TRACERS FACILITATE STIMULATION JOB EVALUATION
Radioactive Tracers Facilitate Stimulation Job Evaluation
Logging tools can now quantify multiple isotopes, including the volume of individual isotopes present and their radial position away from the wellbore. In conjunction with those improvements, tracers have been developed that eliminate “wash off” effects of conventional tracers. By precisely locating the presence and concentration of traced proppant at the wellbore, better evaluations can be made of vertical and radial proppant distribution near the wellbore and fracture aperture width.
A comprehensive study of 98 wells with 136 fracture stages in four different basins has been completed. Each stage was traced and logged. Spectral gamma ray logs were compared with conventional openhole logs, sonic stress logs where available, and cased hole logs such as cement bond and production logs. This data was then compared on a well-by-well basis with the fracture design program, post treatment stimulation reports, and production history.
Several trends were identified while building this massive stimulation evaluation database. Problems that potentially could be solved using tracer technology are:
- Fracture height greater than design
- Unstimulated perforation sets within a stage
- Understimulated pay intervals