Predicting the gains of deliquification - ALRDC - 1... · Predicting the gains of deliquification ....

Gas Well Deliquification Workshop

Sheraton Hotel, Denver, Colorado

February 17 – 20, 2013

Wouter Schiferli, Jordy de Boer, Erik Nennie (TNO)

Predicting the gains of deliquification

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

Denver, Colorado

2

Project structure and goals

• Joint Industry Project for 4 parties

– EBN, GDFSUEZ, ONE, Total E&P

• Goal: Transfer US knowledge on deliquification to Europe

Three phases:

1. Literature search

– What techniques are applied, and how widely

– Many common techniques in the US are not applied in Europe

2. Engineering guidelines to predict most suitable technology

– Implemented as Excel-based tool

3. Quantitative tool

– Calculate benefits of various technologies

– Can serve as input to economic screening process


Denver, Colorado

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Need for quantitative analysis

• Selection methodology yields candidate technologies

• Actual deployment decision is a balance between:

– Production and UR gain over time

– CAPEX/OPEX

• TNO’s expertise lies in modelling

– Models were implement for a range of techniques

– Implemented in a GUI for quick screening

– Calculates modified production profile after implementing each

technology

• CAPEX/OPEX analysis left to operator


Denver, Colorado

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Technologies included in the tool

• Allow the operator to evaluate the benefit of using

– Velocity string

– Foam

– Wellhead compression

– Eductor

• Performance measured by

– Ultimate recovery / abandonment pressure

– Production profile and required power over time

– Gas lift

– ESP

– Plunger lift

– Tail pipe


Denver, Colorado

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Methodology

• Basic wellbore and reservoir model required

• Wellbore model calculates BHP

• Reservoir model

– Simulates depletion

– Includes reservoir pressure drop

• Semi-steady state models describing each technique

– Goal: translate technique to modified well lift performance

– Reservoir model is not modified


Denver, Colorado

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Wellbore modelling

• Correlation required to calculate wellbore dp

– Deviated wells

– Variable diameter

• Many correlations are proprietary, choice was limited

– Gray standard Gray does not handle deviated wells

– Beggs and Brill universal

– OLGA ss proprietary

• Beggs and Brill was chosen

– Good match with OLGA

– Inclinations from horizontal to vertical


Denver, Colorado

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Reservoir modelling

• Tank (material balance model):

• With re reservoir drainage radius, and ϕ porosity

• Pressure drop is modelled using A and F factors:

• A, F can be calculated from reservoir parameters

– Ideally should be known from well tests


Denver, Colorado

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Base modelling method

• Beggs and Brill: tubing TPC at constant WHP

• Reservoir IPR calculated, including depletion

• Operation point continuously calculated

• Loading occurs at TPC minimum

– End of production

– Yields abandonment pressure

WHP

Line P Choke

assumed

open

BH

P

Gas flow

Depletion

Tubing TPC

Loading


Denver, Colorado

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Modelling mitigation measures

• Mitigations modelled in different ways

• Completion (diameter) change:

– Velocity string

– Tailpipe

• Change in boundary condition:

– Eductor: performance diagrams

– Wellhead compression: simplified analytical model

• Other models:

– Gas lift – BHP is minimized, staying within available power

– ESP – liquids are produced by pump through separate string

V string

loading

BH

P

Gas prod

Tubing TPC

Tubing loading

V string TPC


Denver, Colorado

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Modelling: foamer

• Assumed to be added continuously

– Start-up not taken into account

– Cap-string type of application

• Foaming mechanism is complex

– Reduction in surface tension

• Reduces critical rate to 75% of original rate

– Foam formation

• Increases gas-liquid surface area

• Reduced density, improved liquid transport

• Further reduction in critical rate to 50% or less

• Full modelling not feasible

– Reduction in critical rate is input to the tool

WHP

Line P Choke

assumed

open


Denver, Colorado

Modelling: plunger lift

• Most effective in smaller tubing (up to 3.5”)

• Usually requires installation of new tubing

• Most effective when annulus pressure buildup possible

– Low-set downhole packer is unfavourable

• Production is first assumed to occur through small string

– When close to loading, plunger installed (see below)

