Geological Modelling And Resource Estimation Of ... · PDF fileGeological Modelling And Resource Estimation Of Maastrichtian Coal Deposit Within Anambra Basin, ... Cretaceous stratigraphy,

INTERNATIONAL JOURNAL OF TECHNOLOGY ENHANCEMENTS AND EMERGING ENGINEERING RESEARCH, VOL 2, ISSUE 12 52 ISSN 2347-4289

Copyright © 2014 IJTEEE.

Geological Modelling And Resource Estimation Of Maastrichtian Coal Deposit Within Anambra Basin, South-Eastern Nigeria: A Guide For Investors Y.S. Agunleti, K. Peter Eta-Zuma Group West Africa, Plot 26 Gudu District, Abuja Nigeria Email: [email protected] ABSTRACT: There is no doubt that one of the oldest industries in the history of man is coal mining industries. In Nigeria, coal mining can be traced to Ogbete coal mine in Enugu as far back as 1916. Today’s mining engineers are the link between production and technical services by determining the direction the project will take and how it will get there. These cannot be over-emphasized with the immense contribution of the geologist for effective delivery of a cost effective mine plan. These processes are integrated with each other in a flow-geological model, to mine design, to mine plan, to production schedule and to mine reclamation. A well-integrated process flow allows the engineers to mesh and sequence steps in the process, maintaining the consistency of data that leads to meaningful results. One of the most commonly used software packages in geological modeling for coal is GemcomMinex. It’s effective software used in the study area “Okobo” to calculate the coal reserves and conduct mine planning and scheduling of mine activities. Strater 4 is a powerful and innovative well log, borehole and cross section plotting software which is gaining relevance in exploration for stratified deposit. The graphical view of drill-hole data at various intervals within the studied area shows an average depth of 20m as studied in a 2-dimension view showing coal stratification withinMamu formation and an average thickness of 1.92mfor 78,929tonnes of coal. Keywords: Maastrichtian, GemcomMinex, Strater 4, Mine and Stratification INTRODUCTION The planning of mine both surface and underground mine requires a complex blend of technical expertise, experience and subjective design criteria implemented by mining professionals not limiting the effective geological modeling by the geologists. In other to achieve this task, the procedure has largely moved from the previous manual means to the modern tools and techniques that enables flexibility and enhances greater degree of accuracy and confidence. An area of 44,929 km

2located in Ankpa Local

Government Area of Kogi State, Nigeria was studied for this research. It is bordered in the east by Benue State and in the South by Enugu State. Geographically located within Sheet 249SW (Figure: 1) between (354729, 358407) E and (829224 and 832923) N (32N UTM and WGS 84). Coal quality analysis was conducted at SGS South Africa with generally acceptable standard codes of ISO and resource estimation base on JORC standards.

Fig.1: Location of the Study Area



BRIEF GEOLOGY OF ANAMBRA BASIN Sedimentation in the Lower Benue Trough commenced with the marine AlbianAsu River Group, although some pyroclastics of Aptian - Early Albian ages have been sparingly reported (Ojoh, 1992). The Asu River Group in the Lower Benue Trough comprises the shales, limestones and sandstone lenses of the Abakaliki Formation in the Abakaliki area and the Mfamosing Limestone in the Calabar Flank (Petters, 1982). Mid-Santonian deformation in the Benue Trough displaced the major depositional axis westward which led to the formation of the Anambra Basin.

Sedimentation in the Anambra Basin thus commenced with the Campanian-Maastrichtian marine and paralicshales of the Enugu and Nkporo Formations, overlain by the coal measures of the Mamu Formation. The Enugu and the NkporoShales represent the brackish marsh and fossiliferous pro–delta facies of the Late Campanian–Early Maastrichtian depositional cycle (Reijers and Nwajide, 1998). The coal-bearing Mamu Formation and the Ajali Sandstone accumulated during this epoch of overall regression of the Nkporo cycle. Figure 2 shows the general geology of southeastern Nigeria

Fig. 2: Geological map of Southeast Nigeria; Courtesy NGSA



MATERIALS AND METHOD Ten (10) borehole drilling were carried out in the study area with a depth of drilling ranges from (14.2 to 20.3) meters. The cores(Fig. 3) were logged and recorded appropriately on the core log sheet. The entire ten borehole intercepted coal and was correlated with the aid of geological software. Boart Longyear 2008 rig with specifications as 9.4m mast length,76mm bit diameter, 73mm core barrel diameter, 70mm diameter drill stem, 3m length drillstem,1250rpm

maximum head speed ,3500 psi maximum operation pressure, 47011Nm (3925lbft) maximum head torque, 85km/h maximum wind resistance and 4184N(9326lbft) feed thrust was used to acquire the core logs. The holes were drilled at an angle of 90

0 to depth where coal was

intercepted. Software used includes GemcomMinex 6.05, Strater 4 Golden software, Arc GIS 10, Surfer 10 and Global Mapper 11.

