Pitfalls in prestack inversion of merged seismic surveys

Modern 3D seismic surveys are often of such good quality and 3D interpretation packages so user-friendly that seismic interpretation is no longer exclusively carried out by geophysicists. This ease-of-use has also been extended to more quantitative workflows, such as 3D prestack inversion, putting it in the hands of the “nonexpert” — be it geologist, engineer, or new-hire geophysicist. Indeed, given good quality input seismic data, almost any interpreter who can generate good well ties and define an accurate background model of P-impedance, S-impedance, and density can generate a quality prestack inversion. Two of the authors are new geophysicists who fell into the prestack inversion “pit.” Fortunately, they were able to recognize that something was wrong. We applied prestack inversion to gathers that were carefully reprocessed by a major service company. The problem, however, was not with the processing, but with our lack of understanding of the input legacy data that formed part of a larger “megamerge” survey. Not all of the surveys that were merged had the same offset range. In the migration step, gaps in long offsets of the older surveys were not muted. Migration noise from newer surveys was allowed to fill this space. We share our initial workflow and suspicious results. We also clarify the meaning of “fold” and “offset” for prestack-migrated gathers. In addition to presenting some QC tools useful in analyzing megamerge surveys, we show how, by limiting the offsets used in our prestack inversion, we obtain less aggressive but still useful results.

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THE APPLICATION OF 3D SEISMIC INTERPRETATION TECHNIQUES FOR OPTIMISING WELL PLACEMENT: FORTESCUE FIELD RE DEVELOPMENT, GIPPSLAND BASIN

The APPEA Journal ◽

10.1071/aj96002 ◽

1997 ◽

Vol 37 (1) ◽

pp. 31

Author(s):

P.J. Ryan ◽

T.E. Vinson

Keyword(s):

High Precision ◽

Seismic Data ◽

Development Program ◽

Seismic Interpretation ◽

3D Seismic ◽

Well Placement ◽

Seismic Waveform ◽

Attribute Analysis ◽

Definition Of ◽

Gippsland Basin

In order to achieve successful drilling results on mature fields, geophysical analysis has become increasingly focussed on the application of high precision 3D seismic interpretation and analysis techniques. These techniques were critical to the success of the re-development program recently completed on the Fortescue Field* Gippsland Basin. Fortescue, initially developed in 1983, contains an estimated oil reserve of 300 million barrels. The field is currently over 80 percent depleted. To offset declining production and develop remaining reserves, an 18 well additional drilling program together with upgrades to platform topsides and production facilities was conducted on the field from October 1994 to October 1996.Many of the proposed additional drilling opportunities relied on oil being trapped structurally updip from existing completions. Given the size (approx. 1 MSTB) and subtle, low relief nature of the targets being pursued, the precision of conventional 3D seismic interpretation techniques was inadequate to optimise the location of wells. This necessitated the development of a series of specific tools that could provide high resolution definition of both the trap and lithology as well as optimising well placement.These high precision interpretation techniques include: reservoir subcrop edge prediction through qualitative calibration of geological models to seismic data: the assessment of overburden velocity distortions of the seismic time field by utilising isochron mapping and interval attribute analysis; and prediction of trap geometries and lateral stratigraphic variations by the application of seismic waveform attributes.The application of these advanced 3D seismic interpretation techniques and their integration with related geoscience and engineering technologies resulted in the completion of a successful 18 well re-development program for the Fortescue field.