Line P

WHP


Denver, Colorado

Modelling: plunger lift

• Method developed to compare plunger to velocity strings

• Calculates a “TPC” for the plunger lift system

• Assumptions:

– Gas influx constant throughout cycle

– Plunger rise velocity 5 m/s

– No slip past plunger

• Based on modified Foss-Gaul guidelines


Denver, Colorado

Case: 3.5” vertical well

• Near-vertical well

• 12000’ of 3.5” tubing

• 500’ of 5” liner to perforations

• Initial Pres 340 bar (4900 psia)

• 22 bar (300 psia) THP

• LGR 80 m3/1e6Sm3 (14 bbl/MMscfd)

• Loading observed at 70,000 Sm3/d (2.4 MMscf/d)

• Decision required on mitigation method


Denver, Colorado

Output results

• Various techniques compared on basis of recovery

• Base case (BC) prediction

– Loading at 75,000 Sm3/d (field: 70,000)

– Production ends at 100 bar res pressure

• Gas lift / ESP appear very effective

– Can produce virtually dry gas

– Requires high gas lift rates

– Takes long to obtain high recovery

• Economics play large role in decision

– Left to operator


Denver, Colorado

Brief analysis

BC VS WHC ED ESP FM PL GL TP

UR [%] 69.9 79.8 81.8 80.2 88.3 78.1 83.3 90.2 71.4

Pab [bara] 100.1 67.0 60.5 66.1 39.0 72.9 55.6 32.7 95.2

CGP [106 Nm3] 479.1 546.9 560.3 552.1 604.6 534.7 570.5 617.6 488.8

Gain [%] 0.0 14.2 16.9 14.3 26.2 11.6 19.1 28.9 2.0


Denver, Colorado

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Conclusions

• Tool was developed to predict performance of mitigation

measures

• Based on (semi) steady state models

– Beggs & Brill pressure drop correlation

– Reservoir depletion and pressure drop

– Compressor, pump and eductor models

– Simplified pump and foam modelling

• Performance was considered realistic for most wells

• Beggs & Brill seems less suitable for specific cases

– LGR >> 100

– Larger diameter wells (>4”)

– May be solved by implementing different correlations


Denver, Colorado

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Outlook for follow-up programme

• Improving range of application

– Further validation against field trials

– Integrating other common pressure drop correlations

• Adding additional functionality

– Improved pseudo-pressure reservoir model

– Better modelling of first phase of production (e.g. by including a

choke model)

• Intermittent production requires more advanced modelling

– Coupled dynamic well and reservoir model

– Models available, but not readily integrated in fast tool

• Contents of follow-up programme are currently being discussed

– New participants welcome


Denver, Colorado

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Flow assurance course • Date: April 14 – 17, 2013

• Location: TNO, Delft

• Fundamentals of multiphase flow in flowlines and wellbores

• Practical Flow Assurance

– Multiphase dynamics: liquid loading, slug flow

– Solid deposition, integrity, heavy oil

– Well control, reservoir inflow

• Exercises

– Liquid hold-up in pipelines, severe slugging, slug catcher sizing, etc.

• Presenters:

– Prof. René Oliemans (Emeritus, TU Delft)

– Prof. Ruud Henkes (TU Delft / Shell Global Solutions)

– TNO Fluid Dynamics

• To keep updated, contact presenter

• More details and registration at www.tno.nl/FAcourse2013

•


Denver, Colorado

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Presenter details

• Wouter Schiferli

– TNO

– Fluid Dynamics Department, Delft, NL

• T: 088-8666488

• E: [email protected]


Denver, Colorado

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Copyright

Rights to this presentation are owned by the company(ies) and/or author(s) listed on the title page. By submitting this presentation to the Gas Well Deliquification Workshop, they grant to the Workshop, the Artificial Lift Research and Development Council (ALRDC), and the Southwestern Petroleum Short Course (SWPSC), rights to:

– 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

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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.

The views, opinions, and conclusions expressed in these presentations and/or training materials are those of the author and not necessarily those of the Sponsoring Organizations. The author is solely responsible for the content of the materials.

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