166487649 Schlumberger Log Interpretation Charts

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Symbols Used in Log Interpretation

Gen-1 (former Gen-3) d_h Hole diameter d_i d_j h ∆rj (Invasion diameters) Adjacent bed Zone of transition or annulus Flushed zone Adjacent bed (Bed thickness) Mud h_mc dh R_m Rs Rs Resistivity of the zone

Resistivity of the water in the zone Water saturation in the zone

R_mc Mudcake Rm f S_{x o} Rx o Rw S_w Rt R_i Uninvaded zone Purpose

This diagram presents the symbols and their descriptions and rela-tions as used in the charts. See Appendixes D and E for

identifica-Description

The wellbore is shown traversing adjacent beds above and below the zone of interest. The symbols and descriptions provide a graphical

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General

Gen

Estimation of Formation Temperature with Depth

Purpose

This chart has a twofold purpose. First, a geothermal gradient can be assumed by entering the depth and a recorded temperature at that depth. Second, for an assumed geothermal gradient, if the tem-perature is known at one depth in the well, the temtem-perature at another depth in the well can be determined.

Description

Depth is on the y-axis and has the shallowest at the top and the deepest at the bottom. Both feet and meters are used, on the left and right axes, respectively. Temperature is plotted on the x-axis, with Fahrenheit on the bottom and Celsius on the top of the chart. The annual mean surface temperature is also presented in Fahrenheit and Celsius.

Example

Given: Bottomhole depth = 11,000 ft and bottomhole

tempera-ture = 200°F (annual mean surface temperatempera-ture = 80°F). Find: Temperature at 8,000 ft.

Answer: The intersection of 11,000 ft on the y-axis and 200°F on the x-axis is a geothermal gradient of approximately 1.1°F/100 ft (Point A on the chart).

Move upward along an imaginary line parallel to the con-structed gradient lines until the depth line for 8,000 ft is intersected. This is Point B, for which the temperature on the x-axis is approximately 167°F.

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General

Gen General

Estimation of Formation Temperature with Depth

Gen-2 (former Gen-6) 80 100 150 200 250 300 350 60 100 150 200 250 300 350 27 50 75 100 125 150 175 16 25 50 75 100 125 150 175 Temperature (°F) Temperature (°C)

Temperature gradient conversions: 1°F/100 ft = 1.823°C/100 m 1°C/100 m = 0.5486°F/100 ft Depth (thousands of feet) Depth (thousands of meters) Annual mean surface temperature Annual mean surface temperature 5 10 15 20 25 1 2 3 4 5 6 7 8 0.6 0.8 1.0 1.2 1.4 1.6°F/100 ft 1.09 1.46 1.82 2.19 2.55 2.92°C/100 m B A Geothermal gradient

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General

Gen

Estimation of R

mf

and R

mc

Fluid Properties _{(former Gen-7)}Gen-3

Purpose

Direct measurements of filtrate and mudcake samples are preferred. When these are not available, the mud filtrate resistivity (Rmf) and

mudcake resistivity (Rmc) can be estimated with the following

methods. Description

Method 1: Lowe and Dunlap

For freshwater muds with measured values of mud resistivity (Rm)

between 0.1 and 2.0 ohm-m at 75°F [24°C] and measured values of mud density (ρm) (also called mud weight) in pounds per gallon:

Method 2: Overton and Lipson

For drilling muds with measured values of Rmbetween 0.1 and

10.0 ohm-m at 75°F [24°C] and the coefficient of mud (Km) given

as a function of mud weight from the table:

Example

Given: Rm= 3.5 ohm-m at 75°F and mud weight = 12 lbm/gal

[1,440 kg/m3_].

Find: Estimated values of Rmfand Rmc.

Answer: From the table, Km= 0.584.

Rmf= (0.584)(3.5)1.07= 2.23 ohm-m at 75°F. Rmc= 0.69(2.23)(3.5/2.23)2.65= 5.07 ohm-m at 75°F. log = .R . . R mf m m ⎛ ⎝⎜ ⎞ ⎠⎟ 0 396−

(

0 0475×ρ

)

R K R R R R R mf m m mc mf m mf =

( )

=

( )

⎛ ⎝⎜ ⎞ ⎠⎟ 1 07 2 65 0 69 . . . . Mud Weight lbm/gal kg/m3 _K m 10 1,200 0.847 11 1,320 0.708 12 1,440 0.584 13 1,560 0.488 14 1,680 0.412 16 1,920 0.380 18 2,160 0.350

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10 20 50 100 200 500 1,000 2,000 5,000 10,000 20,000 50,000 100,000 300,000 2.0 1.5 1.0 0.5 0 –0.5 2.0 1.0 0

Total solids concentration (ppm or mg/kg) Multiplier

†_{Multipliers that do not vary appreciably for low concentrations} (less than about 10,000 ppm) are shown at the left margin of the chart Li (2.5)† NH4 (1.9)† Na and CI (1.0) NO₃ (0.55)† Br (0.44)† I (0.28)† OH (5.5)† Mg Mg K K Ca Ca CO3 CO₃ SO4 SO₄ HCO3 HCO₃ General Gen Purpose

This chart is used to approximate the parts-per-million (ppm) con-centration of a sodium chloride (NaCl) solution for which the total solids concentration of the solution is known. Once the equivalent concentration of the solution is known, the resistivity of the solution for a given temperature can be estimated with Chart Gen-6. Description

The x-axis of the semilog chart is scaled in total solids concentration and the y-axis is the weighting multiplier. The curve set represents the various multipliers for the solids typically in formation water.

