Gravel-pack damage removal in horizontal and vertical wells

Abstract

Abstract Gravel-packs can be damaged by a variety of mechanisms which include scale formation, fines migration, paraffin and asphaltene deposition resulting in a damage skin of 10-300. Frequently damage removal treatments do not remove this damage completely from all the producing zones, resulting in a short treatment life and/or inadequate production. This can be attributed to poor diversion and/or improper damage characterization. This paper focuses on several aspects of improved damage removal in gravel-packed wells. A methodology to assist in the proper identification of the damage mechanism and the design process for more effective treatments is presented. An integrated approach using an overall systems analysis coupled with log, water analysis and numerical simulations of the gravel-pack/matrix damage removal is recommended. A numerical model to simulate acid treatments of gravelpacked well is presented and used to evaluate several treatments performed on wells from the Gullfaks field in the North Sea. Results indicated greater than 75% of the damage is in the gravel pack. The model incorporates a detailed wellbore model integrated with a reservoir mode for simulation of acidizing treatments in horizontal and vertical gravel-packed wells. An algorithm for quantifying the damage in the gravelpack is discussed in detail. Various diversion techniques and fluid formulations are evaluated using the simulator and compared to field results with emphasis on pre and posttreatment production logs. The results of this study helped us establish guidelines for identifying the damage mechanism and in designing optimal treatments for matrix stimulation of gravel-packed wells.