Ellington & Associates, Inc.

Petrography, Fluid Inclusion Analysis, and Microthermometry

Fluid inclusions are tiny quantities of liquid, gas, or mixtures of the two, trapped as impurities within minerals. They provide the best source of information concerning the occurrence of fluids in natural samples. Petrographic examination of these fluid inclusions is an important step in the reconstruction of the PVTX (Pressure-Volume-Temperature-Composition) evolution in order to distinguish the various compositional types and generations of fluid inclusions in the sample of interest and to identify their mechanisms of formation and ages (primary, secondary or pseudo-secondary) relative to each other and to the surrounding minerals.

Microthermometry is the measurement of temperatures at which phase-transitions occur in fluid inclusions as they are cooled or heated on a special microscope stage. It provides quantitative data regarding the minimum temperature of mineral precipitation and the salinity of the precipitating pore-fluid. Microthermometry also provides information to determine the temperature at which a diagenetic mineral formed, the thermal history of the rock, and the composition of the fluids that flowed through a rock during its history. In conjunction with the burial history of a given sample, the fluid inclusion data indicate the timing of different diagenetic events such as the precipitation or dissolution of different cement phases.

The results of fluid inclusion analyses when combined with the composition of recovered oil, gas, and water provide more accurate and efficient models of the degasification processes taking place during oil production, better estimation of the effects on reservoirs due to mineral and bitumen precipitation, and, therefore, better predictions of present and future oil production.

Analysis