Fundamentals of log analysis. Part 6 -- Determining basic log analysis parameters: a, m, n and R{sub w}

Journal Article · Sun Dec 01 04:00:00 EST 1996 · World Oil

OSTI ID:415704

Hunt, E R; Pursell, D A; Aly, A M ^[1]

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1. S.A. Holditch and Associates, College Station, TX (United States)

This article will discuss novel approaches to determine basic log analysis parameters a, m, n and R{sub w}. These parameters are not universal and must be determined for each field study. The generalized form of Archie`s equation is S{sub w}{sup n} = aR{sub w}/{phi}{sup m}R{sub t}. As one can see, water saturation is a function of formation porosity ({phi}), formation resistivity (R{sub t}), cementation exponent (m), saturation exponent (n), a constant (a) and formation water resistivity (R{sub w}). Porosity is calculated from a combination of sonic, neutron and density logs. Formation resistivity (R{sub t}) is determined from either the dual laterolog or dual induction log. Parameters a, m and n are formation properties and ideally would be determined in the lab. Because this is cost prohibitive, other techniques are used to find values for these parameters. Formation water resistivity is determined using various techniques. Knowledge of basic parameters is essential when determining water saturation. Often, quick look log analysis involves assuming known values for a, m, n and R{sub w}, and reading average values of {phi} and R{sub t} from well logs. Relatively small errors in a, m, n and R{sub w} will cause large errors in calculated water saturation.

• OSTI ID: 415704
• Journal Information: World Oil, Journal Name: World Oil Journal Issue: 12 Vol. 217; ISSN 0043-8790; ISSN WOOIAS
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
DATA ANALYSIS
ELECTRIC CONDUCTIVITY
POROSITY
RESERVOIR FLUIDS
RESERVOIR ROCK
SATURATION
WELL LOGGING