Interactions between fractures in adjacent horizontal wells and development of methods for mitigating their costly negative effects has become the focus of much discussion and debate within the fracturing community. The impetus for this attention has been the impact of these interactions on productivity and mechanical integrity of these wells. Faced with these challenges, a group of 15 subject-matter experts representing different parts of the fracturing community held a 2-day meeting in December 2018 for a very open and confidential discussion of the technical foundation of the various aspects of the subject: what are the root causes of these interactions, their types, consequences, industry experience with various mitigating actions, and what has worked and what has not. At the conclusion of the meeting, the group decided to prepare a report of its deliberations and make it available as a service to the industry.
Soon after the start of the discussions, the group recognized the multiplicity of terms used for each of the various aspects of the subject. Furthermore, these terms were viewed to be vague and without a descriptive technical foundation. Having been developed during the early days of discovery of these events, they generically identified them as problems with minimum regard to the technical roots of their occurrence, variations in their types, or cause-and-effect relationships that may exist between the type of events and their impact on well productivity or mechanical integrity. Development of proper technically-based terms and their definitions were the first outcome of the group’s deliberations. The terms defined below are reflective of the relevant applicable technologies and are intended to be descriptive of the physical events that occur during these events that control their behavior. It is the group’s hope that use of these terms will increase clarity and accuracy to the extensive technical content currently devoted to this subject.
To start with, the term “frac-driven interaction (FDI)” was recommended for defining the broader overall subject. This term is offered as replacement for “frac hit,” “frac bashing,” “frac intersection,” etc., all of which have a negative connotation. It was argued that a neutral term is more suited for describing these events, since all FDIs do not harm adjacent passive wells. Some of them can in fact provide valuable information about engineering characteristics of the created fractures and detecting their existence and identifying their type can serve a useful purpose by offering the information needed for the next generation of fracturing treatments. Additionally, the term “frac hit” projects an unnecessarily negative impression to the public, environmental groups, and state and federal regulating agencies.
The definitions offered to identify the status of wells and fracturing are listed below.
Active well. The well where fracturing (or refracturing) operations are currently taking place.
Passive wells. Wells offset to the active well. These wells may be shut in and their pressure monitored for diagnostic purposes. In practice, these wells are often already fractured.