William T. Stoeckinger
Consulting geologist
Independence, Kan.
Revenue from coalbed methane gas sales is growing and currently far exceeds that of what little conventional gas is produced in southeastern Kansas.
And this only 2-1/2 years after Stroud Oil Properties, Wichita, brought in the first coalbed methane well in the Sycamore Valley in Montgomery County 6 miles north of Independence. 1
Another operator contributing to the success is Conquest Oil, Greeley, Colo. Conquest acquired a lease with 20 old wells near Sycamore, recompleted five of them in Weir coal, and has installed a compressor. It hopes to begin selling a combined 300 Mcfd soon.
Great Eastern Energy Denver, reportedly can move 2 MMcfd from its Sycamore Valley holdings.
The fever is spreading into Northeast Kansas, where a venture headed by Duncan Energy Co. and Farleigh Oil Properties, also of Denver, plan 12 coalbed methane wildcats.
The two companies received in October 1991 from the Kansas Corporation Commission (KCC) a 40 acre well spacing for seven counties and an exclusion from burdensome gas testing procedures. The test procedures are on the books but not applicable to coal gas wells.
WHAT IT MEANS
Kansas Gov. Joan Finney made a commitment in late 1991 as part of the Kansas Energy Policy Committee to encourage development of coalbed methane production.
Alas, the phenomenon is a reality and applications for a Natural Gas Policy Act Sec. 107 classification covering gas from coal seams are picking up at the KCC in Wichita. The reason for the rush is that wells must be qualified for the tax credit before yearend 1992.
Stroud's experience supports the conclusion that exploring for coal gas is rewarding in a mature oil and gas province such as Southeast Kansas (Fig. 1).
Stroud's gas sales from Sycamore field show the classical "negative decline" as dewatering proceeds.
A few additional facts:
- All 13 wells are single completion, even though there are several seams. Ten of Stroud's wells are completed in Weir coal for an average IP of 47 Mcfd, four are completed in Riverton coal, and one well is completed in Bartlesville sand.
- Wells were drilled on 80 acre tracts.
- The gas market is a local end-user that pays about $1.60/Mcf with renegotiation once a year.
- All produced water is funneled into one Arbuckle disposal system.
- Final well costs are $32,000/well.
Curiously the wells seem to produce 1 bbl of salty water for each thousand cubic feet of gas.
In December 1991 the field averaged 650 Mcfd with 20% downtime and produced 700 bbl of water. The discovery well averaged 120 Mcfd.
The author believes the water volume will decline as gas production rises, but sometimes it takes an act of faith supported by patience and fortitude.
COMPLETION TECHNIQUE
Completion is the black box, and each operator uses his own method.
No two wells are treated the same. Consequently, comparisons and standards are statistically impossible.
Stroud followed a simple schedule (Fig. 2).
It perforated the discovery well at 931-934 ft with four shots per foot. The frac job consisted of 426 bbl of cross-linked fluid with 52% pad and 3% flush, and 30,000 lb of 12/20 sand mixed at 1-9 lb/gal at 20 bbl/min.
The schedule worked well in Sycamore Valley but has produced poor results at Valeda, Kan., 25 miles southeast.
Based on 40 wells in six distinct areas there is a strong correlation between well performance and degree of measured stress. The better wells are stressed less than 1 psi/ft.
Stresses, as measured by initial shut-in pressure (Fig. 2), increased drastically by the end of the stimulation.
Characteristically, the last recorded ISIP is only several hundred pounds per square inch below final surface treating pressures. The explanation seems to be in pore pressure buildup. 2
Without using the tax credit and at currently low gas prices, Stroud expects payout to occur within 3-1/2 years, assuming 700 Mcfd in sales.
If the tax credit is brought into the equation, payout is shortened to 18 months.
REFERENCES
- Stoeckinger, W.T., Kansas coalbed methane comes on stream, OGJ, June 4, 1990, p. 88.
- Khodaverdian, M. Influence of near wellbore effects on treatment pressures in coals, Paper No. 9121 in, Coalbed Methane 1991 Symposium, Tuscaloosa, Ala.
Copyright 1992 Oil & Gas Journal. All Rights Reserved.
