Laboratory Experiment No. 7 Porosity Determination by Saturation Method Objective: To measure the effective porosity of a reservoir rock. Theory: See Experiments #2, 3. Procedure: 1. Measure the dry weight and dimensions of your core. (i.e. Measure length and diameter at least four different locations and record all data). 2. Place the core plug inside the flask filled with brine. Carefully place the sample by sliding down the side of the flask to avoid breakage of the core. 3. Close and seal the top of the flask with a proper stopper. Attach the vacuum hose to the side inlet on the glass flask and start the vacuum pump. 4. Continue to operate the vacuum pump until no more bubbles are displaced from the sample. 5. Stop the vacuum pump and remove the saturated sample. 6. Measure the weight of the saturated sample. Results: 1. Compute the bulk volume for each core based on the measured dimensions. 2. Calculate the weight and volume of water in the core. Use the following equations. Weight of Brine = Saturated Weight of Core − Dry Weight of Core 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝐵𝑟𝑖𝑛𝑒 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑃𝑜𝑟𝑒𝑠 = 3. Calculate the porosity for each core using the following equation: 𝑃𝑜𝑟𝑜𝑠𝑖𝑡𝑦 = 4. 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐵𝑟𝑖𝑛𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝐵𝑟𝑖𝑛𝑒 𝑃𝑜𝑟𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 𝐵𝑢𝑙𝑘 𝑉𝑜𝑙𝑢𝑚𝑒 Compare the results for porosity with the porosity obtained with other methods measured in Experiments 1, 2, and 3. Laboratory Experiment No. 8 Resistivity Measurement of Cores Objective: To measure the resistivity of brine saturated core sample. Theory: The pore formations contain minerals, rock fragments, and void space. In general, the solids are non-conductors and the electrical properties of rock depend on the fluids existing in the pores. The three types of fluids that are interest to the petroleum engineer are oil, water, and gas. Oil and gas are non-conductors and the water is a conductor if it contains dissolved solids. The current is conducted in water due to movement of ions. The resistivity is the reciprocal of conductivity. The resistivity of a saturated core (Rcore) in ohm-m units is given by: where 𝑅𝑅𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 = 𝑟𝑟𝑐𝑐 𝐴𝐴 𝐿𝐿 rc : Resistance of a brine saturated core, ohm. L : Length of core, meters A : Cross-sectional area of the core, m2 The electrical properties of a rock can be related to the porosity by use of formation factor. The formation factor (F) defined by Archie is given as: F= 𝑅𝑅𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑅𝑅𝑤𝑤 where the Rw represent the resistivity of brine saturating the core. Also the formation factor is related to the porosity in the following form: F = a∅−m Where ∅ a : : Porosity, fraction. Represents the tortuosity with a value equal to or greater than one. m : The cementation value varies between 1 and 2, but generally 2 is used for consolidated clean sandstones Procedure for Brine Resistivity: 1. Pour sufficient amount of brine in a clean beaker. The beaker should be properly cleaned and dried. Insert the plastic connected to the tip of the resistivity cell and fill the measuring cylinder. Make sure the brine covers the both electrodes. 2. Turn on the RCL meter . 3. Set the numeric panel on number 7 “Z-𝜃𝜃”. 4. Connect one of the clips to the Black port “CA” and the other clip to the red port “CB”. 5. Read the “Z” value as your water resistance on the RCL panel. 6. Turn power switch to off position and disconnect current and potential lines. 7. Clean the resistivity cell with distilled water. Return all used equipment to their original locations. Procedure for Core Resistivity: 1. Obtain a clean and dry core. Measure the diameter and length. 2. Saturate the clean and dry core with the brine. 3. Remove the chamois skin disks from the core retainer rings and soak them with brine. If necessary, squeeze out excess brine. Place the chamois skins back to the core holders. 4. Carefully place the saturated core between two electrodes. Wipe off excess brine prior to placement and make sure the core is in contact with the electrodes. 5. Connect the RCL clips to the top of the core holder caps. 6. Read the “Z” value as your core resistance on the RCL panel. 7. Turn power switch to off position and disconnect the clips. 8. Remove the core from the holder and clean the chamois and electrodes of the core holder. 9. Return all used equipment to their original locations. Results 1. Calculate the resistivity of the brine in ohm-m by multiplying it’s resistance with the cell constant (=0.001). 2. Calculate the resistivity of the saturated sample using the length and cross-sectional area. 3. Calculate porosity values using a=1 and m=2. 