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.

REVEALING UNDETECTED GEOLOGICAL STRUCTURE WITHIN NGIMBANG FORMATION IN THE NGIMBANG-1 WELL, NORTHEAST JAVA BASIN, INDONESIA, BASED ON VITRINITE REFLECTANCE DATA

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

REVEALING UNDETECTED GEOLOGICAL STRUCTURE
WITHIN NGIMBANG FORMATION IN THE NGIMBANG-1 WELL, NORTHEAST JAVA BASIN, INDONESIA, BASED ON VITRINITE REFLECTANCE DATA

Kuwat Santosa¹ and Eddy A. Subroto²

¹Department of Geological Engineering, FTM, UPN Yogyakarta
²Geology and Paleontology Research Division, FIKTM, Institut Teknologi Bandung

ABSTRACT

Indication the occurrence of geological structure in the Ngimbang- 1 well, East Java, has never been reported. The Kujung and Ngimbang Formations found in the Ngimbang-1 well is always interpreted being normal. During this work, sediment samples of the Kujung and Ngimbang Formations from two wells, i.e. Ngimbang-1 and Kujung-1 were analysed for their maturity based on vitrinite reflectance technique and, by doing so, it was revealed that a geological structure should occur within the Ngimbang Formation in the Ngimbang-1 well.

In Kujung- 1 well, the only Kujung Formation sample analysed indicates that its maturity based on vitrinite reflectance (Ro) is 0.2%, whereas some samples obtained from the Ngimbang Formation show Ro values between 0.25 to 0.45%. These values indicate a continuation of maturation without any disturbance. In fact, both formations reveal immaturity for hydrocarbon generation.

In Ngimbang- 1 well which is around 22 km far from the Kujung- 1 well, the vitrinite reflectance values observed in the Kujung Formation samples range from 0.37 to 0.38%, however, Ro values for the Ngimbang sediments are between 0.45 and 2.26% with a significant jump from 0.44 to 1.1%. The high Ro values may be due to a rework process, but the consistent and continue increase of the maturation (after significantly jump) in this well is most likely because of a normal maturation process rather than a rework. This is supported by SCI data that show a similar case, i.e. a sudden increase of SCI values from 4.5 to 8.0 was also observed within the Ngimbang Formation. Maturation in the Ngimbang-1 shows a span of maturity from immature to over mature, up to dry gas window. Geological data of the area reveals a normal fault occurred in between the Kujung high and the Ngimbang low. This fault is interpreted being most likely responsible for the significant increase of the maturity in the Ngimbang-1 well.

OLIGOCENE – EARLY MIOCENE PALEOGRAPHY MODEL SOUTH BALAM TROUGH, CENTRAL SUMATRA BASIN

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

OLIGOCENE – EARLY MIOCENE PALEOGRAPHY MODEL  SOUTH BALAM TROUGH, CENTRAL SUMATRA BASIN

Agus Susianto ¹, Edi Suwandi Utoro ¹, & Satia Graha ^1
1 PT. Chevron Pacific Indonesia
ABSTRACT

South Balam trough is one of the most prolific petroleum systems in the Central Sumatra Basin. Current study to construct 3 dimensional paleography model give better understanding geological history of this area. This paper demonstrates effectiveness of paleogeography construction as media to transfer knowledge of interpretation.

This study use seismic and well log to construct chronostratigraphic correlation and structural maps. Cores and sidewall cores are used to interpret depositional environment and relative ages. Integration of these two approaches provides comprehensive understanding of geological history in each chronostratigraphic interval and then visualized as a paleogeographic model.

Two major chronostratigraphic intervals were constructed. During Oligocene, extensional tectonic was dominant resulted in half graben that represents lake formation. This component of paleogeographic setting consists of border fault fan delta, axial stream deposits and deep lacustrine shale. In Early Miocene, this area evolved to a shallow marine setting with fluvial and deltaic deposition.

The construction of paleography model is essential in order to understand petroleum system of an area.

AUTO DATA TRANSFER: ENABLING E&P BUSINESS BY INCREASING DATA AVAILABILITY THROUGH STANDARD DATA PROCESS AND FLOW

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

AUTO DATA TRANSFER: ENABLING E&P BUSINESS BY INCREASING DATA AVAILABILITY THROUGH STANDARD DATA PROCESS AND FLOW

Setiabudi, Triatmojo R.^' , Ismayadi, Budhi.^' , & Roza, Ellinda.^'
1Data Management, Information Technology, Technology Support, PT. Chevron Pacific Indonesia
ABSTRACT

An effort was made to seek data management solution adopted for supporting E&P business process in PT. Chevron Pacific Indonesia, Central Sumatra, Indonesia. Managing a huge dataset involving approximately 11000 wells with all subset related data, which reside on multiple applications and databases, requires comprehensive approaches on data management methods & technology. Separate databases that are connected to multiple applications may result in problem on data availability issue, and become a common problem for big oil companies. Most of applications and databases in Exploration and Production (E&P) business do not have direct interaction due to vendor proprietary. Mean time Geoscientists need data available in timely fashion for their collaborative work so that they could use E&P data to produce fast and accurate decisions. Multifunction team effort was conducted to answer the above problems with applying data management concept on current E&P applications technology. Solutions are built in the form of analysis and development of common standard data flow and process, naming standardization, and automatic data transfer tool to consolidate data into corporate database and E&P applications. Data management methods being addressed include how to build standard data management process, validate data, consolidate, and monitor process. IT data management solutions were implemented using current available data manipulation technology of native applications, PL/SQL, and AWK UNIX script. Implementation strategy was based on ideas to combine IT tools and applied data management & technology, and standard workflow procedures. The final results of this effort cover data management solutions that include recommendations, processes, and tools.

WLDM (WELL LOG DATA MANAGEMENT) STANDARD WELL LOG DATA MANAGEMENT PROCESS AND TOOL TO IMPROVE RESERVOIR MANAGEMENT WORK

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

WLDM (WELL LOG DATA MANAGEMENT)
STANDARD WELL LOG DATA MANAGEMENT PROCESS AND TOOL TO IMPROVE RESERVOIR MANAGEMENT WORK

Elsie Desianty^', Tom Zalan^', Bruce Biodeau^', & Rudi Arief^'
'PT Chevron Pacific Indonesia, Sumatra, Indonesia
ABSTRACT

Digital archival databases are evolving to become perhaps the only source for well data. It is imperative that sustainable processes be put in place that will improve the content, quality, and reliability of the digital databases.

CPI has developed a Well Log Data Management (WLDM) process to document, capture, and retain well data. A critical part of this data management process is to provide user access to the data through web- based tools, providing logging request data tracking. The idea is that if the users rely on the digital database as their primary source for well data, then they will make the effort to improve the content and reliability of the database, which has been neglected up until now.

A cross-functional team (IT, Formation Evaluation, Operation Data Management, Asset Management Team, and WellWork) was formed to develop the process, build and test the tools. The process starts with a user requesting a logging job and goes through loading the well log data into CPI’s Well Master Data Repository. Users can track a logging job, service ticket, logging deliverables; assess data quality, track log data, and invoice through one window.

In addition to improving data longevity and accessibility, the WLDM process also ensures compliance with MIGAS regulations for data management. Data obtained from general survey and exploration/exploitation belongs to the government of Indonesia and it must be managed and utilized appropriately.

Well Log Data Management process is very important to support operating unit well data business. Faster and more convenient data availability will provide more accurate data for the user and asset teams to make decisions to increase production and better assess opportunities to meet CPI business objectives.