Kapitel 0 - Vorlesungsinhalte - Organische Geochemie · 2018. 10. 22. · Erkundung Seismik und Logging 08.07.2009 Fallbeispiel Erdöllagerstätte ... in the recording equip-ment,

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Kapitel 0 - Vorlesungsinhalte

Vorlesungsinhalte

06.05.2009 Produkte der Entstehung von Erdöl und Erdgas

13.05.2009 Thermische Reifung, Expulsion, sekundäre Migration, Lagerstättenfüllung, Fallentypen

20.05.2009 Oil/Source Korrelation

27.05.2009 Aufsuchung von Erdöl/Erdgaslagerstätten Geophysikalische Methoden, BeckenmodelleSedimentologische Modelle, Feldzyklus

22.04.2009 Einführung mit Überblick über Inhalte und Zielsetzung der Vorlesung - Marktökonomie

29.04.2009 Biochemische und geologische Bedingungen der Entstehung von Erdöl und Erdgas

03.06.2009 Well Logging Techniken

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Kapitel 0 - Vorlesungsinhalte

Vorlesungsinhalte

17.06.2009 Reservoir – Eigenschaften und ProduktionErkundung Geochemie

24.06.2009 Bohrtechniken für Exploration und Exploitation

onshore-offshore, casings, blow-out-preventer

01.07.2009 Reservoirmodelling, Zyklen einer Lagerstätten-entwicklung, Dekommissionierung und Umwelt-management

10.06.2009 Reservoir – Eigenschaften Erkundung Seismik und Logging

08.07.2009 Fallbeispiel Erdöllagerstätte

14.07.2009 Fallbeispiel Erdöllagerstätte

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Kapitel 5 - Aufsuchung von Erdöllagerstätten - Seismik

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Seismic in Petroleum Exploration

The seismic reflection method works by bouncing sound waves off boundaries between different types of rock. The reflections recorded are plotted as dark lines on a seismic section. A seismic section resembles a geological cross-section, but it needs to be interpreted.

A major difference between a geological cross-section and a seismic section is that the vertical axis is in time, rather than depth. In the earth's crust, seismic waves travel typically at about 6,000 m/s (21,600 km/h) so that 1 second of two-way travel time corresponds to about 3 km of depth.

Another difference is that the reflections are plotted halfway between the source and the receiver. These are referred to as unmigrated data. The process that moves the reflections in their correct spatial position is referred to as migration, and the resulting seismic section is referred to as a migrated section. Interpreters like to use both.

The seismic reflection method is the geophysical technique which produces the best images of the subsurface. These data resolve mappable features such as faults, folds and lithologic boundaries measured in the 10's of meters, and image them laterally for 100's of kilometers and to depths of 50 km or more. Seismic reflection (refraction for very deep structures) profiling is the principal method by which the petroleum industry explores for hydrocarbon-trapping structures in sedimentary basins.

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Acquisition of Seismic Data

During a seismic survey, a cable with receivers attached to it at regular intervals is laid out along a road or towed behind a ship. The source moves along the seismic line and generates seismic waves at regular intervals such that points in the subsurface, such as point P above, are sampled more than once by rays impinging on that point at different angles. As a shot goes off, signals are recorded from each geophone along the cable for a certain amount of time, producing a series of seismic traces. The seismic traces for each shot (called a shot gather) are saved digitally in the recording unit.

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Wiggle traces for a shot on parrallel beded strata. Sensors (geophones) are laid out along a section to collect reflected energy. This is called a common mid-point gather (CMG).

Wiggle traces recorded at different spacing from energy source (shot or sweep point) have to be processes to form a continuous seismic section.

The variety of methods applied is generally known as migration.

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In settled or sensitive areas energy isgenerated by bumper trucks. Severalof these pulse a short (milliseconds)coordinated high energy sweep ofvibrational energy into the ground. Thepulses can be repeated multiple timesand records be stacked to enhanceintensity and minimize noise.

Seismic energy on land is mostly created by explosi-ves in shallow bore-holes

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Acquisition of Seismic Data on Sea

Energy blast is created by an airgun and recorded by a hydrophone array (fixed to a streamer) towed by the same vessel (reflection seismic) or the air gun is operated froma second ship (refraction).

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Small dimension unit (3D-P-cable) for nearshore 3D seismic applications.

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Small dimension unit (3D-P-cable) for nearshore 3D seismic applications.

Fluid escape structures.

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Acquisition and Migration of Seismic Data

filtering and/or muting (zeroing of the data). 5 A correction is made for the time the reflected ray spends travelling laterally, to line up the reflected arrivals. 6 Thetraces are added to produce a single output trace. This process, referred to as stacking, cancels out random noise and re-enforces the reflected signals. 7 The waveform is then shrunk by frequency filtering or deconvolution to improve the resolution. 4 to 7 is repeated for each common reflection point, and the resulting seismic traces are displayed as a seismic section 8 which is then interpreted 9.

