Formation damage, causing a reduction in the permeability of a porous formation adjacent to a production/injection well, commonly occurs during drilling operations on a worldwide basis. This damage can fall into a number of categories (mechanical, chemical, biological) depending on the type of reservoir, drilling fluid and drilling practices used. This thesis provides a comprehensive overview of the wide range of different types of formation damage that can occur in various situations, and presents a detailed methodology for the screening and determination of which types of formation damage are most likely to impact well productivity or injectivity in a given situation. It also provides recommendations for the reduction of the impact of damage in these situations. Extensive discussion of the use of underbalanced drilling technology as a means to reduce formation damage during drilling operations is also presented. Some formation damage mechanisms, which this research has determined are unique to underbalanced drilling, are presented. A detailed screening protocol for evaluating whether underbalanced drilling is the most effective technology to use to reduce the impact of formation damage is also presented. It is shown that, in many cases, although superficially underbalanced drilling appears to be attractive, unless properly designed and executed, underbalanced operations may actually cause more damage and productivity/injectivity reduction than well-designed and executed conventional overbalanced technology in the same situation. The thesis provides a detailed flowsheet protocol for the rapid categorization and evaluation of drilling induced formation damage for various reservoir types and indicates the specific laboratory tests and procedures which should be followed in order to properly evaluate the severity of these damage mechanisms. Proper use of these procedures will allow a standardized evaluation procedure for the systematic evaluation and reduction of drilling induced formation damage in a wide variety of common drilling applications.
Bibliography: p. 424-448