Abstract
An original polymer technology, successfully used in Underground Gas Storage (UGS) wells, has been recently applied in offshore gas producing wells. Many gas wells in this area are facing combined water and sand problems due to reservoir depletion, water entries and clayey formation. To avoid critical problems connected to water/sand production, the most common action has been so far to reduce gas production by choking down the wells.
The new technique consists of bullhead injection of water soluble polymers with the main objective to form an adsorbed polymer layer on the surface of the rock, thus providing stabilization. In addition, the products have RPM properties (Relative Permeability Modifiers). They have little impact on gas permeability while strongly reducing water permeability. The combination of both effects will result in a reduction of water and sand production.
Laboratory studies were performed to optimize polymer formulation and evaluate flow properties in reservoir cores. Because of the low reservoir rock permeability (around 10-20 mD), high focus was put on polymer injectivity and RPM effects.
Since 2013, nine offshore gas wells have been treated with polymers. Treatments have shown positive results combining gas rate increase up to 100% and water reduction around 50% while stopping the sand. Details regarding well and polymer selection, job design, execution and production data are provided.
