Introduction stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering (stratification). Stratigraphy, from Latin stratum + Greek graphia, is the description of all rock bodies forming the Earth's crust and their organization into distinctive, useful, mappable units based on their inherent properties or attributes in order to establish their distribution and relationship in space and their succession in time, and to interpret geologic history. Stratum (plural=strata) is layer of rock characterized by particular lithologic properties and attributes that distinguish it from adjacent layers.

History of stratigraphy begin by Avicenna (Ibn Sina) with studied rock layer and wrote The Book of Healing in 1027. He was the first to outline the law of superposition of strata:^[1] "It is also possible that the sea may have happened to flow little by little over the land consisting of both plain and mountain, and then have ebbed away from it. ... It is possible that each time the land was exposed by the ebbing of the sea a layer was left, since we see that some mountains appear to have been piled up layer by layer, and it is therefore likely that the clay from which they were formed was itself at one time arranged in layers. One layer was formed first, then at a different period, a further was formed and piled, upon the first, and so on. Over each layer there spread a substance of differenti material, which formed a partition between it and the next layer; but when petrification took place something occurred to the partition which caused it to break up and disintegrate from between the layers (possibly referring to unconformity). ... As to the beginning of the sea, its clay is either sedimentary or primeval, the latter not being sedimentary. It is probable that the sedimantary clay was formed by the disintegration of the strata of mountains. Such is the formation of mountains."

The theoretical basis for the subject was established by Nicholas Steno who re-introduced the law of superposition and introduced the principle of original horizontality and principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment.

The first practical large scale application of stratigraphy was by William Smith in the 1790s and early 1800s. Smith, known as the Father of English Geology, created the first geologic map of England, and first recognized the significance of strata or rock layering, and the importance of fossil markers for correlating strata. Another influential application of stratigraphy in the early 1800s was a study by Georges Cuvier and Alexandre Brongniart of the geology of the region around Paris.

In the stratigraphy you can find term of

- Stratigraphic classification. The systematic organization of the Earth's rock bodies, as they are found in their original relationships, into units based on any of the properties or attributes that may be useful in stratigraphic work.

- Stratigraphic unit. A body of rock established as a distinct entity in the classification of the Earth's rocks, based on any of the properties or attributes or combinations thereof that rocks possess. Stratigraphic units based on one property will not necessarily coincide with those based on another.

- Stratigraphic terminology. The total of unit-terms used in stratigraphic classification.It may be either formal or informal.

- Stratigraphic nomenclature. The system of proper names given to specific stratigraphic units.

- Zone.Minor body of rock in many different categories of stratigraphic classification. The type of zone indicated is made clear by a prefix, e.g., lithozone, biozone, chronozone.

- Horizon. An interface indicative of a particular position in a stratigraphic sequence. The type of horizon is indicated by a prefix, e.g., lithohorizon, biohorizon, chronohorizon.

- Correlation. A demonstration of correspondence in character and/or stratigraphic position. The type of correlation is indicated by a prefix, e.g., lithocorrelation, biocorrelation, chronocorrelation.

- Geochronology. The science of dating and determining the time sequence of the events in the history of the Earth.

- Geochronologic unit. A subdivision of geologic time.

- Geochronometry. A branch of geochronology that deals with the quantitative (numerical)measurement of geologic time. The abbreviations ka for thousand (103), Ma for million (106), and Ga for billion (milliard of thousand million, 109) years are used.

- Facies. The term "facies" originally meant the lateral change in lithologic aspect of a stratigraphic unit. Its meaning has been broadened to express a wide range of geologic concepts: environment of deposition, lithologic composition, geographic, climatic or tectonic association, etc.

- Caution against preempting general terms for special meanings. The preempting of general terms for special restricted meanings has been a source of much confusion.

