ABSTRACT

Current oil and gas exploration drilling in Canada's Arctic poses potential water pollution hazards to the sensitive environment of the North. Much of this drilling is now concentrated in low lying areas subject to flooding, such as the Mackenzie Delta, and in late 1973 drilling began in the shallow regions of the Beaufort Sea. This industrial activity can constitute a source of water pollution if drilling fluids are discharged to adjacent surface waters.

A literature review has revealed little information on the water pollution characteristics of drilling fluids. In order to evaluate the pollution aspects and to identify appropriate environmental controls, an industry/government research program was established in 1973 to determine the magnitude of the problem, and, as a result of these investigations, to develop effluent standards and guidelines for the disposal of waste drilling fluids.

This paper describes the studies being conducted and highlights the results of the 1973 work.

On the basis of the results obtained todate, indications are that water base drilling fluids constitute a wastewater with characteristics capable of causing water pollution. Furthermore, such wastes have been demonstrated to be acutely toxic to fish.

INTRODUCTION

The potential water pollution problems associated with the handling and disposal of waste drilling fluids is a relatively recent concern in Canada's Arctic regions. Between 1929 and 1973 over seven hundred wells have been drilled in the Yukon Territory and the Northwest Territories, with more than 75% of these being drilled since the end of 1965. Figure 1 illustrates the steadily increased drilling activity in recent years. Of special significance is the fact that the most recent drilling is occurring in areas where direct discharge of waste drilling fluids may occur as, for example, the Mackenzie Delta and immediate offshore areas. The accepted practice in waste drilling fluid handling for onshore operations has been the construction of a sump or reserve pit to collect and contain waste mud, drill cuttings, waste lubricating oils, and rig wash water. Collectively, these waste materials are called sump fluids. Drilling operations located on the Mackenzie Delta are subject to annual flooding, which has resulted in direct discharge of the waste fluids in the sump with the flood waters.

In the case of offshore drilling in Canada's Arctic, total containment of waste fluids is difficult because of space limitations, transportation problems during breakup and freeze-up, and other operational problems resulting from sub-zero temperatures. The only alternative in these cases where transportation to land is restricted, is to dump water base drilling fluids and drill cuttings into surface waters, as is commonly practiced worldwide. Even though surveillance of offshore drilling operations in the Gulf of Mexico has revealed that this practice results in no apparent detrimental effects to marine lifel, 2, it has been recognized that the Arctic marine ecology differs significantly from other marine areas. Consequently, more stringent environmental controls such as treatment or containment of waste drilling muds, careful selection of mud components or separation of toxic or deleterious components may be necessary for this region.

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