1.0 SUMMARYThe objectives of this saturation determination experiment are to study the procedures in cleaning of the core samples from residual fluids and to define and determine the oil and gas saturation of a core sample using the Dean-stark distillation-extraction method. But due to technical and laboratory problem, we were unable to conduct this experiment. However, we managed to do some research and finding about saturation determination, procedure in cleaning of the core samples from residual fluids and about the Dean-stark distillation-extraction method in order to achieve the understanding and objectives of this experiment without conducting the experiment.We suppose to heat the hydrocarbon solvent which is toluene to its boiling point which is 110 C. Its vapour will move upward and the rock sample becomes immerse in the toluene vapours that begin to extract the oil and water present in the rock sample. Then the rising vapour will be condense in condenser and collected in the graduated tube.Since toluene is completely miscible with the extracted oil, the condensed liquid in the graduated tube will consist of two liquid phases which are water and mixed hydrocarbon phase containing toluene and oil from the rock sample. Due to higher density, the water phase will settles at the bottom of the graduated tube while the solvent overflow and drips back over the rocks sample. This process should be continuing until no more water is collect in the receiving tube.

2.0 INTRODUCTIONWhen the core arrives in the laboratory, plugs are usually drilled 20 to 30 cm apart throughout the reservoir interval. All these plugs are analyzed with respect to porosity, permeability saturation and lithology. Fluid saturation can be determined by a few methods which include injection of solvent, centrifuges flushing, gas driven solvent extraction and Dean-stark distillation-extraction.The Dean-stark distillation-extraction is appropriate for plug samples and for rotary sidewall cores. This method of determination fluids saturation depends upon the distillation of water fraction and solvent extraction of oil fraction from the sample. Besides, this method provides a direct determination of water content. The oil and water are extracted by dripping a solvent, usually toluene or a mixture of acetone and chloroform aver the plug samples. In this method, water and solvent are vaporized, re-condensed in cooled tube in on the top of apparatus and water is collected in calibrated chamber.The set up basically consist of a longneck round-bottom flask that contains a suitable hydrocarbon solvent such as toluene, a heating element or electric heater to boil the solvent, a condenser and a graduated tube receiver to measure the volume of extracted fluids.

3.0 OBJECTIVES1. To study the procedure in cleaning of the core samples from residual fluids.2. To define and determine the oil and gas and water saturation of a core sample using Dean-stark distillation - extraction method.

4.0 THEORYFluid saturation can be determined by a few methods which includes injection of solvent, centrifuges flushing, gas friven solvent extraction and Dean-stark distillation-extraction. The Dean-stark Distillation-extraction method of determining fluids saturation depends upon the distillation of water fraction and solvent extraction of oil fraction from sample. The Dean-Stark method provides a direct determination of water content. The oil and water are extracted by dripping a solvent, usually toluene or a mixture of acetone and chloroforms over the plug samples. In this method, water and solvent are vaporized, re-condensed in a cooled tube in on the top of apparatus and water is collected in calibrated chamber. The Dean and Stark procedure can be used to measure water content of a diverse range of samples, and has been extensively used in industrial laboratories to measure water in petroleum oils. The oil content is calculated from weight difference and therefore it is important that no sand grains be lost from the core during the analysis, as this would result in erroneously high calculated residual oil saturation.The principle of operation is straightforward. When the core to be analyzed is weighed, the resulting measurement will consist of the weight of the sand grains, as well as the oil and water present in the pore space. The sample is then placed within a tear in the apparatus, and this unit is suspended above a flask containing a solvent such as toluene. Whatever the solvent, it must have a boiling point higher than water and be both immiscible with and lighter than water. The dripping solvent mixes with oil from the sample, and both the solvent and oil are returned to the solvent flask. The process continues until the sample is raised to the boiling point of water. When it does, the water vaporizes, rises in the condensing tube until it is condensed, and falls back into the calibrated tube. Because it is heavier than the solvent, it collects at the bottom of the tube, where its volume can be measured. When successive readings indicate no additional water recovery has occurred, we know all water has been removed from the sample, and the water volume is recorded for further calculations.

