RECOMMENDED LOGGING PROGRAM
In the past, too few logs were run, even after the advent of many of the modern logging and analysis techniques. Thus re-evaluation of by-passed reserves, definition of geological prospects, and seismic modeling suffer today for the false economy of the past. The best procedure to follow is to run a comprehensive suite of logs. Clearly there are economic constraints, such as in shallow gas or coal bed methane projects, where a full suite of logs is not helpful. You may be required to carefully tailor the log suite to suit the circumstances. Here are my recommendations.
CRAIN'S RECOMMENDED LOGGING PROGRAM
normal (fresh) mud systems, use:
The SP, gamma-ray, caliper, borehole volume integration, and sonic integration curves should be included on the induction sonic, and the caliper, gamma-ray, density correction, cable tension, and photo electric capture cross section (PE) should be included on the density-neutron. The newest version of each tool should be used, especially in overseas, offshore, or frontier locations.
Display both density porosity and neutron porosity on sandstone scale in sand-shale sequences, and limestone scale in carbonate sequences. Use dolomite scale sparingly and only in pure dolomite sequences.
extras in fresh mud include:
In salt mud, or high resistivity formation with fresh mud, replace or augment the induction with array or high resolution laterolog, with a microspherically focused log.
In fractured reservoirs, add the dipole shear sonic log with crossed dipoles and the resistivity image log to define fracture orientation and stress regime. Post-processing for fracture aperture and fracture porosity is recommended.
In radioactive reservoirs, add the gamma ray spectral log to distinguish uranium, potassium, and thorium.
In very shaly
sands, or in carbonates with micritic or highly varying pore
geometry, run a nuclear magnetic resonance log to determine
irreducible water saturation.
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