4.1 H OMOGENEOUS RESERVOIR SECTION MODELING
4.1.3 Results and discussion
A typical development for oil production from a reservoir is shown in Figure 15. In the beginning, the production liquid will normally be oil. As time passes, the production of water is increased. Production will stop when it is no longer economical to produce from the reservoir.
Figure 15 A typical development of oil production
Phase behaviour
The phase behaviour of the reservoir changes from the beginning of the production until water breakthrough occurs. Figure 16 to Figure 18 describe the behaviour of water flow in the reservoir in YZ-direction during production. During production, the water phase rises from the bottom of reservoir until it reaches the wellbore.
Figure 16 Saturation of oil before water break through
Figure 17 Saturation of oil during water break through
Figure 18 Saturation of oil after water break through
Initially the reservoir contains pure oil which is shown by red colour in Figure 19 and water is used as a pressure drive from the bottom of the reservoir.
Figure 19 Saturation of water at the beginning of production
Figure 20 to Figure 22 describe the behaviour of water flow in the reservoir in XZ-direction during production. The water starts to move towards the well from the heel side. Before water break through, the saturation of water is higher at the bottom of the reservoir and it is decreasing near the well bore. As time passes, the saturation of water is increasing near the well bore.
These phase contours contribute for the understanding of the behaviour of fluid flow in the reservoir.
Figure 20 Saturation of water before water break through
Figure 21 Saturation of water during the break through at first valve in the heel
Figure 22 Saturation of water during the break through at three valves in heel side
Pressureprofile
The pressureprofile in the well at the beginningof productionis shown in Figure 23. The pressurein the toe is 121.3 bars and it is observedthat the pressuregradually decreases towardsheel.This pressuredifferencebetweenheel and toe is due to friction loss along the well. Thusthedrawdownpressureat toeis lower thanthedraw downat heel.This is a reason for occurringearlybreakthroughat theheelsideof thewell bore.
Figure 23 Pressureprofile in well
The simulationfor eachAICV is performedwith 92 % choking of water.This meansthat 92
% of wateris chokedat waterbreakthroughlocally througheachAICV.
Accumulated water flow
Figure24 showstheaccumulatedwaterflow throughtheconventionalICD andtheAICV.
Figure 24 Accumulatedwater volumeflow with time
Accordingto the figure, the waterproductionthroughICD increasescontinuouslyafter water breakthroughwhile the water production is controlled by using AICV. This is the main characteristicsof AICV. This meansthattheAICV actionis simulatedsuccessfully.
In the casewith ICD, there is no water productionrestriction in the local zone. Thus the water-cut increasescontinuouslyasshownin Figure 24.
Choke position
The chokepositionfor ICD andAICV with time is shownin the Figure25 for this particular case.The figure showsthat theinitial productionis the samefor both ICD andAI CV cases.It alsoshowsthat both caseshavefully openchokeat the beginningof production.This means that the choke position is 100%. After 4 days, the water breakthroughoccurs and the productionof water startedalong with oil. This meansthat the water-cut increases.When water-cut reachesa value of 40% in the entire well, the controller startsto operateand the choke position beginsto reducegradually as shown in Figure 25 for both ICD and AICV cases.
Figure 25 Chokeposition variations with time
The first waterbreakthroughoccursin the heelsideof the reservoir dueto draw-down effect.
The first AICV in the heel chokesthe water production locally while other AICVs are producingoil. After sometime, breakthroughoccurs in the secondAICV andthat particular AICV also chokeslocally. In the similar manner,other AICVs will closelocally after water breakthroughin eachvalve.Thusthe water-cut will be controlledandremainlow. So that the
chokeposition of entire well is openas 100% and remainsopenuntil the water-cut reaches thesetpoint value.
But in the samereservoirsectionwith ICD, thereis no any watercontrolling mechanismthat restrictstheflow of waterlocally. The waterbreakthroughstartsto occurfrom theheelsideof the reservoir.The water-cut increasesand reachesthe set point value earlier than in AICV case.Thus,thecontrolleron theplatformstartsto choketheproduction.
