ABSTRACT:

An aggressive design and testing program to address a wide range of technical and environmental issues has been implemented specifically for optimizing frac-and-pack process in the Adriatic Sea in Italy. Three formulations of visco-elastic surfactants have been developed to improve productivity and reduce environmental issues in these dirty, unconsolidated sandstone reservoirs. The first applied visco-elastic surfactant (VES) carrier fluid utilized a cationic surfactant while the newly developed fluid systems utilize anionic and zwitterionic surfactants. Laboratory testing has focused on improving fracture conductivity, reducing formation damage, and complying with Italian environmental regulations. This paper describes the laboratory development and field use of an environmentally friendly VES system, which complies with current offshore Italian regulations. In formations with high clays content filtrate from cationic VES fluids exhibited low retained permeability due to surfactant adsorption on the clays. Methanol was added to these fluids to solve this problem, however environmental constraints requires methanol to be eliminated. Recent laboratory tests have proved that the newly developed anionic and zwitterionc VES fluids achieve excellent permeability recovery after backflooding without requiring methanol. The laboratory study was also performed to optimize the VES concentration as a function of the desired rheological and suspending properties. The zwitterionic VES could also be formulated with heavy brines (CaCl2) and seawater thus providing a significant cost savings.Results of this process confirm that environmentally friendly systems provide dramatically improved, cost effective fluids while reducing the environmental impact of VES application with alcohols. The paper will also present a field case incorporating details of execution and production results. The treatment process has been constantly reviewed to provide a more technical and environmentally acceptable service

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