MANAGING CORE SAMPLING BIAS IN RESOURCE MODELLING AT BATU HIJAU PORPHYRY COPPER GOLD DEPOSIT

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

MANAGING CORE SAMPLING BIAS IN RESOURCE MODELLING AT BATU HIJAU PORPHYRY COPPER GOLD DEPOSIT

Johan Arif, Nugraha Jakamartana, Wawan Hermawan & Koko Suhanto

Mine Geology Department,
PT Newmont Nusa Tenggara, NTB - Indonesia.

ABSTRACT

Batu Hijau is a copper-gold mining operated by PT Newmont Nusa Tenggara, a joint venture between Newmont Mining Corporation (45%), Sumitomo Corporation (35%) and PT Pukuafu Indah (20%). Project to date, the core generated exploration block model has underpredicted the blasthole generated ore controlled Cu metal by approximately 18% and Au metal by 15%. Monthly reconciliation shows a consistent underprediction suggesting that a bias exists in either the samples used or the model generation itself. Since start-up, various in-house sampling trials and statistical analysis were carried out to investigate the source of the bias. Although inconclusive, it became apparent that the core sampling was underestimating the grade while the blastholes were slightly overestimating the grade. It was also apparent that the degree of bias varied by geology, whereby the host lithologies showed a greater bias than the intrusives.

A consultant was engaged to review all data compiled to date and also review all sampling and resource modeling methodologies. The consultant’s findings supported the in-house findings that physical losses of sulphides during the drilling and sampling processes were the predominant cause for the bias. A mathematical correction function was derived to correct for the bias. A methodology to demonstrate the loss of sulphides during the drilling / sampling process was also proposed.

The consultant explored earlier in-house findings that the bias was spatially controlled solely by, or a combination of, lithology, alteration, depth and grade. The conclusion was that the majority, but not all of, the bias could be explained by grade. This followed earlier findings that there was less bias in the central high grades and a greater bias towards the lower grade peripheries. This relationship would also prove to be simpler to apply than relationships derived by individual geology types. It also followed the fines loss theory well – if the assumption is that a consistent amount of fines is lost across all grade ranges, then the percentage impact will be greater in the lower grade peripheries where a lower amount of sulphides exist. At the conclusion of the 2002 drilling, two models were built, one with the addition of the 2002 drilling and one with the addition of the 2002 drilling and the bias correction applied to the composites. A backward looking analysis was carried out for the period 2001 to October 2002. The model generated from grade bias corrected composites proved to be in line with actual production for the period. Proven to be robust, the end of 2002 Batu Hijau reserves were reported using the grade corrected model.

Blasthole Sampling for Grade Control in Open Pit Mine at Batu Hijau Porphyry Copper-Gold Deposit, Sumbawa-Indonesia

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

Blasthole Sampling for Grade Control in Open Pit Mine at Batu Hijau Porphyry Copper-Gold Deposit, Sumbawa-Indonesia

Johan Arif, Eddy Priowasono, Dini Rachmawati, Onie Handayani & Agung Naruputro

Mine Geology Department,
PT Newmont Nusa Tenggara, NTB - Indonesia.

Abstract

The principal objective of an optimised grade control procedure is to maximise the financial return from short-term mining of a bench, taking into account the related costs of sampling. Any interpretation of ore outlines based on poor quality sample data (regardless the sample density) will produce sub-optimal results and cause misclassification of ore and waste will leads to financial loss. Most of open mine operations using blasthole sampling as a tool for grade control purposes. Blastholes are drilled in the mine benches with the aims of placing charges for blasting. At Batu Hijau mine, typical hole size is 31 cm in diameter, which create a meter high by 3 meter cone of cutting weighting about 2.5 tonnes. Blast hole sampling is not conducted during operation but after the drill rig has moved on by a small sampling crew. Currently, the sampling methode is not an auto sampling, but conducted by the sampler crew using spear pipes. The pipe has a 6-cm diameter and sharpened on a 45-degree angle on the one end. Prior sampling the subdrill is removed from the surface of the cone then 12 stabs are taken around the pile (six opposite direction). The total weight of the each blasthole sample is between 6-10 kg, which contained in calico bags. The method is simple and highly efficient; a four persons sampler crew can take 100 samples in about 4 hours.

