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COVENANT UNIVERSITY, CANNANLAND

OTA, OGUN STATE.

DEPARTMENT OF PETROLEUM ENGINEERING

EXPERIMENT 1:

POROSITY (USING POROSIMETER)

GROUP 5

EMORDI CHIKA JESSICA

12CN013994

MARCH, 2017

Table of Contents

ABSTRACT 3

INTRODUCTION 4

EXPERIMENTAL APPARATUS 6

PROCEDURE 7

SAFETY MEASURES 7

Maintenance 7

Precaution Taken 7

RESULTS 8

DISCUSSIONS 9

CONCLUSION 10

REFERENCES 11

ABSTRACT

Porosity is an important property of a reservoir rock that determines the economic relevance of the reservoir to the operator/owner, it is important therefore to determine the porosity of the reservoir rock. The porosity of a material can be determined in different way but in this experiment i would be looking at the use of the Ofite model 350 core porosimeter.

This report contains the procedures i used to carry out the experiment, the dimensions of my core sample, my results and conclusions.

INTRODUCTION

Porosity is one of the most important parameters for the reservoir rock. It describes the storage capacity of the rock (Dandekar, 2013), and is described as the part of a rock that does not consists of solid grains but consists of open pores. Porosity is defined as the ratio of the pore volume (PV) to bulk volume (BV). The porosity may be divided into total porosity and effective porosity. The total is the ratio of all the pore spaces in a rock to the BV of the rock,

'= (Total pore volume)/(Total or bulk volume)  ............ (1)

This illustrates that the reservoir rock total porosity may be very high with no conductivity to fluids residing in the ores due to the lack of interconnectivity. While the effective porosity is the ratio of all interconnected pore spaces in a rock to the BV.

   

Figure 1: conceptual representation of different types of pores in a reservoir rock

It may be classified according to its origin as either primary or secondary porosity. The primary porosity is also called the original porosity and is developed during the deposition of the rock. Secondary porosity is described as porosity that has developed after the deposition of the sediments, mainly due to geological activities. Porosity can range from less than 1% for solid granite to more than 50% for peat and clay, and it ranges from 15% to 25% in normal reservoirs. Several parameters influence the porosity, such as grain shape, grain size, sorting, packing and compaction. Porosity is measured as a fraction or most commonly as percentage [%].

'=PV/BV  ...................... (1)

BV=''HR^2 ............... (2)

PV =7758''',bbl

WHERE

' = Porosity, %

PV = Pore volume, cm3

BV = Bulk volume, cm3

H=Height of the core, cm

R= Radius of the core, cm

EXPERIMENTAL APPARATUS

The OFITE Model 350 Core Porosimeter:

This equipment if=s used for measuring effective porosity of a core sample using Nitrogen gas as a source of pressure

 

Figure 2 : porosimeter  

Veneer calliper

Figure '': veneer calliper

This is used to take measurements of the core samples for more accuracy

PROCEDURE

1. Before starting a test, I placed all valves in the vertical position.

2. I turned the unit on and allowed it to warm up for 5 to 10 minutes. After the unit warms up, the display read zero.

3. I measured and recorded the diameter and length of the core with the calipers included with the unit.

4. I unscrewed the sample holder and insert the core specimen. I screwed the sample holder back into place just until it stops.

5. I turned the 'P2 Test' valve to the 'Off' position.

6. I rotated the regulator clockwise until the pressure reads approx. 180 psi (1,242 kPa).

7. I turned the 'P1 Lock In' valve to the 'Off' position.

8. I allowed P1 to stabilize and recorded the value.

SAFETY MEASURES

Maintenance

The O-ring contained within the sample holder should be periodically checked and replaced.  

By applying a thin film of typical bearing grease to the O-ring its life can be prolonged.

Precaution Taken

I ensured that the connection to the gas source (cylinder was tightly fixed to prevent the evacuation of gas).

I made sure that the pressure values stabilized before taking my readings of pressure.

I ensured that I turned off the pressure test to off position before opening the core holder to avoid accident due to high pressure.

RESULTS

Length of the Core Sample = 20.5mm

Diameter of the Core Sample = 20.5mm

P1, psi = 153

P2, psi =57.18

V1 = 60.18cm3

V2 = 165.31cm3

Core bulk volume (cm3) VB='''D/4'^2*L

Vb='(''*2.05)/4'^2*2.05='3.3006 *2.05=6.766cm'^3

V_3=V_1  P_1/P_2

V_3=60.18*153/57.18=161.027'cm'^3

Core Grain Volume, VG (cm3) = V2-V3 = 165.31-161.027

= 4.283cm3

Core Pore Volume, VP = VB-VG = 6.766-4.283

      = 2.483cm3

Porosity,'' = V_P/V_B   ''100%

''=2.483/6.766'' 100% = 36.698%

DISCUSSIONS

Based on the calculated porosity of 36.698% using the porosimeter and gas the core is considered sufficiently porous.

Errors

There were errors that might happened during the experiment and might caused in data inaccuracy and miscalculation of the result

The experiment can only count effective porosity (interconnected pores). We cannot determine the whole porosity due to possibility of isolated pores.

Human errors also might happen, i.e. mistake at diameter and length measurement (wrong start, too tight or loose in measurement)

CONCLUSION

The porosity of the core plug sample can be determined by the OFITE model 350 core porosimeter with gas saturation method, making sure that no empty space in the matrix cup is necessary to make the measurement more accurate. At the end of this experiment i got the porosity of my core sample to be 36.698%

References

James A. Craig; O. D. Orodu. Reservoir/Core Analysis Laboratory   Manual, February 2015

Dandekar, Y. A. (2013). POROSITY. In Y. A. Dandekar, Petroleum Reservoir Rock and Fluid Properties (pp. 19-23). CRC press..

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