Unconventional Reservoir characterization and Sensitive Attributes Determination: A Case Study of Eastern Sembar Formation, Lower Indus Basin, Pakistan

Geophysics ◽  
2020 ◽  
pp. 1-67
Author(s):  
Muhammad Abid ◽  
Liping Niu ◽  
Jiqiang Ma ◽  
Jianhua Geng
Keyword(s):  
Organic Matter ◽  
Seismic Data ◽  
Wave Impedance ◽  
P Wave ◽  
Indus Basin ◽  
Brittleness Index ◽  
Poor Correlation ◽  
Unconventional Reservoir ◽  
Geomechanical Properties ◽  
Lower Indus Basin

The Sembar Shale formation in Lower Indus Basin Pakistan is thought to contain significant potential of unconventional resources; however, no detailed study has yet been carried out to quantify its potential. In conventional oil and gas exploration, reservoir rocks have been the main focus therefore, limited number of wells target the Sembar Formation. To explore its regional view, the seismic characterization of these shale is required. Generally, a poor correlation is generally observed between P-wave impedance and the reservoir and geomechanical properties of rocks, making it challenging to characterize them using seismic data. We present a workflow for characterizing the seismic derived unconventional prospect of the Sembar Shale using prestack seismic data along with well logs. The logging results of the two wells show that organic matter richness of well A is in high to very high values while, well B is in low to very low values. Considering the mineral composition and brittleness index evaluation the Sembar Shale in well A is brittle to less brittle in nature. The organic content, porosity, and brittleness index results in well A makes the Lower Cretaceous Sembar Formation favorable to be considered as a potential organic shale reservoir. Four sensitive attributes, derived through integration of the rock petrophysical, geochemical and geomechanical parameters, are correlated with P-wave impedance. The correlation of each sensitive attribute has been applied to characterize the Sembar Shale potential. These attributes are first-order indicators to depict organic matter, porosity and geomechanical properties. This attribute approach is further validated through rock physics modeling. The workflow presented in this study can be employed to assess unconventional reservoir potential of the Sembar Formation in other parts of the basin.

Inversion and interpretation of a 3D seismic data set from the Ouachita Mountains, Oklahoma

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. B37-B45 ◽  
Author(s):  
Abuduwali Aibaidula ◽  
George McMechan
Keyword(s):  
Seismic Data ◽  
Acoustic Impedance ◽  
3D Visualization ◽  
Wave Impedance ◽  
P Wave ◽  
3D Seismic ◽  
S Wave ◽  
Ouachita Mountains ◽  
Data Set ◽  
3D Seismic Data

Acoustic impedance inversion (AI) and simultaneous angle-dependent inversion (SADI) of a 3D seismic data set characterize reservoirs of Mississippian Morrowan age in the triangle zone of the frontal Ouachita Mountains, Oklahoma. Acoustic impedance of the near-angle seismic data images the 3D spatial distributions of Wapanucka limestone and Cromwell sandstone. Lamé [Formula: see text] ([Formula: see text] and [Formula: see text]) and [Formula: see text] sections are derived from the P-wave and S-wave impedance ([Formula: see text] and [Formula: see text]) sections produced by the SADI. Lithology is identified from the gamma logs and [Formula: see text]. The [Formula: see text], [Formula: see text], and [Formula: see text] are interpreted in terms of a hydrocarbon distribution pattern. The [Formula: see text] is used to identify high [Formula: see text] regions that are consistent with high sand/shale ratio. The estimated impedances and derived Lamé parameter sections are consistent with the interpretation that parts of the Wapanucka limestone and Cromwell sandstone contain potential gas reservoirs in fault-bounded compartments. The Cromwell sandstone contains the main inferred reservoirs; the two largest of these are each [Formula: see text] in pore volume. The inversion results also explain the observed low production in previous wells because those did not sample the best compartments. We propose a single new well location that would penetrate both reservoirs; 3D visualization facilitates this recommendation.

scholarly journals Seismic Driven Geomechanical Modeling of Uplifted and Subsided Wells in Mumbai Offshore and Its Engineering Implications

2021 ◽  
Vol 6 (4) ◽  
pp. 1025-1043
Author(s):  
Venkatesh Ambati ◽  
Nagendra Babu Mahadasu ◽  
Rajesh R. Nair
Keyword(s):  
Seismic Data ◽  
Young Modulus ◽  
Reservoir Management ◽  
Brittleness Index ◽  
3D Seismic ◽  
Diverse Range ◽  
Geomechanical Properties ◽  
The North ◽  
Rock Hardness ◽  
Earth Models