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Imposing interpretational constraints on a seismic interpretation CNN

Geophysics ◽

10.1190/geo2020-0449.1 ◽

2021 ◽

pp. 1-36

Author(s):

Haibin Di ◽

Cen Li ◽

Stewart Smith ◽

Zhun Li ◽

Aria Abubakar

Keyword(s):

Seismic Data ◽

Recent Progress ◽

Facies Analysis ◽

Three Dimensional ◽

Seismic Interpretation ◽

3D Seismic ◽

Geologic Time ◽

Seismic Amplitude ◽

Subsurface Geology ◽

3D Seismic Data

With the expanding size of three-dimensional (3D) seismic data, manual seismic interpretation becomes time consuming and labor intensive. For automating this process, the recent progress in machine learning, particularly the convolutional neural networks (CNNs), has been introduced into the seismic community and successfully implemented for interpreting seismic structural and stratigraphic features. In principle, such automation aims at mimicking the intelligence of experienced seismic interpreters to annotate subsurface geology both accurately and efficiently. However, most of the implementations and applications are relatively simple in their CNN architectures, which primary rely on the seismic amplitude but undesirably fail to fully use the pre-known geologic knowledge and/or solid interpretational rules of an experienced interpreter who works on the same task. A general applicable framework is proposed for integrating a seismic interpretation CNN with such commonly-used knowledge and rules as constraints. Three example use cases, including relative geologic time-guided facies analysis, layer-customized fault detection, and fault-oriented stratigraphy mapping, are provided for both illustrating how one or more constraints can be technically imposed and demonstrating what added values such a constrained CNN can bring. It is concluded that the imposition of interpretational constraints is capable of improving CNN-assisted seismic interpretation and better assisting the tasks of subsurface mapping and modeling.

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Space-time continuum in seismic stratigraphy: Principles and norms

Interpretation ◽

10.1190/int-2017-0061.1 ◽

2018 ◽

Vol 6 (1) ◽

pp. T97-T108 ◽

Cited By ~ 6

Author(s):

Farrukh Qayyum ◽

Christian Betzler ◽

Octavian Catuneanu

Keyword(s):

Seismic Data ◽

Seismic Stratigraphy ◽

Seismic Interpretation ◽

Space Time ◽

Practical Significance ◽

3D Seismic ◽

Close Link ◽

Time Continuum ◽

3D Seismic Data ◽

Stratigraphic Succession

Seismic stratigraphy is not only a geometric understanding of a stratigraphic succession, but it also has a close link to the space-time continuum started by H. E. Wheeler (1907–1987). The science follows the fundamental principles of stratigraphy, and the norms that govern seismic interpretation play a fundamental role due to their practical significance. The birth of computer-aided algorithms paved a new platform for seismic interpretation. The ideas from A. W. Grabau (1870–1946) and Wheeler were brought to a new level when space-time continuum was represented using 3D seismic data. This representation is commonly referred to as the Wheeler transformation, and it is based on flattening theories. Numerous algorithms have been introduced. Each suffers from its own problem and follow some assumption. The hydrocarbon industry, as well as academia, should seek a solution that is globally applicable to a stratigraphic succession irrespective of resolution, geologic challenges, and depositional settings. We have developed a review of the principles and norms behind these algorithms assisting in developing the space-time continuum of a stratigraphic succession using 2D/3D seismic data.

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On Including Near-surface Zone Anisotropy for Static Corrections Computation—Polish Carpathians 3D Seismic Processing Case Study

Geosciences ◽

10.3390/geosciences10020066 ◽

2020 ◽

Vol 10 (2) ◽

pp. 66

Author(s):

Mateusz Zaręba ◽

Tomasz Danek ◽

Jerzy Zając

Keyword(s):

