Water Well Journal
Issue link: https://read.dmtmag.com/i/543740
Sample Container Types Sample retention may not seem all that complicated, but managing the amount of information and the shear po- tential bulk of samples can be difficult. Fortunately, there are many options available for sample retention, depend- ing on your specific needs. For a smaller footprint, there are sev- eral systems available to help minimize the volume and delivery method of potential cutting samples. Let's discuss some of the different types of drill cutting sample containers. The following is by no means an ex- haustive review but merely a sampling of the available systems. Resealable Plastic Sample Bag The resealable plastic bag is a com- mon item for sample collection on envi- ronmental projects. There are many different styles and sizes available. The one-gallon and one-quart bags are popular among environmental field geologists. The reason for their popularity? They are generally inexpensive, come clean for food grade use, and are readily disposable. These bags can hold a significant amount of sample, but do not make for a long-term storage solution due to the eventual breakdown of the plastic mate- rial when exposed to the elements. Another drawback is the amount of space required to box and store the samples for future reference. Cloth Sample Bag The cloth sample bag has long been the standard sample container for col- lecting geologic samples on well sites. The bags come in a wide range of sizes ranging from 3.5-inch × 5-inch to 10-inch × 17-inch. A popular size for water well application is the 4.5-inch × 6-inch bag. These bags generally come with a waterproof label to retain well and depth information on the sample bag. (Hubco Inc. 2009) A common drawback to this con- tainer is the ability to keep the bags or- ganized and identifiable once time has passed and the samples are stored back at the office. After a few years of col- lecting samples, you can have a room overflowing with boxes of cloth bags full of cuttings. Whirl-Pak ® Disposable Sampling Bag The Whirl-Pak sample bag is a popu- lar bag for sample retention. It comes in several sizes ranging from 3-inch × 7- inch to 4.5-inch × 9-inch and is made of polyethylene. The uniqueness of the product is the ability to scribe information into the sample bag in a provided area and the closure system. The closure system con- sists of a metal strip located at the top of the clear bag. After the sample is placed into the bag, the bag is then whirled around the strip. Once the bag is sealed, the metal strips are bent at each end to prevent the bag from coming open. (Consolidated Plastics 2015) Petrolog The Petrolog is a 3-inch × 5-inch booklet containing 10 adhesive rows for sample collection. Using a 10-foot sam- ple interval, each booklet can hold up to 100 feet of sample. Each booklet is pro- vided with an inside and exterior page for describing well information, sample characterization, and depth. The Petrolog is well suited for dis- seminating formation information to colleagues through the mail. (U.S. Geo- Supply Inc. 2010) This system has a small storage footprint but little sample content and is useful for viewing with a hand lense or microscope. Sample Envelope The sample envelope is made of heavy kraft paper that provides resist- ance to puncture from small rock and sample chips. The sample envelope comes in several sizes. Some of the more popular sizes for sample retention are the 3-inch × 5-inch, the 4-inch × 7- inch, and the 5-inch × 9-inch. Well in- formation, formation description, and depth can be recorded on each envelope. Once the sample is placed into the envelope, it is sealed with a metal tab to prevent sample spillage. In addition to collecting the samples in envelopes, they can be stored in labeled storage boxes for future reference. (U.S. Geo- Supply Inc. 2010) Rock Chip Storage Case The rock chip storage case comes in several different sizes with 10 to 40 compartments per tray. These trays are handy for collecting samples from drilled wells for future evaluation. A completed well, depending on the sam- ple interval, may only take a couple of trays. The compartments are generally small and do not hold a bulk sample. There is generally only enough sample available for sample description using a hand lens or microscope. (U.S. Geo- Supply Inc. 2010) Parting Thoughts As a geoscientist, I love to collect drill-cutting samples of wells I log. I have boxes of samples piled every- where. From time to time, I even go back and look at them, but mostly I glue the interesting samples to glass slides for use under the microscope. As a drilling contractor, we drill too many wells to collect and retain samples of every well. However, whether you are a geoscientist or a drilling contrac- tor, you know when you're drilling a complicated or complex well. These wells tend to stand out from the straightforward ones. Geologic sample retention for these wells is a relatively inexpensive insurance policy against fu- ture unforeseen problems that may arise. Remember, once the well is in and the cuttings are gone, what is beyond the ground surface is anybody's guess. References Consolidated Plastics. 2015. Whirl-Pak ® Disposable Sampling Bags. Website accessed June 21, 2015. www.con- solidatedplastics.com/Whirl-Pak supsup-Disposable-Sampling-Bags- C3171.aspx. WWJ FIELD NOTES from page 33 waterwelljournal.com 34 August 2015 WWJ Managing the amount of information and the shear potential bulk of samples can be difficult.