Abstract.

Oil and gas drilling activities in Alberta generate a variety of wastes that must be disposed of in an environmentally acceptable manner. Diesel invert mud drilling wastes are one of the more difficult types to dispose of due to the presence of hydrocarbons and salts. In 1989 a joint research program funded by the Alberta Research Council and Alberta Land Conservation and Reclamation Council was initiated to develop environmentally acceptable land application rates of diesel invert wastes for soils in Alberta and to model the fate of these wastes. The work was undertaken as four individuai but closely linked experiments. The characterization experiment included the sampling of the waste materials and indigenous soils from the field site and the subsequent analytical work provided the basis for the degradation, greenhouse, and field experiments.

The degradation experiment established to determine the rates of decomposition of the oil fraction in the waste included three temperatures for incubation (5°C, 15°C, and 25 OC), six incubation periods (O, 1, 3, 9, 25 and 52 weeks), and five waste application rates (O, 0.5%, LO%, 1.5% and 3.0% oil and grease in the soil-waste mixture). The rate of oil degradation decreased with increasing oil content with optimum rates at 0.5% to 1.0%.

The greenhouse experiment was undertaken to measure the relative impact of the oil materials and salts present in the waste on soil quality and plant growth and quality. The variables included one soil, two wastes (washed to remove salts and unwashed) eight application rates, one crop (brome grass) and three replicates.

Yields declined from the control level as waste application rate increased.

A replicated field plot experiment to validate and calibrate the results of the degradation and greenhouse experiments involving oil application rates of O, 1.0%, 2.0%, 3.0% and 4.0% was implemented. Frequency of application included single applications with and without a vegetation cover, and multiple application plots.

Results based on three years of sampling and analysis indicate that oil degrades more rapidly when applied at the lower (1.0% and 2.0% oil) rates. Chlorides have moved rapidly down the soil profile with accumulations occurring below the 1 m depth.

1. INTRODUCTION

Oil and gas drilling activities in Alberta, which is the main oil and gas producing province in Canada, generate a variety of wastes that must be disposed of in an environmentally acceptable manner. Diesel invert mud drilling wastes are one of the more difficult types to dispose of due to the pesence of hydrocarbons and salts. In 1989 a joint research program funded by the Alberta Research Council and Alberta Land Conservation and Reclamation Council was initiated to develop environmentally acceptable land applicati

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