Seismic Data ◽

Three Dimensional ◽

Seismic Signal ◽

Surface Zone ◽

3D Seismic ◽

Near Surface ◽

Seismic Surveys ◽

Geological Interpretation ◽

Geological Conditions ◽

Static Corrections

Obtaining the most accurate and detailed subsurface information from seismic surveys is one of the main challenges for seismic data processing, especially in the context of complex geological conditions (e.g., mountainous areas). The correct calculation of static corrections allows for the reliable processing of seismic data. This, in turn, leads to better geological interpretation. A seismic signal passing through a near-surface zone (NSZ) is adversely affected by the high heterogeneity of this zone. As a result of this, observed travel times often show anisotropy. The application of refractive waves and the time delay solution without taking into account the effects caused by the complex anisotropy of an NSZ does not meet the standards of modern seismic surveys. The construction of the NSZ model in mountain regions with the use of refraction may be extremely difficult, as the vertical layers can be observed very close to the surface. It is not sufficient to apply regular isotropic refractive solutions in such conditions. The presented studies show the results of taking into account the anisotropy of an NSZ in the calculations of static corrections. The presented results show that this step is critical for the detailed processing of three-dimensional (3D) seismic data collected in the difficult region of the Carpathians in Southern Poland.

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Multiclient 3D Seismic Surveys in Trinidad and Tobago – Towards a Policy

10.2118/spe-169969-ms ◽

2014 ◽

Author(s):

W.. De Landro-Clarke ◽

P.. Bradshaw-Niles

Keyword(s):

Trinidad And Tobago ◽

Seismic Data ◽

Policy Making ◽

Great Success ◽

3D Seismic ◽

Seismic Surveys ◽

The Government ◽

Petroleum Sector ◽

Industry Conditions

Abstract It is said that it is politics not science that finds oil, by this is meant that the policies of governments create the conditions conducive to the exploration for petroleum. The converse is also true; lack of policy can also remove incentive to explore. The government of Trinidad and Tobago has applied many policies with respect to the petroleum sector, some with great success but there is always a need for dynamism in policy making to keep pace with changing industry conditions and to remain competitive. This paper is aimed at moving policy forward for obtaining new seismic data on open marine acreage through the use of 3D multiclient surveys.

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Imaging the near surface using velocity inversions of ultra-high-density 3D seismic data

The Leading Edge ◽

10.1190/tle40080584.1 ◽

2021 ◽

Vol 40 (8) ◽

pp. 584-589

Author(s):

Tim Dean ◽

Margarita Pavlova ◽

Matthew Grant ◽

Martin Bayly ◽

Denis Sweeney ◽

...

Keyword(s):

Seismic Data ◽

Coal Industry ◽

High Density ◽

Rock Properties ◽

3D Seismic ◽

Near Surface ◽

Seismic Surveys ◽

Weathered Layer ◽

History Of ◽

The Cost

Within the coal industry, there is a rich history of the use of the surface seismic method, principally for exploration and employing sparse 2D lines for broad resource delineation and structural modeling. However, the acquisition of 3D seismic surveys adjacent to open-cut mines (from which the majority of coal is extracted) for superior resource definition ahead of their expansion has been explored only recently. Although the reflection results are extremely useful and enable the mapping of faults with sub-5 m throws, there is still interest in determining if the seismic data can be used to image both structures and rock properties in the near surface. In addition to mapping near-surface structures that have geotechnical implications, the ability to map the overburden properties (which can be quite heterogeneous) is desired. Before mining activities can take place, the overburden needs to be removed. The cost of the removal method employed is directly affected by the depth of the weathered layer and rock properties. In particular, hardness can vary significantly. In this paper, we demonstrate how high-density seismic data originally acquired for reflection processing can be processed to generate high-resolution velocity (both VS and VP) depth volumes, which enable the successful identification of shallow structures and the creation of highly detailed near-surface rock-property volumes.

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Detailed 3D-Seismic Interpretation Using HFI Seismic Data, Fault Throw, and Stress Analysis for Fault Reactivation in the Cogollo Group, Lower Cretaceous, Urdaneta West Field, Maracaibo Basin

10.2118/95060-ms ◽

2005 ◽

Cited By ~ 1

Author(s):

Miguel Angel Galarraga ◽

Birger Hansen

Keyword(s):

Stress Analysis ◽

Seismic Data ◽

Lower Cretaceous ◽

Seismic Interpretation ◽

Fault Reactivation ◽

3D Seismic ◽

Maracaibo Basin

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THE SUBSURFACE STRUCTURES IN KOCR FIELD IN THE NIGER DELTA, NIGERIA, USING 3D SEISMIC TIMELAPSE DATA

Geological Behavior ◽

10.26480/gbr.01.2021.07.12 ◽

2020 ◽

Vol 5 (1) ◽

pp. 07-12

Author(s):

Igwenagu Chinyere L. ◽

Uko Etim D ◽

Tamunobereton -Ari I. ◽

Amakiri Arobo R.C.

