Oil production from the Llanos foreland basin in Colombia is seriously affected by sand production and high water cut. Sand production has been successfully controlled with horizontal openhole gravel packs; however, early water breakthrough causing water cuts as high as 90% remained a challenge. As a result, operators were forced to shut down some new wells just a few months after placing them on production. A new production logging approach was performed in five horizontal Hocol S.A. (subsidiary of Ecopetrol) wells. In terms of reservoir behavior, the results revealed the following:

• Even if a well was drilled across the same formation, productive sands were identified that would behave differently.
• Some reserves were not produced as a result of formation heterogeneity in the varied sands.
• Despite effective water control by inflow control devices in the gravel-packed wells, production reserves remained behind.

With this new challenge in mind, a new sand control completion was developed with the following objectives:

• Ensure complete annular gravel pack for effective sand production control.
• Create compartments along the horizontal openhole section to improve drawdown management in the various sands.
• Produce each productive sand selectively to characterize and evaluate the full potential for each zone.

The completion used a multizone, single-selective horizontal openhole gravel pack. The design was based on shunt-tube technology with swell packers as external isolation and a hybrid inner selective string design. The most innovative element of this completion was gravel packing of the entire completion to provide sand management, while offering the benefits of inflow control devices for water breakthrough management and selectivity. During the completion operation, the gravel-pack assembly was run and the rapid swelling swell packers were swelled using a new swelling fluid that allowed the swelling to take place before gravel packing the well. Once the swell packers were swelled, the gravel-pack operation began and it was confirmed that every segment was gravel packed, even after the swell packers were in place, thanks to the implementation of downhole gauges throughout the completion. Once the well was completed, the production group installed selective production and inflow control strings to produce the well.

The first completion installation was performed in July 2013. The operator performed characterization tests for each productive sand, with results for each sand indicating successful zonal isolation. The results also provided valuable data for reservoir characterization and selection of reservoir management strategies. The addition of new reserves confirmed the value and effectiveness of this new completion technology and its application.