Geostatistical estimation of reserves in the Abu-Tartur phosphate deposits western desert, Egypt.

(1987) Geostatistical estimation of reserves in the Abu-Tartur phosphate deposits western desert, Egypt. Masters thesis, King Fahd University of Petroleum and Minerals.


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The Abu Tartur Plateau lies between the Kharga and Dakhla oases in the Western Desert of Egypt and contains the largest phosphate deposit in the country. The phosphates are found in two main horizons within the late Campanian, Sibaiya Formation. The estimation of the reserves in the lower phosphate horizon is the main objective of this study. The basic data for this study was derived from a drilling program conducted by the Egyptian Geological Survey and included the phosphate grade (P 0 %) and the thickness data from 347 vertical holes drilled on a regular grid of 400m x 400m dimensions. Preliminary statistical analysis of the data was carried out to determine the sampling distributions of the variables, P 0 (%), thickness (m) and accumulation (%m). These distributions are characterized by slight skews, negative for P 0 % and positive for both thickness and accumulation. The results of variogram modelling indicate that spherical models can appropriately be fitted to all experimental variograms. A compound spherical model was fitted to the horizontal variogram for P 0 %, and simple spherical models to the horizontal variograms of both thickness and accumulation. Fitting a random stratified grid to the drill-hole intersections, the estimates for the total tonnage, the total phosphate content and the mean grade within the central part of the lower phosphate horizon have been obtained. The estimation variances associated with each estimate were derived using model variograms. The confidence intervals for the estimates at 95% confidence level are as follows: tonnage = 308.36 + 13.56 Mt; total phosphate content = 80.05 Mt; and mean grade = 26.00 + 0.19%. The two dimensional block kriging of the deposit was carried out to obtain estimates for blocks of 400m x 400 m x 1m dimensions. The kriged estimats and the corresponding relative kriging standard deviation for a total of 3752 blocks were computed. The kriging standard deviations are relatively small, indicating the reliability of the kriged estimates. Finally, using the distribution of kriged block estimates, a grade-tonnage curve based on the selective mining units of 25m x 25m x 1m dimensions was constructed. The tonnage of phosphate corresponding to a given cut-off grade can be read off this curve.

Item Type: Thesis (Masters)
Subjects: Earth Sciences
Department: College of Petroleum Engineering and Geosciences > Geosciences
Committee Advisor: Sahin, Ali
Committee Members: El-Naggar, Z.R. and Saif, Saiful-Islam
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 13:43
Last Modified: 01 Nov 2019 13:48