MINERA ESCONDIDA Gerencia de Servicios metalurgicos

Mine Plant Integral Planning and Precrushing

Modelos Predictivos de Velocidad de Sedimentación y % Humedad Residual,

para las Plantas (LS – LC) yTranque de Relave FY04-FY05-08

N-12Bco 3055

N-11Bco 2920

Mirada al Noroeste

Proyecto considera 1200 muestras de las cuales hemos analizado 500 aproximadamente

Figura: Vista 3D de la Velocidad de sedimentación para losbancos 2920 y 2650 en el sector de las expansiones N11 y N12

Figura: Vista 3D de los volúmenes con bajo porcentaje de humedad residual.

Semana kTon CUT FE BWI Total Kton KTon. Baja VS KTon. Buena VS Período Ley de Corte % Baja VS % Buena VSEne04_S1 2,205,158 1.71 2.02 12.6 2,205,158 977,110 1,228,048 1 al 12 Enero 0.59 44.3% 55.7%Ene04_S2 1,265,308 1.77 1.86 12.7 1,265,308 662,989 602,319 13 al 19 Enero 0.61 52.4% 47.6%Ene04_S3 1,258,655 1.64 1.84 12.8 1,258,655 588,911 669,744 20 al 26 Enero 0.65 46.8% 53.2%Ene04_S4 786,779 1.46 1.67 13.2 786,779 467,006 319,773 27 al 31 Enero 0.63 59.4% 40.6%Feb04_S1 2,331,833 1.40 1.76 13.8 2,331,833 986,812 1,345,021 1 al 9 Febrero 0.50 42.3% 57.7%Feb04_S2 1,619,019 1.72 1.89 13.2 1,619,019 896,194 722,825 10 al 16 Febrero 0.77 55.4% 44.6%Feb04_S3 1,574,138 2.03 1.85 13.2 1,574,138 388,565 1,185,573 17 al 23 Febrero 0.69 24.7% 75.3%Feb04_S4 1,161,165 1.61 2.03 13.9 1,161,165 122,133 1,039,032 24 al 29 Febrero 0.68 10.5% 89.5%Mar04_S1 2,789,017 1.52 2.06 12.5 2,789,017 859,684 1,929,333 1 al 8 Marzo 0.75 30.8% 69.2%Mar04_S2 1,759,993 1.82 1.84 14.1 1,759,993 308,294 1,451,699 9 al 15 Marzo 0.96 17.5% 82.5%Mar04_S3 1,348,367 1.89 2.08 13.3 1,348,367 338,173 1,010,194 16 al 22 Marzo 0.74 25.1% 74.9%Mar04_S4 1,850,149 1.93 1.88 13.9 1,850,149 366,861 1,483,288 23 al 31 Marzo 0.84 19.8% 80.2%Abril 2004 7,549,048 1.55 2.15 13.5 7,549,048 1,693,348 5,855,700 1 al 30 abril 0.60 22.4% 77.6%Mayo 2004 6,210,022 1.89 1.88 14.0 6,210,022 1,238,726 4,971,296 1 al 31 Mayo 0.83 19.9% 80.1%Junio 2004 5,457,959 1.89 1.97 14.3 5,457,959 703,609 4,754,350 1 al 30 Junio 0.70 12.9% 87.1%

Total 39,166,610 1.73 1.96 13.6 39,166,610 10,598,415 28,568,195 27.1% 72.9%

Tabla: Resumen alimentación FY04, para la velocidad de alimentación

Semana Ton Ton. %HR < 30 Ton. %HR > 30 % (%HR < 30) % (%HR > 30)Ene04_S1 2,205,158 814,659 1,390,499 36.9% 63.1%Ene04_S2 1,265,308 463,602 801,706 36.6% 63.4%Ene04_S3 1,258,655 476,958 781,698 37.9% 62.1%Ene04_S4 786,779 266,173 520,606 33.8% 66.2%Sub-Total 5,515,900 2,021,392 3,494,509 36.3% 63.7%

Feb04_S1 2,331,833 612,824 1,719,010 26.3% 73.7%Feb04_S2 1,619,019 328,907 1,290,112 20.3% 79.7%Feb04_S3 1,574,138 320,825 1,253,313 20.4% 79.6%Feb04_S4 1,161,165 144,907 1,016,258 12.5% 87.5%Sub-Total 6,686,155 1,407,463 5,278,693 19.9% 80.1%

