Fisher, Kevin, ProTechnics, Kessler, Calvin, Halliburton Energy Services, Rambow, Fritz, Shell EP Technology Applications and Research, Tucker, Charles, Shell Exploration and Production Company, Madigan, William, Multiphysics Numerical Research Group
Completions in poorly consolidated formations often require gravel packing or frac packing to eliminate the inflow of formation fines. The effectiveness of gravel placement in the screen-casing annulus or openhole annulus or behind casing (such as when prepacking perforation tunnels) may be qualitatively evaluated with treatment-pressure data. Voids in the gravel-packed screen-casing or openhole annulus are evaluated with data from density, neutron, gamma-tracer, or pulsed-neutron logs. When radioactive materials are used for evaluating proppant placement in the formation, however, gamma measurements are affected by the background signal produced by these materials. This signal makes conventional density and pulsed-neutron silicon-activation techniques ineffective.
A high-resolution, memory gamma-gamma density logging tool has been developed that measures changes in the bulk density of the annular region of a gravel-pack completion. The source-to-detector spacing and source strength have been optimized to minimize the effects of variations in borehole fluid and of changes in casing-screen size and geometry. Most importantly, this measurement will not be affected by the presence of radioactive tracers used to evaluate proppant placement.
The new memory-based logging system allows the tool to be placed in the washpipe prior to the completion and for the logging pass to be recorded as the washpipe is retrieved from the well. Significant savings in rig costs and in time to production are gained through use of the washpipe-conveyed memory logging technique. This paper reviews the measurement principles of the tool and presents data from tests in calibration pits.