Title: Static/Dynamic Settling of Proppant in Non-Newtonian
Hydraulic Fracturing Fluids
Author(s):Mahmoud Asadi, Stim-Lab and S.N. Shah, The University
of Oklahoma and David L. Lord, Halliburton Energy Services
Presentation: 1999 SPE Mid-Continent Operations
Symposium
Location: Oklahoma City, Oklahoma USA
Date: March 28-31, 1999
Abstract: Experimental data and analysis are presented on the static and dynamic settling of proppant in non-Newtonian hydraulic fracturing fluids. A unique High Pressure Simulator (HPS) that closely models reservoir hydraulic fractures is used to study proppant- settling behavior under both static and dynamic conditions. A system of optical fibers and Light Emitting Diodes (LED) acting as a vision system were imbedded in the platens representing fracture walls for quantification of proppant settling under various fluid injection conditions.
Hydraulic fracturing fluids tested include slurries of 35 lb/Mgal guar linear gel with 6 ppg 20/40 mesh sand, 60 and 40 lb/ Mgal hydroxypropyl guar (HPG) linear gels both with 4 ppg 20/40 mesh sand, and borate-crosslinked 35 lb/Mgal guar gel with 7.3 ppg 20/40 mesh sand. Test conditions cover a shear rate range of 60 to 120 sec-1. In addition, the effect of an enzyme breaker on proppant settling rate under static conditions was studied. Tests were conducted with a fracture gap width of 0.375 in. under ambient conditions.
Analysis of the dynamic condition indicates that proppant settling within the studied linear and crosslinked gels is non-linearly dependent on shear rate. Under static conditions, studied linear gel slurries settled 40 to 50 times faster than that of the studied crosslinked gel containing breaker. It is also shown that an increase in shear rate induces proppant settling in borate-crosslinked 35 lb/Mgal guar gel while it reduces the settling rate in 35 lb/Mgal guar linear gel.