Scale Flow Assurance Workflows in Multiphase Flow SimulationMack Shippen - SchlumbergerPIPESIM Product Champion

OLI Simulation ConferenceNovember 17, 2010

Abstract

Multiphase flow simulation is critical to the understanding of impact of flow assurance issues on oilfield production system design and operation. While the modeling of organic solids such as hydrates, waxes and asphaltenes has in recent years become commonly available in multiphase flow simulators, detailed modeling of inorganic scales has been regarded as a more specialist discipline due to the inherent complexities of water chemistry. Consequently, scale prediction methods currently available in upstream multiphase flow simulators are quite simplified. As scaling behavior for a given fluid is governed by the prevailing pressures and temperatures, accurate prediction of the occurrence, location and severity of scaling depends on accurate modeling of the pressure and temperature profiles along the complete production system. This work aims to combine state-of-the-art scale prediction models with state-of-the-art multiphase flow and heat transfer simulation technology to better understand scaling behavior and quantify risks in performing flow assurance studies. A workflow is presented which describes the coupling of the scale model with multiphase flow simulation and presents an example case study to illustrate the benefits of this approach.

Overview

Background – Multiphase Flow SimulationMechanism of ScaleChem – PIPESIM WorkflowCase StudySummary and Future Work

Overview

Background – Multiphase Flow SimulationMechanism of ScaleChem – PIPESIM WorkflowCase StudySummary and Future Work

Total Production System

Completion

Choke

Safety Valve

Tubing

Flowline

Pump

CompressorSeparator

Export lines

Riser

Reservoir

gas

oil

ΔP3 = PUSV – PDSV

ΔP1 = PR – Pwfs

ΔP6 = PDSC – PRB

ΔP8 = Psep – PCD

ΔP10 = PCD – PGD

ΔP11 = PPD – PLD

ΔP4 = Pwf – Ptf

ΔP7 = PRB – PsepΔP9 = Psep – PPD

Pressure Loss in System

•Flow in porous media•Multiphase Flow in pipes•Chokes/restrictions•Pumps/Compressors

ΔT1 = TR – Twfs

ΔT5 = Ttf – TDSC

ΔT6 = TDSC – TRB

ΔΤ10 = TCD – TGD

ΔΤ11 = TPD – TLD

ΔT4 = Twf – Ttf

ΔT7 = TRB – Tsep

Temperature Changes in System

•Convection (free, forced)•Conduction•Elevation•Radiation•JT Cooling/Heating•Frictional Heating

Segmentation

Node taken at Bottom Hole model reservoir to separator

Pwf PR

Inflow = PR – Pwf

Psep

Outflow = Pwf – Psep

Nodal Analysis

OutflowInflow

PR

PR

Psep

PsepPwf

Pwf

Flowrate

Nodal Analysis

Overview

Background – Multiphase Flow SimulationMechanism of ScaleChem – PIPESIM WorkflowCase StudySummary and Future Work

PVT File Structure

•Mass Fraction against total composition •Density•Viscosity•Heat Capacity•Enthalpy•Entropy•Thermal Conductivity•Compressibility factor•Surface tension against gas phase•Interfacial tension against other liquid phase•Molecular Weight

•Liquid 3•Water ice•Hydrate type 1•Hydrate type 2•Wax•Asphaltene•Scale total•Scale species 1•Scale species 2•Scale species…

•Mass Fraction•Density•Thermal Conductivity•Phase appearance curves•Etc.

•Gas•Hydrocarbon liquid •Aqueous liquid

Vapor/Liquid Phases Solid Phases (Optional)

V/L Phase Properties

Solid Phase Properties

Fluid Property File Generation

ScaleChem PIPESIM

PVT Tables

PVT Calculations – Loose vs. Tight

LooseAdvantages

Fast Simple to Implement

TightAdvantages

More accurate Can mix fluidsCan sensitize on fluid properties (eg. watercut)

Overview

Background – Multiphase Flow SimulationMechanism of ScaleChem – PIPESIM WorkflowCase StudySummary and Future Work

Case Study

Fluid Composition

Component  Mol %Carbon Dioxide 2.7Methane 34.6Ethane 7.0Propane 6.5Isobutane 1.5Butane 4.1Isopentane 1.9Pentane 2.6Hexane 3.6C7+ 35.5

C7+ BP 344ºFC7+ MW 283

Species mg/LCationsNa+ 20,400 K+ 402 Ca++ 20 Mg++ 829 Ba++ 1 NH4+ 104 AnionsCl‐ 37,000 

SO4‐‐ 20 HCO3‐ 715 

Watercut 50 %Gas‐Oil Ratio 640scf/STB

Hydrocarbon WaterStock Tank Properties

Phase Envelope

Nodal Analysis

Tubing ID = 3 1/2”

Tubing ID = 2.41”

Skin = 0.7

Skin = 10

Phase Envelope

Phase Envelope 2

Pressure-Temperature Profile

Nodal Analysis – Possible Scale Impact

Tubing ID = 1.4”

Tubing ID = 2.9”

Skin = 0.7

Skin = 10

Results Available

Phase Envelope– Scale Appearance Lines (Total & by species)Profile Plots– Total Scale Mass Fraction (eg. ppm, mg/L)– Scale Species Mass Fraction– Scale Species Pre- and Post- Scale IndexSystem Plots– Max. Scale Mass Fraction/branch– Max. Pre-Post Scale Index/branch

Overview

Background – Multiphase Flow SimulationMechanism of ScaleChem – PIPESIM WorkflowCase StudySummary and Future Work

Summary

ScaleChem-PIPESIM workflow leverages complex water chemistry analysis and rigorous multiphase flow simulationCan be used to predict occurrence, location and severity of scale precipitation for entire production systemAvailability:– ScaleChem ?– PIPESIM 2011 – Summer 2011

Future work

Tight coupling at engine levelInput for pipe corrosion calculationsBlack Oil scale analysis?

Questions?