Geologic Model for a Single Well

Jul 23, 2024

Geologic Model for a Single Well

Introduction

  • Presenter: Doug Weibulls
  • Focus: Basic workflow in creating a good geologic model for a single well
  • Objective: Show the thought process in building models and using the best data and assumptions
  • Case Study: Munster Line 1 (M1) Well in the Munster Ron Basin, NW Europe

Initial Model

  • Based on assumptions about tectonic, depositional, and thermal history
  • Complex area, experienced at least one major erosional unconformity
  • Acknowledge gaps and uncertainties
  • Plans to propose modifications to initial assumptions

Munster Line 1 Well

  • Drilled in 1961, depth ~6000m
  • Studied by German scientists
  • Location: Red dot in Munster Ron Basin, NW Europe (close to Dutch-German border)
  • Geological Context: Result of thrust slices during the Variscan orogeny in the late Carboniferous

Historical Significance

  • First burial history curve published by Nikolai Lapatin in 1971
  • The concept: TTI method, precursor to modern basin modeling

Geo History Plot Analysis

  1. 335 MA to 300 MA: Rapid sediment accumulation (Carboniferous rocks)
  2. Hypothesis: Rapid deposition corresponds to foreland basin development
  3. Annotation: Unconformity and transition from subsidence to uplift around 300 MA
  4. Interpretation: Variscan orogeny and related uplift/erosion events
  5. Elevation Interpretation: Magnitude and timing of uplift and erosion (syn orogenic and post orogenic)

Paleo-Elevation and Subsidence

  • Late Carboniferous Period: Rapid accumulation (foreland basin hypothesis)
  • Elevation History: Interpretation of Veriscan mountain height over time
  • Erosion & Subsidence: Impact on model accuracy

Tectonic Events and Geo History

  1. Foreland Basin Development: Related to Variscan orogeny
  2. Uplift and Erosion: Documented major unconformity
  3. Sediment Removal: Reconstructing periods from Late Permian through Middle Jurassic
  4. Model Adjustments: Reduce tectonic subsidence, Paleo elevation adjustments
  5. Key Issues: Erosional gap, sediment thickness, and sedimentation rates

Factors to Consider

  • Differences between neighboring basins
  • Complex Mechanics: Juxtaposition with thrusting, mechanism of rapid subsidence
  • Alternative Proposals: Continuing erosion versus rapid subsidence mechanisms
  • Critical Examination: Data trustworthiness and its implications

Role of Uncertainty

  • Model Building: Mixture of facts and interpretations
  • Data Gaps: Unconformities, paleo-heat flow uncertainties
  • Model Refinements: Iterate based on new data or insights
  • Fresh Eyes Concept: Crucial for successful modeling and analysis

Important Data Types

  1. Down Hole Temperatures: Wireline logging runs and temperature profiles
  2. Thermal Indicator Data: Reflectance values of Carboniferous coal samples
  3. Plate Tectonic History: Contextual understanding of model location
  4. Structural Data: Tectonic plates positioning and historical evolution

Comparison to Analog Collisions

  • India-Eurasia Collision: Example but different due to direct collision
  • Allegheny Orgeny: Less direct, more comparable to M1 well
  • Subduction & Compression: Analysis for proper tectonic modeling

Paleo Heat Flow Analysis

  • Importance of paleo heat flow for proper temperature gradient modeling
  • Historical Context: Associated volcanism, hydrothermal effects, and pluton emplacement
  • Challenges: Identifying heat flow patterns back in time
  • Standards: Modern methods and empirical models for correction

Final Model & Implications

  • Revision of initial assumptions and geological history
  • Incorporation of new insights from thermal and tectonic data
  • Significant change from initial to final model: reduced elevation and tectonic subsidence

Final Thoughts

  • Importance of critical analysis and flexibility in model building
  • Learning to distinguish facts from interpretations
  • Future work: Include aspects not covered in current video like source rocks, generation, etc.

Conclusion

  • Emphasis on the importance of a thorough and iterative approach to geological modeling
  • Encouragement for fresh data scrutiny and continuous model refinement

Thanks for watching.