In this paper we report the results of blasthole sampling study counducted at Batu Hijau mine using various non-auto sampling tools. The aims were to compared the available techniques and define the ‘best practice’ for blasthole sampling. Six sampling methods were tested at more than 30 blasthole piles representing the various lithology, mineralisation, alteration, grade and physical condition of the piles. The methods are namely spear pipe, gilson splitter, under the deck, auger and cone and quarter. In comparing the results, cone and quarter method was assumed as the best representation value of the cutting piles, since it has the largest amount taken from the pile. The study results indicated that the spear sampling is the best options available. It is a simple and efficient method that collects a reasonable accuracy. The recommendations were emphasized on closer supervision on samplers as well periodic re­training on sampling method and also reminding the importance of sample quality. The blasthole cutting piles were easily destructed by water, hence twenty four-hours sampling was highly recommended especially in wet seasons thus removing rainfall as source of sampling error.

THE MORPHIC FIELD AND ITS IMPLICATIONS TO GEOSCIENCES AND ORGANIZATIONS

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

THE MORPHIC FIELD AND ITS IMPLICATIONS TO GEOSCIENCES AND ORGANIZATIONS

Prof. Dr. Suprajitno Munadi
(LEMIGAS)

ABSTRACT

The new development in science postulates that universe is nothing but a vibration of energy. Matter is nothing but a vortex of energy. If matter is removed, then space and time will disappear. Space and time do not exist independently in the universe, they are created by movement. During the development of a matter,both energy and information are involved. Energy is the fuel and information is the guidance. This guidance is received from an intelligent source through resonance. During the evolution of an organism, the morphic field plays an important role to synchronize the inner vibration of the organism with intelligent source outside it. Resonance is the way the organism communicates with intelligence source which guides its evolution.

In living organism the required information for its growth, evolution and development are located in the DNA, the genetic code which consists more than 3 billion of information. There is an on-off mechanism which triggers the DNA so that only 5-10 % of this information is activated each time. Activation is postulated to be carried out by intelligence source outside them through the morphic resonance. Using similar analogy, “the geological DNA” should exist somewhere in the earth which transceives the morphic resonance from intelligence source, which enables rocks undergone specific processes and yield a specific pattern. This geological DNA seems to be a strange word in geosciences.

Apart from the implication of the above theorem in geosciences, an effort to extend its implementation for the sake of managing organization or behavior of the society is also introduced.

“A DUAL MONOBORE COMPLETION” IN VICO INDONESIA : A NEW COMPLETION SOLUTION FOR MULTI LAYER RESERVOIRS IN MATURE GAS FIELD

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

“A DUAL MONOBORE COMPLETION” IN VICO INDONESIA :
A NEW COMPLETION SOLUTION FOR MULTI LAYER RESERVOIRS IN MATURE
GAS FIELD

Sumaryanto, Budi Srisantoso
Base Management Team VICO Indonesia
ABSTRACT

VICO Indonesia is a mature field that has been produced for about 30 years; the reservoir management challenge is to optimize the well completion in order to have good commercial rate and optimizing reserves recovery from even marginal reservoir.

The completion called “Dual Monobore” has just been implemented in VICO Indonesia, as a new completion to optimize both gas production and reserves recovery from multi layer gas reservoirs. This completion still uses monobore completion concepts, but now it has the flexibility to share the production between depletion drive reservoir and water drive reservoir in 2 different strings, allow adding or isolating the individual zone and smaller tubing size to avoid liquid loaded problem. Up to date, more than 15 (fifteen) wells has been drilled and completed as dual 3-1/2” monobore.

This paper will share the well performance, advantages and some operational completion practices improvement to reduce problem associated with dual monobore completion in multi layer reservoirs and mature gas field.