VES Fluid Allows Minimized Pad Volumes and Viscosity to Optimize Frac-Pack Geometry: Completion Type Evolution in Barbara Field, Central Adriatic Sea

Abstract

Abstract When frac-packing near contacts with undesirable fluids, fracture height growth must be minimized. Likewise, when fracturing relatively low-permeability gas sands, the required tip-screenout event may be difficult to obtain due to excessive fluid efficiency leading to excessive fracture growth. One technique to address both of these problems is the use of non-viscosified brine as a fracturing fluid (i.e., water-fracturing). Water-fracturing limits fracture growth due to its high leakoff, and allows pad volumes to be minimized because proppant concentrations are maintained at low levels throughout the treatment. However, the technique does suffer in that the proppant carrying ability of water does not allow proppant concentration to exceed about 2.5 – 3 PPA. This constraint can lead to reduced near-wellbore fracture conductivity as compared to a properly executed frac-pack using crosslinked fluids. A fluid that has good leakoff and good proppant carrying capacity will provide the opportunity to bridge the gap between water-fracturing and crosslinked gel frac-pack operations. A new generation visco-elastic surfactant (VES) fluid provides this opportunity. The Barbara field in the Adriatic Sea is a shallow dry gas field and formation sand has to be controlled with gravel pack. It was originally completed with standard gravel packing procedures, which were migrated to water-fracturing techniques during the mid-1990's. While this completion method proved successful, it was desired to increase fracture conductivity while continuing to control fracture geometry. The use of a low-concentration VES fluid allowed such optimization of the frac-pack process, leading to significant productivity improvements. This paper reviews the evolution of completion techniques in the Barbara field that has led to these productivity improvements.