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1 Mar 2012

Image Log Interpretation

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by Prof. Peter Lloyd.

Faculty of Mining and Petroleum Engineering ITB, 25 – 27 January 2012, organized a Short Course: “Image Log Interpretation” by Hon. Prof. Peter Lloyd from Herriot Watt University, Pet. Eng. Dept. France. The event attended by 30 participants consisting of students and lecturers from the Faculty of Mining and Petroleum Engineering ITB, UNPAD, UI and Trisakti.

The course has been designed for geoscientists, engineers and other technical staff  who want to analyze and integrate image log and dip data to enhance their  understanding of exploration plays and field development. It leans heavily on worked class examples and case studies. Instead of interpreting image and dip data in isolation, the course shows how they can be used in conjunction with cores, other logs, modern depositional analogues, outcrop studies and hi-resolution seismic data to refine reservoir models.

Day 1: Acquisition/Processing. Struct. & Frac. Analysis

• Image & Dip Acquisition & Processing (incl. LQC)
– Measurement principles and wellsite acquisition & LQC – Value of high resolution image data
– Image processing & display
– Dip computation and trouble shooting Exercise: LQC acquisition data

• Exercise with some real data
– Image & dip processing and LQC
– Image description & interpretation steps
– Comparison with core photos and description

• Structural analysis using image & dip data
– Structural dip trends and structural dip removal – Unconformities
– Normal and growth faults
– Reverse and thrust faults
– Are faults sealing?
Exercise: Structural dip patterns
Exercise: Effect of dip removal
Exercise: Unconformities
Exercise: Fault models (drag effects)
Exercise: Image & dip examples across fault planes

• Fracture systems
– Fracture types; open, healed, vuggy, syneresis
– Natural or induced; borehole breakout & tensile fractures Fracture orientation
– Case study: Identifying & evaluating producing horizons in fractured basement offshore Vietnam
Exercise: Fracture identification – 1
Exercise: Fracture identification – 2
Exercise: Fracture identification – 3

Day 2: Stratigraphic Principles & Continental Settings

• Stratigraphic analysis using image & dip data
– Depositional environments & facies analysis – Lithofacies from log & image data
– Lithology, grain size variation, need to integrate – Geometry
– Sedimentary structures
– Paleocurrent directions
– Integration & modelling at the field level
Exercise: Grainsize motifs (and advantages of integration) Exercise: Sedimentary features
Exercise: More sedimentary features

• Eolian (wind-blown) sediments
– Sedimentary structures & dune forms
– Complexities in deposition setting & stratigraphic section Exercise: Idealized dips through transverse dunes

• Fluvial (river) sediments
– Fluvial settings (various models)
– Braided system lithotypes & sedimentary features
– Meandering system lithotypes & sedimentary features – Point bar development (predictions)
– Case study from Kalimantan; integrating high resolution seismic attributes with petrophysical data to fine tune a depositional model and site new wells; radically increasing oil recovery in the field.
Exercise: Current bedding & channel flow direction

Day 3: Coastal, Shelf and Deepwater Settings

• Deltaic sediments
– Delta classifications and models
– Associated sand geometries
– Image & dip character in distributary fronts & channels
– Case study from South Sumatra basin; developing a play concept to identify most prospective area within structural closure
Exercise: Palaeogeographic concept map from image/dip data

• Coastal & Shelf silici-clastic sediments
– Interrelation of coastal & shelf depositional settings
– Facies variation in prograding coastal sequences
– Idealized dip and grain motifs in bar/barrier sands
– Image & dip examples in shelf bar and barrier island sands
– Case study: distinguishing channel from bar sands in tidal settings, and its importance on reservoir characteristics
– Using high resolution images to interpret thinly bedded reservoirs Exercise: Barrier bar orientation
Exercise: Understanding why sands with similar lithofacies have radically different production characteristics

• Carbonate shelf sediments
– Carbonate models and facies in coastal and shelf settings
– Carbonate reefs, and orienting reefal trends
– Porosity enhancement and reduction
– Poro-perm trends and characteristics
Exercise: Features within a carbonate section
Exercise: Features within a carbonate reservoir

• Deepwater sediments
– Deepwater sediment depositional models
– Image & dip character in proximal & distal settings
– Improving log interpretation by modelling thin bed effects
– Orienting channel sands using image & dip data
– Integrating to the seismic scale
Exercise: Deepwater lithofacies
Exercise: Sedimentary structures
Exercise: Channel orientation
Exercise: Sand body recognition & orientation

References & recommended reading:

• Ancient Sedimentary Environments, Richard Selley.
• Atlas of Borehole Imagery, AAPG Datapages, edited by Laird Thompson.
• Sedimentary Environments and Facies, edited by Howard Reading
• AAPG Memoir 31: Sandstone Depositional Environments, edited by Peter Scholle & Darwin Spearing.
• AAPG Memoir 33, Carbonate Depositional Environments, edited by Peter Scholle, Don Debout and Clyde Moore.
• AAPG Memoir 80: Integration of Outcrop and Modern Analogs in Reservoir Modelling, edited by Michael Gramer and Mitch Harris.

Special acknowledgements to the PE Department of Heriot Watt University for helping with some of the outcrop photos and geological models, as well as Al Gilreath and Mike Grace who have shared with me some of their examples and teaching material. I’d also like to recognize my co-authors of the several case studies presented during the class.