Fluid properties including equation of state modeling with optical constraints

Abstract

The invention relates to a method of determining an unknown property or information of a reservoir fluid. The method includes measuring a set of responses of a measuring instrument to the fluid and measuring one or more physical or chemical properties of the fluid. The method further includes determining the unknown property or information of the fluid based on the relationship between the instrument responses and the measured properties of the fluid using equation-of-state (EOS) model.

Description

TECHNICAL FIELD[0001]This invention relates to characterization of oil and gas reservoirs, and more particularly to using equation of state modeling for reservoir characterization in connection with drilling operations.BACKGROUND OF THE INVENTION[0002]A reservoir is formed of one or more subsurface rock formations containing oil and / or gas. The reservoir rock is porous and permeable. The degree of porosity relates to the volume of liquid and gas contained in the reservoir. The permeability relates to the reservoir fluid's ability to move through the rock and be recovered for production to the surface.[0003]Reservoirs are conventionally drilled using drilling fluid (e.g., “mud”). The drilling fluid includes particulate material. The fluid used in the drilling fluid generally includes clay and / or either water or another organic material (e.g., oil or organic-based mud (“OBM”)). The purposes of the drilling fluid include: (1) to add pressure to keep the drill hole from collapsing (such...

AI Technical Summary

Problems solved by technology

A disadvantage in drilling overbalanced is formation damage that occurs when drilling fluids, solids, fines, and chemicals that are circulated into the wellbore to maintain the overbalanced condition penetrate into the formation.

Such penetration, or skin damage, impedes or stops hydrocarbons that would otherwise flow into the wellbore during production operations.

However, overbalanced drilling technique may be required for wellbore control, particularly for preventing formation fluids (or reservoir fluids and / or native fluids) from flowing uncontrolled into the wellbore.

When overbalanced drilling technique is used, drilling fluid filtrate will tend to penetrate the surrounding formation.

Such contaminations often interfere with attempts to sample and analyze the reservoir fluid, when logging a wellbore to discover an oil-bearing formation.