Geochemical conditions of cuttings disposal and utilization in Siberian peat-bog geosystems

Vast majority of Siberian oil and gas fields are located within peat-bog geosystems, exhibiting the following specific geochemical characteristics: decreased mineral substance content to ensure normal functioning conditions of forest biogeocoenosis in taiga zones; increased concentration of organic substances, iron compounds, ammonium and nitrate ions; acid reaction environment and excessive moistening. Such benign environments affect the growth of hydrophylic swamp vegetation. The comparative chemical composition analysis of solid substances in mud pits, mineralized soils, peats and swamp waters indicate that solid and liquid drilling wastes (cuttings) are applicable for the reclamation of disturbed peat bog areas. This could be paradoxical except for the fact that there is a higher content of calcium, magnesium, potassium and nitrogen compounds in these drilling wastes than in the peats and swamp waters. However, there exist definite constraints in applying drilling wastes for land reclamation. These drilling wastes contain a significant amount of sodium and chlorides inhibiting any variety of vegetation. Drilling wastes for reclamation of disturbed peat soils could be used only in the following two cases: (1) positive toxic component sedimentation and \ or (2) natural decrease of toxic component concentration during storage in mud pits. Regardless of the significant dissolved salt waters in pit waters, they continue to be undersaturated pertaining to aluminosilicate sources. At the same time, pit waters are oversaturated in carbonate minerals and humacite of metals providing possible concentration decrease of various liquid-phase substances in cuttings during their storage in mud pits. Thermodynamic modeling of the chemical composition changes in pit waters highlights the key role of the carbonate barrier which determines the continuous removal of calcite and dolomite from the solution. In this case, only clay minerals and humacite of metals become sediments, resulting in the natural decrease of macro-component concentrations in pit waters up to 40% even in lack of specific exposure limits. This, in turn, furthers additional concentration decrease of dissolved and suspended substances in pit waters. Natural decrease of the total dissolved salt content in pit waters is more than 40% which shows their mixing with pit waters due to the leak-off of these mud pits. Cuttings mixed with utility fluids, swamp waters, peats and quicklime could be used for the reclamation of disturbed peat bog areas producing favourable functioning conditions for non-swampy forest ecosystems due to the decrease of sodium, chloride, organic acid and toxic micro-element concentrations in the cuttings and simultaneous content increase of biogenic substances, calcium, magnesium, potassium, nitrogen and other fertilizer elements in reclamation soil.

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