Mar04_S1 2,789,017 288,132 2,500,885 10.3% 89.7%Mar04_S2 1,759,993 244,462 1,515,530 13.9% 86.1%Mar04_S3 1,348,367 341,810 1,006,557 25.3% 74.7%Mar04_S4 1,850,149 159,049 1,691,100 8.6% 91.4%Sub-Total 7,747,526 1,033,453 6,714,072 14.5% 85.5%

Abril 2004 7,549,048 1,041,098 6,507,949 13.8% 86.2%

Mayo 2004 6,210,022 415,482 5,794,541 6.7% 93.3%

Junio 2004 6,180,910 949,826 5,231,085 15.4% 84.6%Total 39,889,561 6,868,714 33,020,849 17.22% 82.78%

Nota: HR es la humedad residual

Tabla: Resumen alimentación FY04 para la Humedad Residual.

BHP BILLITONMINERA ESCONDIDA LIMITADA

GEOMETALLURGY

Geomet Long Term Models NOV03Revisiting same data & using plant results

• Recovery Flotation model developed with especial efffort to improve empirical factors and real differences between Los Colorados and Laguna Seca as feedback to the models.

• Copper Concentrate Grade Addition of new drillhole data

• Updated congrade calculation equations from mineralogy. Used same congrade model for both plants adding 1% to LC (empirical)

• Hardness model with same data and improved definition of drivers and domains using UCS-PLT

ESCONDIDA

• TPH models using new plant data, particularly %+100#, limiting SPI values and recalculated TPH. Recalculated plant Tph values is unique valid approach (filter plant limitations prior to comparison against forecast)

• MEL TPH model incorporates SPI as upper limit for TPH capping based upon real plant events.

• CEET TPH for FY05 and 5Yr planning. Updating with new samples in march 04

GEOMET ESCONDIDA THROUGHPUT

•MEL TPH model completed as required for use in FY05 Budget.

•Use of andesite and porphyry in estimation of F80

• Use of BWi in estimation of P80 instead of fixed values (as in Oct02) with capping at 230 µ for Los Colorados and 215 µ for Laguna Seca

•Maximum Tph fixed at 6000 for Los Colorados and 5500 for Laguna Seca

•Use of Spi for the 1st time as a capping value for Tph from real plant events information

Spi Tph LC Tph LS70 – 80 4,168 4,00080 – 90 3,889 3,800>= 90 3,600 3,500

GEOMET ESCONDIDA THROUGHPUTReconciliation

Reconciliation Model TPH MEL & CEET Nov03 v/s Real Los Colorados Recalculated

4,000

4,500

5,000

5,500

6,000

Jul-02

Ago-02

Sep-02

Oct-02

Nov-02

Dic-02

Ene-03

Feb-03

Mar-03

Abr-03

May-03

Jun-03

Jul-03

Ago-03

Sep-03

Oct-03

Nov-03

Dic-03

Ene-04

Feb-04

Mar-04

Abr-04

May-04

Jun-04

TPH

-20

-15

-10

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

% Dif

DIF REL Plant-Mod (BlkParc) TPH_Real LosColorados TPH_Recalc LosColorados

CEET Nov03 (MinnovEx) TPH MelNov03(BlkParc)

JUL02-OCT03 CALIBRATION FOR NOV2003 MODEL WEAK UNDERESTIMATION -1.3% RELATIVE

+0.7% RELATIVEUNDERESTIMATIONSUBJECT TOPLANT CHANGES

BHP BILLITONMINERA ESCONDIDA LIMITADA

Pre-Crushed Feed for SAG Mills

Throughput : Effect of “fines” –1/2”

Fines Effect on TPOH (-1/2")Laguna Seca y Los Colorados (SAG3)

y = 44,648x + 542,83R2 = 0,6192

y = 82,845x - 8,1522R2 = 0,9401

0

1000

2000

3000

4000

5000

6000

20 30 40 50 60 70

minus 1/2" (%)

TP

OH

LC_TPOH

LS_TPOH

Lineal (LC_TPOH)

Lineal (LS_TPOH)

Factibilidad en licitación

8% a 10% aumento TPH cuando exista limitación SAG

MUS$ 20-25Planta de Prechancado

Estado ActualBeneficioInversiónProyecto

Pre-Crushed Feed

Se comienza a realizar un estudio a nivel conceptual.

Alternativas a ser estudiadas :

a.- Planta de Chancado separada para Los Colorados y Para Laguna Seca.

b.- Planta de Clasificación, donde el bajo tamaño de harneros alimenta a los Colorados y el Sobre tamaño es tratado en planta de Chancado para alimentar Laguna Seca