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TORP Investigating Recent Successes Using Gelled
Polymer Treatments
The Tertiary Oil Recovery Project (TORP) at the University of Kansas has a long history of research and field applications of gelled polymers. Gel polymer treatments are nothing new to the midcontinent, however recent treatments in Kansas Arbuckle producing wells are proving to be more effective in controlling water production and increasing oil production than past treatments.
TORP is meeting with service companies and oil operators to develop a database on the treatments conducted to date and investigating areas where university engineers and scientists can be of assistance in better defining where and how to apply this technology. Questions looking to be answered include candidate well selection, treatment sizing and modeling what actually occurs during and after the treatments.
Comparing recent treatments to earlier ones indicate several differences. Recent successful treatments are using the MARCITSM technology and much larger volumes of gel. Recent treatment volumes range from 1,500 to 5,000 barrels versus the few hundred barrels historically used. MARCITSM is the acronym for MARathon Conformance Improvement Treatment. This polymer gel was developed in the mid-1980's by Marathon Oil Company and licensed to various service companies in the early 1990's. The MARCITSM technology consists of mixing dry polymer in water and crosslinking it with chromium triacetate at the surface, as opposed to previous systems where polymer and crosslinker mix in the reservoir. Gels have viscosity slightly greater than fresh water to rubber can be created in virtually any water, at temperatures up to 240oF, in high TDS, H2S and CO2 environments. Gel strength is a function of polymer concentration and the gel is considered to be permanent after placement.
J.T. Portwood with TIORCO, Inc. recently presented results
of treatments his company has conducted in Kansas Arbuckle reservoirs
at several PTTC workshops. His summary included that since November
1997, twenty-one wells in three fields have been treated using
these larger treatments - Bemis Shutts (17 wells), North Hampton
(3 wells) and Blue Hills (1 well). The economic success rate
has been 100%, with payouts of total costs (polymer, plus well
preparation and workover) being less than six months. Average
pre-treatment production was 3.9 bbls of oil per day (BOPD),
411 bbls of water per day (BWPD) and a water-to oil ratio (WOR)
of 106. Average polymer treatment volume has been 3,796 bbls
(range 3,000 to 5,200 bbls). Average treatment cost is $35,071
or $9.24 per bbl of gel). Average post-treatment production in
the Bemis Shutts is 89 BOPD, 82 BWPD and 0.9 WOR; North Hampton
is 148 BOPD, 67 BWPD and 0.5 WOR; Blue Hill is 40 BOPD, 150 BWPD
and 3.8 WOR. He also stated that incremental reserves based on
one customer's evaluation were estimated at 540,000 bbls of oil
for three leases in the Bemis Shutts Field. Finding costs in
three leases in the field range from $0.59 to $2.35 per incremental
barrel. Savings in water handling costs alone are projected to
exceed $1.4
million.
Mr. Portwood summarized his talk by stating lessons learned to date which include: (1) acidizing to clean the wellbore before pumping gel is important, (2) end treatment when surface pressure reaches 100 to 200 psi, (3) overflush to clear conductivity paths around the wellbore, and (4) use as much gel as economically feasible.