Example

Given: Formation water sample with solids concentrations

of calcium (Ca) = 460 ppm, sulfate (SO4) = 1,400 ppm,

and Na plus Cl = 19,000 ppm. Total solids concentration = 460 + 1,400 + 19,000 = 20,860 ppm.

Find: Equivalent NaCl solution in ppm.

Answer: Enter the x-axis at 20,860 ppm and read the multiplier value for each of the solids curves from the y-axis: Ca = 0.81, SO4= 0.45, and NaCl = 1.0. Multiply each

concentration by its multiplier:

(460 × 0.81) + (1,400 × 0.45) + (19,000 × 1.0) = 20,000 ppm.

Equivalent NaCl Salinity of Salts

Gen-4 (former Gen-8)

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Gen

General

Concentration of NaCl Solutions

Gen-5 ° = ° − API 141 5. 131 5. sg at 60 F g/L at 77°F ppm grains/gal at 77°F °F/100 ft °C/100 ft °API Oil Gravity Concentrations of NaCl Solutions

Temperature Gradient Conversion Specific gravity (sg) at 60°F Density of NaCl solution at 77°F [25°C] 0.15 150 200 300 400 500 600 800 1,000 1,500 2,000 3,000 4,000 5,000 6,000 8,000 10,000 15,000 20,000 30,000 40,000 60,000 80,000 100,000 150,000 200,000 250,000 10 1.00 1.005 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.12 1.14 1.16 1.18 1.20 1.0 1.5 2.0 2.5 3.0 0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98 1.00 1.02 1.04 1.06 1.08 3.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 100 90 80 70 60 50 40 30 20 10 0 1.8 1.9 2.0 12.5 15 20 25 30 40 50 60 70 80 90 100 125 150 200 250 300 400 500 600 700 800 900 1,000 1,250 1,500 2,000 2,500 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 12,500 15,000 17,500 0.2 0.3 0.4 0.5 0.6 0.8 1.0 1.5 2 3 4 5 6 8 10 15 20 30 40 50 60 80 100 125 150 200 250 300 1°F/100 ft = 1.822°C/100 m 1°C/100 m = 0.5488°F/100 ft

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Gen General

Resistivity of NaCl Water Solutions

Purpose

This chart has a twofold purpose. The first is to determine the resis-tivity of an equivalent NaCl concentration (from Chart Gen-4) at a specific temperature. The second is to provide a transition of resis-tivity at a specific temperature to another temperature. The solution resistivity value and temperature at which the value was determined are used to approximate the NaCl ppm concentration.

Description

The two-cycle log scale on the x-axis presents two temperature scales for Fahrenheit and Celsius. Resistivity values are on the left four-cycle log scale y-axis. The NaCl concentration in ppm and grains/gal at 75°F [24°C] is on the right y-axis. The conversion approximation equation for the temperature (T) effect on the resistivity (R) value at the top of the chart is valid only for the temperature range of 68° to 212°F [20° to 100°C].

Example One

Given: NaCl equivalent concentration = 20,000 ppm. Temperature of concentration = 75°F. Find: Resistivity of the solution.

Answer: Enter the ppm concentration on the y-axis and the tem-perature on the x-axis to locate their point of intersec-tion on the chart. The value of this point on the left y-axis is 0.3 ohm-m at 75°F.

Example Two

Given: Solution resistivity = 0.3 ohm-m at 75°F. Find: Solution resistivity at 200°F [93°C].

Answer 1: Enter 0.3 ohm-m and 75°F and find their intersection on the 20,000-ppm concentration line. Follow the line to the right to intersect the 200°F vertical line (interpolate between existing lines if necessary). The resistivity value for this point on the left y-axis is 0.115 ohm-m.

Answer 2: Resistivity at 200°F = resistivity at 75°F × [(75 + 6.77)/ (200 + 6.77)] = 0.3 × (81.77/206.77) = 0.1186 ohm-m.

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General

Gen

Resistivity of NaCl Water Solutions

Gen-6 (former Gen-9) °F 50 75 100 125 150 200 250 300 350 400 Resistivity of solution (ohm-m) ppm 10 8 6 5 4 3 2 1 0.8 0.6 0.5 0.4 0.3 0.2 0.1 0.08 0.06 0.05 0.04 0.03 0.02 0.01 200 300 400 500 600 700 800 1,000 1,200 1,400 1,700 2,000 3,000 4,000 5,000 6,000 7,000 8,000 10,000 12,000 14,000 17,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 100,000 120,000 140,000 170,000 200,000 250,000 280,000 Conversion approximated by R2 = R1 [(T1+ 6.77)/(T2+ 6.77)]°F or R2 = R1 [(T1+ 21.5) /(T2+ 21.5)]°C 300,000 NaCl concentration (ppm or grains/gal) grains/gal at 75°F 10 15 20 25 30 40 50 100 150 200 250 300 400 500 1,000 1,500 2,000 2,500 3,000 4,000 5,000 10,000 15,000 20,000

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General

Gen

Density of Water and Hydrogen Index of Water and Hydrocarbons

Gen-7

Purpose

These charts are for determination of the density (g/cm3_{) and}

hydro-gen index of water for known values of temperature, pressure, and salinity of the water. From a known hydrocarbon density of oil, a determination of the hydrogen index of the oil can be obtained. Description: Density of Water

Example: Density of Water

Given: Temperature = 200°F [93°C], pressure = 7,000 psi, and salinity = 250,000 ppm.

Answer: Density of water = 1.15 g/cm3_.