Keyword(s):

Seismic Data ◽

Niger Delta ◽

3D Seismic ◽

Hydrocarbon Production ◽

Seismic Surveys ◽

Subsurface Structures ◽

Decline Rate ◽

Good Repeatability ◽

Niger Delta Basin ◽

Monitor Data

The subsurface structures in KOCR Field, in the Coastal Swamp Niger Delta, Nigeria, are here presented, using seismic 3D timelapse. The KOCR Field lies on latitudes 4o50’58’’-4o55’19’’N and longitudes 6o18’41’’- 6o26’41’’E with aerial extent of 840km2. The base (1997) and the monitor (2009) seismic surveys resulted in a 4D response difference. The Base and Monitor data have a root-mean-square repeatability ratio (RRR) of 0.38 implying a very good repeatability when considering the acquisition, processing and environmental noises. Data processing and interpretation were carried out using Petrel software. The average thickness of the reservoir is about 69m at the depth of 3932m. Reservoir pressure decline rate of 0.062psi/day resulted in production decline rate of 1192.21bbl/day. Structural interpretation of seismic data reveals a highly-faulted field. Fault and horizon interpretation shows closures that are collapsed crestal structures. All the interpreted faults are normal synthetic and antithetic faults which are common in the Niger Delta basin. The lengths, dips and orientations of the faults and horizons, in the base and monitor stacks, are equal indicative of no faults reactivation that could have resulted from hydrocarbon production. The results of this work can be used in reservoir, field and environmental management in the area of study.

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Full-volume 3D seismic interpretation methods: A new step towards high-resolution seismic stratigraphy

Interpretation ◽

10.1190/int-2018-0184.1 ◽

2019 ◽

Vol 7 (3) ◽

pp. B33-B47 ◽

Cited By ~ 5

Author(s):

Victorien Paumard ◽

Julien Bourget ◽

Benjamin Durot ◽

Sébastien Lacaze ◽

Tobi Payenberg ◽

...

Keyword(s):

High Resolution ◽

Seismic Data ◽

Sedimentary Basins ◽

Seismic Stratigraphy ◽

Seismic Interpretation ◽

3D Seismic ◽

Data Set ◽

Seismic Sequences ◽

3D Seismic Data ◽

Full Volume

Following decades of technological innovation, geologists now have access to extensive 3D seismic surveys across sedimentary basins. Using these voluminous data sets to better understand subsurface complexity relies on developing seismic stratigraphic workflows that allow very high-resolution interpretation within a cost-effective timeframe. We have developed an innovative 3D seismic interpretation workflow that combines full-volume and semi-automated horizon tracking with high-resolution 3D seismic stratigraphic analysis. The workflow consists of converting data from seismic (two-way traveltime) to a relative geological time (RGT) volume, in which a relative geological age is assigned to each point of the volume. The generation of a horizon stack is used to extract an unlimited number of chronostratigraphic surfaces (i.e., seismic horizons). Integrated stratigraphic tools may be used to navigate throughout the 3D seismic data to pick seismic unconformities using standard seismic stratigraphic principles in combination with geometric attributes. Here, we applied this workflow to a high-quality 3D seismic data set located in the Northern Carnarvon Basin (North West Shelf, Australia) and provided an example of high-resolution seismic stratigraphic interpretation from an Early Cretaceous shelf-margin system (Lower Barrow Group). This approach is used to identify 73 seismic sequences (i.e., clinothems) bounded by 74 seismic unconformities. Each clinothem presents an average duration of approximately 63,000 years (fifth stratigraphic order), which represents an unprecedented scale of observation for a Cretaceous depositional system on seismic data. This level of interpretation has a variety of applications, including high-resolution paleogeographical reconstructions and quantitative analysis of subsurface data. This innovative workflow constitutes a new step in seismic stratigraphy because it enables interpreters to map seismic sequences in a true 3D environment by taking into account the full variability of depositional systems at high frequency through time and space.

