Screenout Detection and Avoidance

Abstract

A screenout (SO) event is defined as premature termination of a propped hydraulic fracture (PHF) treatment due to bridging of the proppant at a restriction, usually located at the near-wellbore area or at the perforations—and not at the perimeter tip of the fracture. Numerous Screenout Detection (SD) methodologies have been presented over the past 60 years which are designed to predict the likelihood of a SO event based on analysis of minifrac data, or real-time data—during the mainfrac. Three simple SD and numerous screenout avoidance (SA) methods are presented. The SD methods are: enhanced fracture entry friction (FEF) analysis, median ratio (MR) and inverse slope (IS). Analyses with the first two methods require data from a step-down test (SDT), while the third method uses data which are analyzed in real-time during the mainfrac. By knowing the potential for a SO event or by having advance warning of the onset of a SO event, one is able to apply design modifications for the mainfrac, or is able to initiate abrupt, or incremental step displacement (flush) and achieve SA, or to extend the PHF treatment to improve placement by attaining increased net-pressure gain. The theory and logic of the SDT and of the three methods includes discussion on: the balloon analogy, stagnation pressure, fracture toughness and fracture tip dilatancy. Both the MR and the IS methods do not require a computer or software and all three methods are very easy to use at the well location by the on-site engineer. All three methods are very inexpensive. Numerous publications have dealt with SA over the past 70 years, and have presented design modification procedures, and wellbore intervention procedures, which are presented briefly. These procedures when implemented individually, or in combination, have proven to be very useful in: Preventing SO events, achieving positive SA outcomes, by enabling the safe and effective placement of PHF treatments.