From 2001 to 2005, Quest Resource Corp. developed a set of procedures to collect, desorb, and calculate the gas contents for coal and carbonaceous shales using air rotary drill cuttings in eastern Kansas. These proce- dures are fast, inexpensive, and reliable; and they can be eas- ily completed by staff geolo- gists in the field and in the lab. The resulting gas content data were used to make exploratory and well completion decisions in eastern Kansas.

CARBONACEOUS SHAI.E GAS CONTENT DATA* Table 1

The coal gas content data obtained from the desorption of air rotary drill cuttings were compared to the well production data. A direct correlation exists between the coal gas content and the average daily well production. In most cases, the higher the gas content of the coals, the more productive the well. Low coal gas content resulted in poorly producing wells with marginal economics.

Sample collection

From 2001 to 2008, the author collected and desorbed 1,127 air rotary drill cuttings samples from 217 wells in eastern Kansas.

Three quarters of these samples were from Quest Resource wells. The other samples were from wells drilled by SEK Energy LLC, Hopewell Operating Inc., N&B Enterprises, and Carroll Energy LLC. Another 239 samples from 5 5 wells are included in this study that were collected and desorbed by other Quest Resource and SEK Energy geologists in eastern Kansas.

Collection procedures

Sample collection procedures were developed by Quest geologists with the assistance of Well Refined Drilling and L&S Well Services personnel.1

With air rotary drilling rates varying from 100 to 250 ft/hr and high pressure cuttings returns, various different collection techniques were attempted.

The cuttings from a coal will normally return to the surface in less than 2 min after being drilled, and the cuttings from a 2 -ft thick coal will exit the blooie line in less than 30 sec. Thus, it is absolutely necessary for the wellsite geologist to: 1) know the stratigraphy during drilling, 2) know when to expect to intersect each coal or carbonaceous shale, 3) continuously monitor the cuttings stream, 4) be prepared to collect a sample at a moment's notice, and 5) collect a high percentage of the exiting cuttings in order to obtain sufficient sample for a desorption canister.

The following sampling procedures were found to be the most effective. The wellsite geologist continuously monitors the cuttings stream at the end of the blooie line by using sieves that are either hand-held or attached to a piece of PVC pipe. A large bucket of fresh water to wash the cuttings is placed next to the end of the blooie line.

By continuously monitoring the cuttings stream and with stratigraphie data from nearby wells, the geologist is able to anticipate the next zone to be sampled. The driller assists with this process by conveying to the geologist when the drilling rate changhes.

When coal or carbonaceous shale cuttings are first observed, or are anticipated, the geologist (or a drill helper at the geologist's direction) takes an expanded metal trash can and places it over the end of the blooie line at an angle. This takes a fair degree of strength, and safety clothing (including a heavy long- sleeve shirt, boots, leather gloves, safety glasses with side shields, and hard hat) is required.

Three or more trash cans need to be available, in cases where the zone to be collected is over 2 ft in thickness. It is often necessary to rotate the trash can during collection, since the cuttings stream will quickly abrade holes in the side of the expanded metal trash can.

Sample preparation

After the sample is collected in the expanded metal trash can, it is immersed in a large bucket of drill water and agitated to remove fine cuttings and clay. Then the sample is placed in the desorption canister, packing the sample as the canister is filled to within 1A - in. of the top.

If there is not sufficient sample to fill a 12 -in. canister, smaller canisters (2 in., 4 in., or 6 in. in height) are used. If there is still 1 1A in. or more of headspace at the top of the canister after filling, it is recommended that the canister be filled to 1A in. of the top with drill water. After filling the canister, it should be placed in a cool place in the summer or in a heated vehicle in the winter, until it is transported to the laboratory for desorption. Canisters need to be stored and transported upright.

PENNSYLVANIAN COAl. GAS CONTENT DATA* Table 2

It is difficult to calculate the gas content of a mixed coal and carbonaceous shale sample. This is due to the fact that the recovered gas desorbs from both the carbonaceous shale and the coal. The Mulky coal, Croweburg coal, and Tebo coal all have overlying carbonaceous shales. Cuttings samples of these coals will always contain carbonaceous shale.

Every effort should be made to separate the coal cuttings from the carbonaceous shale before placing the sample in a canister. The coal can be separated from the carbonaceous shale by panning. The different panning methods include: 1 ) rotating the sample in the expanded metal trash can in the large tub of water, 2) swirling the cuttings with water in a large rubber tub, or 3) agitating the sample in a large sieve in water.

The coal, being less dense, will work its way to the top of the slurried sample, where it can be skimmed off. It is much more desirable to have a small canister (2 -in.