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Lecture 3 Types of Data, Lecture notes of Geophysics

Seismic reflection is a method of exploration geophysics that provides information about the sub-surface structure of the seafloor. The general principle involves sending artificially generated acoustic waves down the water column and into the seafloor, where the different structures and objects within the Earth's crust reflect this energy back according to their acoustic impedance.

Typology: Lecture notes

2020/2021

Uploaded on 04/15/2021

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F W Schroeder โ€˜
04 L 3 - Types of DataCourtesy of ExxonMobil
Lecture 3
Lecture 3
Mega-Regional
Present Circulation Plate Reconstructions Maps showing Features
Local
Cores Logs
Outcrops Well-Seismic Ties
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Download Lecture 3 Types of Data and more Lecture notes Geophysics in PDF only on Docsity!

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Lecture 3 Lecture 3

Mega-Regional

Present Circulation Plate Reconstructions Maps showing Features

Local

Outcrops Cores Logs Well-Seismic Ties

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Data Types Vary with Scale

From a basin-scale analysis to a field-depletion

study, we want to integrate information from all

available sources

Regional Analysis Basin Analysis Block Analysis Prospect Analysis Field Analysis Compartment Analysis

Mega-Regional

Fine-Scale

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Mega-Regional Analysis

Usually mega-regional analysis is performed to :

  • (^) Decide which basins hold sufficient potential
  • (^) Determine how much to bid for blocks
  • (^) Provide regional settings to help understand the characteristics of a field
  • (^) To guide step-out wells, i.e., those that extend beyond a known field in search of a similar HC accumulation

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Local Data - Surface

Measured
Sections
20 ft
  • (^) Surface Measurements/Observations
    • (^) Topographic/Bathymetric maps
    • (^) Surface geology (structure & stratigraphy)
    • (^) Nearby outcrops (or analogs)
    • (^) Heat flow measurements
    • (^) HC seeps
    • (^) Etc.
Outcrop Studies (age-equivalent or analogs)

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Data from Wells

  • (^) Samples
    • (^) Conventional Cores
    • (^) Sidewall Cores
    • (^) Cuttings
  • (^) Measurements
    • (^) Wire-line Logs
    • (^) Pressure
    • (^) Temperature
    • (^) Fluid samples
    • (^) Flow Properties
    • (^) Vertical Seismic Profiles (VSP)

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Well Samples: Conventional Cores

  • (^) Coring apparatus positioned at

the bottom of the drill stem

  • (^) Often gets intact samples of 1

meter or more

  • (^) Good for analyzing lithology,

sedimentary features, porosity,

permeability, paleontology (ages,

environments)

  • (^) Interval is cored โ€˜blind,โ€™ i.e.,

before the interval is logged

  • (^) Expensive (2 round trips for the

drill stem = lots of rig time)

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Well Samples: Cuttings

  • (^) The โ€˜rubbleโ€™ that comes up the sides of the well bore with the circulating fluid
  • (^) Can provide samples for certain kinds of analysis โ€“ e.g., lithology, paleo
  • (^) Not suitable for porosity, permeability, sedimentary structures (pulverized)
  • (^) Very inexpensive โ€“ no lost rig time
  • (^) PROBLEM โ€“ no control on the depth from which the samples came from โ€“ any zone not cased

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Well Measurements: Wire-line Logs

  • (^) A well log is a record ofA well log is a record of one or more physical one or more physical measurements as a measurements as a function of depth in a function of depth in a borehole borehole Gamma Ray Resistivity Density Depth

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

What Logs Measure

  • (^) Lithology/Mineralogy
  • (^) Porosity
  • (^) Fluid Type
  • (^) Fluid Saturation
  • (^) Permeability Property Property
  • (^) Stratigraphy
  • (^) Downhole Pressure
  • (^) Density
  • (^) Acoustic Velocity

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Geophysical Data

Objective:

Take measurements at the surface that

give us an image of the subsurface

Analogy:

A sonogram

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

Raw Seismic Data

Device

Device

For the explosion we just considered .. Listening device #1 records a reflection starting at 0.4 seconds Listening device #2 records a reflection starting at 0.8 seconds

To Image the Subsurface, We Use Many Shots (explosions)

and Many Receivers (listening devices)

Arranged in Lines either on Land or Offshore

Time

F W Schroeder โ€˜ Courtesy of ExxonMobil L 3 - Types of Data

From Raw Data to an Image

Subsurface โ€˜Imageโ€™ Data Processing Stream Field Record (marine) http://www.ig.utexas.edu/people/staff/ mrinal/Results/carlos_nn1_files/ image006.jpg Offset Time