As shownin Figure 25, the productionwell beginsto chokeearlier in ICD casethan in the AICV case.This early chokingin ICD caseleadsto thereductionof oil production.
Accumulated oil production
Figure26 showstheaccumulatedoil productionversustime for both ICD andAICV cases.It is observedthattheinitial oil productionis samefor both cases. After waterbreakthrough,the cumulativeoil productionin theICD casedecreasesearlierthanin AICV case.The reasonfor this is becauseof earlierchokingof well in ICD casethanin AICV case.The chokingof well with ICD is performedearlier since set point value for water-cut is reachedearlier. This chokingleadsto thereductionof oil productionfrom thereservoir.
The AICVs are autonomousand doesnot requireany externalforce to control.[13] Another importantcharacteristicof AICV is that it canoperatereversiblyalso.[18] This meansthat if the AICV encountersoil again,it autonomouslyopensandoil productioncontinuesin order to increasethe recovery.The same action was observedafter 10 days of productionin the AICV case. Thus the accumulatedoil productionis further increasedafter 10 daysasshown in Figure27.
Figure 27 Variation of accumulatedoil productionwith timefor AICV case
Water movementtowardsthe producingvalve is shownin phasediagramfor comparisonin Figure28 andFigure 29. Thesefigures show the oil saturationduring re-opening of AICV.
Red colour is pure oil and saturationof oil is decreasingbelow the basepipe. Thesephase diagramsare takenat different daysof oil production,Figure 28 at 9 days,while Figure 29 was at 11 daysof production.Before day 10, oil is producedfrom the reservoiraroundthe basepipe which lies 6m below the top surface.After 10 days,the productionwell encounters higheroil concentrationfrom the upperpartof the reservoirwhich containsonly heavyoil, so
that water-cut decreases below the set point and AICV opens autonomously and starts to produce oil.
Figure 28 Phase diagram at 9 days for AICV case
Figure30 showsthe initial oil production ratefrom the well. For both ICD andAICV cases, the initial oil production rate is approximately250m3/day from 99.2m section and 2430 m3/dayfrom thewholereservoirsectionwith tenvalves.
Figure 30 Initial oil productionratesfor both ICD andAICV cases
In AICV case,the initial oil production is same as in ICD case. The accumulatedoil productionis increasedby usingAICV which is shownin Figure26.
This simulation shows that the recovery with AICV is increasedby approximately21%
comparedto conventionalpassiveICD.
Accordingto Figure31, the water breakthroughoccursafter 3.9 daysthroughinflow control deviceon the heelsideandafter 4.2 dayson the toe sideof the reservoir.It canbe observed that the water-cut is increasingafter water breakthroughin ICD case. The reasonfor this is that the local devices in this zone have not any water production restriction. At water breakthrough, theaccumulatedoil productionis approximately9500m3for ICD case.
Figure 31 Water-cut throughlocal devicein thecasewith ICD
5 Conclusion
The aim of this thesis is to perform a near well simulation of heavy oil reservoir section using different types of inflow control devices and water drive. OLGA-Rocx was used as a software tool in order to simulate oil production, including the AICV behavior.
AICV is self-regulated and does not require any external force to control. When water breakthrough occurs, the AICV chokes the water production autonomously. This valve is also reversible. This means that if the AICV encounters oil again, it autonomously opens and oil production continues in order to increase the recovery. The reverse action of AICV was simulated successfully.
Two simulation cases for a thin horizontal reservoir section of 992m with water drive were considered. One case is with the conventional ICD and another is with InflowControl’s new technology AICV. The simulation cases were controlled with respect to the water-cut in the entire well. When the water-cut reaches a value of 40% in the entire well, the controller starts to operate and the choke position begins to reduce gradually.
The initial total oil production for both cases was 2500m3/day. The water-cut in the entire well increases more rapidly in the case with ICD than with AICV. The ICD case reaches the 40% water-cut value earlier than AICV case. Thus the well with ICD begins to choke the production earlier than the AICV case. This choking reduces the final accumulated oil production in the well in ICD case. The simulation shows that the recovery of heavy oil production with AICVs is increased by approximately 21% compared to conventional ICDs.
