Fluid Saturations. Fluid Saturation Expected saturation values Saturation from laboratory measurements AZMAN IKHSAN/SKP3323

Transcription

1 1 Fluid Saturation Expected saturation values Saturation from laboratory measurements It is expected that students will be able to: define saturation of fluids in porous rocks calculate saturation explain saturation measurement using Retort, Soxhlet Extractor and calculate the saturation values AZMAN IKHSAN/SKP3323

2 2 Define What is fluid saturations in porous rock? Laboratory methods saturation determination Explain and calculate saturation values from Retort and Soxhlex Extractor Application of saturation data Examples on the use of saturation reservoir engineering calculations

3 3 Definition Generally, a hydrocarbon formation was initially filled with water. Hydrocarbon migrated into the formation and filled fraction of he void spaces that were initially filled by water. As a result the formation is now filled with water and hydrocarbon, and the quantity of each fluid must be determined.

4 4 Definition Fluid saturation in a porous media is a fraction of the fluid in the pore spaces of the rock. If V V w p water volme in the pore volume of pore The water saturation in the poreis given by, S w S w V V w p water satiration in fraction or S w S w V V w p * 100 % water saturation in percent

5 5 Methods to determine saturation Many methods are available, only 3 will be discussed: 1. Retort Distillation Method 2. Solvent extraction (Soxhlet Extractor and Dean-Stark) 3. Centrifugal Method

6 6 Methods to determine saturation 1. Retort Distillation Method Increase temperature up to F Water of crystallization Interstitial water

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8 8 Methods to determine saturation 2. Solvent extraction (Soxhlet Extractor and Dean-Stark) Extract until there is no more increment of water collected S w S w V V w p water saturation in fraction S o S o weight of saturated core (gm) - weight of dried core (gm) - weight of oil density (gm/cc) * volume of pore(cc) oil saturation in fraction water (gm)

9 9 Methods to determine saturation 3. Centrifugal Method Solvent tube Core plugs A solvent is injected into the centrifuge just off center. Owing to centrifugal force it is thrown to the outer radii, being forced to pass through the core sample. The solvent remove the water and oil from the core. The outlet fluid is trapped, and the quantity of water in the core is measured.

10 10 Methods to determine saturation Factors affecting fluid saturations of cores Fluid content from the core sample (core taken from field) has change from its original content in the reservoir. a. Coring in the formation is influenced by drilling fluid invasion during drilling b. Bringing the core sample to the surface will cause pressure decline and the expansion of water, oil and gas

11 11 Use of saturation data from lab. 1. Determine level of oil-water contact 2. Not accurate to be used in calculating hydrocarbon volume in the reservoir due to the above reasons

12 12 Use of saturation data from lab. 1. Determine level of oil-water contact 2. Not accurate to be used in calculating hydrocarbon volume in the reservoir due to the above reasons Initial oil in - place S water saturation, fraction A area of formation, acres h tickness of formation, kaki porosity,fraction B N w oi N 7758* A* h * * (1 S oil formation volume factor, bbl/stb initial oil in - place, STB 7758 bbl/(acre - foot) wi ) / B oi

13 13 Several terms on saturation Connate water (Air konat) (S wc ): water entraped in the intertices of the rock (either sedimentary or extrusive igneous) at the time the rock was deposited. Interstitial water (air celahan): Water that occurs naturally within the pores of rock. Water from fluids introduced to a formation through drilling or other interference, such as mud and seawater, does not constitute interstitial water. Interstitial water, or formation water, might not have been the water present when the rock originally formed. In contrast, connate water is the water trapped in the pores of a rock during its formation, also called fossil water.

14 14 Beberapa istilah ketepuan air Irreducible water saturation (Ketepuan air tak terkurang ) (S wir ): the fraction of pore volume occupied by water in a resevoir at maximum hydrocarbon saturation. In water-wet rock, it represents the layer of adsorbed water coating solid surfaces and the pendular grain contacts and at pore throaths. The irreducible saturation of a fluid is the minimum saturation of that fluid attainable when that fluid is displaced from a porous medium by another fluid immmiscible with the first. The lowest water saturation, that can be achieved in a core plug by displacing the water by oil or gas. The state is usually achieved by flowing oil or gas through a water-saturated sample, or spinning it in a centrifuge to displace the water with oil or gas. The term is somewhat imprecise because the irreducible water saturation is dependent on the final drive pressure (when flowing oil or gas) or the maximum speed of rotation (in a centrifuge). The related term connate water saturation is the lowest water saturation found in situ. Residual oil (minyak baki) (S or ): Oil remaining in the reservoir rock after the flushing or invasion process, or at the end of a specific recovery process or escape process.

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