Example: Hydrogen Index of Salt Water

1.20 Pressure NaCl 14.7 psi 1,000 psi 7,000 psi 25 50 100 Temperature (°C) Temperature (°F)

Hydrogen Index of Salt Water

Hydrogen Index of Live Hydrocarbons and Gas

Salinity (kppm or g/kg) Hydrocarbon density (g/cm3₎ 150 200 0.85 440 400 300 200 100 40 Hydrocarbons Water 0.90 0.95 1.00 1.05 1.10 1.15 1.05 1.2 1.2 1.0 1.0 0 0 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1.00 0.95 0.90 0.85 0 50 100 150 200 250 Water density (g/cm3₎ Hydrogen index Hydrogen index 250,0 00 ppm 200,000 ppm 150,000 pp m 100,000 ppm 50,000 ppm Distilled wate r © Schlumberger

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General

Gen

Purpose

This chart can be used to determine more than one characteristic of natural gas under different conditions. The characteristics are gas density (ρg), gas pressure, and hydrogen index (Hgas).

Description

Example

Given: Gas density = 0.2 g/cm3_{and temperature = 200°F.}

Find: Gas pressure and hydrogen index.

Answer: Gas pressure = approximately 5,200 psi and Hgas= 0.44.

Density and Hydrogen Index of Natural Gas

Gen-8 0 0.1 0.2 0.3 0.4 0.5 100 200 300 400 17,500 15,000 12,500 10,000 7,500 5,000 2,500 Temperature (°F) Pressure (psi) Gas gravity = 0.65 Gas density (g/cm3₎

Gas pressure × 1,000 (psia) 0 0.1 0.2 0.3 0.7 Hgas Gas temperature (°F) Gas gravity = 0.6 (Air = 1.0) 0.6 100 150 200 250 300 350 0.5 0.4 0.3 0.2 0.1 0 0 2 4 6 8 10 Gas density (g/cm3₎ 14.7 © Schlumberger

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General

Purpose

This chart is used to determine the sound velocity (ft/s) and sound slowness (µs/ft) of gas in the formation. These values are helpful in sonic and seismic interpretations.

Description

Enter the chart with the temperature (Celsius along the top x-axis and Fahrenheit along the bottom) to intersect the formation pore pressure.

Gen General

Sound Velocity of Hydrocarbons

Gen-9 Gas gravity = 0.65 Natural Gas 50 100 150 200 250 300 350 0 1,000 2,000 3,000 4,000 5,000 200 250 300 17,500 15,000 12,500 10,000 7,500 5,000 2,500 14.7 400 500 1,000 2,000 Temperature (°C) Pressure (psi) Temperature (°F) Sound velocity (ft /s) Sound slowness (µs/ft) 0 50 100 150 200 © Schlumberger

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Gas Effect on Compressional Slowness

General

Gen-9a

Gen

Purpose

This chart illustrates the effect that gas in the formation has on the slowness time of sound from the sonic tool to anticipate the slowness of a formation that contains gas and liquid.

Description

Enter the chart with the compressional slowness time (∆tc) from the

sonic log on the y-axis and the liquid saturation of the formation on the x-axis. The curves are used to determine the gas effect on the basis of which correlation (Wood’s law or Power law) is applied. The slowing effect begins sooner for the Power law correlation. The Wood’s law correlation slightly increases ∆tcvalues as the formation

liquid saturation increases whereas the Power law correlation decreases ∆tcvalues from about 20% liquid saturation.

100 0 200 100 200 µs/ft 110 µs/ft 90 µs/ft 70 µs/ft 50 ∆tc (µs/ft) sandWet Sandstone 80 60 40 20

Wood’s law (e = 5) Power law (e = 3) Liquid saturation (%)

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General

Gas Effect on Acoustic Velocity

Sandstone and Limestone Gen-9b

Limestone Sandstone 0 10 20 30 40 25 0 0 5 10 10 15 20 20 25 30 40 20 15 10 5 0 Porosity (p.u.) Porosity (p.u.) Velocity (1,000 × ft/s) Velocity (1,000 × ft/s) Vp Vs Vs V_p No gas Gas bearing No gas Gas bearing Gen Purpose Description © Schlumberger

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General

Gen

Purpose

Longitudinal (Bulk) Relaxation Time of Pure Water

This chart provides an approximation of the bulk relaxation time (T1) of pure water depending on the temperature of the water. Transverse (Bulk and Diffusion) Relaxation Time of Water in the Formation

Determining the bulk and diffusion relaxation time (T2) from this

chart requires knowledge of both the formation temperature and the echo spacing (TE) used to acquire the data. These data are pre-sented graphically on the log and are the basis of the water or hydrocarbon interpretation of the zone of interest.

Description

Longitudinal Relaxation Time

The chart relation is for pure water—the additives in drilling fluids reduce the relaxation time (T1) of water in the invaded zone. The

two major contributors to the reduction are surfactants added to the drilling fluid and the molecular interactions of the mud filtrate con-tained in the pore spaces and matrix minerals of the formation.

Transverse Relaxation Time

The relaxation time (T2) determination is based on the formation

temperature and echo spacing used to acquire the measurement. The TE value is listed in the parameter section of the log. Using the T2measurement from a known water sand or based on local

experience further aids in determining whether a zone of interest contains hydrocarbons, water, or both.

Nuclear Magnetic Resonance Relaxation Times of Water

Gen-10

Longitudinal (Bulk) Relaxation Time of Water Temperature (°C) Relaxation time (s) 100 10 1.0 0.1 0.01 20 60 100 140 180 T1

Transverse (Bulk and Diffusion) Relaxation Time of Water

Temperature (°C) Relaxation time (s) 100 10 1.0 0.1 0.01 20 60 100 140 180 T₂(TE = 0.2 ms) T₂(TE = 0.32 ms) T2(TE = 1 ms) T₂₍TE = 2 ms) © Schlumberger

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General

Gen

Nuclear Magnetic Resonance Relaxation Times of Hydrocarbons

Gen-11a

Purpose

Longitudinal (Bulk) Relaxation Time of Crude Oil

This chart is used to predict the T1of crude oils with various

viscosi-ties and densiviscosi-ties or specific graviviscosi-ties to assist in interpretation of the fluid content of the formation of interest.

