Structure of giant buried mud volcanoes in the South Caspian Basin: Enhanced seismic image and field gravity data by using normalized full gradient method

2018 ◽  
Vol 6 (4) ◽  
pp. T861-T872
Author(s):  
Mehrdad Soleimani ◽  
Hamid Aghajani ◽  
Saeed Heydari-Nejad
Keyword(s):  
Seismic Data ◽  
Root Zone ◽  
Gravity Data ◽  
Complex Structure ◽  
Normal Faults ◽  
Mud Volcanoes ◽  
South Caspian Basin ◽  
Structural Interpretation ◽  
Seismic Image ◽  
Normalized Full Gradient

Defining the root zone of mud volcanoes (MVs), structural interpretation, and geologic modeling of their body is a problematic task when only seismic data are available. We have developed a strategy for integration of gravity and seismic data for better structural interpretation. Our strategy uses the concept of the normalized full gradient (NFG) for integration of gravity and seismic data to define geometry and the root zone of MVs in the southeast onshore of the Caspian Sea. Our strategy will increase the resolution of the seismic envelope compared with the conventional Hilbert transform. Prior to interpretation, we applied the NFG method on field gravity data. First, we perform a forward-modeling step for accurate NFG parameter definition. Second, we estimate the depth of the target, which is the root zone of the MV here. Interpretation of field gravity data by optimized NFG parameters indicates an accurate depth of the root zone. Subsequently, we apply the NFG method with optimized parameters on a 2D seismic data. Application of our strategy on seismic data will enhance resolution of the seismic image. The depth of the root zone and the geometry of the MV and mud flows was interpreted better on the enhanced image. It also illustrates the complex structure of a giant buried MV, which was not well-interpreted on conventional seismic image. Interpretation of the processed data reveals that the giant MV had lost its connection to its reservoir, whereas the other MV is still connected to the mud reservoir. The giant MV is composed of complex bodies due to pulses in the mud flows. Another MV in the section indicates narrow neck with anticline and listric normal faults on its top. Thus, application of the NFG concept on seismic image could be considered as an alternative to obtain enhanced seismic image for geologic interpretation.

The structure of the northeastern Gulf of St. Lawrence, Canada: new insight from geophysical data analysis

2001 ◽  
Vol 38 (11) ◽  
pp. 1495-1516 ◽  
Author(s):  
Nathan Hayward ◽  
Sonya A Dehler ◽  
Gordon N Oakey
Keyword(s):  
Seismic Data ◽  
Gravity Data ◽  
Complex Structure ◽  
Gravity Anomalies ◽  
Geological Structure ◽  
Geophysical Data ◽  
Normal Faults ◽  
Middle Ordovician ◽  
Clastic Rocks ◽  
Lower Amplitude

An improved compilation of magnetic and gravity data has been interpreted in conjunction with seismic reflection profiles to provide new information about the complex structure of the northeastern Gulf of St. Lawrence, Atlantic Canada. This region was affected by plate divergence and convergence events during the Grenville and Appalachian orogenies and the opening of the Iapetus Ocean. The Anticosti Basin, which developed as a foreland basin over the margin of Laurentia, is filled with a thick succession of Cambrian to Silurian sedimentary strata. Most of the interpreted magnetic and gravity anomalies have sources within the basement rocks, which is interpreted as Grenville crust beneath much of the study area. A V-shaped zone of lower amplitude gravity and magnetic anomalies in the center of the region is associated with a slight thickening of Cambrian to Middle Ordovician sedimentary rocks over a downthrown block of anorthositic Grenville crust, with a locally lower density and magnetization. Extensional faults bordering the zone presently display 130–250 m of downthrow at basement depths, increasing to the southeast, but show no disruption of strata younger than Middle Ordovician. A magnetic low 200 km to the northeast is of similar geophysical character and is associated with a similar geological structure. Numerous NE-trending normal faults associated with segmentation of the Grenville basement are manifested in the magnetic and seismic data. Related anomaly sources are also present within the overlying Ordovician calcareous and clastic rocks that were deposited during extension associated with the onset of the Taconian orogeny. Other anomalies are associated with faulting and folding of shallower strata, and seismic data indicate that some of the NE-trending faults were reactivated as thrusts towards the close of the Taconian orogeny in the Late Ordovician. The geophysical data show no evidence of significant deformation north of the western margin of Newfoundland that would be associated with later compressive events of the Acadian orogeny.

