Barite-Sag Management: Challenges, Strategies, Opportunities

Abstract

fax 01-972-952-9435. AbstractBarite sag continues to be a recurring, potentially serious problem on many directional wells. Despite concerted efforts by the drilling industry and early progress, recent continued improvements in sag mitigation have been limited. Sag is a particular problem on HTHP wells and in deepwater wells where ECD management is required. These wells pose difficult drilling conditions where drilling practices may offset sag-management advancements.The sag "magic bullet" has thus far been elusive. This is understandable since sag is affected by many parameters and their interactions are difficult to quantify. While the importance of mud rheology is well known, attempts to find the key rheological parameter have not been completely successful. Furthermore, lack of industry standards to measure and report barite sag has limited the availability of usable field data. Sound engineering strategies and guidelines have helped, but clearly more developments are needed.The primary objectives of this paper are to (a) examine key barite-sag challenges, (b) characterize current best practices, and (c) discuss strategies, opportunities, and active programs for step improvements. Recent barite-sag case histories from the Gulf of Mexico, West Africa, and Atlantic Canada are included to set the proper perspectives.

Dynamic settling of particles in shear flows of shear-thinning fluids

“…The concentration field is provided by (16). It is insightful to plot the characteristic curves in the (x, z) plane and examples for n = 1/3 and 2/3 are plotted in figures 1 and 2.…”

“…We note that the concentration field is given by (16), in which the dimensionless settling velocity is given by (43). The characteristics are determined by (13) using the dimensionless flow velocity (42) and settling velocity (43).…”

“…Because it allows particles to be carried long distances in relatively low-shear flows, it can be a desirable effect in, for example, the transport of drill cuttings; however, it is among the factors implicated in undesirable phenomena such as barite sag [16]. (Confusingly, it may act in conjunction with Boycott settling, also referred to in the literature as 'dynamic settling'.)…”

Dynamic settling of particles in shear flows of shear-thinning fluids

“…We calculate the steady-state concentration, C ∞ , using the method of characteristics as in §2.1. We note that the concentration field is given by (16), in which the dimensionless settling velocity is given by (43). The characteristics are determined by (13) using the dimensionless flow velocity (42) and settling velocity (43).…”

“…This dependence of settling velocity on the background flow is sometimes referred to as 'dynamic settling' and has been known for many years in the oil and process engineering communities [12,13,2,14,15]. Because it allows particles to be carried long distances in relatively low-shear flows, it can be a desirable effect in, for example, the transport of drill cuttings; however, it is among the factors implicated in undesirable phenomena such as barite sag [16]. (Confusingly, it may act in conjunction with Boycott settling, also referred to in the literature as 'dynamic settling'.)…”