Transverse (Bulk and Diffusion) Relaxation Time

Description

Longitudinal (Bulk) Relaxation Time

This chart is divided into three distinct sections based on the compo-sition of the oil measured. The type of oil contained in the formation can be determined from the measured T1and viscosity determined

from the transverse relaxation time chart.

Transverse (Bulk and Diffusion) Relaxation Time of Crude Oil

T1 (s)

Longitudinal (Bulk) Relaxation Time of Crude Oil

Viscosity (cp) 0.1 1 10 100 1,000 10,000 100,000 0.001 0.01 0.1 1 10 0.0001 T2 (s) Viscosity (cp) 0.1 1 10 100 1,000 10,000 100,000 0.001 0.01 0.1 1 10 0.0001 Diffusion (cm2_/s)

Hydrocarbon Diffusion Coefficient 10–3 10–4 10–5 10–6 10–7 150 0 50 100 200 Temperature (°C) Oil (9° at 20°C) Oil (40° at 20°C) Diffusion (10–5 _cm2_/s)

Water Diffusion Coefficient

Temperature (°C) 0 50 100 150 200 0 5 10 15 20 Light oil: 45°–60° API

0.65–0.75 g/cm3

Medium oil: 25°–40° API 0.75–0.85 g/cm3

Heavy oil: 10°–20° API 0.85–0.95 g/cm3 TE = 0.2 ms TE = 0.32 ms TE = 1 ms TE = 2 ms T1 © Schlumberger

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General

Nuclear Magnetic Resonance Relaxation Times of Hydrocarbons

Gen-11b 0 0.2 0.4 0.6 0.8 1.0 1.2 0 0.2 0.4 0.6 0.8 1.0 1.2 Hydrocarbon density (g/cm3₎ Hydrogen index

Hydrogen Index of Live Hydrocarbons and Gas 0 2 4 6 0 6,000 9,000 25°C 75°C 125°C 175°C

Longitudinal (Bulk) Relaxation Time of Methane Pressure (psi) 3,000 12,000 10 8 Diffusion (cm2_/_s) 10–2 0.001

Transverse (Bulk and Diffusion) Relaxation Time of Methane

TE = 2 ms 100 10–4 0.01 0.1 1 10 10–3 T2 (s) TE =1 ms TE = 0.32 ms TE = 0.2 ms T1 (s) 10 15 20 25 30 35 50 100 150 200

Methane Diffusion Coefficient

Diffusion (10–4_cm2_/_s₎ Temperature (°C) 1,600 psi 3,000 0 0 5 8,300 15,500 22,800 3,900 4,500 0 0 Gen General Purpose

Methane Diffusion Coefficient

This chart is used to determine the diffusion coefficient of methane at a known formation temperature and pressure.

Longitudinal and Transverse Relaxation Times of Methane

Hydrogen Index of Live Hydrocarbons and Gas

This chart is used to determine the hydrogen index from the hydro-carbon density.

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General

Capture Cross Section of NaCl Water Solutions

Gen Purpose

The sigma value (Σw) of a saltwater solution can be determined from

this chart. The sigma water value is used to calculate the water satu-ration of a formation.

Description

Charts Gen-12 and Gen-13 define sigma water for pressure condi-tions of ambient through 20,000 psi [138 MPa] and temperatures from 68° to 500°F [20° to 260°C]. Enter the appropriate chart for the pressure value with the known water salinity on the y-axis and move horizontally to intersect the formation temperature. The sigma of the formation water for the intersection point is on the x-axis.

Example

Given: Water salinity = 125,000 ppm, temperature = 68°F at ambient pressure, and formation temperature = 190°F at 5,000 psi.

Find: Σw at ambient conditions and Σwof the formation.

Answer: Σw = 69 c.u. and Σw of the formation = 67 c.u.

If the sigma water apparent (Σwa) is known from a clean water

sand, then the salinity of the formation can be determined by enter-ing the chart from the sigma water value on the x-axis to intersect the pressure and temperature values.

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General Gen Ambien t 200°F [93°C] 68°F [20°C] 400 °F [205 °C] 300°F [150 °C] 200°F [93 °C] 68°F [20 °C] 400°F [205°C] 300°F [150°C] 200°F [93°C] 68°F [20°C] 1,000 psi [6.9 MPa] 5,000 psi [34 MPa] 300 275 250 225 200 175 150 125 100 75 50 25 0 100 75 50 25 0 100 75 50 25 0 300 275 250 225 200 300 275 250 225 200 300 275 250 225 200 175 150 125 100 75 50 25 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 125 150 175 175 150 125 Equivalent water salinity

(1,000 × ppm NaCl)

Capture Cross Section of NaCl Water Solutions

Gen-12 (former Tcor-2a)

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General

Capture Cross Section of NaCl Water Solutions

Gen-13 (former Tcor-2b) Gen 10,000 psi [69 MPa] 500°F [260 °C] 400°F [205 °C] 300 °F [150 °C] 200°F [93 °C] 68°F [20 °C] 400°F [205 °C] 300°F [150 °C] 200°F [93 °C] 68°F [20 °C] 400°F [205 °C] 300°F [150 °C] 200°F [93 °C] 68°F [20 °C] 15,000 psi [103 MPa] 20,000 psi [138 MPa] 300 275 250 225 200 175 150 125 100 75 50 25 0 100 75 50 25 0 100 75 50 25 0 300 275 250 225 200 300 275 250 225 200 300 275 250 225 200 175 150 125 100 75 50 25 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Equivalent water salinity (1,000 × ppm NaCl) 125 150 175 175 150 125

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Purpose

Sigma hydrocarbon (Σh) for gas or oil can be determined by using

this chart. Sigma hydrocarbon is used to calculate the water satura-tion of a formasatura-tion.

