USGS Geothermal

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Reservoir Characterization using Production
Logs

• Dan Amyotte, PL Interpretation Mgr.
• Denver Data Services

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Discussion Outline
1) Why Production Logs? 2) Single Phase
Production Log Interpretation 3) Spinner RPS -gt
Fluid Velocity -gt Flow Rate 4) Determining
Hold-up in Multiphase Flow Regimes 5) Field
Examples
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Why Run PLs?
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Why Run PLs?
Production monitoring is often carried out on a
periodic basis to quantify zonal contributions to
the total well production. The information is
used in reservoir simulation studies for
production history matching and material-balance
calculations. Well diagnostics often leads to
intervention to remedy a production problem. The
most common goal is the detection of water
breakthrough, with a work-over decision to be
made. Injection monitoring is carried out to
determine the amount of water or gas being taken
by each layer in the reservoir. This is important
for reservoir simulation. These surveys are
usually quite straightforward to carry out. Well
testing applications of PL provide both pressure
and flow rate data during well tests.
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PSP
GR CCL
Pressure
Temperature
Fluid Density
Capacitance
Spinner
GHOST
Gas Holdup Bubble Counts
DEFT
Dual-axis Calipers
Water Holdup Bubble Counts
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Basic PL Interpretation

• Mono Phase Flow Rate
• Velocity x Area
• Multi Phase Flow Rate
• Phase Velocity x Phase Holdup x Area

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Spinners are turbine flowmeters
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CONVENTIONS
Cable Velocity
Spinner RPS
Fluid Velocity
-Negative
- Negative
Positive
Positive
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Ideal Response of the Spinner with Fluid Velocity
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Mechanical effects at low flowrates
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Flowing Fluids add their Velocity to that of the
Tool
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Estimation of Flow Rate with Spinner
(Single-Phase)
0 5 10
15 20
6000 6100 6200 6300 6400
A
B
Depth (m)
C
D
0 5 10
15 20
Spinner rotation (RPS)
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Estimation of Flow - Answers (Single-Phase)
0 5 10
15 20
6000 6100 6200 6300 6400
A
B
Depth (m)
C
D
0 5 10
15 20
Spinner rotation (RPS)
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Spinner calibration passes
In-Situ Flowmeter Calibration Plot
E
E
RPS
D
C
D
m
y
B
A
C
Vt
Down
Up
Cable Speed
B
A
- 0 Cable Speed

• 0
• RPS

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Example 1

• Construct flowmeter calibration plot
• Determine the fluid velocity
• Determine the flowrate if a fluid velocity of
  29.9 ft/min is equivalent to 1000 bbl/d

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Example 1 Answer
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Spinner Response Equation

• Vfa(SpinnerRPS/Slope)-CableSpeedThreshold

RPS
Th
CS
Vfa
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Determine Rate from Vfa and ID
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Spinner Reversal
Spinner, rps
Tool moving slower than the fluid (rps)
Spinner reversed
Tool moving faster than the fluid (-rps)
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Effect of change in Diameter
Casing / hole size change
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Determining Holdup (Required for Multi-phase
Flow)
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Holdup Measurement

• Main purposes for determining holdup
• Determine volumetric flow in two and three-phase
  flow
• Show entry points in two and three-phase flow.
• Holdup tools
• Pressure Derivative
• Nuclear Fluid Densitometer (NFD)
• Gradiomanometer fluid density tool
• FloView (Liquid/ Hydrocarbon Differentiation)
• GHOST (Gas/Liquid Differentiation)
• HUM

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Hydrostatic Pseudo-Density

• dp/dz is the differentiation of the pressure
  measurement versus depth.
• Needs correction for friction and deviation.
• Inherently noisy.
• Because of the high resolution of pressure
  gauges, dp/dz values are very exact, although of
  very poor resolution.

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NFD - Nuclear Fluid Densitometer
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Holdup from density

• Mass conservation
• Ah rh Aw rw A rlog
• yh rh yw rw rlog
• y is the holdup
• yw yh 1
• yw (rlog - rh) / (rw - rh)

yw Aw/A yh Ah/A
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Example

• Gas density rh 0.3 g/cc
• Water density rw 1.1 g/cc
• Log density rlog 0.85 g/cc
• Holdup yw (0.85 - 0.3) / (1.1 - 0.3)
• yw 69

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Use of Temperature Measurement (the original
Production Log!)
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Temperature log Well producing liquid
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Field Examples
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Example 1
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Example 1 - Analysis
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Example 2
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Example 3
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Questions?
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Conversions

• 1 gpm 0.06309 l/sec 34.3 bbl/day
• 1 l/sec 15.85 gpm 543.8 bbl/day