Using Chemicals to Optimize Conformance Control in Fractured Reservoirs Page: 7 of 21
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This research project has three objectives. The first objective is to develop a capability to predict
and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The
second objective is to develop procedures for optimizing blocking-agent placement in wells
where hydraulic fractures cause, channeling. The third objective is to develop procedures to
optimize blocking-agent placement in naturally fractured reservoirs. This research project
consists of three tasks, each of which addresses one of the above objectives. Our work is directed
at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.
GEL PROPAGATION THROUGH FRACTURES
New Model. Recently', we introduced a new model for gel propagation and dehydration during
extrusion through fractures. This model was based on Eq. 1, which described the rate of water
leakoff (u1, in ft3lft2/d or ft/d) from the gel through a fracture face during gel extrusion.
u= 0.05 f'... ............................................................................................................................... (1)
In this equation, t is time in days. Eq. 1 was based on a fit of leakoff data from seven experiments
(Fig. 1), in which 24-hr-old Cr(III)-acetate-HPAM gels were extruded through seven separate
fractured cores (650-mD Berea sandstone). Specifically, our experiments used an aqueous gel
that contained 0.5% Ciba Alcoflood 935 HPAM (molecular weight =5x106 daltons; degree of
hydrolysis 5% to 10%), 0.0417% Cr(III) acetate, 1% NaCl, and 0.1% CaC12 at pH=6. All
experiments were performed at 410C (1050F). The gelant formulations were aged at 41*C for 24
hours (5 times the gelation time) before injection into a fractured core. All fractures had nominal
widths of 0.04 in. The fracture dimensions in these experiments were 48x1.5x0.04 in.,
12x12x0.04 in., or 6x1.5x0.04 in. Gel injection velocities (fluxes), based on the cross-section of
the fracture, ranged from 129 to 33,100 ft/d. Eq. 1 provided an excellent description of the water
leakoff data from these experiments (Fig: 1). Details can be found in Ref. 1.
. k w,= 277 darcy-ft,
1 w = 0.04 in.
Average Iniection Flux
n " 129 ft/d (12x12-in. fracture)
0.1 413 ft/d (6x1.5-in. fracture)
" 413 ft/d (12x12-in. fracture)
" 413 ft/d (48x1.5-in. fracture)
o 1,030 ft/d (48x1.5-in. fracture)
e 4,130 ft/d (48x1.5-in. fracture)
. 33,100 ftld (48x1.5-in fracture)
0.0001 0.001 0.01 0.1 1 10
Fig. 1-Average leakoff rates in 0.04-in.-wide fractures.
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Seright, Randal S. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs, report, April 19, 2000; Tulsa, Oklahoma. (https://digital.library.unt.edu/ark:/67531/metadc702203/m1/7/: accessed May 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.