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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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.
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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 โblind,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 โrubbleโ 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 โImageโ Data Processing Stream Field Record (marine) http://www.ig.utexas.edu/people/staff/ mrinal/Results/carlos_nn1_files/ image006.jpg Offset Time