1 The data are read and the shot records (i.e. all traces recorded for a given shot) are displayed. 2 Bad seismic traces, due to noise or a short circuit in the recording equip-ment, are edited out.3 The traces are then reordered so that each gather of traces belongs to a common reflection point. 4 Non-reflected arrivals, such as surface waves and direct arrivals, are removed by digital

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Resolution of seismic data improves with data storage and handling.

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A seismic a line with sonic logs from two intersecting wells spliced in.

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The same seismic a line with sonic logs from two intersecting wells spliced in after inversion. Color key indicates acoustic impedance.

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This acoustic impedance slice map shows the arithmetic average of the acoustic impedance over a 10 ms window below the channel top event.

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This is the crossplot between the well porosities and acoustic impedance values. The red line is the regression fit, and the correlation is –0.65.

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The porosity map based on well log data after simple kriging.

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The acoustic impedance inferred porosity map after co-kriging.

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The acoustic impedance inferred porosity map after co-kriging using multilinear regression analysis.

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Comparison of porosity maps:Note the increase in geological information as we move from

(a) the map from wells alone to

(b) map from wells and seismic, and finally to

(c) map from the multi-attribute transform.

(a)

(b)

(c)


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Figure (2) 3D 4C time domain processed data. Left : Inline from pp data through the gas affected

area . Right : Equivalent inline from ps data through the centre of the gas affected area

Affect of

shallow gasImproved

Resolution

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Synthetic Seismic Sections – Seismic Tomography

The observed data is generated by Elastic Modeling algorithm.

Synthetic seismic lines: (a), (b) The predicted and the actual model parameters of the 10 layer model. The blue one is the actual and the redone is the predicted. (c) Observed and (d) Predicted angle gathers of the 10 layer model for GA inversion code with Elastic Impedance forward modeling.

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Zero-offset section of a line from 3D volume of overthrust model.

2-D post-stack depth migration result.

The same line after 2D pre-stack depth migration.

Migration of Seismic Sections

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The 2D post-stack Kirchhoff time migration results.

The same line after 2D Pre-stack Kirchhoff time migration results.

Migration of Seismic Sections

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Traveltime tomographic forward modeling with first arrival traveltime contours(ms) for 2D overthrust model. The shots are located (a) at the center of themodel and (b) at the surface.

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End of Seismic Applicationin Subsurface Structure

Imaging

Start of SeismicApplication in Matrix Property Prediction

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Acquisition of Seismic Data - AVO

Amplitude Variation with Offset (AVO) allows to infer matrix properties (or changes thereof, i.e. gas/water contact) including in particular composition of fluids residing in pore space and thus significantly enhances application of seismic techniques in exploration.

Negative AVOTop of gas horizon

Positive AVOBase of gas horizon

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Negative Amplitude Offset at top of gas sand increases with distance to CMP.

No Amplitude Offset in water filled pore space with increasing distance to CMP.

Positive Amplitude Offset at base of gas sand increases with distance to CMP.

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Gas horizonPositive AVO

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gas horizontop negative AVObase Positive AVO

upper water horizontop: no systematic AVObase: Small negative AVO

lower water horizontop: negative AVObase: no systematic AVO

while logging fluid bearing horizons (gas or water) are identified by low g-ray, high p-velocity, low density; note high resistivity in gas bearing sand

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AVO and Logging used for detection of pay zones in GOM block 474.

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Upper anomaly amplitude map (in color) at Lisa Anne, which iscorrelated to the upper anomaly at King Kong. The King Kong Fieldgives rise to the NW/SE trending amplitude anomaly seen in Block473; the western portion of the field shows a similar amplitudeanomaly in the adjacent Block 472 to the west. The amplitude anomalyin the SE corner of Block 474 outlines the Lisa Anne Prospect. Contoursshow the upper anomaly depth structure.

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Wireline log data for the Anadarko Green Canyon Block 474 No. 1 well that tested the Lisa Anne Prospect.

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GR, P-wave, density, and impedance profiles for the Green Canyon Block 474 #1 well. The right track shows a 1D synthetic seismogram.

Sand intervals with low velo-cities due to low gas satu-ration are colored yellow while sands with velocities indicating brine saturationare colored blue.

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Identification of pore fluid units in the Anadarko Green Canyon Block 474 No. 1 well for depth interval 11,200 to 11,800 ft .

Brine saturated sands are colored blue; sands containing low gas saturation are colored yellow.

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Seismic profile of a gas chimney 4 miles ne´of the Lisa Anne Prospect.

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Seismic Data - AVO

Seismic section profile with strong AVO for Corvette Prospect.

Documents

Kapitel 0 - Vorlesungsinhalte - Organische Geochemie · 2018. 10. 22. · Erkundung Seismik und Logging 08.07.2009 Fallbeispiel Erdöllagerstätte ... in the recording equip-ment,