Fluid Saturation Determination
Assignment Fluid Saturation Determination
You are your company’s petrophysicist responsible for a company-operated acreage concession. You have been asked to explain what is meant by the term irreducible water saturation, and to summarize its use in evaluating a hydrocarbon accumulation.
Solution
The irreducible water saturation, Swirr, is that fraction of the pore space occupied by water when the hydrocarbon content is at its maximum. Irreducible water saturation is normally associated with the capillary pressure exerted on the rock-fluid system and is defined as the pore volume of water that cannot be forced out of the pore system at a given threshold capillary pressure during a primary drainage process, such as the initial charging of a hydrocarbon reservoir.
The irreducible water saturation value is normally used to calculate the initial hydrocarbon volume in place in static reservoir modeling. The irreducible water saturation is usually determined through special core analysis.
The irreducible water saturation is also an important attribute to quantify a reservoir’s petrophysical quality in terms of the flow capacity. High in-situ capillary pressure causes connate water saturation in reservoir rocks to approach the irreducible state, thereby providing a direct link between electrical and hydraulic conductivities.
Assessment Fluid Saturation Determination
1. Reservoir rocks are often assumed to be originally water-wet because the large majority of the sediments forming today’s reservoirs were originally laid down in aqueous depositional environments, such as __. (Select all that apply.)
A .oceans Correct ✔
B .lakes Correct ✔
C .deserts
D .rivers Correct ✔
E .deltas Correct ✔
2. What are the component fluids within a hydrocarbon reservoir rock’s pore spaces? (Select all that apply.)
A .Oil Correct ✔
B .Water Correct ✔
C .Cement
D .Gas Correct ✔
E .Minerals
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