References
1. Ahmed, T., Reservoir engineering handbook. 2006, Amsterdam: Elsevier. XV, 1360 s.
: ill.
2. Pirson, S.J., Oil reservoir engineering. 1958, New York: Mcgraw-Hill. x,735 s. : ill.
3. Bellarby, J., Well Completion Design, ed. I. Edition. Vol. 56. 2009. 726.
4. Crowe, C.T., D.F. Elger, and J.A. Roberson, Engineering fluid mechanics. 2001, New York: Wiley. XI, 714, [36] s. : ill.
5. Streeter, V.L., Fluid mechanics. 1983, London: McGraw-Hill. 562 s.
6. Group, S., User Manual, version 7.1.4. SPT Group.
7. Economides, M.J., A.D. Hill, and C. Ehlig-Economides, Petroleum production systems. 1994, Englewood Cliffs, N.J.: PTR Prentice Hall. X, 611 s. : ill.
8. Guo, B., W.C. Lyons, and A. Ghalambor, Petroleum production engineering: a computer-assisted approach. 2007, Amsterdam: Elsevier. XIX, 288 s. : ill.
9. Sigurd M. Erlandsen and Svein Omdal, S.A., Trend Breaking Completions. 2008 10. F.T. Al-Khelaiwi and V.M. Birchenko, H.W.U., SPE; M.R. Konopczynski, Well
Dynamics-Halliburton, SPE; and D.R. Davies, Heriot Watt University, SPE, Advanced Wells: A Comprehensive Approach to the Selection Between Passive and Active
Inflow-Control Completions. SPE Production & Operations, 2010. Volume 25, Number 3: p. pp. 305-326.
11. Vidar Mathiesen, H.A., Bjørnar Werswick, Geir Elseth, Statoil ASA, Autonomous Valve, A Game Changer Of Inflow Control In Horizontal Wells., in Offshore Europe, 6-8 September 2011, Aberdeen, UK2011, Society of Petroleum Engineers: Aberdeen, UK. p. 10.
12. V.M. Birchenko, K.M.M., D.R. Davies, Reduction of the horizontal well's heel–toe effect with inflow control devices. Journal of Petroleum Science and Engineering,
14. Aadnoy, B.S. Autonomous Flow Control Valve or “intelligent” ICD. [cited 2013 18.03.2013]; Available from:
http://www.hansenenergy.biz/HANSEN_Energy_Solutions/InflowControl2008B.pdf.
15. Martin Halvorsen; Geir Elseth, S.O.M.N., Statoil ASA, Increased oil production at Troll by autonomous inflow control with RCP valves, in SPE Annual Technical
Conference and Exhibition2012, Society of Petroleum Engineers: San Antonio, Texas, USA.
16. Halliburton. HS Series Interval Control Valves. Available from:
http://www.halliburton.com/public/wd/contents/Data_Sheets/web/H06970_HS_Series _ICV.pdf.
17. Maduranga Amaratunga, K.P., Anita Bjerke Elverhøy, Truls Erik Haugen, Raju Aryal and Farzan Sahari Moghaddam, CFD MODelling of heavy oil production with inflow control device 2012.
18. 25/05/2013]; Available from: http://www.inflowcontrol.no/.
