Integrated petrophysical laboratory measurements and well ...



integrated petrophysical laboratory measurements and well logging analysis for reservoir characterization of Kareem formation in belayim marine oil field, gulf of suez, egypt.

by: said a. aly, nasser m. hassan and ayman s. el-sayed

Geophysics Department, Faculty of Science, Ain Shams University.

abstract: The coordination of wireline logging data and petrophysical laboratory information proved to be valuable for evaluating the petrophysical parameters and studying the reservoir characterization of the Kareem Formation in the Belayim marine oil field, Gulf of Suez, Egypt.

Some Kareem Formation samples obtained from 113-m-13 well have been subjected for both insoluble residue and petrophysical analyses in order to outline the most important rock properties. However, the amounts of carbonate, sand, silt and clay were determined through the insoluble residue technique. Also, the porosity, rock density, permeability, the true and apparent electrical resistivity, formation resistivity factor, resistivity index, tortuosity and water saturation were measured through the laboratory petrophysical analysis.

The well logging analysis was carried out through a computer program (Creative-007), to calculate the percentages of the lithologic constituents, the formation porosity, the true resistivity and the water and hydrocarbon saturation.

Integrated results of the laboratory measurements and well logging analysis revealed that the Kareem Formation have a good quality reservoir rocks for oil potentiality in Belayim marine oil field.

introduction

The area of interest lies in the Belayim marine oil field and it is located in the eastern side of the Gulf of Suez, 165 Kms southeast of the Suez City. The field covers an area of about 9 Kms to the west of Sinai shoreline (Fig. 1) and generally in deep marine water (30-40 m.). Belayim marine oil field produces oil from the Miocene and Pre-Miocene reservoirs. The Miocene reservoirs include the Kareem and Rudeis Formations. The Kareem Formation is of prime interest in this work, where rocks of high hydrocarbon potential in terms of source, reservoir and seal are encountered in this unit (Fig. 2).

Belayim marine oil field was discovered in 1961. Since 1961 till now, more than 60 wells were drilled for development of this field. This extensive development phase in such field is based mainly on the evaluation of reservoir characteristics. Accordingly, the main goal for the present study is to contribute through the petrophysical laboratory measurements and well logging analysis to discover the reservoir characterization of the Kareem Formation in this area for more development activities.

The petrophysical laboratory measurements for ten core samples obtained from 113-m-13 well include the insoluble residue analysis to determine the amount of carbonate, sand, silt and clay in combinations with petrophysical analysis to determine the physical properties of rocks which are related to the presence of pore space and fluid saturations. The insoluble residue technique was deal with by several authors such as McQueen (1931), Ireland (1958) and Tickell (1965). The method of Tickell (1965) was used in this study for the discrimination of the remaining materials of rock fragments into carbonate, sand, silt and clay. The obtained core samples were laboratory prepared for further determination of storage properties. This preparation starts with the cutting of core samples into the optimum size, generally into cubes of different dimensions. Then, the obtained samples were cleaned from residual fluids by using an organic solvent (Keelan, 1972). Such process is ended by drying all cores by vacuum controlled temperature of magnitudes ranged from 80-90 (C for a minimum of 6 hours according to the American Petroleum Institute (1960). After this preparation, the core samples are ready for the measurements of the rock density, formation porosity, permeability and electrical resistivity. These laboratory measurements were executed in the National Research Center and the Egyptian Petroleum Research Institute laboratories.

On the other hand, the given well logging data are evaluated to conclude the petrophysical parameters of the Kareem Formation through the formation evaluation system. The theory of this system of well logging analysis depends on the total use of the computer through equations and formulae for the needed petrophysical parameters especially those concerning lithology, porosity and fluid saturations. The software program (Creative-007) used for the petrophysical calculation in this study was based on a broad range of interpretation techniques (Aly, 1989).