4. Compare your porosity results in this experiment with porosity results obtained in experiments 1, 2, 3, and 7 in a table and make a discussion. Bassam Almulhim-800125192 Experiment #7 Porosity Determination by Saturation Method Group A, #1 23/02/2018 PNGE432-007 Petroleum Reservoir Engineering Laboratory Dr. Mehrdad Zamirian West Virginia University Department of Petroleum and Natural Engineering - Objectives: The main target of this experiment is to calculate the porosity of the selected core samples by measuring the weight of the core samples after saturating them. - Theory: The effective porosity of a sample is totally different than the total porosity of the same sample. The total porosity is defined as the total porosity of the rock, which consist of the porous and the grains. On the other hand, the effective porosity is the porosity of the porous media that the fluid can fill. The total porosity is always equal or larger than the effective porosity. Porosity defined as the pore spaces between the rocks that the fluid can go throw, so high porosity means good reservoir. Porosity is unitless and has a number between 0 and 1. Mathematically, porosity can be defined as the pore volume over the bulk volume of the rock. Porosity equation can be written as: 𝑃𝑜𝑟𝑜𝑠𝑖𝑡𝑦 % = 𝑉𝑝 ∗ 100 𝑉𝐵 𝑑2 ∗ ℎ ∗ 𝜋 𝑉𝐵 = 4 𝑚𝑤𝑎𝑡𝑒𝑟 = 𝑊𝑠𝑎𝑡𝑢𝑟𝑎𝑡𝑒𝑑 − 𝑊𝑑𝑟𝑦 𝜌𝑏 = 𝑚 𝑉𝑝 In this experiment, the two samples were already fully with brine saturated to determine the weight of the water inside the pores of the samples by subtracting the weight of the sample after saturation from the dry weight of the sample obtained from previous experiments. After that, the pore volume is calculated by dividing the mass obtained by the density of water, which is 1 g/cc. Finally, the porosity is determined using the above equation. However, the brine content or saturation was assumed to be negligible since it’s very low and and density was assumed to be the density of water. - Procedure: First, the core sample was obtained from the pinch after leave it to fully saturate for a week. However, the students have to make sure to dry the sample carefully with a tissue. Then, the sample is weighted using an electronic balance and record the weight. Next, weight the next sample. Finally, return the samples and clean the area and cover the balance. - Results and Calculations: Table 1: useful results calculated in experiment #1 d (cm) h (cm) W(dry) (g) VB (cc) Sample A 2.5 4.095 45.28 20.1012 Sample B 2.5 4.14 45.28 20.3222 Table 2: calculalted saturated wieght for sample A,B W (Sat) (g) • Sample A 48.7114 Sample B 48.8877 Sample Calculation: Sample A: 𝑉𝐵 = 𝜋 ∗ (2.5)2 ∗ 4.095 = 20.1012 𝑐𝑐 4 𝑚𝑤𝑎𝑡𝑒𝑟 = 𝑊𝑠𝑎𝑡𝑢𝑟𝑎𝑡𝑒𝑑 − 𝑊𝑑𝑟𝑦 = 48.7114 − 45.28 = 3.4314 𝑔 𝑉𝑝 = 𝑚 3.4314 𝑔 = = 3.4314 𝑐𝑐 𝑔 𝜌 1 𝑐𝑐 𝑃𝑜𝑟𝑜𝑠𝑖𝑡𝑦 % = 3.4314 ∗ 100 = 17.0706 % 20.1012 Below are the tables for the results calculated from this experiment for the two core samples and tables to compare the results of the porosity calculations from the previous experiments: Table 3: experiment#7 results VB (cc) m (water),(g) Vp (cc) Porosity % Sample A 20.1012 3.4314 3.4314 17.0706 Sample B 20.3222 3.6077 3.6077 17.75 Table 4: Effective porosity results Effective porosities values (%) Sample A Sample B Exp#2 14.25% 14.94% Exp#3 15.69% 16.61% Exp#7 17.07% 17.75% Table 5: Total porosity values for sample A, and B Total porosity values (%) Sample A Sample B Exp#1 14.84% 15.79% The values for the effective porosities should be the same for all the experiments. In addition, all of the effective porosities values should have values that are less than the total porosity, but some of the values do not follow these rules due to the human error, machine error, and unit error. The concentration of any material can be calculated using a very simple mathematic equation, which is mass of the solute divided by the volume of the solution. If any student wants to make a 35k ppm of brine, he or she should use 35g of brine with 1L of water. Brine is commonly used in drilling mud industry today since it has similar behavior of sea salt water. Brine can also be the same as salt in terms of behavior. - Conclusion: The effective porosity of the two prepared core samples was calculated after weighting each core sample after they fully saturated. The saturated weight was used to calculate the difference of the dry and saturated weight for both core samples. After that, the pore volume was calculated and the effective porosity. The results for both core samples were compared with other porosity results calculated in previous experiments. There were some differences because of some errors and human error is one of them. - References: • Texas Brine Company, LLc, http://www.texasbrine.com Bassam Almulhim-800125192 Experiment #8 Resistivity measurement of cores Group A, #1 03/02/2018 PNGE432-007 Petroleum Reservoir Engineering Laboratory Dr. Mehrdad Zamirian West Virginia University Department of Petroleum and Natural Engineering - Objective: The target of this experiment is to determine the resistivity of the two prepared core samples after fully saturate them with brine. - Theory: This experiment generally deals with resistivity and resistance. Resistivity is known as capital R with unit of Ω. 