Appendices
Appendix 1: Master’s Thesis task description
Appendix 2: Rocx setting
# Version: 1.0.0.0
# Input file created by Input File Editor.
# 4/27/2013 12:29:29 PM
# ModelDescription:Case I: Reservoir section 992X80X20 with pipeline at 6 mtr from top of reservoir section.
# Oil Viscosity: 100 cP
# Reservoir permeability: 5 Darcy
# Pressure in reservoir: 130 bar
*GEOMETRY RECTANGULAR
# Number of grid blocks in horizontal and vertical direction
# ---
# Direction vector for gravity
# ---
visctemp 100
gascomponent BO_Gas_0 gor 0
watercomponent BO_Water_0 watercut 0
*RESERVOIR_PARAMETERS
# Permeability (mDarcy) in principal directions
# ---
kro
Pcgo
# Pressures
Appendix 3: OLGA settings for ICD case
Overall setting Flow model OLGA Mass eq scheme 1STORDER
Integration Simulation starttime 0 Simulation stoptime 100 d
Branches No. of Pipes No. of Sections Min. Section
Length At Max. Section
Length At
PIPELINE 1 20 49.6 M PIPE-1 49.6 M PIPE-1
FLOWPATH_1 1 20 49.6 M PIPE-1 49.6 M PIPE-1
Pipe no. Branch Label Diameter Roughness XEnd YEND Wall 1 - 1 PIPELINE PIPE-1 0.2 M 2.8E-05 M 992 M 0 M WALL-1 2 - 1 FLOWPATH_1 PIPE-1 0.2 M 2.8E-05 M 992 M 0 M WALL-1
5. Insulation and Walls
5. 1 Material
Label Density Conductivity Heat Capacity E-modulus MATER-1 7850 50 500
MATER-2 2500 1 880
5. 2 Walls
Label Material Wall thickness Elastic WALL-1 MATER-1 0.009 OFF
Label Type Pressure Temperature GMF
INLET CLOSED -1
OUTLET CLOSED 50 bara 22 -1
NODE_1 CLOSED -1
NODE_2 PRESSURE 120 bara 100 -1
6. 2 Heattransfer
Branch Pipe Interpolation Houteroption. Hambient Tambient PIPELINE PIPE-1 SECTIONWISE HGIVEN 1E-06 W/M2-C 100 FLOWPATH_1 PIPE-1 SECTIONWISE AIR 1E-06 100
6. 3 Initial Conditions
Branch Pipe Mass Flow VoidFractio n PIPELINE PIPE-1 0 0 FLOWPATH_1 PIPE-1 0 0
7. Equipment
7. 1 Valves
POS-18 FLOWPATH_1 PIPE-1 18 POS-19 FLOWPATH_1 PIPE-1 19 POS-20 FLOWPATH_1 PIPE-1 20
Appendix 4: OLGA settings for AICV case
Overall setting Flow model OLGA Mass eq scheme 1STORDER
Integration Simulation starttime 0 Simulation stoptime 100 d
Branches No. of Pipes No. of Sections Min. Section
Length At Max. Section
Length At
PIPELINE 1 20 49.6 M PIPE-1 49.6 M PIPE-1
Pipe no. Branch Label Diameter Roughness XEnd YEND Wall 1 - 1 PIPELINE PIPE-1 0.2 M 2.8E-05 M 992 M 0 M WALL-1 2 - 1 FLOWPATH_1 PIPE-1 0.2 M 2.8E-05 M 992 M 0 M WALL-1
5. Insulation and Walls
5. 1 Material
Label Density Conductivity Heat Capacity E-modulus MATER-1 7850 50 500
MATER-2 2500 1 880
5. 2 Walls
Label Material Wall thickness Elastic WALL-1 MATER-1 0.009 OFF
Label Type Pressure Temperature GMF
INLET CLOSED -1
OUTLET CLOSED 50 bara 22 -1
NODE_1 CLOSED -1
NODE_2 PRESSURE 120 bara 100 -1
6. 2 Heattransfer
Branch Pipe Interpolation Houteroption. Hambient Tambient PIPELINE PIPE-1 SECTIONWISE HGIVEN 1E-06 W/M2-C 100 FLOWPATH_1 PIPE-1 SECTIONWISE AIR 1E-06 100
6. 3 Initial Conditions
Branch Pipe Mass Flow VoidFractio n PIPELINE PIPE-1 0 0 FLOWPATH_1 PIPE-1 0 0
7. Equipment
7. 1 Valves
POS-18 FLOWPATH_1 PIPE-1 18 POS-19 FLOWPATH_1 PIPE-1 19 POS-20 FLOWPATH_1 PIPE-1 20