Integrated results of both laboratory measurements of core samples and well logging analysis are used for reservoir characterization of the Kareem Formation. Within the context of this study, the evaluation of petrophysical properties from the two ways and the accuracy of the results are described in detail.

petrophysical laboratory measurements

1- Methodology and techniques:-

In general, the laboratory measurements of core samples provide a direct measure of the storage properties of the Kareem Formation. These laboratory measurements can be discussed as follows:-

The insoluble residue was determined by digesting the crushed sample in a hot diluted hydrochloric acid. The discrimination of the rock lithology of each studied sample into carbonate, sand, silt and clay were determined.

The bulk density ((b) of each rock sample was determined according to the method described by Dakhanova (1977) and Ragab and Ayyad (1985). The grain density ((g) of each studied sample has been measured by the pycnometer method (Dortman, 1984). The rock porosity of each rock sample is measured by the saturation method which introduced by Melcher technique (Dakhanova, 1977). The permeability of the rock sample was measured by using the profile permeameter. The amount of carbonate, sand, silt and clay, (b, (g, (e, (t and K of studied rock samples are given in table (1).

|S. No. |Depth in m. |Carb. (%) |Sand |Silt & Clay (%) |(b |(g |(e |(t |K |

| | | |(%) | |gm/cc |gm/cc |(%) |(%) |mD. |

|1 |2587.65 |7.47 |88.34 |4.19 |1.65 |2.58 |6.84 |58.86 |63.09 |

|2 |2588.20 |7.54 |85.85 |6.61 |1.73 |2.57 |1.92 |53.50 |1.26 |

|3 |2588.85 |10.13 |81.13 |8.74 |1.82 |2.54 |2.17 |46.75 |1.78 |

|4 |2623.85 |7.10 |82.25 |10.65 |1.75 |2.69 |3.91 |55.62 |6.31 |

|5 |2677.13 |9.62 |78.38 |12.00 |1.89 |2.51 |1.78 |41.06 |1.12 |

|6 |2678.05 |15.74 |68.24 |16.02 |1.91 |2.62 |2.04 |43.83 |1.41 |

|7 |2696.40 |18.40 |66.14 |15.46 |2.07 |2.64 |1.68 |34.76 |0.82 |

|8 |2696.94 |11.32 |70.69 |17.99 |1.86 |2.53 |3.67 |43.79 |5.42 |

|9 |2704.65 |10.90 |61.90 |27.20 |1.78 |2.19 |2.76 |34.45 |2.82 |

|10 |2705.50 |17.41 |57.03 |25.56 |1.90 |2.23 |3.67 |59.64 |5.01 |

Table (1) : petrophysical properties of studied core samples of Kareem Formation in

113-m-13 well.

Moreover, the apparent electrical resistivity (Ro) of each sample was measured under the normal pressure and temperature at three successive cycles of saturations by NaCl solution of concentrations 6000,60000 and 250000 ppm having resistivities 0.9, 0.12 and 0.042 ohm.m. respectively according to the method described by Parkhomenko (1967). The true electrical resistivity (Rt) was measured using the centrifuge (6000 ppm) at partial water saturation (Sw).

The other electrical properties were computed from the knowledge of both the electrical resistivities (Ro and Rt) and the effective porosity ((e). Accordingly, the formation resistivity factor (F) was calculated during the three runs by using the following formula: -

F = Ro / Rw (Archie, 1942)

The resistivity index (I) and water saturation (Sw) were computed as: -

I = Rt / Ro = Swn (Archie, 1942)

The mounce potential ((() is considered to be a function of the brine concentration and is calculated by using the equation: -

(( = ln F2 / F1 (Perkins et. al., 1954)

The tortuosity (T) is computed by using the equation: -

T = (e F (Gur, 1976)

