Using Aspen HYSYS Upstream for Sizing and Scheduling of Gathering Systems

Authors: Francisco da Silva, James Holoboff, Ahad Sarraf Shirazi (Process Ecology Inc.)
30 June, 2015
Using Aspen HYSYS® Upstream for Sizing
and Scheduling of Gathering Systems
James Holoboff, Managing Partner, Process Ecology Inc.

© 2015 Aspen Technology, Inc. All rights reserved.2
Today’s Presenters
Irina Rumyantseva
Engineering Product Marketing, Aspen Technology
James Holoboff
Managing Partner, Process Ecology Inc.

Overview
• Introduction – Applications for Hydraulics / Dynamics
• Sizing and Scheduling of Gathering Systems
– The Challenge
– Approach to Solving Problem
– Model Development
– Automation
– Results
• Comparison - HYSYS Hydraulics vs. HYSYS Dynamics
• Conclusions

Company Background – Process Ecology
• Founded 2003, Calgary, AB
• Key Competencies
– Engineering consulting, process simulation
– Process engineering & optimization
– Air emissions estimation and management
– Software development

We’ve come a long way … Disney’s Black Hole movie (1979) vs. Interstellar (2014)
With Current Technology, We Can Accomplish Much More
Released 1979
State-of-the art at the time, but …
deemed the most scientifically
inaccurate film of all time (the
black hole is populated by drones
in a burning landscape).
Released 2014
Scientifically accurate, based on
Einstein’s relativity equations
Possible through modern computing
technology

Hydraulics / Dynamics Applications
• Estimation of Slug volume
• Dynamic Model-Based Production System
• Sizing / Scheduling of Gathering Systems

Application 1 – Estimation of Slug Volume
• Background
– Heavy fraction in natural gas condenses;; may result in slugs reaching facilities
– Sizing the slug catcher requires estimation of slug volume and duration
– Conventional Sizing methods may significantly oversize slug catcher
• Slugging Types
– Terrain –induced slugging
– Caused by change of elevation in pipeline
– Hydrodynamic slugging
– Caused by formation of wave on liquid surface as a result of faster moving gas phase
– Pig-Induced slugging
– Caused by pigging operations in pipeline. Pig is designed to push most of the liquid contents to
the outlet

Application 1 – Estimation of Slug Volume
Elevation Profile

Application 1: Liquid Holdup Profile
0
0.0005
0.001
0.0015
0.002
0.0025
0 10000 20000 30000 40000 50000 60000 70000 80000
Liquid holdup
Distance from Compressor1 discharge (m)
Pipe 2 liquid holdup profile

Application 1: Estimation of Slug Volume
500
550
600
650
700
750
1440 2440 3440 4440 5440 6440 7440 8440
Pressure Drop (kPa)
Elapsed Time (min)
Pressure drop in Pipe 2b

Application 1: Estimation of Slug Volume
- Peak of ~ 550 bbl/day
- Most of the liquid is recovered within 1-2 hours

Application 2: Dynamic Model-Based Production
System
• Synchronized integration of a dynamic simulation model of the wells and production
facilities with real-time online data obtained from production field
• Accurate dynamic model of wells and production network
• Online real-time application which transfers data between historian and simulation
model

System

System
• System acts as “virtual instrumentation” for key unmeasured variables such as well flow
rates
• Can monitor performance of specific equipment and support decisions to switch to
production modes such as artificial lift
• Can be run as a look-ahead tool
• Can be used offline to run what-if scenarios
• Real-time models that match field data improve understanding of the overall system
• They provide the tools to translate data into decision support

Part II: Sizing and Scheduling of Gathering Systems
• What is HYSYS Hydraulics?
• What is the challenge?
• What was the approach to solving the challenge?
• What were the results and benefits?

What is HYSYS Hydraulics?
• A solution for integrated upstream asset modeling
• HYSYS Hydraulics can be run in steady-state and dynamic mode
• Flow Assurance - predicts hydrate, wax, asphaltene formation
• Can be used for slugging / pigging analysis
• Network solver – flexible boundary conditions
• Multiple phases, phase slip
• Includes recent fluid flow correlations - TUFFP (Tulsa University)
• Emulsion viscosity models

The Challenge: Network Sizing and
Construction Scheduling
• Challenges include:
– Multiphase flow (condensate) – phase interaction, slip, flow patterns, pressure drop
– Uncertainty in production data
– Uncertainty in exact pipeline routes
– Looping/networking of pipelines
– Location of multiple processing facilities
The Problem: What are the required
pipeline sizes in the different segments of
the gas gathering network, at various
stages of the gathering system?

