| Popis: |
Controlling fluid losses to the formation, both before and after completions, is critical to optimizing production. Fluid-loss control can be achieved through the use of either mechanical or chemical means. Chemical methods control losses to the formation by increasing the base fluid viscosity with linear or crosslinked polymers or by forming a low-permeability filter cake on the formation face. However, performance limitations have prevented the use of such traditional ‘pills’ in high-stress environments, i. e., those that include high temperature, high density, low pH, high differential pressure, and high concentrations of divalent cations, Zn2+ and Ca2+. These limitations result in accepting excessive losses or employing less-than-ideal methods. This paper describes fluid-loss pills developed for high-stress applications for both solids-free and solids-laden systems. Among the new developments are linear gel-based fluids stable at high temperature for extended periods. For example, we present data on HEC-based fluids stable at temperatures as high as 300°F and in densities in excess of 16.5 lbm/gal. Solids-laden pills are presented that have been field tested under severe conditions including high-density zinc brines up to 18.7 lbm/gal and temperatures up to 325°F. Laboratory data are provided that demonstrate effective fluid-loss control for at least 5 days under these extreme conditions. Formation damage and filtercake cleanup results are included. Several solids-free and solids-laden systems are documented through both lab and field case histories. |