The results of the electrical properties of the studied rock samples in 113-m-13 well are given in table (2): -

|S. No|Depth |Rw1 = 0.9 |Rw2 = 0.12 |Rw3 = 0.042 |Rt |I |(( |T |Sw |Swirr |

| | |ohm.m. |ohm.m. |ohm.m. | | | | | | |

| |m. |R1 ohm.m. |F1 |R2 ohm.m. |F2 |R3 ohm.m. |F3 |ohm.m. | |m.v. | |% |% |

|1 |2587.65 | | | | | | | |11.72 |-1.41 |50.82 |29.22 |3.42 |

|2 |2588.20 |64.75 |71.94 |40.47 |337.28 |23.68 |563.76 |1000 |15.44 |1.55 |11.75 |25.45 |3.93 |

|3 |2588.85 |58.06 |64.51 |5.49 |45.78 |4.63 |110.12 |1565.07 |26.96 |-0.34 |11.83 |19.26 |1.97 |

|4 |2623.85 |62.67 |69.63 |18.95 |157.94 |14.14 |336.62 |427.48 |6.82 |0.82 |16.50 |38.29 |2.61 |

|5 |2677.13 |35.94 |39.93 |26.47 |220.61 |17.67 |420.60 |345.64 |9.62 |1.71 |8.43 |32.24 |3.10 |

|6 |2678.05 |18.09 |20.10 |4.26 |35.48 |2.62 |62.35 |373.21 |20.64 |0.57 |6.40 |22.01 |4.54 |

|7 |2696.40 |29.30 |32.56 |17.11 |142.58 |6.04 |143.79 |106.30 |3.63 |1.48 |7.40 |52.50 |1.91 |

|8 |2696.94 |22.29 |24.76 |7.29 |60.78 |6.57 |156.38 |103.71 |4.65 |0.9 |9.53 |46.36 |2.16 |

|9 |2704.65 |17.67 |19.63 |6.74 |56.16 |4.24 |100.83 |68.22 |3.86 |1.05 |7.36 |50.89 |5.19 |

|10 |2705.50 |19.23 |21.36 |19.59 |163.28 |8.38 |199.43 |125.99 |6.55 |2.03 |8.85 |39.06 |2.56 |

Table (2): - Electrical properties of the studied core samples of Kareem Formation in

113-m-13 well.

2- Interpretation

Using the laboratory-measured parameters (Tables 1 and 2) numerous relationships have been constructed, showing some important trends about the petrophysical properties of the reservoir rocks of Kareem Formation. The following part is devoted for the discussion of such relations:-

a) Rock density: - The relationship between bulk density and carbonate content (Fig. 3) shows that the bulk density increases by increasing the carbonate content. This reflects that the bulk density of carbonate is higher as expected than that of sand.

b) Formation porosity: - The relationship between effective porosity ((e) and bulk density ((b) shows that an increase in the porosity of the rock leads to a corresponding decrease in the density (Fig. 4). The effective porosity of the studied core samples is generally low due to the effect of cementing materials such as clay and silt.

c) Permeability :- The relationship between permeability and effective porosity (Fig. 5) is normally a direct relation indicating higher permeability with increasing effective porosity.

d) Electrical resistivity: - The relationships between electrical resistivity (Ro) and tortuosity (T) and that with silt and clay content (Fig. 6) illustrate that the electrical resistivity increases by increasing tortuosity (Fig. 6a) and decreases by increasing the amount of clay content (Fig. 6b). The relationship between true electrical resistivity (Rt) and water saturation (Sw) shows that the true resistivity increases with decreasing the water saturation (Fig. 7).

well logging analysis

1- Formation evaluation technique

2-

The given well log data are evaluated to conclude the petrophysical parameters of the Kareem Formation through the formation evaluation technique. A software program (Creative-007) used in this study contained two parts. The first one includes the environmental corrections for the fluid and rock resistivities and the porosity logs (Density, Neutron and Sonic), while the second one includes the calculations of the main petrophysical parameters.

The calculated petrophysical parameters included the following:-

1) Determination of the rock constituents: - These can be diversified into shale content and non-shale (matrix) content. The volume of shale content (Vsh) is estimated through the mono-and dia-tools shale indicators (Schlumberger, 1972 and Dresser Atlas, 1983). The identification of the matrix (non-shale) rock constituents (sandstone and limestone) and the calculation of their volumes were carried out through the dia crossplots and simultaneous equations technique (Burke et. al., 1969 and Harris et. al., 1969).