Description

One set of charts is for measurement in metric units and the other is for measurements in “customary” oilfield units.

For gas, enter the background chart of a chart set with the reser-voir pressure and temperature. At that intersection point move left to the y-axis and read the sigma of methane gas.

For oil, use the foreground chart and enter the solution gas/oil ratio (GOR) of the oil on the x-axis. Move upward to intersect the appropriate API gravity curve for the oil. From this intersection point, move horizontally left and read the sigma of the oil on the y-axis.

Example

Given: Reservoir pressure = 8,000 psi, reservoir temperature = 300°F, gravity of reservoir oil = 30°API, and solution GOR = 200.

Find: Sigma gas and sigma oil.

Answer: Sigma gas = 10 c.u. and sigma oil = 21.6 c.u. General

Gen

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General

Gen

Capture Cross Section of Hydrocarbons

Gen-14 (former Tcor-1) 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 68 125 200 300 400 500 Reservoir pressure (psia)

0 4,000 8,000 12,000 16,000 20,000 Methane Temperature (°F) Σh (c.u.) Customary 10 100 1,000 10,000 Solution GOR (ft3_/bbl) Liquid hydrocarbons Condensate 30°, 40°, and 50°API 20° and 60°API 16 18 20 22 Σh (c.u.) Metric 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 20 52 93 150 260 Reservoir pressure (mPa)

0 14 28 41 55 69 83 97 110 124 138 Methane Temperature (°C) Σh (c.u.) 205 Liquid hydrocarbons 0.78 to 0.88 mg/m3 0.74 or 0.94 mg/m3 20 22 Σ (c.u.)

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General

EPT* Propagation Time of NaCl Water Solutions

Gen-15 (former EPTcor-1)

Purpose

This chart is designed to determine the propagation time (tpw) of

saltwater solutions. The value of tpwof a water zone is used to

deter-mine the temperature variation of the salinity of the formation water.

Description

Enter the chart with the known salinity of the zone of interest and move upward to the formation temperature curve. From that inter-section point move horizontally left and read the propagation time of the water in the formation on the y-axis. Conversely, enter the chart with a known value of tpwfrom the EPT Electromagnetic

Propagation Tool log to intersect the formation temperature curve

90 80 70 60 50 40 30 20 0 50 100 150 200 250

Equivalent water salinity (1,000 × ppm or g/kg NaCl) tpw (ns/m) 120°C 250°F 100°C 200°F 80°C 175°F 40°C 100°F 150°F 60°C 75°F 20°C 125°F Gen *Mark of Schlumberger © Schlumberger

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General

Gen

EPT* Attenuation of NaCl Water Solutions

Gen-16 (former EPTcor-2)

0 5 10 15 20 25 30

Uncorrected t_pl (ns/m)

0 50 100 150 200 250

Equivalent water salinity (kppm or g/kg NaCl)

Correction to EATT (dB/m) –40 –60 –80 –100 –120 –140 –160 –180 –200 120°C 250°F 100°C 200°F 80°C 175°F 40°C 100°F 150°F 60°C 75°F 20°C 125°F 5,000 4,000 3,000 2,000 1,000 0 Attenuation, Aw (dB/m)

EPT-D Spreading Loss

*Mark of Schlumberger © Schlumberger

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General

Gen

EPT* Propagation Time–Attenuation Crossplot

Sandstone Formation at 150°F [60°C] Gen-16a

Purpose

This chart is used to determine the apparent resistivity of the mud filtrate (Rmfa) from measurements from the EPT Electromagnetic

Propagation Tool. The porosity of the formation (φEPT) can also be

estimated. Porosity and mud filtrate resistivity values are used in determining the water saturation.

Description

Enter the chart with the known attenuation and propagation time (tpl). The intersection of those values identifies Rmfaand φEPTfrom

the two sets of curves. This chart is characterized for a sandstone formation at a temperature of 150°F [60°C].

Example

Given: Attenuation = 300 dB/m and tpl= 13 ns/m.

Find: Apparent resistivity of the mud filtrate and EPT porosity. Answer: Rmfa= 0.1 ohm-m and φEPT= 20 p.u.

1,000 900 800 700 600 500 400 300 200 100 0 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 1.0 40 50 30 20 10 2.0 5.0 10.0 50.0 Attenuation (dB/m) tpl (ns/m) Sandstone at 150°F [60°C]

Rmfa from EPT log (ohm-m)

EP Tpo rosi ty(φ EPT ) 0.02 0.05 0.1 0.2 0.5 *Mark of Schlumberger © Schlumberger

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Gamma Ray—Wireline

Scintillation Gamma Ray—3

3

_⁄

8

- and 1

11

⁄

16

-in. Tools

Gamma Ray Correction for Hole Size and Barite Mud Weight _{(former GR-1)}GR–1

Purpose

This chart provides a correction factor for measured values of forma-tion gamma ray (GR) in gAPI units. The corrected GR values can be used to determine shale volume corrections for calculating water saturation in shaly sands.

Description

The semilog chart has the t factor on the x-axis and the correction factor on the y-axis.

The input parameter, t, in g /cm2_{, is calculated as follows:}

Example

Given: GR = 36 API units (gAPI), dh= 12 in., mud weight =

12 lbm/gal, tool OD = 33_⁄₈_{in., and the tool is centered.}

Find: Corrected GR value.

