Micro-Spherically Focused Log (MSFL™) and Microlog (ML)
The MSFL tool is a pad-type miniature version of the
SFL (Spherically Focused Log) that was developed to
eliminate borehole effects and achieve superior
shallow investigation. The MSFL tool is a stand-alone
logging tool that is wired to be placed anywhere in
the logging tool string. Included in the MSFL tool
string is a ML log that makes two resistivity
measurements, a 2-in. normal and a 1.5-in. lateral. A
caliper measurement of the borehole is also provided
along with the MSFL tool log.
MSFL and ML Tool Features
The MSFL and ML tools contain the following
The MSFL tool measures voltages that represent
five analog parameters:
– MSFL tool survey current (IA)
– MSFL tool survey voltage (VE)
– Caliper potentiometer voltage (CALP)
– Microlog lateral (MINV)
– Microlog normal (MNOR)
The MSFL tool measurement involves only the first
few inches of the formation immediately adjacent to the borehole,
the flushed zone (Rxo), in which drilling fluid has displaced
all formation fluids. Electrodes for the MSFL are imbedded in
a insulating pad mounted on a powered caliper arm
The Microlog has three electrodes spaced 1-in.
apart and positioned vertically on an insulated pad. The microlog
senses the presence or absence of mudcake. The measured voltage
at the 2-in. button and the differential voltage between the 1-in.
and 2-in. buttons are linearly related to the formation resistivity.When
mudcake forms adjacent to permeable formations, mud invasion causes
negative separation in high porosity sands between the 1.5-in.
lateral and the 2-in. normal
MSFL™ and ML Tool Benefits
The MSFL and ML tools offer the following benefits:
The MSFL tool provides a measurement of the flushed
zone resistivity (Rxo) with low mudcake correction. The Rxo is
used in the computation of moved out hydrocarbons
The Microlog provides qualitative estimate of
permeability. Permeable zones allow mud filtrate to invade the
formation, which results in mudcake buildup. Zones that are not
permeable do not allow mud filtrate to invade the formation. Such
zones have no mud cake. The permeability estimates help in making
well completion decisions
Standard MSFL log example from a sequence of high
resistivity carbonate formation and limy shales.
Field example of Microlog.