Conoco Inc. has begun storing exploratory well cuttings in sample bags made from Tyvek spunbonded olefin produced by the parent Du Pont Co.
About 80% of the samples sent to the company's laboratory in Ponca City, Okla., are protected in Tyvek bags because of the olefin's resistance to chemicals, rot, and mildew. Some samples date to the 1940s.
Many of the thousands of varieties of drilling fluids used in exploration can damage storage bags because of their chemical makeup. Tyvek bags are much less susceptible to this type of damage because the material is resistant to most chemicals.
Conoco previously tried storing samples in glass bottles, which were heavy and expensive to ship, and stainless steel containers, which corroded. It also used cotton cloth bags, which have not withstood the test of time in storage.
The equivalent of thousands of feet of rock have been discarded because cotton bags disintegrated.
One service company, Sperry-Sun Drilling Services, Houston, fills about 5,000 Tyvek sample bags each month. It collects hundreds of thousands of samples per year, some of which could sit outside on the drilling rig for 3-4 months. Cotton bags burst at the seams in transit because the cotton had deteriorated.
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