The barrier to imaging wet or oily specimens in their "native" states in a scanning electron microscope (SEM) at high resolution and large depth of focus has been broken by the development of a new microscope known as the environmental scanning electron microscope (ESEM). With the new features built into the ESEM, the need for preparing samples with various specimen-destroying preparation techniques has been eliminated. For example, wet reservoir rocks can be imaged and analyzed in their "native" state, without drying, freezing, or coating with a conductive layer, by saturating the ESEM specimen chamber with water vapor {PH2O = ~0.46 psi [3.2 kPa] at 25°C [77°F]} during examination. The ESEM also allows dynamic experiments to be performed in a variety of gases at pressures up to 0.6 psi [4kPa] and temperatures up to 1000°C.

This paper presents the key features of the ESEM which distinguish it from the conventional SEM, and results of some ESEM feasibility studies important in petroleum technology such as matrix acidization, water-flooding, and clay and cement hydration. The results indicate that the ESEM combined with the energy-dispersive x-ray spectroscopy is a powerful new technique capable of providing a new understanding of many exploration and production related studies not previously possible with conventional "high-vacuum" SEM microscopy.

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