Shaly sand cross-plot: a mathematical treatment

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Log Anal.; (United States)

OSTI ID:7239843

Krug, J A ^[1]; Cox, D O

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1. Colorado School of Mines, Golden

The evaluation of shaly sand formations can be made using any paired combination of density log, neutron log, and acoustic log. Given two different logs, the log equations may be solved simultaneously for the effective porosity and shale percent. However, this method is tedious when hand calculating a shale/sand sequence; an alternative approach of cross-plotting the data and graphically solving the equations is usually followed. The cross-plot technique has the disadvantage of at times also being tedious and insufficiently precise. Therefore, an analytical technique resulting in an easily used equation for porosity and shale percent is desirable. These equations are obtained by mathematically describing the shaly-sand cross-plot. The derivation of the porosity and shale percent equations is presented in the following section assuming 100 percent water saturated sand. The following two sections present the derivation for a gas or light hydrocarbon correction in clean sands and in shaly sands. The density-neutron log combination is of primary concern in this paper and only this cross-plot will be discussed. However, the same derivation technique and calculation procedures discussed here are applicable to the other log combinations.

• OSTI ID: 7239843
• Journal Information: Log Anal.; (United States), Journal Name: Log Anal.; (United States) Vol. 17:4; ISSN LGALA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
440400 -- Well Logging Instrumentation
47 OTHER INSTRUMENTATION
DATA ANALYSIS
GAMMA-GAMMA LOGGING
GEOLOGIC DEPOSITS
METAMORPHIC ROCKS
NEUTRON LOGGING
PETROLEUM DEPOSITS
POROSITY
RADIOACTIVITY LOGGING
RESOURCES
ROCKS
SAND
SHALES
WELL LOGGING