PLC Density Log Split - Active Learnercloud1.activelearner.com › ... › PLC_Density_Log1.pdf · basic physics of the Density Log and Litho-Density Logs Discuss the units and the

Density Log

POROSITY LOGGING CORE

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

Describe the logging tool configuration in the borehole and thebasic physics of the Density Log and Litho-Density Logs

Discuss the units and the scale used for Density log data

Explain how Density log data are used to calculate porosity andwhat are the required “inputs”

Describe the effect of free gas saturation on the bulk density(rb) log and the impact on calculated porosity if 100% liquid isassumed

Discuss how the correction curve and caliper curve are usedtogether to quality check bulk density log data

═════════════════════════════════════════════════════════════════════════Porosity Logging Core

© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________

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POROSITY FROM DENSITY AS SINGLE SENSOR

Several applications

Porosity estimation

Lithology estimation

Prediction of hydrocarbon density

Input to synthetic seismograms (density x velocity)

Formation mechanical properties and rock physics

TYPICAL DENSITY TOOL CONFIGURATION

Formation Density Compensated (FDC)

Density Tool responds to electron density of the formation in front of the tool.

Density Log response; combination of matrix density and density of fluids in the invaded zone in their relative proportions. For simplicity, we have considered ρw = ρmf.

Density Log

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© PetroSkills, LLC., 2016. All rights reserved.

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TYPICAL DENSITY TOOL CONFIGURATION

The Density Log measures bulk density of formations in open-hole (g/cc).

In a known lithology, the bulk density is used to determine formation porosity.

Also an important reference for detecting light hydrocarbons.

The Density Log has earned its reputation as the most reliable and useful porosity log.

GAMMA RAY INTERACTIONS

Cesium 137 Emission

Limit of GR detection

PEF



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LOGGING TOOLS AVAILABLE

Wireline Density Measurements LDT = Litho-Density Tool, Schlumberger ZDEN = Litho-Density Tool, Baker Atlas SDLT = Litho-Density Tool, Halliburton MPD = Litho-Density Tool, Weatherford

LWD Density Measurements ALD = Litho-Density, Sperry (Halliburton) ADN & CDN = Litho-Density, Anadrill (Schlumberger) MDL = Litho-Density, Baker-Huges Inteq AZD = Litho-Density, Weatherford

DENSITY CORRECTION BY SPINE AND RIBS

(mm)(6.35) (12.7) (19.05)

(6.35) (12.7) (19.05)(mm)

Density Log

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LOG OF CORRECTED BULK DENSITY

(1198.26 kg/m3)

(0.1524 m) (0.4064 m) .

VS. CALIPER CURVES

(0.1524 m) (0.4064 m)

(454 kg)



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VS. CALIPER CURVES

A. This hole wasdrilled with an8-½ inch (18 mm)

drill bit.

(0.1524 m) (0.4064 m)

(454 kg)

VS. CALIPER CURVES

Good qualitative indication of log quality

Should be ~ 0 in smooth borehole

Barite mud exception

Can be good fractureindicator as well

(0.1524 m) (0.4064 m)

(454 kg)

Density Log

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DENSITY TOOL RESPONSE EQUATION

b = Φ [Sxow + (1-Sxo)h] + (1 - Φ)ma

b : Formation bulk density

ma : Matrix density

f : Fluid density

w : Water density

h : Hydrocarbon densityΦ : Formation porosity

Sxo : Invaded zone water saturation

Rearrange to calculate porosity, Phi

Quartz 2.65 g/cc

Calcite 2.71 g/cc

Dolomite 2.87 g/cc

ma b

ma f

- =

-

DENSITY VALUES IN FORMATION EVALUATION (G/CC)

Reservoir matrix

Quartz (sandstone) 2.65

Calcite (limestone) 2.71

Dolomite 2.87

Pore fluids

Fresh water 1.00

Salt water (200 g/l (200 kg/m3)) 1.13

Fresh water with 30% residual oil 0.90 – 0.94

Fresh water with 30% residual gas 0.73 – 0.74

Other minerals

Halite (rock salt) 2.03

Anhydrite 2.98



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CORE POROSITY CALIBRATION

Co

re p

oro

sity

(%

bv)

Log density (g/cc)

Apparent fluid

Density

fl

Core matrix density

ma

DENSITY LOG RESPONSE CHART

Porosity = 25%

Density Log

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Remember:Sand (quartz rich)Limestone (calcite rich)

PEF (OR PE) CURVE

“Essentially” porosity independent

Typical values• Sand = 1.8• Limestone = 5.1• Dolomite = 3.1• Salt = 4.7• Anhydrite = 5.1

Original density log was developed in the 1960s

Measured bulk density

Called Formation DensityCompensated Log (FDC)

Photoelectric Factor Curve(PEF) was later developed

Density log was renamed Litho-Density Tool (LDT)

Single curve lithologyindicator

LITHO-DENSITY TOOLS: PEF (OR PE) CURVE

Photoelectric Factor (PEF) Incident low energy gamma ray absorbed by electron and

electron ejected from the atom PEF = (Z/A)exp 3.6 Where: Z = atomic no.

A = atomic weight

Measures different part of decay spectrum

Can be highly affected by barite muds

Single curve lithology indicator



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PE VS. POROSITY: LITHO-DENSITY TOOLS

Chart Use:

Read PEF

Read Bulk Density

Determine Porosity %

Porosity = 20%

SUMMARY: DENSITY AS SINGLE SENSOR

Source for porosity and lithology information

Litho-density (PEF) provides additional lithology information

Pad contact tool Rugose hole implications Barite mud implications Fracture identification implications

Can be combined with other porosity devices to define lithology,porosity, shale content

Depth of investigation shallow (< 50 cms)

Vertical resolution ~ 20 cms

Density Log

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LEARNING OBJECTIVES

Describe the logging tool configuration in the borehole and thebasic physics of the Density Log and Litho-Density Logs

Discuss the units and the scale used for Density log data

Explain how Density log data are used to calculate porosity andwhat are the required “inputs”

Describe the effect of free gas saturation on the bulk density (rb)log and the impact on the calculated porosity if 100% liquid isassumed

Discuss how the correction curve and caliper curve are usedtogether to quality check bulk density log data



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Documents

PLC Density Log Split - Active Learnercloud1.activelearner.com › ... › PLC_Density_Log1.pdf · basic physics of the Density Log and Litho-Density Logs Discuss the units and the