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Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 1 Integrated Understanding of Enhanced Reservoir Properties through Fracturing and Dissolution.

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Presentation on theme: "Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 1 Integrated Understanding of Enhanced Reservoir Properties through Fracturing and Dissolution."— Presentation transcript:

1 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 1 Integrated Understanding of Enhanced Reservoir Properties through Fracturing and Dissolution Fatima Al Darmaki 1, David A. Lawrence 1, Richard P. Singleton 1, Budideti A. Reddy 1, Georgeta Popa 1, Pascal Cortes 2 Case Study from the Late Jurassic Arab Formation in a Large Gas Field, Onshore UAE 1 Al Hosn Gas, Abu Dhabi 2 Badley Ashton & Associates, Abu Dhabi

2 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 2 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

3 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 3 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

4 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 4 Introduction & Field Overview SW of Abu Dhabi city Field discovered in 1966 Oil production from Upper Cretaceous Target: gas & condensate from Late Jurassic Arab Formation A total of 7 appraisal wells drilled into Arab Reservoir Development drilling started on NW flank Results from first development wells showed enhanced properties in the main reservoirs SW of Abu Dhabi city Field discovered in 1966 Oil production from Upper Cretaceous Target: gas & condensate from Late Jurassic Arab Formation A total of 7 appraisal wells drilled into Arab Reservoir Development drilling started on NW flank Results from first development wells showed enhanced properties in the main reservoirs

5 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 5 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

6 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 6 Arab Formation Depositional Model Chronostratigraphic setting of the Arab Formation Adapted from Azer and Peebles (1998) SW NE Carbonate Ramp Setting Arab D Arab C Arab AB Palaeo-environments of the Arab Formation Oolitic grainstone SOGAS Arab Depositional Model lime mudstones and anhydrites Dolomitic limestone Main Field area Reservoir Data Reservoir Ave Porosity Ave Perm U.Arab AB % 1.0 – 2.0md L. Arab C % 0.7 – 8.0 md L. Arab D 6-8% 0.05 – 1.0 md Main Field area Reservoir Data Reservoir Ave Porosity Ave Perm U.Arab AB % 1.0 – 2.0md L. Arab C % 0.7 – 8.0 md L. Arab D 6-8% 0.05 – 1.0 md Outer Ramp Mid Ramp Subtidal Intertidal Sabkha 0 2 km 2 ft Inner Ramp Marine lime-mudstone Minor Wackestone to Packstone

7 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 7 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

8 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 8 Well location Map and 2D Seismic Section A1-1V A2-1V D3-1&2H D2-1H D4-1H D1-1D Arab C Structural Map A1-1V A 6-1V A 3-2S A 4-1V A5-1D A2-1V A 7-1V BHI Log IL 7300 Vertical exaggeration: 2:1 Arab NW SE 0 10 km km

9 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 9 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

10 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 10 Fracture Analysis in Arab A/B Members Fracture Analysis from Resistivity Image Data Correlated with other Open Hole Logs 11.5 ft Discontinuous Resistive Fractures Gamma RayResistivity Neutron/ Density Whole Core Conti. Conductive Frac. Conti. Resistive Frac. DisCont. Cond. Fra. DisCont. Resistive. Fra. Mixed Fracture

11 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 11 Fracture Analysis in Arab C Member Discontinuous Resistive Fractures Continuous Resistive Fractures 5.5 ft Fracture Analysis from Resistivity Image Data Correlated with Core Image and Open Hole Logs Gamma RayResistivity Neutron/ Density Conti. Conductive Fracture Conti. Resistive Fracture DisCont. Cond. Fracture DisCont. Resistive. Fra. Mixed Fracture Whole Core

12 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 12 Fracture Analysis in Arab D Member Fracture Analysis from Resistivity Image Data Correlated with Core Image and Open Hole Logs Discontinuous Conductive Fractures Continuous Conductive Fractures 6 ft Whole Core Conti. Conductive Fracture Conti. Resistive Fracture DisCont. Cond. Fracture DisCont. Resistive. Fra. Mixed Fracture Gamma RayResistivity Neutron/ Density

13 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 13 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

14 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 14 Fracture Trends in Arab A/B Members A1-1V A 6-1V A 3-2S A 4-1V A5-1D A2-1V A 7-1V D4-1H D2-1H D1-1D D3-1&2H Few fractures are observed in Arab A/B including conductive, resistive and mixed features Varying strike orientations were interpreted, mainly NNW-SSE and WNW- ESE DisCont. Resistive Fracture Mixed Fracture Conti. Conductive Fracture Conti. Resistive Fracture DisCont. Conductive Fracture No fractures have been interpreted through Arab AB Members 0 10 km N= 22 N= 6

