Abstract
Single-selective gravel pack completions with zonal isolation can be very expensive particularly in offshore environment where rig costs are high. Conventionally, such completions involve perforating and gravel packing of each zone separately, with multiple trips in and out of the hole. A typical procedure consists of the following 6 round-trips excluding a wire-line trip to set the sump packer and running in hole with the production tubing: (1) Perforating the lower zone, (2) Gravel packing the lower zone, (3) Running and setting the packer plug to isolate the lower zone, (4) Perforating the upper zone, (5) Retrieving the packer plug, (6) Gravel packing the upper zone, with a GP assembly that includes an isolation assembly for lower zone. The first two trips can be combined into one trip by using a single trip perforating and gravel packing system, reducing the number of round trips to 5. In addition, fluid loss control pills are quite often required after perforating.
In this paper, we present a new technique for single selective sand control completions in cased holes that allows perforating and gravel packing of both zones with a zonal isolation device between the zones bypassed through shunt tubes for gravel packing the bottom zone. This procedure reduces the number of round-trips from 6 (compared to conventional) or 5 (compared to single trip option for the lower zone) to 1, saving a minimum of 4 round-trips, in addition to eliminating fluid loss control pills throughout the whole operation. This technique has recently been used in an BP-Amoco well in Trinidad where the lower zone is expected to water out sooner than the upper zone and the production is commingled. This application resulted in 17% savings to BP- Amoco in completion costs, in addition to an increase in production from 800 bopd to 1,200 bopd. Details of the tool modifications and the field application (design, execution and evaluation) are discussed along with an economic comparison to earlier practices.
