE 171768

Reservoir pressure and PI – very important elements for effective gas-lift design and efficient operation – are mostly unknown over life cycle.

For shale reservoirs pseudo-steady state or steady state IPR curves are not applicable.

Transient IPR models – found in the literature – are based on initial pressure.

Feb. 11 - 14, 2019 6 2019 Artificial Lift Strategies for Unconventional Wells Workshop

Oklahoma City, OK

Pressure & PI Behavior

Graphic shows PR and PSRV behavior in a shale well. PSRV may be calculated by

reservoir simulation or Rate Transient Analysis. A complex approach for

production application like gas-lift.

Dynamic Nodal Analysis (DNA) – SPE 190950

Efficient, faster and practical algorithm to calculate the PSRV and PI using operation data

Time (days)

Pw

s

PI

Time (days)

PR

PSRV

Reservoir Pressure

Figures show examples of IPRs using Pinitial & PSRV.

PIs obtained are different and can significantly affect optimization-decisions for a gas-lift well.

Dynamic Nodal Analysis (DNA) – SPE 190950

Efficient, faster and practical algorithm to calculate the PSRV and PI using operation data.


Oklahoma City, OK

SPE 171768

Case Study: Delaware Gas Lift Well


Oklahoma City, OK

Figure shows the completion of “Shale01”:

MD/TVD: 16,650’/11,089’

KOP/HEEL=10,655’/11,664’

Production Casing = 7 5/8”

Production Tubing = 2 7/8”

Lateral = 5,553’

Case Study: Production Data

40-months’ history analyzed

for this gas-lift well Top-left production & injection

rate trends, and

on the bottom-right, wellhead

pressures, and injection choke

trends.


Oklahoma City, OK

SPE-190950-MS

Case Study: Operation Data


Oklahoma City, OK

• Dynamic Nodal Analysis (DNA) algorithm was developed to infer Pws & PI for the 40-months’ production history.

• Once the DNA is performed, traditional Nodal Analysis can be completed with high confidence at any time step. SPE-190950-MS

-

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-

500

1,000

1,500

2,000

2,500

3,000

9/18/2014 7/15/2015 5/10/2016 3/6/2017 12/31/2017

Liq

uid

Ra

tes

(B

LP

D)

Time

Measured & Calculated Liquid Rates

QLMeasure QLCal PI

-

2,000

4,000

6,000

8,000

10,000

12,000

9/18/2014 7/15/2015 5/10/2016 3/6/2017 12/31/2017

Pre

ss

ure

(P

SI)

Time

Static & Flowing Pressure

Pwfcalc1 Pwh Pwfcalc2 Pgauge PSRV

Case Study – Nodal Analysis


Oklahoma City, OK

• Figure shows Nodal Analysis for date-stamp 09-16-2016.

• Five upper valves are closed. • Where and

how much

gas is being

injected?

SPE-190950-MS

Case Study – Advanced GL Valve

Modeling


Oklahoma City, OK

• Looking at the Valve 6 performance for Pcsg values of 882, 936 and 1,000 psi.

• Results indicate no gas being injected in the well for Pcsg of 882 psi, but the operations show 679 MSCFD of gas being injected. • Wrong calculations?

• What is happening?

Valve Performance curve

for 1,000 Psi


for 882 Psi


for 936 Psi

Case Study – Dynamic G/L Analysis

13 Feb. 11 - 14, 2019

• A dynamic gas-lift

model is created and

ran for the same

timestep with the

following results:

− top 5 valves are

closed

− 2 valves act as

operating valves

(Multi-point

injection)

SPE-190950-MS

2019 Artificial Lift Strategies for Unconventional Wells Workshop

Oklahoma City, OK

Operation

Data

Dynamic

Model

Pwh 199.40 200.70

Pcsg 881.71 935.70

Pwf 2,491.47 2,522.00

Ql 767.87 763.00

Qo 125.87 125.00

Qw 642.00 638.00

Qginj 678.94 614.00

Qtg 1,188.06 1,118.00

Case Study – Dynamic G/L Analysis

Feb. 11 - 14, 2019

If we force-open the

Valve no. 5, the

simulations show a

better match with

operation results.

Operation

Data

Dynamic

Model

Pwh 199.40 208.70

Pcsg 881.71 887.70

Pwf 2,491.47 2,571.70

Ql 767.87 751.00

Qo 125.87 123.00

Qw 642.00 628.00

Qginj 678.94 679.00

Qtg 1,188.06 1,177.00

SPE-190950-MS


Oklahoma City, OK 14


Oklahoma City, OK

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0

500

1,000

1,500

2,000

2,500

9/18/14 7/15/15 5/10/16 3/6/17 12/31/17

Liq

uid

Ra

tes

(B

LP

D)

Time

Measured & Calculated Liquid Rates

Liquid Measures QLCal PI

Feb. 11 - 14, 2019

Dynamic G/L Analysis @ Various Time Steps

Conclusions

Gas lift design procedures applicable for

conventional wells cannot necessarily be

applied to unconventional wells without

considering the dynamic changes in

behavior.

Understanding dynamic reservoir behavior

of unconventional wells is a must in order to

efficiently design, effectively operate and

troubleshoot gas lift.



Conclusions

A new workflow, to analyze unconventional gas-lift wells, using dynamic nodal analysis has been presented.

This novel DNA-based workflow offers

Efficient calculation of dynamic PI and PWS using production data over large time-periods.

Validation and troubleshooting of gas-lift well behaviors.

Better understanding of dynamic pressure and PI behavior will help improve design and operation of future gas-lift wells.



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

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