Sand production is a common problem with unconsolidated formations. It is very challenging to successfully remove formation sands with conventional methods in a large deviated wellbore with a low pressure gradient formation1 .
Since 1995, a technology combining concentric coiled tubing (CCT) with a jet pump has been developed and used to remove both the drilling fluids and solids. Initially it was developed for horizontal heavy oil reservoirs where pressures are low and viscosity is high, without placing hydrostatic loads on the reservoir. The job data from more than 600 sand/well vacuuming operations worldwide has been compiled into a database.
This paper reviews the well information and the key operating parameters: maximum depth, bottom hole pressure gradient and pump rate. The engineering challenges, best practices and lessons learned for the sand/well vacuuming process are also summarized. Analysis of this data yields a better understanding about this vacuuming technology and provides good guideline for future practice.
Case histories are provided which demonstrate how to deploy the different sand/well vacuuming bottom hole assemblies (BHA), to; increase the penetration capacity with a jetting tool; entering multi-laterals with an entry guidance system; accessing small size holes with a micro-vacuuming tool; and to achieve extended reach under extreme conditions.
Post job analysis indicates CCT vacuuming technology reduces the skin damage and increases the production compared to non-vacuumed wells. Moreover, the details from sand and other fluid influx profiles obtained along the wellbore based on the analysis of the returns during the vacuuming process, could be used to evaluate well production and assist in formulating a management strategy.