Answer:

Enter the chart at 15.8 on the x-axis and move upward to intersect the 33_⁄₈_{-in. centered curve. The corresponding} 10.0 7.0 5.0 3.0 2.0 1.0 0.7 0.5 0.3 Correction factor t (g/cm2₎ 0 5 10 15 20 25 30 35 40 Scintillation Gamma Ray

33_⁄₈_{-in. tool, centered}

111_⁄₁₆_{-in. tool, centered}

33_⁄₈_{-in. tool, eccentered}

111_⁄₁₆_{-in. tool, eccentered}

GR W d d mud h sonde = ⎛_⎜⎜2 54.

( )

−2 54.

(

)

⎞_⎟⎟ t= ⎛

( )

−

( )

⎝ ⎜⎜ ⎞_⎠⎟⎟ = 12 8 345 2 54 12 2 2 54 3 375 2 15 . . . . .88g cm/ 2. © Schlumberger

(34)

Purpose

These charts are used to further correct the GR reading for various borehole sizes.

Description

Two components needed to complete correction of the GR reading are determined with these charts: barite mud factor (Bmud) and

borehole function factor (Fbh).

Example

Given: Borehole diameter = 6.0 in., tool OD = 33_⁄₈_{in., the tool}

is centered, mud weight = 12 lbm/gal, measured GR = 36 gAPI.

that value on the lower chart for Fbh versus

(dh– dsonde) on the x-axis. Move upward to intersect

the 33_⁄₈_{-in. curve, at which F}_bh_{= 0.81.}

Determine the new value of t using the equation from Chart GR-1:

The correction factor determined from Chart GR-1 is 0.95. Gamma Ray—Wireline

Scintillation Gamma Ray—3

3

_⁄

8

- and 1

11

⁄

16

-in. Tools

Gamma Ray Correction for Barite Mud in Various-Size Boreholes _{(former GR-2)}GR-2

1.2 1.0 0.8 0.6 0.4 0.2 0

Mud weight (lbm/gal)

7 8 9 10 11 12 13 14 15 16 17 18 19 20 1.2 1.0 0.8 0.6 0.4 0.2 0 Fbh 0 1 2 3 4 5 6 7 8 9 10 dh – dsonde (in.) B_mud

33_⁄₈_{-in. tool, centered} 111_⁄₁₆_{-in. tool, centered}

33_⁄₈_{-in. tool, eccentered} 111_⁄₁₆_{-in. tool, eccentered}

33_⁄₈_{-in. tool} 111_⁄₁₆_{-in. tool} GR t=Wmud ⎛

( )

dh −

(

dsonde

)

⎝ ⎜⎜ ⎞_⎠⎟⎟ 8 345 2 54 2 2 54 2 . . . = ⎛

( )

−

( )

⎝ ⎜⎜ ⎞_⎠⎟⎟ = 12 8 345 2 54 6 2 2 54 3 375 2 4 8 . . . . . g ccm/ 2. © Schlumberger

(35)

Gamma Ray—Wireline

Scintillation Gamma Ray—3

3

_⁄

8

- and 1

11

⁄

16

-in. Tools

Borehole Correction for Cased Hole _{(former GR-3)}GR-3

Purpose

This chart is used to compensate for the effects of the casing, cement sheath, and borehole fluid on the GR count rate. The correc-tion brings the cased hole count rate in line with the measured openhole GR count rate.

Description

In small boreholes the count rate can be too large, and in larger boreholes the count rate can be too small. The chart is based on lab-oratory work and Monte Carlo calculations to provide a correction factor for application to the measured GR count rate in cased hole

Find: Corrected GR value.

Answer:

Enter the chart at t = 10.95 on the x-axis. At the

inter-10.0 7.0 5.0 3.0 2.0 1.0 0.7 0.5 0.3 Correction factor 0 5 10 15 20 25 30 35 40 Scintillation Gamma Ray

33_⁄₈_{-in. tool} 111_⁄₁₆_{-in. tool} t (g/cm2₎ GR t=Wmud ⎛

( )

dh −

(

dsonde

)

⎝ ⎜⎜ ⎞_⎠⎟⎟ 8 345 2 54 2 2 54 2 . . . = ⎛

( )

−

( )

(36)

Purpose

This chart is used to provide a correction factor for GR values measured with the SlimPulse third-generation slim measurements-while-drilling (MWD) tool or the E-Pulse electromagnetic telemetry tool. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate openhole size. Interpolate between lines as necessary. At the intersection point, move hori-zontally left to the y-axis to read the correction factor that the SlimPulse or E-Pulse GR value was multiplied by to obtain the corrected GR value in gAPI units.

Gamma Ray—LWD

SlimPulse* and E-Pulse* Gamma Ray Tools

Bit Correction for Open Hole GR-6

11 10 9 8 7 6 5 4 3 2 1 0 Correction factor

8 9 10 11 12 13 14 15 16 17 18 19 6-in. bit 7-in. bit 8.5-in. bit 9.875-in. bit 12.25-in. bit 13.5-in. bit 17.5-in. bit GR *Mark of Schlumberger © Schlumberger

(37)

Gamma Ray—LWD

ImPulse* Gamma Ray— 4.75-in. Tool

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the ImPulse integrated MWD platform. These environ-mental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the ImPulse GR value was multiplied by to obtain the corrected GR value in gAPI units. 1.75 1.50 1.25 1.00 0.75 Correction factor

(38)

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the PowerPulse 6.75-in. MWD telemetry system and TeleScope 6.75-in. high-speed telemetry-while-drilling service. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The cor-rected GR value is used in the water saturation equation to compen-sate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the PowerPulse or TeleScope GR value was multiplied by to obtain the corrected GR value in gAPI units.

