Abstract
Abstract The effectiveness of frac-pack operations can be easily monitored by using radioactive tracers. The fluid and solid components of materials placed downhole can be tagged with different gamma-ray-emitting isotopes. After the pumping operations have been completed, specialized gamma ray logging sondes can be run in the well to establish the precise locations of the tagged materials. Directional gamma ray measurements determine the azimuthal placement distributions. Gamma ray spectral energy measurements allow the contributions of individual isotopes to be separated so that the vertical extent and radial displacement efficiency of the individual components pumped can be established. This technology can be used to evaluate frac-packs and most other downhole placement operations. The knowledge of where materials are actually placed during downhole pumping operations provides unique diagnostic information. This allows subsequent operations to be improved and made more effective as necessary. This paper reports on frac-pack operations in the shallow, unconsolidated sands of the Duri field in Indonesia. Gamma ray spectroscopy and directional gamma ray logs were run in several wells as part of a study to determine frac-pack performance. The gamma ray directional logs show a number of significant asymmetries where sand was apparently placed on one side of the wellbore. There was some evidence of "ballooning" in several zones where the frac-pack pushed the formation sand away from the borehole. The gamma ray spectroscopy logs offered supporting evidence which was confirmed by additional laboratory analysis. The interpretation of all the gamma ray log results confirmed the frac-pack operations. The log results also provided evidence regarding the detailed manner in which the frac-pack was placed and gave rise to some adjustments to enhance frac-pack procedures. This project demonstrated that frac-pack technology resulted in increased oil production and utilization of frac-pack operations will continue. However, maintenance requirements were not reduced as much as desired because of proppant flowback. Methods for further reducing costs are being investigated.
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