5.0 APPARATUS1. Dean-stark apparatus2. Rock sample(core plug)3. Solvent6.0 PROCEDURE1. Weigh a clean, dry thimble. Use tongs to handle the thimble.2. Place the cylindrical core plug inside the thimble, and then quickly weigh the thimble and sample.3. Fill the extraction flask two-thirds full with toluene. Place the thimble with sample into the long neck flask.4. Tighten the ground joint fittings, but do not apply any lubricant for creating tighter joints. Start circulating cold water in the condenser.5. Turn on the heating jacket or plate and adjust the rate of boiling so that the reflux from the condenser is a few drops of solvent per second. The water circulation rate should be adjusted so that excessive cooling does not prevent the condenser solvent from reaching the core sample.6. Continue the extraction until the solvent is clear. Change solvent if necessary.7. Read the volume of collected water in the graduated tube. Turn off the heater and cooling water and place the sample into the oven (from 105 to 120 ), until the sample weight does not change. The dried sample should be stored in desiccators.8. Obtain the weight of the thimble and the dry core.9. Calculate the loss in weight WL, of the core sample due to the removal of oil and water.10. Measure the density of a separate sample of the oil.11. Calculate the oil, water and gas saturations after the pore volume Vp of the sample is determined (O.Torsaeter, 2000).

7.0 RESULTSSample No: Porosity, :WorggWdryGwg/cm3og/cm3Vwcm3WoGVocm3Vpcm3SoSwSg

WhereWorg: Weight of original saturated sampleWdry: Weight of desaturated and dry sample

Equations:WL = Worg - WdryWo = WL - WwVb = (D/2)2 LVp = VbWhere D and L are diameter and length of the core sample, respectively.

8.0 DISCUSSIONThe main objective of this experiment is to determine the oil, water and gas saturation of a core sample. Saturation is the measure of how much porosity of porous medium been occupied by fluid. Fluid saturation is defined as the ratio of the volume of fluid in a given core sample to the pore volume of the sample.

The experiment need to be carried in such orders as first weighed a clean, dry thimble and then place the cylindrical core plug inside the thimble, and then quickly weigh the thimble and sample. Next filled the extraction flask two-thirds full with toluene and placed the thimble with sample into the long neck flask. After that, start circulating cold water in the condenser Turn on the heating jacket or plate and adjust the rate of boiling so that the reflux from the condenser is a few drops of solvent per second. Continued the extraction until the solvent is clear. By the time it finish, Turn off the heater and cooling water and place the sample into the oven (from 1050C to 1200C), until the sample weight does not change meanwhile the dried sample should be stored in a desiccators. Then, the weight of the thimble and the dry core is obtained in order to calculate the loss in weight WL, of the core sample due to the removal of oil and water. Measure the density of a separate sample of the oil and last calculate the oil and water saturation.However, due to unavoidable technical problems we are unable to carry out this experiment thoroughly. For the information, as we know it is important to consider the saturation change occurring in the core from in-situ to surface conditions. Such as the condition, suppose a core is being recovered while drilling a well with water-based drilling mud. Water from the drilling mud will enter the rock expulsing oil. The result as the core is lifted, the reduction in pressure will cause the oil to release gas and this will expand expulsing oil and water out of the rock.

9.0 CONCLUSIONThe main objective of this experiment is to determine the oil, water and gas saturation of a core sample using the Dean-stark distillation. Through this experiment we can also study the procedures in cleaning of the core samples from residual fluids. But due to technical and laboratory problem, we were unable to conduct this experiment. Saturation is the important parameter that we should know to estimate how much fluids occupied in the pore space. The fluids are oil, water or gas. As we know it is important to consider the saturation change occurring in the core from in-situ to surface conditions. Such as the condition, suppose a core is being recovered while drilling a well with water-based drilling mud. Water from the drilling mud will enter the rock expulsing oil. The result as the core is lifted, the reduction in pressure will cause the oil to release gas and this will expand expulsing oil and water out of the rock.

10.0 REFERENCES1. Dean-Stark apparatus. (2013, March 15). Retrieved May 19, 2013, from Dean-Stark apparatus: http://en.wikipedia.org/wiki/Dean-Stark_apparatus2. O.Torsaeter, M. A. (2000, August). Experimental Reservoir Engineering Laboratory Workbook. Retrieved May 19, 2013, from Experimental Reservoir Engineering Laboratory Workbook: http://www.ipt.ntnu.no/~oletor/kompendium4015.pdf3. http://www.ipt.ntnu.no/~oletor/kompendium4015.pdf

11.0 APPENDICES

Figure 1: Modified Dean and Stark Extraction apparatus for determining Toluene insoluble in phosphorus (Dean-Stark apparatus, 2013).

Figure 2: Dean Stark apparatus (Dean-Stark apparatus, 2013).

1:Stirrer bar/anti-bumping granules2:Still pot3:Fractionating column4:Thermometer/Boiling point temperature5:Condenser6:Cooling water in7:Cooling water out8:Burette9:Tap10:Collection vessel

Figure 3: Dean-Stark apparatus (Dean-Stark apparatus, 2013)9