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Metode Inversi AVO Simultan untuk Mengetahui Sebaran Hidrokarbon Formasi Baturaja, Lapangan "Wine”, Cekungan Sumatra Selatan

Jurnal Offshore: Oil, Production Facilities and Renewable Energy ◽

10.30588/jo.v1i1.239 ◽

2017 ◽

Vol 1 (1) ◽

pp. 26

Author(s):

Anastasia Neni Candra Purnamasari

Keyword(s):

Seismic Data ◽

Inversion Method ◽

3D Seismic ◽

Inversion Process ◽

Avo Inversion ◽

Prestack Inversion ◽

Impedance Inversion ◽

Hydrocarbon Distribution ◽

3D Seismic Data ◽

Range Of Values

Data seismik 3D (CDP gather) pada daerah penelitian dilakukan proses inversi prestack yaitu inversi AVO simultan untuk mengetahui sebaran hidrokarbon. Data seismik 3D terbentang dengan jangkauan inline 1003-1302 dan xline 5002-5300. Metode inversi AVO simultan dilakukan dengan data masukan berupa angle stack yang diinversi secara bersama-sama (simultan) untuk menghasilkan impedansi-P, impedansi-S dan densitas. Dari hasil inversi impedansi-P dan inversi impedansi-S didapatkan nilai lambda-rho dan mu-rho sebagai hasil turunannya. Kisaran nilai hasil inversi impedansi-P, impedansi-S, densitas, lambda-rho dan mu-rho pada porous limestone formasi Baturaja yaitu nilai impedansi-P sekitar 11000-13500 m/s*g/cc, nilai impedansi-S sekitar 6500-7400 m/s*g/cc, nilai densitas sekitar 2,52-2,6 g/cc, nilai lambda-rho sekitar 36-70 Gpa*g/cc dan nilai mu-rho sekitar 41-59 Gpa*g/cc. Berdasarkan map slice hasil inversi impedansi-P, map slice hasil inversi impedansi-S, map slice hasil inversi densitas, map slice hasil inversi lambda-rho dan map slice hasil inversi mu-rho dapat diketahui area persebaran hidrokarbon pada formasi Baturaja. Persebaran hidrokarbon berada di sekitar sumur TT.3D seismic data (CDP gather) in the study area was carried out a prestack inversion process, namely simultaneous AVO inversion to determine the distribution of hydrocarbons. 3D seismic data stretches with inline range 1003-1302 and xline 5002-5300. Simultaneous AVO inversion method is done with input data in the form of angle stack which is inverted together (simultaneously) to produce P-impedance, S-impedance and density. From the results of P-impedance inversion and S-impedance inversion, the values of lambda-rho and mu-rho are derived as a result of their derivatives. The range of values of P-impedance inversion, S-impedance, density, lambda-rho and mu-rho in porous limestone formation i.e. the P-impedance value around 11000-13500 m/s*g/cc, the S-impedance value around 6500-7400 m/s*g/cc, the density value around 2.52-2.6 g/cc, the lambda-value rho around 36-70 Gpa*g/cc and your value around 41-59 Gpa*g/cc. Based on the P-impedance inversion map slice, S-impedance inversion map slice, density inversion map slice, lambda-rho inversion map slice and mu-rho inversion map slice can be known the area of hydrocarbon distribution in the Baturaja formation. Hydrocarbon spread is around the TT well.

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