Using petrophysics and cross‐section balancing to interpret complex structure in a limited‐quality 3-D seismic image

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1760-1773 ◽  
Author(s):  
Bob A. Hardage ◽  
Virginia M. Pendleton ◽  
R. P. Major ◽  
George B. Asquith ◽  
Dan Schultz‐Ela ◽  
...  
Keyword(s):  
Cross Section ◽  
Seismic Data ◽  
Complex Structure ◽  
Negative Influence ◽  
Near Surface ◽  
Structural Interpretation ◽  
West Texas ◽  
Seismic Image ◽  
Variable Surface ◽  
Seismic Area

A study was done to characterize deep, prolific Ellenburger gas reservoirs at Lockridge, Waha, West Waha, and Worsham‐Bayer fields in Pecos, Ward, and Reeves counties in West Texas. A major effort of the study was to interpret a 176-mi2 3-D seismic data volume that spanned these fields. Well control defined the depth of the Ellenburger, the principal interpretation target, to be 17 000–21 000 ft (5200–6400 m) over the image area. Ellenburger reflection signals were weak because of these great target depths. Additionally, the top of the Ellenburger had a gentle, ramp‐like increase in acoustic impedance that did not produce a robust reflection event. A further negative influence on seismic data quality was the fact that a large portion of the 3-D seismic area was covered by a variable surface layer of low‐velocity Tertiary fill that was, in turn, underlain by a varying thickness of high‐velocity salt/anhydrite. These complicated near‐surface conditions attenuated seismic reflection signals and made static corrections of the data difficult. The combination of all these factors has caused many explorationists to consider this region of west Texas a no‐record seismic area for deep drilling targets. Although the 3-D seismic data aquired in this study produced good‐quality images throughout the post‐Mississippian section (down to ∼12 000 ft, or 3700 m), the images of the deep Ellenburger targets (∼20 000 ft, or 6100 m) were limited quality. The challenge was to use this limited‐quality 3-D image to interpret the structural configuration of the deep Ellenburger and the fault systems that traverse the area so that genetic relationship could be established between fault attributes and productive Ellenburger facies. Two techniques were used to produce a reliable structural interpretation of the 3-D seismic data. First, log data recorded in 60-plus wells within the 3-D image space were analyzed to determine where there was evidence of overturned and repeated units caused by thrusting and evidence of missing sections caused by normal faulting. These petrophysical analyses allowed reliable fault patterns and structural configurations to be build across 3-D seismic image zones that were difficult to interpret by conventional methods. Second, cross‐section balancing was done across the more complex structural regimes to determine if each interpreted surface that was used to define the postdeformation structure had a length consistent with the length of that same surface before deformation. The petrophysical analyses thus guided the structural interpretation of the 3-D seismic data by inferring the fault patterns that should be imposed on the limited‐quality image zones; the cross‐section balancing verified where this structural interpretation was reliable and where it needed to be adjusted. This interpretation methodology is offered here to benefit others who are confronted with the problem of interpreting complex structure from limited‐quality 3-D seismic images.

Pitfall experiences when interpreting complex structure with low-quality seismic images

2015 ◽  
Vol 3 (1) ◽  
pp. SB29-SB37 ◽  
Author(s):  
Bob A. Hardage
Keyword(s):  
Seismic Data ◽  
Structural Model ◽  
Signal To Noise Ratio ◽  
Complex Structure ◽  
Lessons Learned ◽  
Structural Deformation ◽  
Structural Interpretation ◽  
Seismic Image ◽  
Data Volume ◽  
Seismic Images