Network Schematic
Plant A
Plant B
32 wells, 2 plants
Many looped lines
Wells are being drilled over next 8
years
Pipelines will be built as needed

Model Setup in HYSYS Hydraulics (Steady-State)
• Rigorous multiphase pressure drop and heat
transfer correlations
• Rapid estimation of unknown profiles using
Google Earth
• Automation tool to transfer forecast data to the
simulation model
• Automation tool reports/interprets simulation
results and identifies segments where
constraints are violated

Model Setup
• 32 wells, 2 plants, looped lines
• All pipelines / wells (for all future times)
modeled. Sections of model ignored
depending on modeled year/quarter.
• Well data imported from master
spreadsheet, based on selected model
year/quarter.

Automation Tool:
Enable Quick Configuration of Model
• Select Quarter/Year
• Load HYSYS case / Transfer Data
• Run
• As system is analyzed, if flowrates change, they can easily be managed in master
spreadsheet
• Key assumptions (well temperatures, plant inlet pressures) can be managed in master
spreadsheet

Model Constraints
• Plant A limit of 50 MMSCFD – suction pressure calculated to limit this rate
• Maximum pipe size – 12” (16” for short segments)
• Ratio of velocity to erosional velocity not to exceed 55%

Model Calibration
• 25-35 bbl/MMSCF liquids in
produced gas
• Selection of appropriate
pressure drop correlation
crucial
• Calibration done for well-
defined isolatable pipeline
• Tulsa correlation gave the
best match

System Analysis
• Model/automation tool enabled quick analysis of the system at each quarter
• Segments exceeding constraints could easily be identified, and modifications made
• In the example below, in consultations with client, 16” pipe (instead of 10”) was installed
to alleviate the high velocity

Results
• A series of recommendations for each quarter from 2015-2022 – where to add pipelines
and what size – i.e., the “drilling program”
• This enables capital spending to be determined over the next few years of production
• Trade-offs identified and reviewed: e.g., postpone capital spending with parallel lines

Benefits
• Provided critical data for scheduling and budgeting purposes
• Provided notifications regarding technical issues, such as potential reversal of flow
direction in certain network segments
• Model is now an asset for the client and can be used for future studies as conditions
change
Key Benefit: Projection was not a guess –
sound science and engineering was efficiently
used to develop the drilling program.

Are there advantages to using HYSYS Dynamics vs. HYSYS Hydraulics?
Part III: HYSYS Hydraulics vs. HYSYS Dynamics
• Why Consider HYSYS Dynamics?
– It is beneficial to consider alternatives within HYSYS
– HYSYS Steady-State cannot be used for this sort of analysis
– HYSYS Dynamics is well-established and has been used for many applications

Hydraulics vs. Dynamics- Results
• Plant A pressure
– In Dynamics, plant pressure can be directly calculated by
having a flowrate spec at plant A “sink”, while in Hydraulics
estimating plant A pressure (with a flow constraint) is an
iterative procedure
• Flow rate and direction in two branches from Plant A:
Parameter Name Unit Hydraulics Dynamics % Difference
Plant A pressure kPag 1,688 1,612 4.5
“Branch 1” flowrate MMSCFD 5.5 5.3 3.6
“Branch 2” flowrate MMSCFD 21.5 21.7 0.9

Well Pressure Predictions –
Hydraulics vs. Dynamics
Well Pressure (kPa)
Hydraulics
Pressure (kPa)
Dynamics
% Difference
b-74-A 1,338.6 1,303.6 2.6
c-51-A 1,218.5 1,212.5 1.0
c-54-A 1,423.1 1,348.3 5.3
c-17-H 1,634.3 1,482.9 9.3
15-1 1,820.1 1,468.9 19.1
c-64-H 1,936.0 1,473.2 23.9
The results are fairly close at some locations while they deviate 20% or
more at others

