Published: 08/03/2010
Published: 08/03/2010
Underground gas storage wells in Italy created a major challenge for attaining high gas rates during completions because of multiple sand bodies with shale interlayers 0.5 to 3.0 m thick. Subhorizontal (slanted) drilling with openhole gravel packs or expandable screens was the standard choice for completing these wells. This strategy, however, worked only for completing a single sand body. Another problem occurred in the presence of shale—the openhole expandable screens could not be used in fine sand. To avoid reducing gravel-pack permeability due to shale erosion during the gravel placement, size 40 to 60 US Mesh sand had to be used, and the shale sections had to be isolated.
This area in Italy required an effective, reliable sand control completions technique for the long term that would provide optimal production from the gravel-pack zones. A chemical solution was preferred to stabilize the shale sections during gravel packing.
For three experimental wells, the brine used for gravel packing was treated with a shale stabilizer. The stabilizer was included in both the precompletions displacement fluid and the gravel-pack carrier fluid to prevent shale erosion and permanently stabilize the shale. A comprehensive laboratory study was performed to prove the strategy’s effectiveness for preserving shale during precompletions, completions, and postcompletions operations.
The openhole gravel pack with the shale stabilizer resulted in a complete pack for the three wells. Clear brine returns were confirmed by turbidity measurements and an X-ray diffraction analysis of the returned fluids.
The successful execution of the three gravel-pack treatments proved the effectiveness of the shale-stabilizing chemical for enhancing the hardness of the shale and avoiding erosion during gravel placement. This simple chemical technique provided an alternative to the use of expandable systems purely for shale isolation. It was easily incorporated into gravel-pack completions without negative impact on completions time.
The simple chemical technique enhanced the hardness of the shale, prevented erosion, and provided an alternative to the use of expandable systems purely for shale isolation.
Challenge: Find reliable gravel-pack completions technique for multiple-sand-body wells with shale interlayers.
Solution: Treat brine with a shale- stabilizing chemical to enhance hardness of shale and prevent erosion.
Results: Successfully packed wells while avoiding erosion. Easily incorporated chemical technique into gravel-pack completions with no negative impact on completions time.