15 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 15 The majority of the interpreted fractures in Arab C were resistive Few conductive and mixed fractures were interpreted in the study wells Several strike orientations were interpreted in Arab C and show dominant strikes along NNW-SSE and WNW-ESE Subordinate trends in broadly NNE-SSW and ENE-WSW directions and parallel to the main fault trends Fracture Trends in Arab C Member A1-1V A 6-1V A 3-2S A 4-1V A5-1D A2-1V A 7-1V D4-1H D2-1H D1-1D D3-1&2H 0 10 km DisCont. Resistive Fracture Mixed Fracture Conti. Conductive Fracture Conti. Resistive Fracture DisCont. Conductive Fracture N= 50 N= 33 N= 6

16 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 16 Highest fracture intensity observed in Arab D and most were continuous and discontinuous conductive fractures Relatively few resistive fractures were also interpreted in this interval. Strike orientations of fractures in Arab D are dominantly NNW-SSE and WNW- ESE. Subordinate trends in broadly NNE- SSW and ENE-WSW direction and parallel to the main fault trends Fracture Trends in Arab D Members A1-1V A 6-1V A 3-2S A 4-1V A5-1D A2-1V A 7-1V D4-1H D2-1H D1-1D D3-1&2H DisCont. Resistive Fracture Mixed Fracture Conti. Conductive Fracture Conti. Resistive Fracture DisCont. Conductive Fracture 0 10 km N= 544 N= 75 N= 67

17 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 17 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

18 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 18 Fracture Density Variations in Arab Members A1-1V A 6-1V A 3-2S A 4-1V A5-1D A2-1V A 7-1V D1-1D D2-1H D3-1&2H D4-1H 0 10 km D1-1DD2-1HA7-1V TD in Arab D

19 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 19 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

20 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 20 Stylolitic bedding and Stylo-Fracture in Arab C Member Circumferential Core Photo Borehole Image NSN NNS Non- mineralized open fractures Partly cemented fractures Stylofrac and subparallel stylolitic bedding

21 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 21 Circumferential Core Photo Thin-section photomicrographs SN Borehole Image Stylolitic bedding and Stylo-Fracture in Arab D Member N N S Bedding Mudstone Bedding Stylofrac Partly cemented fractures associated with stylofrac Non-mineralized open fractures associated with stylofrac N

22 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 22 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

23 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 23 Porosity – Permeability Analysis in Arab C A6-1V A2-1V A4-1V A5-1D A7-1V D1-1D 2 Normal Trend Enhanced Trend Por:24.6% K: 41 mD Por :23% K: 2.4 mD 2

24 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 24 Porosity – Permeability Analysis in Arab D Mostly plugs with fractures &/or stylolites + some vugs Enhanced K A6-1V A2-1V A4-1V A5-1D A7-1V D1-1D Por :21% K: 2.4 mD 1 Por :10% K: 1.3 mD 3 Por :8.7% K: 0. 1 mD

25 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 25 Outline of Presentation Introduction & Field Overview – Arab Formation Depositional Model – Well Location Map and 2D Seismic Section Fracture Analysis in Arab Members – Fracture Orientation Trends Within Arab Members – Fracture Density Variations in Arab Members Impact of Diagenesis & Dissolution in Arab Main Reservoirs Porosity-Permeability Analysis in Arab Main Reservoirs Layering Control on Fracturing in Arab Formation Conclusions & Implications

26 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 26 Layering Control on Fracturing in Arab Formation Diffuse (layer-bound) fracturing faults / fractures Jubaila Arab D Arab C Arab AB Arab Formation SW NE

27 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 27 Layering Control on Fracturing in Arab Formation Diffuse (layer-bound) fracturing faults / fractures SW Jubaila Arab D Arab C Arab AB Arab Formation NE Cementation Halo Around Faults / Fractures Dissolution in more permeable layers & along diffuse fractures/ stylolites

28 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 28 Conclusions & Implications The first development wells encountered significantly enhanced reservoir properties in both Arab C and D reservoirs. Highest fracture intensity in Arab D followed by Arab C and A/B members. Conductive fractures are observed mainly in Arab D, while the resistive fractures are interpreted in Arab C member. Conductive fractures show two predominant strikes WNW- ESE & NNW-SSE whilst resistive fractures show various orientations. Most fractures are layer-bound concentrating at mechanical contrasts, often associated with stylolites. Enhancement of reservoir properties is related to both dissolution along deep-rooted faults/fracture corridors and bedding-parallel where the stylolites occurred. Reservoir connectivity, well productivity and drainage area especially in the Arab D still carry high uncertainties which are being reduced by focused continued data acquisition, integration and modeling efforts.

29 Abu Dhabi Gas Development Company Ltd. CONFIDENTIAL Page 29 ACKNOWLEDGEMENTS Al Hosn Gas, ADNOC & Oxy Management for permission to present Badley Ashton & Associates support and Baker Hughes for Borehole Image interpretation and support


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