Fiber-Enhanced Visco-Elastic Surfactant Fracturing Enables Cost-Effective Screenless Sand Control

Abstract

Abstract Many gas reservoirs in the Adriatic Sea, offshore Italy, are formed of laminated, low permeability dirty sandstones, requiring gravel packing for sand control. Numerous gravel-packed wells are either sanded up and shut in, or are underperforming due to fines plugged gravel-pack screens, which cannot currently justify the expense of an immediate and cost-prohibitive full rig workover. Frac and packs are performed to increase productivity bypassing near wellbore damage, interconnecting multiple sandstone layers and decreasing fluid velocities in the formation, thus reducing fines production. Significant interest exists to enhance fracture performance, deferring and reducing re-completion costs. This paper discusses various rigless performed rehabilitations of failed sand control completions, highlighting the evolution of fracture fluid selection, optimization of the fracture placement and achieved geometries with seawater-based visco-elastic surfactant fluids and the use of speciality glass fibers for fracture pack stabilization and enhanced proppant transport. This combined rehabilitation technique enabled screenless sand control completion and is allowing low cost rehabilitation of plugged or failed sand screens and the development of any numbers of gas layers which otherwise could not be drained using conventional sand control technologies. This completion technology potentially allows to significantly adding gas or oil reserves, the development of the normally by-passed upper gas layers, which would require costly workover re-completion using conventional technologies. Procedures, experiences and results are presented, validating the -enhanced visco-elastic surfactant fracturing concept enabling screenless sandface completion for controlling sand production. Rigless rehabilitation has confirmed being an efficient solution and allows cost-effective production increase. Background Evaluation of numerous fracturing treatments performed in the Adriatic Sea, confirmed the selected fracturing methods and fluids used were not optimizing gas production. In-depth analysis of past fracture performances showed that the conventional frac fluids in use cannot create the fracture geometries needed - wide and short - to produce the Adriatic Sea reservoirs effectively. Required mature tip-screen-out fractures are not obtainable with brine and polymer-based fluids; and fracture geometries are unfavorable in respect to fracture length and width - brine created fractures were not sufficient, HEC fluids generated fractures were too long and too narrow, for effective gas production. Table 1 summarizes the results of the analysis using brine, HEC and the industry's first visco-elastic (VES) fracturing fluid (ClearFRAC) during fracturing lithologically similar nearby Emma gas field and the application of the visco-elastic fracturing fluid - also called VES - results accomplished on Giovanna gas field.