𝑚. However, resistance is known as small r with unit of Ω, their dimension is different. Furthermore, there is a relationship between resistivity and resistance, resistivity is the special electrical resistance of a sample, so the shape is very important when resistivity is calculated. The equation of resistivity with resistance can be written as 𝑅 = 𝑟∗𝐴 𝐿 . So any cube sample that has 1 m2 area and length of 1 m, and the 1 Ω current passes throught 𝑉 this sample with 1 voltage, then this sample has a resistivity of 1 Ω. 𝑚. 𝑟 = 𝐼 . There are three terms that are going to be used in this experiment which are Rw, which is the water resistivity Rt,, which is he true resistivity and Ro, which is the resistivity of a sample that is 100% saturated with brine. Rw has 100% porosity and 100% water saturation. Rt has water saturation and porosity values that are not equal to 100%. Ro has 100% water saturation and porosity not equal to 100%. Ro and Rt are the same in this experiment because we have only one type of fluid. The relationship between the resistivity and rock properties can be shown 𝑅 as formation factor: 𝐹 = 𝑅 𝑜 , which is always greater than 1.and formation factor 𝑤 and porosity equation (Archie’s equation): 𝐹 = 𝑎𝜙 −𝑚 ,a is the tortuosity factor = 1 1 ,and m is the cementation factor = 2, so 𝐹 = 𝜙2 because we don’t have a wide range of porosities. However, when we have wide range of porosities and plot them versus formation factor in log-log scale. There will be a straight line with a slope of (m) and intercept of (a). In this experiment, resistance will be measured first, and then the resistivity will be calculated, and finally the porosity using the formation factor equation. When it comes to water resistivity, there is an equation that we can calculated the resistivity of water through it using the water resistance because water doesn’t have a shape, but it takes the shape of the container, which we have the area and length of that container already. 𝑅𝑤 = 0.001𝑟𝑤 . The machine that used in this experiment is RCL, which means resistance capacitance induction, which measures the resistance of a material and then calculate the resistivity after having the area, length, and resistance of that material. - Procedure: The first thing to do is to measure the water resistivity. The water resistivity tower has to be connected to the RCL, and the tube in the water resistivity tower has to be filled with brine to measure the resistance of the brine. After that, the resistivity of water can be calculated using the equation discussed in the theory part. First of all, the sample is placed is the core holder tight to let the current passes through the sample, and don’t dry both ends of the sample before placing it. Then, release the arm to make sure the sample is tight in the core holder. Finally, read the resistance value in the RCL, and make sure to write the first value seen. - Results and Calculations: The below table summarizes the results for this experiment: Table 1: results for both samples A, and B Sample A Sample B r (ohm) Ro(ohm.m) F (frac.) 177.34 165.76 2.13 1.97 21.9 20.24 Table 2: water reistance and resistivity rw (ohm) Rw (ohm.m) 97.32 0.0973 Porosity (%) 21.4 22.22 • Sample Calculation: Sample A: 𝑅𝑜 = 𝑟 ∗ 𝐴 177.34 ∗ 4.91 = = 2.13 𝑜ℎ𝑚. 𝑚 𝐿 4.095 𝑅𝑤 = 0.001𝑟𝑤 = 0.001 ∗ 97.32 = 0.0973 𝑜ℎ𝑚. 𝑚 𝐹= 𝐹= 𝑅𝑜 2.13 = = 21.9 𝑅𝑤 0.0973 1 1 1 √ √ → 𝜙 = = = 21.4 % 𝜙2 𝐹 21.9 Table 3: Effective porosity results Effective porosities values (%) Sample A Sample B Exp#2 14.25% 14.94% Exp#3 15.69% 16.61% Exp#7 17.07% 17.75% Exp#8 21.4% 22.22% Table 4: Total porosity values for sample A, and B Total porosity values (%) Sample A Sample B Exp#1 14.84% 15.79% There were a difference between the effective porosity values calculated from previous experiments and effective porosity values for samples A, and B for this experiment. There are some errors that played a big role in changing the values one from another, which are the human error, and machine error. However, the total porosity values from experiment 1 are smaller than some of the effective porosity values calculated in previous experiments and that’s because the same errors discussed above. - Conclusion: The effective porosity was calculated after measuring the resistance for both core sample A, and B. The process was to calculate the resistivity from the recorded resistance, then the formation factor is calculated after determine the water resistivity. Finally, the porosity is calculated using the formation factor equation with knowing the cementation and tortuosity factors, which assumed to be known in this experiment. The results showed differences with the porosity values calculated in previous experiment and that’s because the human, and machine errors. - References: • “Formation Resistivity Factor.” Perm Inc. Tipm Laboratory, perminc.com/resources/fundamentals-of-fluid-flow-in-porousmedia/chapter-2-the-porous-medium/formation-resistivity-factor/. 
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