North Burbank Unit 1,440-Acre Polymer Flood Project Design

Abstract

Substantial areas of the North Burbank Unit, Osage County, Oklahoma, gave poorer than average response to waterflooding. After studies showed that the performance of these areas could be traced to greater than field average heterogeneity, a pilot polymerflood was conducted during the period from 1970-1979. Good response to polymerflooding, followed by economic evaluation of proposed expanded operations, led to the design and implementation of a 1440 acre commercial scale project. The project involved injection of fresh water preflush during the period from September, 1980 to late April, 1981. Then a liquid emulsion type polyacrylamide was blended to 500 ppm in fresh water and injected at a total rate of 63,000 BPD until approximately 4.4 percent of the pore volume had been injected. This was followed by a water spacer, and a 0.8 percent (PV) slug of aluminum citrate containing 500 ppm of aluminum was injected as a cross-linking agent into those two-thirds of the injectors which were expected to present no injectivity problems. Following injection of a second water spacer, 500 ppm polymer injection was resumed. Plans call for injection of polymer at 500 ppm until the total amount reaches 15 percent of pore volume. This will be followed by polymer slugs of 250 ppm (10 percent of pore volume) and 50 ppm (15 percent of pore volume), fresh water (20 percent of pore volume), and finally drive (produced) water. Any localized channeling problems will be handled by treating individual injection wells with crosslinking agents such as aluminum citrate. Methods of scaling up pilot results to the 1440- acre commercial project, site selection, design of the fresh water preflush, estimation of aluminum citrate requirements, and project costs are discussed.

Application of Freshwater and Brine Polymer Flooding in the North Burbank Unit, Osage County, Oklahoma

“…The successful Block A freshwater polymer flood extended the producing life of the large, but marginally economical, NBU (>350 million bbl oil remaining). 4. The chromium propionate polymer-flood process was shown to be as effective in lllboratory coreflooding tests in brine as the aluminum citrate/polymer process was in fresh water.…”

“…Incremental oil recovery from polymer flooding was projected to be 2.70 MMSTB before the project began. 4 Fig. 9 is a plot of total unit oil production, along with oil production from the Block A polymer-flood area.…”

Integrated Evaluation of Surfactant-Polymer Floods

“…Gel treatments can greatly enhance reservoir sweep if applied before injection of large volumes of expensive polymer or surfactant formulations (Trantham, et al 1982). Also, if one or more high permeability stratums are watered out, there may be considerable value in applying profile modification methods before starting the EOR project (Wang, et al 2007).…”

Geologic Problems Related to Characterization of Clastic Reservoirs for EOR

“…The low formation parting pressure also prevented high injection rates. 18 The oil-wet nature of reservoir rocks resulting from a coating of the iron-rich clay mineral chamosite on 70% of the pore surfaces causes adsorption of sulfonate surfactant and leads to inefficient displacement of oil. The relative displacement index measured on a Burbank sandstone core from Tract 97 has an average value of -0.45,14 indicating the highly oil-wet nature of the sand.…”

“…18 Correlation and mapping of the various permeability zones from available information on depositional history and core, log, and highresolution seismic data and integration of this information with reservoir engineering data (tracer test, pressure-transient list) would be critical in assessing the magnitude of the crossflow problems likely to be encountered in different parts of the reservoir.…”