PECULIARITIES OF HYDROCARBONS AND WATER BEHAVIOR AT TIGHT GAS RESERVOIRS

摘要

The traditional development methods of tight reservoirs of so-called Achimovskoe formations (Urengoy oil-gas-condensate field) will cause of great losses of hydrocarbons. The main sources of the troubles that will be come up at the development of those reservoirs are the structure peculiarities of reservoir rocks and the composition peculiarities of hydrocarbon fluids. Our investigations showed that phase behavior of hydrocarbons and water trapped in a porous medium was transformed quantitatively and qualitatively. The larger a specific surface the stronger an effect. The low permeability (less than 10~(-15) m~2) and high porosity (16-18%) of Achimovskoe formations consisted of tight sands, clays and limestone indicate about a very large specific surface of these reservoirs. A spacious surface predetermines the phase behavior and the filtration nature of hydrocarbons and water. A hydrocarbon fluid of these formations contains a lot of condensate (250-500 g/m~3) and paraffins (greater than 5%). Molecules of these substances just as molecules of liquid crystals in a porous medium form the homeotropic oriented quasi-liquid-crystals structures. Molecular orientation of these structures in relation to a porous medium wall predetermines the filtration behavior of a hydrocarbon fluid in all. We believe that in case of selection of the tight reservoirs development methods it is necessary to take into consideration the peculiar phase behavior and therefore the filtration behavior of hydrocarbons and water saturating these tight reservoirs.