Fig. 3: Showing core logs

RESULTS AND DISCUSSIONS Coal geologic model is a structural model delineating the physical attributes of coal deposit at relevant spatial position aimed for effective mine plans. It forms the basis to calculate the resource and reserve estimation. Table 1 presents the borehole elevations, depth and thicknesses of coal intercepted, while figure 4 shows borehole locations within contour map of the area. The correlation of coal thicknesses within the underlying and overlying rock unit was achieved usingstrater 4 geosoft. It is a twodimensional representation of the coal seam defined by parameters such as XYZ (Northing, Easting and elevation), the drill collars, drill intervals and hole I.D.. Three (3) profile line for correlation (Fig.5) drawn across the boreholes are;

1. Profile A-A/ = 173.6m@ 3 Borehole points = 58m

2. Profile B-B/= 164.8m @ 4 Borehole points = 41m

3. Profile C-C/= 137.2m @ 6 Borehole points = 23m

Lithologic log of individual borehole reveal sandstone as oldest overlain by thin carbonaceous shale, coal, undifferentiated clay and capped by the top soil. An average coal thickness of 1.7m from the correlation plots (fig. 6-8) shows a good coal thickness to venture into when compared with international standard for coal mining. Measured resource approach in line with the Australasian Joint Ore Reserves Committee Code (JORC Code)

Standards to report Coal Resources, and Coal Reserves gives in situ coal resource area of 30,707m

2and was use to

run the coal resourceestimation with the use of GemcomMinex. Figure 9-10 shows coal thickness and seam vis-à-vis topography of the area following data set for resource estimation such as Topography, Collar (Northing, Easting, Elevation, Depth, and Dip of borehole), Lithology, Assay, Density and Boundary of the area.



Table 1: Showing Borehole Information

Borehole point

Elevations (m)

Borehole Depth

(m)

Coal thickness

(m)

BH-1 301.7 20.1 2.1

BH-2 319.4 20.3 2.5

BH-3 317.8 18.8 1.2

BH-4 316.3 17.3 2.0

BH-5 294.3 14.2 1.6

BH-6 313.3 14.3 1.2

BH-7 292.5 12.5 0.4

BH-8 299.8 20.1 2.3

BH-10 293.7 20.2 2.0

BH-11 291.6 14.2 1.3

Average borehole

depth =17.2

Average thickness

=1.7

CONCLUSION There are number of accepted ways for coal resource and reserve estimation, however commonly used methods include polygonal estimates as described in Bulletin No. 28 NGS and ‘’Australian Guidelines for Estimating and Reporting of Inventory Coal, Coal Resources, and Coal Reserves, Prepared and Issued by the Coal Fields Geology Council of New South Wales and the Queensland Mining Council – March 2003.” The JORC standards method was adopted and data computed in GemcomMinex software. An assumption used is that the coal thickness is considered to be greater than 0.5m (mineable resource). Meanwhile general depth to coal in the study area established with use of starter 4 ranges from (7-15) m which can be mined through surface mining and thus investment friendly. A more realistic general thickness of overburden of 12.2m with average coal thickness of 1.92m cumulates to have volume of 375,738cu.m for 78,929 tonnes of coal as calculated with the use of GemcomMinex software (Table 2)

ACKNOWLEDGMENT All the data andGemcomMinex software used for this research work are greatly acknowledged to Eta-Zuma Group West-Africa, Abuja-Nigeria.

Fig. 4: Contour map of the area showing borehole location



Fig. 5: Borehole Profile line, Location and Elevations

Fig. 6: Showing cross section view from BH (-8-4-11)



Fig. 7: Showing cross section view from BH (-10-11-6-7)

Fig. 8: Showing cross section view from BH (-1-2-3-4-5-6)



Fig. 9: Showing borehole at sub-surface (Coal in green)

Fig. 10: Showing boreholes and coal seam in blue



Table 2: Coal Resource Estimation within the study area

REFERENCES [1] Ojoh, K. A. 1992: The southern part of the Benue

Trough (Nigeria) Cretaceous stratigraphy, basin analysis, paleo-oceanography and geodynamic evolution in the equatorial domain of the South Atlantic. Nigerian Association of Petroleum Explorationists (NAPE) Bulletin 7, 131-152.

[2] Petters. S. W. 1982: Central West African

Cretaceous-Tertiary benthic foraminifera and stratigraphy. Palaeontographica Abt. A 179, 1-104.

[3] Reijers, T. J. A. and Nwajide, C. S. 1998: Geology

of the Southern AnambraBasin. Unpublished Report for Chevron Nigeria Limited. Field Course Note 66pp

Geological Modelling And Resource Estimation Of ... · PDF fileGeological Modelling And Resource Estimation Of Maastrichtian Coal Deposit Within Anambra Basin, ... Cretaceous stratigraphy,

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