FE 02-11 Intro to Wireline Logging

Nội dung text: FE 02-11 Intro to Wireline Logging

1. Wireline Logs (E-logs) • An indirect analysis of downhole formation features by electronic methods
2. Caliper Log • Measures the inner diameter of the borehole • Variations in borehole diameter are important in wireline log interpretation
3. Spontaneous Potential Log (SP) • Indicates the permeabilities of rocks in the well by measuring the amount of electrical current generated between the drilling fluid and the formation water that is held in pore spaces of the reservoir rock • Recorded in millivolts vs. depth • Porous sandstones with high permeabilities tend to generate more electricity than impermeable shales
4. Resistivity Logs • Determines what types of fluids are present in the reservoir rocks by measuring how effective these rocks are at conducting electricity • Resistivity is the inverse of conductivity • Resistivity is expressed in ohm-meters • Conductivity is expressed in ohms/meter
5. Types of Resistivity Logs • Lateral Focus Log – Sends a current outward to a rock – Accurate in measuring thin beds • Induction Log – A current is induced in formation beds by a magnetic field – Accurate in measuring thin beds • Microresistivity Log – Shows resistance very close to the wellbore – Has 2 curves (one for filter cake resistivity and one <0.5 ft into the formation) – If 2 curves not equal: invasion
6. Density Logs • Also called Formation Density Compensated (FDC) or Litho Density Log (LDL) • Bombards formation with Gamma Rays • Denser formation (less porous): absorbs more Gamma Rays • Determine porosity by measuring the density of the rocks • Overestimate the porosity of rocks that contain gas they result in "crossover" of the log curves when paired with Neutron Logs
7. Dipmeter Logs • Determine the orientations of sandstone and shale beds, faults and fractures in the borehole • Old dipmeters: measured the resistivity of rocks on at least four sides of the borehole • Modern dipmeters: actually make a detailed image of the rocks on all sides of the borehole – Borehole scanners, USI: use sonic – FMS (Formation microscanner) and FMI (Formation micro-imager): use resistivity – STAR: uses sonic and resistivity
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