2) Determination of the rock porosity:- The formation porosity is determined from Density, Neutron and Sonic logs in the clean and shaly zones through Wyllie et al., (1958) and Bateman and Konen (1977).

c) Determination of the true resistivity (Rt) through Schlumberger logic diagram (Schlumberger, 1984).

4) Determination of the water and hydrocarbon saturations through Archie equation (1942) and Indonesia equation (Schlumberger, 1972).

2- Interpretation

The results of the formation evaluation in this study are diversified into three different types of crossplots, M-N and (b - (N crossplots, GR - (b and GR - (N crossplots and litho-saturation crossplot respectively. The first two crossplots give a quick view about the lithologic constituents (shale, sandstone and limestone) in a qualitative way, while the last one reflects the vertical distribution of rock materials and parameters in a quantitative way.

Fig. (8) represents the M-N and (b - (N crossplots of Kareem Formation in 113-m-13 well. These crossplots reflect the abundance of limestone with a minor occurrence of sandstone. The presence of a high shale content shifted the points downward, while the points shifted upward due to the gas and secondary porosity effects. The porosity values of the Kareem Formation is good and reaches up to 25%.

Fig. (9) exhibits the GR - (b and GR - (N crossplots of Kareem Formation in 113-m-13 well. It gives an indication about the lithologic constituents of the Kareem Formation in the form of limestone and sandstone with a high content of shale.

Fig. (10) represents the litho-saturation crossplot of Kareem Formation in 113-m-13 well. It indicates that the limestone is generally increased allover the section, while the sandstone is represented by a few streaks scattered in this unit. The shale content is considerable and it reaches to a high percentage in some zones. The weighted value of porosity (15%) is good for accumulation of water and hydrocarbon saturation. The water saturation is generally lower than hydrocarbon saturation allover the section indicating that the Kareem Formation has a good potentiality for hydrocarbons.

integrating laboratory measurements and

well logging analysis

The results of well logging analysis and petrophysical laboratory measurements reveal almost proportional relationships. Fig. (11) exhibits the correlation between the litho-saturation crossplots of Kareem Formation in 113-m-13 well from both the log and core analysis versus depth. It indicates that the Kareem Formation is mainly composed of calcareous shaly sandstone as described from core analysis, while in well log analysis it is composed from arenaceous shaly limestone. This difference in composition is mainly due to the selected core samples were taken from the sandstone bodies scattered within the Kareem Formation. The water saturation (Sw) is generally lower than the hydrocarbon saturation (Sh) in the two analyses indicating that the Kareem Formation can be considered as good reservoir rocks for producing oil in the study area.

Although the results obtained using the laboratory measurements are in a good agreement with the well logging analysis, the measured parameters in many cases gives lower values due to either the difference in applied techniques or the variation in the environmental conditions of measurements. Moreover, the selected core samples do not represent the whole formation because they are taken at certain depths, while the well logging data represent a continuous log for the variations inherited in rock materials and parameters with depth.

conclusions

Integrated petrophysical laboratory measurements and well logging analysis were carried out for the Kareem Formation in Belayim marine oil field, Gulf of Suez, Egypt. This integrated study assists to understand the characterization of reservoir rocks and how they are related to additional hydrocarbon potentiality. The main results of this study can be concluded as follows:-

1- Most of the petrophysical parameters of the studied core samples are lower in values than those

obtained from well logging analysis due to either the difference in applied techniques or the variation in the environmental conditions of measurements.

2- The difference in the obtained results from both laboratory measurements and well logging analysis is in the rock constituents of Kareem Formation. According to the laboratory measurements, the Kareem Formation is composed of calcareous shaly sandstone, while in well logging analysis it is formed of arenaceous shaly limestone. This is due to that the selected core samples were cut from the sandstone bodies encountered within the Kareem Formation and accordingly, the sandstone content is higher than the limestone content.

3- According to this integrated study, the Kareem Formation is considered as good reservoir rocks due to their high values of effective porosity and permeability.

4- The determined hydrocarbon saturation (Sh) in the both analyses indicates that the Kareem Formation is considered of high potentiality for producing large quantities of oil in this study area.

