Utilizing a newly developed low density zero wash tracer carrier (1.1 - 1.5 gm/cc), acidizing treatments performed across large gross intervals consisting of thinly laminated carbonate/sandstone reservoirs have been more accurately diagnosed with respect to placement efficiency. Multi-isotope tracer in combination with spectral gamma ray logs are used to evaluate and optimize acid treatments involving various diverting processes (i.e., rock salt/benzoic acid; ball sealers). Acid diverter treatments are evaluated using multi-tracer spectral gamma ray logs and subsequent efficiencies shown. A new low density tracer carrier that allows more effective, safer transport and placement of the isotopes was used and significantly improved the log interpretation. Example case histories of acid treatments evaluated using the new low density tracer carrier will be presented for treatments done in Utah, U.S.A.

  1. Acid treatments performed in long multi-perforated intervals using various diverting techniques were shown to have different coverage distribution than expected or indicated by treatment pressures.

  2. A new low density tracer carrier provides a clearer log definition where multi-isotopes are used to define acid stage and diverter stage distribution.

Applications

Acid treatment diversion efficiency and effectiveness can be more accurately diagnosed with the new low density solid isotope carrier instead of previously used highly adsorptive liquid tracers. Actual treatment placement can be more specifically defined without problems caused by wellbore contamination using liquid tracers. Log definition was improved as well by using the new low density solid, as opposed to liquid tracers.

A new tracer carrier to allow improved evaluation of acid treatment placement using diverters has been used and demonstrated to be more reliable than other solid or liquid carriers.

A low density, specially sized, ceramic material was developed and used to contain multi-isotopes: Ir-192, Sc-46, and Sb-124, so they could be transported more easily in acid treatments to evaluate both stage and diverter placement efficiency. This carrier helps eliminate loss of isotope to tubular surfaces.

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