Structural interpretation of seismic data presents numerous opportunities for encountering interpretational pitfalls, particularly when a seismic image does not have an appropriate signal-to-noise ratio (S/N), or when a subsurface structure is unexpectedly complex. When both conditions exist — low S/N data and severe structural deformation — interpretation pitfalls are almost guaranteed. We analyzed an interpretation done 20 years ago that had to deal with poor seismic data quality and extreme distortion of strata. The lessons learned still apply today. Two things helped the interpretation team develop a viable structural model of the prospect. First, existing industry-accepted formation tops assigned to regional wells were rejected and new log interpretations were done to detect evidence of repeated sections and overturned strata. Second, the frequency content of the 3D seismic data volume was restricted to only the first octave of its seismic spectrum to create better evidence of fault geometries. A logical and workable structural interpretation resulted when these two action steps were taken. To the knowledge of our interpretation team, neither of these approaches had been attempted in the area at the time of this work (early 1990s). We found two pitfalls that may be encountered by other interpreters. The first pitfall was the hazard of accepting long-standing, industry-accepted definitions of the positions of formation tops on well logs. This nonquestioning acceptance of certain log signatures as indications of targeted formation tops led to a serious misinterpretation in our study. The second pitfall was the prevailing passion by geophysicists to create seismic data volumes that have the widest possible frequency spectrum. This interpretation effort showed that the opposite strategy was better at this site and for our data conditions; i.e., it was better to filter seismic images so that they contained only the lowest octave of frequencies in the seismic spectrum.

scholarly journals Appraising structural interpretations using seismic data — Theoretical elements

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. N29-N40
Author(s):  
Modeste Irakarama ◽  
Paul Cupillard ◽  
Guillaume Caumon ◽  
Paul Sava ◽  
Jonathan Edwards
Keyword(s):  
Seismic Data ◽  
Structural Model ◽  
Synthetic Data ◽  
Target Region ◽  
Structural Interpretation ◽  
Vertical Seismic Profiling ◽  
Seismic Image ◽  
Vsp Data ◽  
Phase Shift Data ◽  
Seismic Images

Structural interpretation of seismic images can be highly subjective, especially in complex geologic settings. A single seismic image will often support multiple geologically valid interpretations. However, it is usually difficult to determine which of those interpretations are more likely than others. We have referred to this problem as structural model appraisal. We have developed the use of misfit functions to rank and appraise multiple interpretations of a given seismic image. Given a set of possible interpretations, we compute synthetic data for each structural interpretation, and then we compare these synthetic data against observed seismic data; this allows us to assign a data-misfit value to each structural interpretation. Our aim is to find data-misfit functions that enable a ranking of interpretations. To do so, we formalize the problem of appraising structural interpretations using seismic data and we derive a set of conditions to be satisfied by the data-misfit function for a successful appraisal. We investigate vertical seismic profiling (VSP) and surface seismic configurations. An application of the proposed method to a realistic synthetic model shows promising results for appraising structural interpretations using VSP data, provided that the target region is well-illuminated. However, we find appraising structural interpretations using surface seismic data to be more challenging, mainly due to the difficulty of computing phase-shift data misfits.

Structural Features Controls of Coalbed Methane (CBM) Accumulation in the Weibei CBM Field, Southeastern Ordos Basin

2014 ◽  
Vol 962-965 ◽  
pp. 79-82 ◽  
Author(s):  
Ya Dong Bai ◽  
Tao Tao Yan ◽  
Jian Guo Wu ◽  
Yong Luo
Keyword(s):  
Theoretical Analysis ◽  
Seismic Data ◽  
Coalbed Methane ◽  
Ordos Basin ◽  
Structural Features ◽  
Gas Content ◽  
Normal Faults ◽  
Distribution Characteristics ◽  
Structural Interpretation ◽  
High Consistency

Based on the structural interpretation of seismic data, we analyzed the gas controlling effects of folds and faults on CBM accumulation qualitatively. Meanwhile, we discussed the lateral sealing ability of the major overthrust faults quantificationally by bringing in “Shale Gouge Ratio (SGR)”, which is proved to be applicable in analyzing the gas controlling effects of faults. The results of the theoretical analysis show that overthrust faults have better sealing effects than normal faults, and synclines are more conducive to CBM accumulation than anticlines. The SGR computed results show a high consistency with the distribution characteristics of the CBM gas content. In all, the folds have little controlling on CBM accumulation, and the faults play a major role in the gas controlling on CBM accumulation in the Weibei CBM field.

scholarly journals Comparing global tomography-derived and gravity-based upper mantle density models

