Exploration

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ExplorationProduction 101
IPAMS 2004
Susan M. Landon
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How do we pick the spot for that wildcat well?!?
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OBJECTIVES OFPETROLEUM GEOLOGY

• Find and Effectively Produce Oil and Natural Gas
• Improve Predictability
• Reduce Risk

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GEOLOGICAL REQUIREMENTS FORHYDROCARBON
ACCUMULATIONS

• Source Rock
• Migration Path
• Reservoir Rock
• Trap
• ? Timing

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What is Petroleum?

• Petroleum a natural yellow-to-black flammable
  liquid hydrocarbon found beneath the earths
  surface
• Hydrocarbonan organic compound made up of
  carbon and hydrogen atoms

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What are Hydrocarbons?
Mixtures of hydrogen and carbon atoms with
various impurities like sulfur, oxygen, etc.
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Hydrocarbon Composition

• Carbon Hydrogen Hydrocarbon
• Atoms Atoms Molecules
• H
• C H H C H
• H

Methane gas CH4simplest hydrocarbon molecule
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Gas Composition
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The Alphabet Game

• LNG Liquefied Natural Gas
• LPG Liquefied Petroleum Gas
• NGL Natural Gas Liquids

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Origin of Hydrocarbons

• Generated from organic matter preserved in the
  sediments
• As sediments are subjected to higher temperatures
  with increasing burial, the organic matter is
  simplified to molecules of carbon and hydrogen
  with some impurities

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Quality of Source Rock

• Quality of a source rock (how much hydrocarbon
  can the organic matter generate) is measured by
  the amount of organic carbon present in the rock
  Total Organic Carbon
• 1 or more TOC is considered poor
• 3 to 5 or greater is considered a good source
  rock

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Type of Organic Matter
Plant material tends to generate gas Algal and
animal material (amorphous organic matter) tends
to generate oil Oil can be cracked to gas (just
like in a refinery) when it is subjected to high
enough temperatures
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RESERVOIR ROCK Porosity percent by volume of
pore space in the rock how much fluid or gas
will fit between the grains () Permeability
measure of the degree of difficulty the fluid or
gas has in moving through the rock (darcies or
millidarcies)
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Types of Porosity
Intergranular
Dissolution
Fracture
Clays deposited on grains creating microporosity
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Oil-stained Thin SectionWhite Pine Mine -
Wisconsin
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Migration of Oil and Gas
Caprock or Seal
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Types of Hydrocarbon Traps

• Structural
• Stratigraphic
• Combination
• Unconventional (basin-centered, coalbed methane,
  shale gas)

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Structural Traps
Oil Seeps
Oil field
Oil field
Anticlinal Trap
Source Rock
Fault Trap
Monroe and Wicander, 1992
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Stratigraphic Traps
Unconformity Trap
Source Rock
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Combination Trap
/Seal
/Seal
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TIMING..
Traps must be in place before oil and gas begin
to migrate.
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Basin-Centered (Continuous)Trap
An unconventional trap - regional - diffuse
boundaries - low permeability reservoir -
frequently abnormally pressured - closely
associated with source rocks
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Types of Data

• LIBRARY!
• What has been done before?
• Field work
• Information from Drilling ?

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Field Geology
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Drilling
Most of the data used to find and
efficiently produce hydrocarbons comes from
wells that have been drilled. What data do we
need and how do we integrate and interpret the
data to determine where to drill?
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Data Collected From Wells

• Drilling time record of how fast the bit is
  cutting downward
• Mud Log - measured gas released by drilling
• Cuttings chips of rock cut by the bit and
  described by the well site geologist
• Core special bit cuts a cylinder of rock
• Drill Stem Tests samples fluid and measures
  pressure
• Wireline Logs

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Wireline Logging
RIG
Logs measure physical characteristics of
the rocks drilled. A tool is lowered down the
well bore and, as it is pulled back to the
surface, it measures a property like natural
radioactivity.
Computer
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Typesof Logs
1 2 Rock/fluid 3 4
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• Gamma Ray
• Caliper (dashed)
• (diameter of hole)
• 3. Spontaneous Potential
• 4. Electrical Resistivity
• 5. Density
• 6. Sonic

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Log Response to Rock
Beach Sand
Channel sand
Neutron Porosity ()
GR (API)
Bulk Density (gm/cc)
Density decreases Porosity increases
From Hancock, 1992
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Formation Image Log
Bedding
Fracture
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Formation Image Log
Bedding Planes
Horizontal Well Bore
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Types of Maps

• Topographic maps - variation in elevation
• Geologic maps - distribution of geologic features
• Structure maps - variation in the shape of a
  subsurface layer
• Isopach maps - equal thickness
• Contour map of any distribution of values
• Anything else you can think of!

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Structure Map

• Show the shape of a subsurface rock layer,
  usually with reference to sea level
• Show structural features such as folds and faults

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Fluvial Deposition
Map View of River Meander
Point Bars
Cross Section
Point Bar
Grain size decreasing upwards
Erosion
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Coyote CreekField
Isopach Map
Berg, 1986
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Channel Sandstone Reservoir
100
0
Berg, 1986
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Cross Section
Structural cross section - shows present
day geometry of the rock layers in the
subsurface. Ranger Formation, Wilmington Field,
CA
From Morton-Thompson and Arnold, 1992
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Cross Section
Stratigraphic cross section - provides a picture
of the history of deposition and structural
development. An internal boundary is the datum.
Ranger Formation, Wilmington Field, CA
From Morton-Thompson and Arnold, 1992
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Geophysical Methods

• Gravity
• Magnetics
• Seismic
• Other techniques

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Technological AdvancementsAn Opportunity
2D
1. Signal emitted by vibrator truck 2. Reflected
waves received by geophones 3. Data transmitted
to laboratory truck
Seismic Profile
3D
Synthesis
4D
(Thanks to Jane Woodward)
http//www.elf.fr/odyssee/us/depot/204.htm
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SeismicLine
Shot Points
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Reflections
Formations
REEF
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3-D Seismic
Courtesy of ExxonMobil
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3-D Seismic
A time slice from a 3-D seismic program in
north Texas - like a map. Can you interpret the
environment of deposition?
From the AAPG Explorer
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Now we have decided where we would like to drill.
How do we obtain permission to drill for and
(hopefully) produce hydrocarbons?
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Leasing Land OwnershipUnited States

• Private - 2/3 of US is in private ownership
• State
• Onshore
• Offshore
• Federal
• Onshore (BLM, Forest Service, DoD, etc.)
• Most Federal land is located west of the
  Mississippi
• Offshore (MMS)

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Basic Land Questions

• Where is the land located?
• Who owns it?
• Is the owner's title clear?
• What rights are needed?

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Where is the land located?

• There are two basic types of land surveys
• Metes and bounds (early surveys)
• Rectangular survey
• Most of the western U.S. is described with by the
  rectangular survey

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Rectangular Survey System
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Typical Section640 acres
ONEMILE
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Who Owns the Land?

• Public Owners
• federal government
• state governments, counties,cities or towns
• school systems
• Private Owners
• ? individuals
• ? companies
• ? institutions