The Panhandle field (RR District 10) was discovered
in 1921 and lies in the southwest corner of the Anadarko basin. It had a primary gas drive mechanism and oil well
drilling was allowed on 10-acre spacings; i.e., wells could not be closer than 660 ft from an adjoining well or 330 ft from a
lease or section line. Most of the early wells were open-hole completions drilled by cable tool rigs. Beginning in the 1930's,
rotary drilling was introduced and most completions were then cased. Secondary recovery techniques have had marginal
success, particularly water floods. Oilfield chemicals were also used for a variety of purposes, not the least of which was
paraffin control. Today, many wells that are still producing are subject to rapid paraffin buildup, which requires periodic pulling
and steam cleaning of the rods and tubing. As of 1984, about 11,500 wells were in operation and the field had produced a total
of approximately 1.4 billion bbl of oil.
(Data taken from the International Petroleum Encyclopedia, 1984.)
The Burnett "J" Lease - RRC Lease No. 01994 - is located in Carson County, TX (RR District 10).
This lease consists of three wells. It was an ideal candidate for cyclic microbial injection because of its location at the periphery of
the Panhandle field, and because of its failing oil and casing head gas production. The "J" Lease also has a history of
moderate to heavy paraffin buildup common to many wells in the area.
This microbial EOR (MEOR) project was initiated for two purposes: (1) to reduce or eliminate paraffin buildup, thereby reducing or
eliminating the associated maintenance costs and loss of production, and (2) to increase oil and/or gas production. Cyclic injection or
"bio-huff 'n' puff" was chosen over field flooding because of cost and manpower considerations. With the cyclic method,
each well is an injection well and a recovery well. Low-volume slugs of Wel-Prep 5™ MEOR fluid were
periodically injected into the well bore, followed each time by lease water (saltwater)
flush, a short shut-in period, and then a return to production. The original treatment schedule called for a
45-day treatment interval during the summer months, shortening to a 30-day interval
during the winter months. This schedule was modified to accommodate the producer's normal servicing routine.
The treatment method was cyclic injection. Initially, 20 gal of kerosene was injected
into the well bore as a pre-flush. The kerosene was followed with approximately
15 gal of WP-5 microbial solution and flushed with 2 bbl of lease water. The well was shut in for 48 to 96 hours and
then turned back into production. Treatments were begun in Dec. 1987 on Wells J-1
and J-3. Well J-2 was added in March 1989. Initially, a 10-gal slug of microbial solution was used per treatment. The volume
was raised to 15 gal in Nov. 1988, because the biological threshold was not being reached at the lower treatment
level. Oil and gas production has been monitored monthly throughout the life of the program.
All oil and gas production data are taken from the Producer's Monthly Report of Oil Wells (Crude Oil and Casing head Gas),
Railroad Commission of Texas, Oil & Gas Div. Form P-1 (see production graphs).
During 1985-87, the "J" lease averaged 0.3
B/D oil with an oil/water ratio of 1:6. Cyclic injections of WP-5 microbial solution
began in Dec. 1987 and were continued at fairly regular intervals. A gradual rise in oil production was evident
from the initial treatment, and the 1990 average through June is 1.5
B/D. Maintenance records show that, during the 32 months of this field trial, five workovers
have been required (rods and tubing pulled and steam cleaned). This equals an average of 1.9 workovers/yr.
Before this treatment program, the yearly average was 4
workovers/yr.
A total of 51 treatments have been made since Dec.
1, 1987. On the average, each well has
been treated once every 57 days with 13.92 gal of microbial solution, 15.8 gal
of kerosene, and 2 bbl of lease water. Average oil production is up 500% from the 1985-87 average of 0.3
B/D to the 1990 average of 1.5 B/D. Maintenance costs for pulling and cleaning rods and tubing owing to paraffin buildup have
decreased from an average of $4,800/yr to $2,250/yr. These figures are based on a $1,200
average cost per workover.