Natural gas migration behind surface casing, from the shallow Devonian shales, has caused many problems for operators in northeast Ohio, northwest Pennsylvania and western New York. Foremost are the problems of rig and well fires during drilling and workover, along with natural gas contamination of shallow fresh-water zones that many persons in rural areas depend on as their sole source of potable water. The problem of gas migration became so severe in northeast Ohio, in January 1985, that the Ohio Department of Natural Resources declared a moratorium on drilling within a limited area of Lake and Ashtabula Counties until a solution could be found.

Three important slurry characteristics had to be addressed in preventing this gas migration: rapid strength development at low temperature, expansion of the set cement, and a short transition time. The transition period is the time it takes the cement to go from a pumpable slurry to a set solid material. A quick-setting cement system was developed capable of satisfying the previously mentioned requirements. At 60°F (15.6°C), approximately 500 psi (3,447 kPa) of compressive strength is obtained in two hours. Transition time from a fluid to a solid is a minimal three to four minutes. This cement also has excellent linear expansion at low temperature.

The use of this quick-setting cement has so successfully controlled gas migration that the Ohio Department of Natural Resources has allowed the resumption of drilling in the affected area. Even where gas migration is not a problem, operators have found that quick-setting cement can substantially reduce WOC time on shallow surface strings set under low-temperature conditions. This paper will further examine the technology associated with this new product, and review case histories where it has been used.

You can access this article if you purchase or spend a download.