Gamma Ray—LWD

PowerPulse* and TeleScope* Gamma Ray—6.75-in. Tools

3.00 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 Correction factor

8 9 10 11 12 13 14 15 16 17 18 19

PowerPulse and TeleScope Gamma Ray

(39)

Gamma Ray—LWD

PowerPulse* Gamma Ray—8.25-in. Normal-Flow Tool

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the PowerPulse 8.25-in. normal-flow MWD telemetry system. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the appropriate correction factor that the PowerPulse GR value was multiplied by to obtain the corrected GR value in gAPI units.

5.00 4.75 4.50 4.25 4.00 3.75 3.50 3.25 3.00 2.75 2.50 Correction factor

8 9 10 11 12 13 14 15 16 17 18 19 9.875-in. bit 12.25-in. bit 13.5-in. bit 17.5-in. bit 10.625-in. bit 14.75-in. bit GR *Mark of Schlumberger © Schlumberger

(40)

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the PowerPulse 8.25-in. high-flow MWD telemetry system. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the PowerPulse GR value was multiplied by to obtain the corrected GR value in gAPI units. Gamma Ray—LWD

PowerPulse* Gamma Ray—8.25-in. High-Flow Tool

(41)

Gamma Ray—LWD

PowerPulse* Gamma Ray—9-in. Tool

Purpose

This chart is used to provide a correction factor for GR values measured with the PowerPulse 9-in. MWD telemetry system. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the PowerPulse GR value was multiplied by to obtain the corrected GR value in gAPI units.

8 9 10 11 12 13 14 15 16 17 18 19 17.5-in. bit 14.75-in. bit 13.5-in. bit 12.25-in. bit 10.625-in. bit 22-in. bit GR *Mark of Schlumberger © Schlumberger

(42)

Purpose

This chart is used to provide a correction factor for GR values measured with the PowerPulse 9.5-in. normal-flow MWD telemetry system. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the PowerPulse GR value was multiplied by to obtain the corrected GR value in gAPI units. Gamma Ray—LWD

PowerPulse* Gamma Ray—9.5-in. Normal-Flow Tool

(43)

Gamma Ray—LWD

PowerPulse* Gamma Ray—9.5-in. High-Flow Tool

Purpose

This chart is used to provide a correction factor for GR values mea-sured by the PowerPulse 9.5-in. high-flow MWD telemetry system. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The cor-rected GR value is used in the water saturation equation to compen-sate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the PowerPulse GR value was multiplied by to obtain the corrected GR value in gAPI units.

8.00 7.50 7.00 6.50 6.00 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 Correction factor

(44)

Purpose

This chart is used to provide a correction factor for GR values measured with the GVR resistivity sub of the geoVISION 63_⁄₄_-in.

MWD/LWD imaging system. These environmental corrections for mud weight and bit size are already applied to the gamma ray pre-sented on the logs. The corrected GR value is used in the water sat-uration equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the GVR GR value was multi-plied by to obtain the corrected GR value in gAPI units.

Gamma Ray—LWD

geoVISION675* GVR* Gamma Ray—6.75-in. Tool

2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 Correction factor

8 9 10 11 12 13 14 15 16 17 18 19 8.5-in. bit 8.75-in. bit 9.875-in. bit 10.625-in. bit 12.25-in. bit GR *Mark of Schlumberger © Schlumberger

(45)

Gamma Ray—LWD

RAB* Gamma Ray—8.25-in. Tool

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the RAB Resistivity-at-the-Bit 8.25-in. tool. These environ-mental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The corrected GR value is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the RAB GR value was multiplied by to obtain the corrected GR value in gAPI units.

(46)

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the arcVISION475 43_⁄₄_{-in. drill collar resistivity tool.}

These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The cor-rected GR value is used in the water saturation equation to compen-sate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the correction factor that the arcVISION475 GR value was multiplied by to obtain the corrected GR value in gAPI units. Gamma Ray—LWD

arcVISION475* Gamma Ray—4.75-in. Tool

1.75 1.50 1.25 1.00 0.75 Correction factor

(47)

Gamma Ray—LWD

arcVISION675* Gamma Ray—6.75-in. Tool

Purpose

This chart is used to provide a correction factor for GR values mea-sured with the arcVISION675 63_⁄₄_{-in. drill collar resistivity tool.}

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis to read the appropriate correction factor that the arcVISION675 GR value was multiplied by to obtain the corrected GR value in gAPI units.

3.50 3.25 3.00 2.75 2.50 2.25 1.75 2.00 1.50 1.25 1.00 0.75 0.50 Correction factor

8 9 10 11 12 13 14 15 16 17 18 19 8.5-in. bit 8.75-in. bit 9.875-in. bit 10.625-in. bit 12.25-in. bit GR *Mark of Schlumberger © Schlumberger

(48)

Purpose

This chart is used to provide a correction factor for GR values measured with the arcVISION825 81_⁄₄_{-in. drill collar resistivity tool.}

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis and read the appropriate correction factor that the arcVISION825 GR value was multiplied by to obtain the corrected GR value in gAPI units.

Gamma Ray—LWD

arcVISION825* Gamma Ray—8.25-in. Tool

(49)

Gamma Ray—LWD

arcVISION900* Gamma Ray—9-in. Tool

Purpose

This chart is used to provide a correction factor for GR values measured with the arcVISION900 9-in. drill collar resistivity. These environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs. The cor-rected GR is used in the water saturation equation to compensate for the shale in the formation.

