Neutron logs

Figure 4-282 shows a typical comparison of wireline and MWD gamma ray and neutron logs in a borehole in excellent hole conditions. The MWD/LWD log matches the wireline log almost perfectly. 

Porosity and Lithology Determination from Litho-Density Log and CNL Compensated Neutron Log... 

Figure 4-303. Porosity and lithology determination from the Litho-Density logs and the CNL Compensated neutron log. Courtesy Schlumberger.) ( trade mark of Schlumberger.)...

Neutron. The neutron porosity values recorded with most tools match closely the wireline thermal neutron logs in the lower porosity ranges (under 25 porosity units). In high porosity zones, the LWD neutron porosities lie between thermal and epithermal wireline values. 

Muller N., RamakrishnanT.S., et al. Time-lapse carbon dioxide monitoring with pulsed neutron logging. 2007 International Journal of Greenhouse Gas Control 1 456-472. 

Neutron porosity For the neutron log, the hydrate response is nearly the same as liquid water. Hydrate is 6% higher than fresh water, somewhat more than that for salt water. Both differences... 

Porosity data can be obtained from laboratory measurements on sidewall samples and core samples from boreholes (e.g. Monicard, 1981), from geophysical well logs (sonic, density and neutron logs Serra, 1987) or from seismic data. 

Fluid saturation, which defi nes oil-water contact, was determined using wireline log interpretation and RFT data. Shaliness was obtained through density/neutron log data and the salinity of the formation water was analysed from RFT sampled water. Additional parameters used in the calculation, such as saturation and cementation exponents (n and m, respectively), and tortuosity coefficient (a), were measured in the laboratory. 

Neutron logs (37) have been used to determine changes in the liquid... 

Sonic and neutron logs from the EFU 41R well showed a gas effect in the lower 3 m of the Ramsey 1 sandstone, the same interval in which the calcite-cemented layers occur (Fig. 2). No... 

Fig. 2. Gamma-ray, neutron and density logs from the East Ford Unit 41 R well. The neutron log shows a gas effeet in the lower Ramsey 1 sandstone below the uppermost calcite-cemented layer.

An automated data collection system (DCS) of approximately 6(XX) channels continuously records the readings of the various sensors on an hourly basis. The DCS scans and records the readings of temperature, humidity, pressure, MPBXs, strain gages, convergence monitors, and current and voltage for heater power. The measurements made by the DCS are referred to as passive monitoring. Other measurements such as ERT, neutron logging, GPR, acoustic emissions, REKA probe, and others are made periodically (every few weeks to few... 

In specific circumstances magnetic susceptibility (alteration of magnetic minerals), IP (clay and sulphide mineral changes) and gamma-ray spectrometry logging may be warranted and useful. Delayed neutron logging has been developed that permits direct measurement of uranium in the borehole—an expensive logging technique of particular value in development activities. 

Pulsed neutron logging is a technique that is generally confined to use in cased holes as opposed to open holes, that is, after the casing is set in the bore hole. It is particularly useful for providing information on porosity and fluid composition and is used to monitor... 

Sommer, F. S. and Jenkins, D. R Channel Detection Using Pulsed Neutron Logging in a Borax Solution, SPE Asia Pacific Oil gas Conference Exhibition, Singapore, February 8-10,1993 (SPE 25383). 

Density, nuclear cross-sections (gamma-gamma-density, neutron log), natural gamma-intensity, nuclear magnetic resonance response... 

CNL Compensated Neutron Log and Litho-Density Tool (freshwater in invaded zone)... 

ElUs, D., Case, C.R., Chiaramonte, J.M., 2003. Tntorial porosity from neutron logs 1 measurement. Petrophysics 44 (6), 383-395. 

Gilchrist, W.A., 2009. Tutorial cmnpensated neutron log response issues. Petrophysics 50 (5), 416 26. 

McNally, G.H., 1987. Estimation of coal measures rock strength using sonic and neutron logs. Geoexploration 24, 381-395. 

Neutron logs. A radioactive somce is transported within the sonde, and the neutron bombardment causes emission of gamma radiation in proportion to the hydrogen content of the formation. As nearly all the hydrogen is present in the fluids, but not in the minerals, the neutron log determines the porosity of the rock. Since not all the pore space is open to flow (some pores contain fluid sealed in by diagenesis) the neutron derived porosity is an upper bound on the flow-related porosity. Neutron logs can be used in cased holes. 

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