A New Technical Standard Procedure To Measure Stimulation and Gravel-Pack Fluid Leakoff Under Dynamic Conditions
Historically, leakoff analyses of stimulation fluids have been performed
using in-house laboratory procedures. The lack of industry standard procedures
to perform leakoff and wall building coefficient analyses of stimulation fluids
has introduced inconsistency in both results and reporting for many years. A
technical standard adopted in 2006 by both API and ISO for static conditions
has provided the oil and gas industry with the first standardized procedure to
measure and report leakoff. However, the more complex testing under dynamic
conditions was not addressed. As a result, a group of industry experts have
compiled their years of experiences in developing a new technical standard to
measure the leakoff characteristics of stimulation and gravel-pack fluids under
dynamic flow conditions.
Stimulation and gravel-pack fluids are defined, for the purpose of this
technical standard, as fluids used to enhance production from oil and gas wells
by fracturing and fluids used to place filtration media to control formation
sand production from oil and gas wells. Leakoff is the amount of fluid lost to
porous media during these operations. The leakoff procedure was developed
through the collaboration of several industry companies by evaluating numerous
in-house laboratory techniques and conducting round robin testing to ensure
that any modifications to these procedures were reliable and repeatable. The
new standard provides a step-by-step procedure that includes fluid preparation,
experimental equipment design, testing procedure, and data analyses for fluids
exhibiting viscosity controlled leakoff or wall building characteristics.
Example calculations are reviewed within this paper.