2020 ◽  
Vol 221 (3) ◽  
pp. 1542-1554 ◽  
Author(s):  
B C Root
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Seismic Data ◽  
Gravity Data ◽  
Heterogeneous Data ◽  
Clear Correlation ◽  
Data Sets ◽  
Satellite Gravity ◽  
Similar Density ◽  
Similar Peak

SUMMARY Current seismic tomography models show a complex environment underneath the crust, corroborated by high-precision satellite gravity observations. Both data sets are used to independently explore the density structure of the upper mantle. However, combining these two data sets proves to be challenging. The gravity-data has an inherent insensitivity in the radial direction and seismic tomography has a heterogeneous data acquisition, resulting in smoothed tomography models with de-correlation between different models for the mid-to-small wavelength features. Therefore, this study aims to assess and quantify the effect of regularization on a seismic tomography model by exploiting the high lateral sensitivity of gravity data. Seismic tomography models, SL2013sv, SAVANI, SMEAN2 and S40RTS are compared to a gravity-based density model of the upper mantle. In order to obtain similar density solutions compared to the seismic-derived models, the gravity-based model needs to be smoothed with a Gaussian filter. Different smoothening characteristics are observed for the variety of seismic tomography models, relating to the regularization approach in the inversions. Various S40RTS models with similar seismic data but different regularization settings show that the smoothening effect is stronger with increasing regularization. The type of regularization has a dominant effect on the final tomography solution. To reduce the effect of regularization on the tomography models, an enhancement procedure is proposed. This enhancement should be performed within the spectral domain of the actual resolution of the seismic tomography model. The enhanced seismic tomography models show improved spatial correlation with each other and with the gravity-based model. The variation of the density anomalies have similar peak-to-peak magnitudes and clear correlation to geological structures. The resolvement of the spectral misalignment between tomographic models and gravity-based solutions is the first step in the improvement of multidata inversion studies of the upper mantle and benefit from the advantages in both data sets.

scholarly journals The structure of the sedimentary complex of the Middle and South Caspian depressions (Azerbaijan sector)

2021 ◽  
Vol 43 (4) ◽  
pp. 199-216
Author(s):  
N.P. Yusubov ◽  
I.S. Guliyev
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Sedimentary Cover ◽  
Clay Content ◽  
Geological Structure ◽  
Point Of View ◽  
South Caspian Basin ◽  
Origin And Evolution ◽  
Geological Interpretation ◽  
High Degree

The high degree of knowledge of the upper horizons of the sedimentary cover of the Middle and South Caspian depressions, given an insufficient increase in hydrocarbon reserves, leads to the need for a detailed approach to the search for oil and gas deposits in deep-seated sediments (over 6 km). During the geological interpretation of new highly informative seismic data, as well as data of deep drilling and petrological core studies, there were revealed obvious shortcomings in the concepts of the origin and evolution of the Middle and South Caspian depressions. These ideas misinterpret evolution, especially the South Caspian Basin, which is characterized by a number of unique features: very thick sedimentary cover (up to 22 km), extremely high sedimentation rate, low heat flow and reservoir temperatures, abnormally high pore and reservoir pressures, high clay content of the section, etc. The main purpose of the study was to elucidate the regional structure and features of the dissection of the sedimentary cover of the Middle and South Caspian depressions, the conditions of occurrence and distribution of facies and thicknesses of individual complexes of deposits. The paper analyzes the results of some previous studies of the geological structure of the Middle and South Caspian depressions based on the data of deep seismic sounding, seismological and gravimetric observations. We consider the main conclusions of these studies, about the geological structure of the sedimentary complex of the region’s, very outdated and subject to revision. The results of seismic stratigraphic analysis of seismic data allowed the authors to identify new data about the tectonic structure and express a completely different point of view regarding the structure of the sedimentary cover in the region. The work also touches on the issue associated with the tectonics of the region and the alleged subduction zone here.

Prestack structural interpretation of seismic data: A case study

1991 ◽  
Author(s):  
J. A. C. Jacobs ◽  
Anne Jardin ◽  
Florence Delprat‐Jannaud ◽  
Roelef Versteeg ◽  
Patrick Lailly
Keyword(s):  
Seismic Data ◽  
Structural Interpretation
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