Reservoir Development Tools

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Reservoir Development Tools

• Chapter 2 (Part 3)

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Reservoir Development Tools

• When information indicates a strong possibility
  of hydrocarbons oil companies will typically
  drill an exploratory well.
• While drilling geologist monitor the well through
  core samples, well logs, and test results.
• Geologist combine all the information and try to
  predict the production possibility of the
  formation.

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Well Logs

• Log Record of information about the formations
  the well has been drilled through.
• Typically two types
• Drillers Logs
• Wire line Logs
• Electric Logs
• Radioactivity Logs
• Acoustic Logs

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Drillers Log

• Record of the kinds of rocks and fluids
  encountered at different depths and anything else
  of interest.
• Mainly when formations are alternating from soft
  to hard rock How long it took to drill through
  a particular formation.
• Good drillers can correlate the time/data with
  other wells in the area and different formations.

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Drillers Log
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Wire Line Logs

• Wire Line A metal line that can be run down the
  hole with a tool attached.
• Conductor Line Wire line that can carry
  electricity to the tool. (Both are commonly
  called Wireline)
• Wire Line involves complex calculations and
  interpretation of the information the tool relays
  to the surface.
• Logging Specialist use the data to compare,
  correlate and track the depth of formations.
• Sonde Instrument lowered down hole that relays
  all the information back to the surface.

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Wire Line Logs
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Electric Logs

• Spontaneous Potential (SP) Log
• Records weak electrical currents that flow
  naturally in the rock next to the wellbore
  (Natural Electricity)
• Shows the boundaries and thickness of each layer
  of rock
• Easiest and most basic log therefore the most
  common
• Induced Electricity Log
• Electrical signal is emitted by the sonde through
  the formation and relays it back to the receiver
  at the surface.
• Receiver measures the formations resistance to
  current or how well it conducts current.
• Resistivity Log Records resistance
• Induction Log Records conductivity

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Nuclear Logs

• Radioactivity Logs
• Measure natural and induced radioactivity in
  formations
• Gamma Ray Log
• Records gamma particles (Gama Rays) that the
  formation gives off naturally.
• Useful in identifying shale and clay-filled
  formations
• Neutron Log
• Sends Neutrons through the formation, when they
  collide with hydrogen it slows them down. This
  slowness is recorded when a lot of hydrogen is
  present in the formation.

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Acoustic Logs

• Acoustic/Sonic Log
• Sonde emits a sound wave through the formation
  that is recorded.
• How fast the sound travels depends on the density
  of the rock.
• The more porous the rock the faster the sound
  waves travel.

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Wire Line Logs
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Sample Logs

• Physical samples of the well bore.
• Typically Two Types
• Core Samples
• Cutting Samples

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Core Samples

• Core Slender column of rock that shows the
  sequence of rock as they appear within the earth.
• Coring Bit Substituted for the drilling bit, it
  has a hollow center that enables the recovery of
  a sample.
• Typically length ranges from 25 to 60 feet.
• When it is brought to the surface it is packaged
  and sent to a lab for analysis.

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Core Samples
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Cutting Samples

• Cuttings rock that is broken up from the well
  bore.
• As the cuttings flow out of the hole they are
  recovered by geologist/mud engineers and studied.
• Not all cuttings come from the bottom, some are
  sloughed off from the sides at various depths.
• Not as accurate as a core sample, but it is still
  widely used and offers useful data to
  geologists/mud engineers regarding the condition
  and characteristics of the hole.

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Drill Stem Test

• Drill Stem Test (DST)
• Primary way to test a formation that has just
  been drilled.
• Formation fluids flow into perforated holes in
  the tool where the pressure is recorded .
• When the pressure is recorded valves inside the
  tool close trapping the fluid inside the tool to
  be used later as a sample for analysis

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Drill Stem Test
Seals off well bore for reading only formation
fluid
Formation Fluid and Pressure
Fluid is trapped inside once measurements have
been made
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Strat Test

• Stratigraphy
• The study of the origin, composition,
  distribution, and sequence of rock strata.
• Strat Test
• Drill a hole primarily to obtain geological
  information, mainly in exploration work.
• Borehole that exposes complete sections of
  formations
• Stratographers analyze the cuttings to create a
  cutting log and look for hydrocarbons.
• Geologist try to follow beds of rock from well to
  well.

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Stratigraphic Correlation

• Stratigraphic Correlation
• The process of comparing geological formations.
• Scientists use data from other wells and compare
  them to predict other sources (formations) of
  hydrocarbons.
• Use of drillers logs, sample logs, electrical
  logs, composition of formations, and area data
  are common methods.
• Sequence Stratigraphy
• Scientist use seismic surveys and deduce how the
  environment existed when a rock layer first
  formed.

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Stratigraphic Correlation
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Maps

• Base Maps
• Show existing wells, property lines, roads,
  buildings and other man made features.
• Topographic Maps
• Show surface features such as mountains and
  valleys
• Bouger Gravity Map
• Underground formations developed from gravity
  surveys.

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Contour Maps (see pg. 43)

• Depicts geologic structure and thickness of
  formations
• Structural Map
• Depicts the depth of a specific formation from
  the surface of the formation
• Isopach Map
• Shows the thickness of a formation. Used mainly
  to calculate how much hydrocarbon remains in a
  formation.
• Lithofacies Map
• Shows the character of the rock itself and how it
  varies horizontally within the formation.
• Biofacies Map Shows the variations in occurrence
  of fossil types

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Vertical Cross Sections

• Represents a portion of the crust as though it
  were sliced
• Shows the structures and fault patterns
• Show anticlinal and fault traps
• Horizontal variations I type and thickness of rock

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Vertical Cross Sections
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Questions

• 1. When do oil companies typically drill an
  exploration well?
• 2. List the two typical types of well logs.
• 3. List the three types of wire line logs.
• 4. What is a sonde?
• 5. List the two types of sample logs typically
  used.
• 6. What is the difference between a coring bit
  and standard drilling bit.
• 7. Define cuttings.
• 8. What is a DST?
• 9. Define stratography.
• 10. List the three types of maps commonly used in
  the oil industry.