• Taking a closer look at 15-1 lateral pipe:
• Large elevation change over a few kilometers
• Pipe is modelled in 3 segments in HYSYS:
Segment No. Length (m) Elevation change (m)
1 930 14
2 1190 -20
3 1150 35
15-1 lateral Hydaulics Dynamics
Pressure drop 145 14

• Liquid holdup profile in Hydraulics:
• In Dynamics liquid holdup is proportional to liquid/vapour volume rates, and constant

• Pipe segment calculations in Dynamics ignore phase slip and assumes both phases are
moving with the same velocity
• This can result in significant differences in pressure drop.
• Conclusions
– Using Dynamics for modeling gathering network can potentially be easier to set up and converge,
but user must be extremely cautious when there is a large elevation change and significant liquid
expected in the network
15-1 lateral
Hydaulics
pipe
Pipe segment
Dynamics
Pipe segment
steady-state
Pressure drop 145 14 148

HYSYS Hydraulic Modeling of Gathering Systems
• Initial convergence of the model is
straightforward
• Steady-state solution provides liquid
hold-up profile in the pipes. Phase slip is
considered in model.
• Dynamic simulation of Hydraulic
flowsheet provides ability to predict
terrain-induced/pig-induced slug;; heat
transfer rigorously modeled
• Model is cumbersome to set up, as only two
pressure nodes can be connected to each
other
• Only a few unit operations are available in
the flowsheet
• Objects inside Hydraulics flowsheet are not
well-exposed in HYSYS API.
• Solver takes more time to converge
especially when there are multiple sinks.
Advantages vs. HYSYS Dynamics Disadvantages vs. HYSYS Dynamics

HYSYS Dynamic Modeling of Gathering Systems
• Takes into account equipment holdup
(system accumulation)
• More pressure drop correlations
available in Aspen Dynamics
• Quicker, easier transition to studying
transient behaviour
• Additional units operations: control
valves, PSVs, pumps, compressors,
etc.
• Hydraulics flow assurance tools (erosion,
corrosion, hydrates, deposit formation
and slugging) are not available in
dynamics
• For steady-state analysis: step-time
sensitive
• Phase slip is not considered in model
Advantages vs. HYSYS Hydraulics Disadvantages vs. HYSYS Hydraulics SS

Recommendations and Conclusions
• HYSYS Hydraulics can be used to address the challenge of sizing and scheduling
gathering systems
• Automation can be used to improve the efficiency and flexibility in configuring the model
• There are alternatives within HYSYS for large gathering system models
• HYSYS Dynamics can be a feasible alternative, and there are some advantages.
However, it must be used with caution for multi-phase systems.

Aspen HYSYS: Process Modeling Training
Aspen HYSYS: Process Modeling (EHY101)
July 6, 2015 – Virtual-Americas
July 13, 2015 – Frankfurt, Germany
January 27, 2015 – Bedford, MA
January 27, 2015 – Calgary, AB, Canada
http://support.aspentech.com/supportpublictrain/CourseInfo.asp?course=EHY101
• Learn to build process simulations using Aspen HYSYS.
• Discover how Aspen HYSYS allows rapid flowsheet construction and bi-directional calculations.
• Investigate how templates and subflowsheets can streamline and organize simulation efforts.
• Learn how to do preliminary cost estimation using Aspen Process Economic Analyzer from the
Aspen HYSYS Environment.

Modeling Heavy Oil & Gas Production and Facilities Using
Aspen HYSYS Upstream
Modeling Heavy Oil & Gas Production and Facilities Using Aspen
HYSYS Upstream (EHY2351)
July 13, 2015 – Virtual-EMEA
July 16, 2015 – Houston, TX
July 20, 2015 – Virtual-Americas
http://support.aspentech.com/supportpublictrain/CourseInfo.asp?course=EHY2351
• Use the new advanced capabilities of Aspen HYSYS to enable shared workflow between
production modeling and facilities modeling.
• Use the improved oil modeling tools in Aspen HYSYS for heavy oil models, hypothetical
components from lab data, tune transport properties to match field data.
• Use Aspen Hydraulics to perform hydraulic calculation and use Aspen HYSYS pipe segment for
Flow assurance calculation

Visit the Process Ecology Website
www.processecology.com
Q&A
James Holoboff
james@processecology.com
Irina Rumyantseva
irina.rumyantseva@aspentech.com

Using Aspen HYSYS Upstream for Sizing and Scheduling of Gathering Systems

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