Description

Enter the chart with the mud weight on the x-axis and move upward to intersect the appropriate bit size. Interpolate between lines as necessary. At the intersection point, move horizontally left to the y-axis and read the appropriate correction factor that the arcVISION900 GR value was multiplied by to obtain the corrected GR value in gAPI units.

(50)

Purpose

This chart is used to provide a correction that is subtracted from the borehole-corrected gamma ray from the arcVISION475 43_⁄₄_-in.

tool. Environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs.

Description

This chart is for illustrative purposes only. The indicated correction is already applied to the gamma ray log.

To determine the correction that was applied to the log output, enter the chart with the borehole size on the x-axis and move upward to intersect the downhole mud weight. From the intersection point move horizontally left to read the correction in gAPI units that was subtracted from the borehole-corrected data.

Charts GR-24 through GR-26 are similar to Chart GR-23 for different arcVISION tool sizes.

Gamma Ray—LWD

arcVISION475* Gamma Ray—4.75-in. Tool

Potassium Correction for Open Hole GR-23

100 90 80 70 60 40 50 30 20 10 6 8 10 12 14 16 18 0 Correction subtracted for 5-wt% potassium (gAPI)

Hole size (in.)

(51)

Gamma Ray—LWD

arcVISION675* Gamma Ray—6.75-in. Tool

Purpose

Description

This chart is for illustrative purposes only. The indicated correction is already applied on the gamma ray log.

50 45 40 35 30 20 25 15 10 5 0 Correction subtracted for 5-wt% potassium (gAPI)

Hole size (in.)

8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 9 ppg 8.3 ppg 10 ppg 12 ppg 14 ppg 16 ppg 18 ppg 20 ppg GR *Mark of Schlumberger © Schlumberger

(52)

Purpose

Description

Gamma Ray—LWD

arcVISION825* Gamma Ray—8.25-in. Tool

100 90 80 70 60 40 50 30 20 10 0 Correction subtracted for 5-wt% potassium (gAPI)

Hole size (in.)

(53)

Gamma Ray—LWD

arcVISION900* Gamma Ray—9-in. tool

Purpose

This chart is used to provide a correction that is subtracted from the borehole-corrected gamma ray from the arcVISION900 9-in. tool. Environmental corrections for mud weight and bit size are already applied to the gamma ray presented on the logs.

Description

To determine the correction that was applied to the log output, enter the chart with the borehole size on the x-axis and move upward to intersect the downhole mud weight. From the intersection point move horizontally left to read the correction curve in gAPI units that was subtracted from the borehole-corrected data.

120 100 80 60 40 20 0 Correction subtracted for 5-wt% potassium (gAPI)

Hole size (in.) 10 9 11 12 13 14 15 16 17 18 19 20 10 ppg 9 ppg 8.3 ppg 12 ppg 14 ppg 16 ppg 18 ppg 20 ppg GR *Mark of Schlumberger © Schlumberger

166487649 Schlumberger Log Interpretation Charts

Contents

Symbols Used in Log Interpretation

Estimation of Formation Temperature with Depth

Estimation of Formation Temperature with Depth

Estimation of R

and R

(

)

( )

( )

Equivalent NaCl Salinity of Salts

Concentration of NaCl Solutions

Resistivity of NaCl Water Solutions

Resistivity of NaCl Water Solutions

Density of Water and Hydrogen Index of Water and Hydrocarbons

Density and Hydrogen Index of Natural Gas

Sound Velocity of Hydrocarbons

Gas Effect on Compressional Slowness

Gas Effect on Acoustic Velocity

Nuclear Magnetic Resonance Relaxation Times of Water

Nuclear Magnetic Resonance Relaxation Times of Hydrocarbons

Nuclear Magnetic Resonance Relaxation Times of Hydrocarbons

Capture Cross Section of NaCl Water Solutions

Capture Cross Section of NaCl Water Solutions

Capture Cross Section of NaCl Water Solutions

Capture Cross Section of Hydrocarbons

EPT* Propagation Time of NaCl Water Solutions

EPT* Attenuation of NaCl Water Solutions

EPT* Propagation Time–Attenuation Crossplot

Scintillation Gamma Ray—3

⁄

- and 1

⁄

-in. Tools

( )

(

)

( )

( )

Scintillation Gamma Ray—3

⁄

- and 1

⁄

-in. Tools

( )

(

)

( )

( )

Scintillation Gamma Ray—3

⁄

- and 1

⁄

-in. Tools

( )

(

)

( )

( )

SlimPulse* and E-Pulse* Gamma Ray Tools

ImPulse* Gamma Ray— 4.75-in. Tool

PowerPulse* and TeleScope* Gamma Ray—6.75-in. Tools

PowerPulse* Gamma Ray—8.25-in. Normal-Flow Tool

PowerPulse* Gamma Ray—8.25-in. High-Flow Tool

PowerPulse* Gamma Ray—9-in. Tool

PowerPulse* Gamma Ray—9.5-in. Normal-Flow Tool

PowerPulse* Gamma Ray—9.5-in. High-Flow Tool

geoVISION675* GVR* Gamma Ray—6.75-in. Tool

RAB* Gamma Ray—8.25-in. Tool

arcVISION475* Gamma Ray—4.75-in. Tool

arcVISION675* Gamma Ray—6.75-in. Tool

arcVISION825* Gamma Ray—8.25-in. Tool

arcVISION900* Gamma Ray—9-in. Tool

arcVISION475* Gamma Ray—4.75-in. Tool

arcVISION675* Gamma Ray—6.75-in. Tool

arcVISION825* Gamma Ray—8.25-in. Tool

arcVISION900* Gamma Ray—9-in. tool

_⁄

_⁄

_⁄