ACKNOWLEDGMENT

The authors are highly indebted to Prof. Dr. Ragab, M. A., National Research Center for his support in measuring the petrophysical properties of the selected core samples. A special thanks to every one in the petrophysical lab. of the Egyptian Petroleum Research Institute for their assistance in some petrophysical laboratory measurements. Thanks are also due to the staff of Belayim Petroleum Company for providing the available data needed to complete this work.

references

ALY, S. A. (1989): “Evaluation of the Petrophysical Properties of the Reservoir Rocks Using Well Logging Analysis in Abu Gharadig Basin, Western Desert, Egypt.” Ph.D. thesis, Faculty of Science, Ain Shams University.

American Petroleum Institute (1960): “Recommended Practice for Core Analysis Procedure“. API-RP. No. 40, 55 pp.

ARCHIE, G.E. (1942): “The Electrical Resistivity Logs as An Aid in Determining Some Reservoir

Characteristics", Trans. AIME, Vol. 146, pp. 54-62.

Bateman, r.m. and konen, c.e. (1977): “Wellsite Log Analysis and the Programmable Pocket Calculator“, SPWLA, 8 th, Annual Logging Symposium, Houston, Texas, June 5-8.

Burke, j.a., campbell, r.l. and schmidt, a.w. (1969): “The Litho-Porosity Crossplots - A Method of Determining Rock Characteristics for Computation of Log Data“; SPWLA , 10 th Ann. Log Symp.

Dakhanova, n.v. (1977): “Determination of the Petrophysical Properties of Samples“. (in Russian) - Nedra, Moscow, pp. 19-59.

Dortman, n.b. (1984): “Physical Properties of Rocks and Core Samples“. Nedra, Moscow, pp. 34-65.

Dresser Atlas (1983): “Log Interpretation Charts“; Dresser Industries, Inc., Houston, Texas. 107 pp.

Gur, m.a. (1976): “Petroleum Engineering.” Ferdinaud Enke Verlagstuttgart, 272 pp.

harris, m.h. and mccammon, r.b. (1969): “A Computer Oriented Generalized Porosity-Lithology Interpretation of Neutron, Density and Sonic Logs“; AIME, Denver, Colorado, U.S.A.

Ireland, h.a. (1958): “Insoluble Residues”. In: Haun, j.d. and Le roy, l.w. (eds) Subsurface Geology in Petroleum Exploration Colorado School of Mines, pp. 75-94.

keelen, d.k. (1972): “A Criteria Review of Core Analysis Techniques”. J. Petrol. Tech., pp. 42-55.

Mc queen, h.s. (1931): “Insoluble Residues as A Guide in Stratigraphic Studies.” Missouri. Geol. Surv., 56 th Biemn Rept. State Geologist, Apr. 1, pp. 103-131.

Parkhomenko, e.l. (1967): “Electrical Properties of Rocks“. Pelnum Press, New York, pp. 59-160.

Perkins, f.m. jr, brannon, h.r. jr. and WINSAUER, w.o. (1954): “Interrelation of Resistivity and Potential of Shaly Reservoir Rock”. Transaction. AIME., V. 201., pp. 176-181.

Ragab, m.a. and ayyad, a. (1985): “Petrophysical and Petrographical Properties of the Nubia Sandstone Core Samples from East Oweinat. Egypt.” Proc. of EGS 4 th Ann. Meet, pp. 280-291.

SCHLUMBERGER (1972): "Log Interpretation, Volume I Principles" Paris, France.

SCHLUMBERGER (1984): "Log Interpretation Charts"; Schlumberger Well Services, Inc.

Tickell, f.g. (1965): “The Techniques of Sedimentary Mineralogy“. Elservier Publishers Co., Amsterdam, pp. 4-38.

Wyllie, m.r., gregory, a.r. and GARDNER, c.h. (1958): “An Experimental Investigation of Factors Affecting Elastic Wave Velocities in Porous Media“ Geophys. Vol. 23, No. 3., pp. 459-493.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download