LECTURE 21

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lecture 21- Well Logging
Hoa Truong
Mind Map by Hoa Truong, updated more than 1 year ago
Hoa Truong
Created by Hoa Truong over 9 years ago
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Resource summary

LECTURE 21
  1. WELL LOGGING
    1. Conventional Logs
      1. Spontaneous potential (SP)
        1. Measures natural electric potential, porosity, well correlation
        2. Resistivity (LLD and LLS)
          1. measure: electric resistivity, deep+shallow logs (flushed zone vs. virgin zone), pemeability, pore fluid type
          2. Gamma-ray (GR)
            1. measure: decay of natural radioisotopes, lithology, grain size, well correlation
            2. Sonics (DT)
              1. Measure: slowness of rock, lithology, porosity
              2. Caliper (CAL)
                1. Measure: borehole diameter, washouts, mudcake, stress-induced failure
                2. Neutron (NPHI)
                  1. measure: hydrogen atoms (water content), lithology, porosity
                  2. Density (RHOB)
                    1. measure: electron density, bulk rock density, lithology, porosity
                    2. Dipmeter
                      1. measure: orientation of dipping surfaces, structural+ stratigraphic analysis
                      2. Measurement/logging while drilling (MWD/LWD)
                        1. log measurement detector can also be mounted in the drill colars behind bit
                          1. Pros: real-time logging while drilling, minimise invasion effects, safer, easier, possible in horizontal/deviated well
                            1. Cons: some not as high quality as wireline logging
                          2. Measurement of physical properties of rocks+fluids vs. depth in a well
                            1. many logs to identify rock types, porosity, oil/water filled
                              1. wireline logging
                                1. housed in pipe (protection), several assemble tools, cable for power+send data back
                                  1. data records as tool move up+down holeat maintain speed to measure depth (200-2000m/hr)
                                  2. Logging truck
                                    1. mounted with cable, winch, depth measurement + computerise record + processing equipment
                                    2. reading: measured property/volume (dimension of volume control: resolution, radius of investigation)
                                    3. Specialist Logs
                                      1. High resolution electrical + acoustic logs
                                        1. pseudo-images of borehole walls
                                          1. high resolution image of borehole: sedimentary structure, fractures, irregularities
                                          2. Small-scale structural + stratigraphic analysis
                                            1. Stress-induced failure of borehole (collapse)
                                              1. Drilling-induced fractures (fluid loss)
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