Sampling of the downhole samples of reservoir oil at non-transfusing oil inflow into the well

Abstract

The aim of bottomhole sampling is to obtain a small volume of fluid, which is identical to the reservoir oil at initial reservoir conditions. The results of study of reservoir oil PVT (abbreviation from Pressure, Volume, Temperature) properties made in the laboratory can then reasonably be applied to identify phase behavior and properties of reservoir fluids under reservoir conditions. Knowledge of PVT properties of reservoir oil is necessary to estimate of oil capacity, designing of reservoir development and its economic viability. PVT properties of reservoir oil are estimated from: the study of subsurface oil samples; the study of recombined samples from the test separator; mathematical simulation using equation-of-state and empirical correlations. Representative samples of the reservoir oil can be collected mainly by subsurface sampling. In cases of extremely tight (low permeable) reservoirs it may be virtually impossible to get sufficient flow rate to lift the liquids without excessive pressure draw-down and corresponding degassing of reservoir oil at bottomhole conditions. This article deals with on technical and technological solution of subsurface oil sampling when an oil not flow to surface. The use of such a method will help to solve the problem of reliable identification of the reservoir oil properties at reservoir conditions.