Log Type Log Name Curve Characteristics Interpretation Lithology Logs Gamma Ray & Spontaneous Potential (SP) Deflection to the right Shale Deflection to the left Sand Resistivity Logs Deep Resistivity High Hydrocarbons Tight Streaks Low porosity Low Shale Wet Sand Separation between the resistivities Formation and drilling fluids are different Formation is permeable Porosity Logs Density … Continue reading Short Cut Interpretation
Tag: Wellbore Evaluation
Micro-Resistivity
These logs are capable of detecting formations less than 1.0in. thick, if the mud cake is very thin. Micro-laterologs can be used in salt muds and high resistivities. Their response will be affected by mud cake greater than 3/8" thick. Typically used to measure Rxo and determine permeable beds by detecting mudcake. Limitations Shallow invasion … Continue reading Micro-Resistivity
Short Spaced Resistivity
Short Normal The usefulness of the curve will be determined by the vertical resolution. The short normal (SN) is useful as long as the contrasts between the drilling fluid and formation resistivities are not too great. Resistivity beds will appear thinner by the arm spacing (16ins.), and conductive beds appear thicker by the same amount. … Continue reading Short Spaced Resistivity
Gamma Ray
Measures the natural resistivity of the formations in the borehole. Good for the identifying lithology and correlation purposes. The GR log usually reflects the shale content of the formations because of the concentrations of radioactive materials in the shales/clay. Shale free sandstones and carbonates have low gamma ray values unless contaminants are present. They are … Continue reading Gamma Ray
Spontaneous Potential (SP)
Spontaneous Potential (SP) This is a record of the direct current voltage differences between the naturally occurring potential maintained by a movable electrode in the borehole and a fixed potential located at the surface. The potential is as a result in the difference between the salinity of the drilling and formation fluid. The SP log … Continue reading Spontaneous Potential (SP)