Reservoir Characterization & Geological Modeling (QCB4043)

RESERVOIR CHARACTERIZATION & GEOLOGICAL MODELING (QCB4043)

  • Lecture Topic: Reservoir Mapping (Lecture 6)

WELL LOG CORRELATION

  • Definition: Well logs provide detailed, location-specific information at the borehole.

  • Correlating Wells:

    • When multiple wells are available in an area, the stratigraphic units can be correlated.

    • Correlation is analogous to a fingerprint (based on characteristic), utilizing the characteristics of well logs.

  • Philosophies of Well Log Correlation:

    • Lithostratigraphy: Correlation based on lithologic units.

    • Chronostratigraphy: Correlation based on interpreted time-equivalent stratal packages (e.g., parasequences).

IMPORTANCE OF CORRELATION

  • Implications:

    • The methodology selected can impact estimates of reserves, development plans, and enhanced recovery strategies.

    • AAPG © 1990 cited.

SUBSURFACE MAPPING

  • Representation:

    • Techniques for mapping a 3D surface and converting data into a usable map format.

RESERVOIR MODELING – KEY STEPS

  • Components of Reservoir Modeling:

    • Seismic Data: Includes PSDM and inversion methods.

    • Detailed Horizons: Set for accurate geological interpretations.

    • Core Data: Vital for volume interpretation and accuracy.

    • Depth Conversion: Convert time to depth using a Porosity/Velocity Transform for 18 time/depth horizon pairs.

    • Tying to Wells: Establishing connections to well data for robustness in models.

    • Dynamic and Static Models: The development of models that are both static in nature and representative of dynamic subsurface behaviors.

MAPPING SUBSURFACE

  • Data Utilization:

    • Mapping utilizes both indirect data (well logs, seismic data, gravity & magnetics) and direct data (cuttings, core samples, sidewell core, and conventional core).

BASEMAPS FOR SUBSURFACE MAPPING

  • Requirements for Basemaps:

    • Should remain uncluttered, containing minimal geographical and cultural data.

    • Essential elements include well locations and seismic line shot points.

SUBSURFACE MAPS AND DATUM

  • Reference Points:

    • Mean Sea Level (MSL), Below Derrick Floor (BDF), Rotary Kelly Bushing (RKB).

  • Common Datum:

    • Set as 0 at Mean Sea Level; subsequential depths below sea level indicated in negative (e.g., -1000 m or -1000 m SS).

CONTOUR MAPS

  • Definition and Process:

    • A contour line delineates points of equal value.

    • Contouring steps include spacing lines appropriately and honoring all available data.

METHODS OF INTERPOLATION

  • Types of Interpolation Techniques:

    • Least squares, tangential, spline, weighted average, minimum curvature, polynomial, hyperbolic, kriging, and trend surface.

ADVANTAGES OF CONTOURING

  • Hand Contouring:

    • Allows incorporation of geological interpretation into maps.

  • Computer Contouring:

    • Offers objectivity, ease of updating, readiness for further processing, suitable for extensive datasets.

DEPTH STRUCTURE MAPS

  • Key Features:

    • Visualization of depth stratigraphy showcasing different structure features.

STRUCTURE CONTOUR MAPS

  • Construction of Structure Contour Maps:

    • Combining contour maps of various layers and visualizing relationships with technological tools.

FAULTED STRUCTURE MAPPING

  • Technique Overview:

    • Contour the surface without faults, contour the fault plane, establish intersection points, correct contours for vertical separation, and subsequently refine the maps.

PARAMETERS MAPPED IN GEOLOGY

  • Other Valuable Mapped Parameters:

    • Extensive surfaces include tops and bottoms of formations, isopachs, fault surfaces, and fluid contacts (e.g., Gas-Oil, Water-Oil).

PETROLEUM GEOLOGY MAPS

  • Isopach Map Definition:

    • A visual representation of equal thickness strata between two planes requiring both top and base information for accuracy.

ISOCHORE MAPS

  • Designed to indicate the thickness of the deposits. (true vertical thickness)

PROPERTIES OF CONTOUR LINES

  • Key Characteristics:

    • Cannot intersect or merge with themselves; must traverse between differing values and display continuity within mapped areas.

CONSTRUCTING MAPS OF FAULTED STRUCTURE

  • Step-by-step Methodology:

    • Include contouring fault surfaces and ensuring accurate representation of the geological characteristics across faults.

OTHER MAPS

  • Facies Map: Represents three-dimensional rock bodies from temporal deposits, highlighting lithologic characteristics, fossil assemblages, and thickness variances.

  • Internal Property Maps: Represent properties over time, including isoporosity, isovolume, isoconcentration, and water encroachment maps.

PALEOGEOGRAPHIC MAPS

  • Used to depict past geological landscapes and evolutionary changes across different epochs.