Seismic data provide evidence about hydrocarbon deposition, geological and geophysical subsurface information, including geomechanical aspects. Deriving and understanding geomechanical properties is crucial for reservoir management as it can avoid drilling and production-related problems that cause environmental impacts associated with land subsidence and uplift. The Poison's ratio (PR), Young Modulus (YM), and elastic moduli for a reservoir block were estimated using 3D seismic pre-stack data and well data. 3D Mechanical Earth Models (MEM) were also developed using the well logs, seismic horizons, and drilling data. Seismic data-derived geomechanical properties were compared with the mechanical earth models for the first time for this field. Well-tie analysis was used for inversion of 3D seismic data to extract detailed waveform and amplitude information. The brittleness index of the subsurface layers was estimated, which is a critical rock property that provides information about rock hardness and fragility phenomenon. The brittleness index has a diverse range from 5-35%, with significant contrast at shallow zones. PR and YM models generated from 3D MEM and seismic data have average values of 0.2 -0.6 and 5 - 28 GPa with significant contrast from shales and carbonates. The study recommends that the drilling through these problematic zones should be avoided to avoid wellbore problems that cause challenges in maintaining wellbore integrity and reservoir management in the North-Heera field, Mumbai Offshore Basin.

Poststack, prestack, and joint inversion of P- and S-wave data for Morrow A sandstone characterization

2015 ◽  
Vol 3 (3) ◽  
pp. SZ59-SZ92 ◽  
Author(s):  
Paritosh Singh ◽  
Thomas L. Davis ◽  
Bryan DeVault
Keyword(s):  
Wave Velocity ◽  
Seismic Data ◽  
Joint Inversion ◽  
Wave Impedance ◽  
P Wave ◽  
S Wave ◽  
Wave Data ◽  
Wave Inversion ◽  
Density Maps ◽  
P Wave Velocity

Exploration for oil-bearing Morrow sandstones using conventional seismic data/methods has a startlingly low success rate of only 3%. The S-wave velocity contrast between the Morrow shale and A sandstone is strong compared with the P-wave velocity contrast, and, therefore, multicomponent seismic data could help to characterize these reservoirs. The SV and SH data used in this study are generated using S-wave data from horizontal source and horizontal receiver recording. Prestack P- and S-wave inversions, and joint P- and S-wave inversions, provide estimates of P- and S-wave impedances, and density for characterization of the Morrow A sandstone. Due to the weak P-wave amplitude-versus-angle response at the Morrow A sandstone top, the density and S-wave impedance estimated from joint P- and S-wave inversions were inferior to the prestack S-wave inversion. The inversion results were compared with the Morrow A sandstone thickness and density maps obtained from well logs to select the final impedance and density volume for interpretation. The P-wave impedance estimated from prestack P-wave data, as well as density and S-wave impedance estimated from prestack SV‐wave data were used to identify the distribution, thickness, quality, and porosity of the Morrow A sandstone. The stratal slicing method was used to get the P- and S-wave impedances and density maps. The S-wave impedance characterizes the Morrow A sandstone distribution better than the P-wave impedance throughout the study area. Density estimation from prestack inversion of SV data was able to distinguish between low- and high-quality reservoirs. The porosity volume was estimated from the density obtained from prestack SV-wave inversion. We found some possible well locations based on the interpretation.

Attribute-assisted footprint suppression using a 2D continuous wavelet transform

2018 ◽  
Vol 6 (2) ◽  
pp. T457-T470 ◽  
Author(s):  
Abdulmohsen Alali ◽  
Gabriel Machado ◽  
Kurt J. Marfurt
Keyword(s):  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Seismic Data ◽  
Wave Impedance ◽  
P Wave ◽  
Continuous Wavelet ◽  
Seismic Attribute ◽  
Attribute Data ◽  
Amplitude Data ◽  
Seismic Acquisition

Acquisition footprint manifests itself on 3D seismic data as a repetitive pattern of noise, anomalously high amplitudes, or structural shifts on time or horizon slices that is correlated to the location of the sources and receivers on the earth’s surface. Ideally, footprint suppression should be handled by denser seismic acquisition and more careful prestack processing prior to seismic imaging. In the case in which only legacy data exist, or when economic and time constraints preclude more expensive acquisition and more careful processing, interpreters must deal with data contaminated by footprint. Although accurate time-structure maps can be constructed from footprint-contaminated data, the effect of footprint on subsequent attributes, such as coherence, curvature, spectral components, and P-wave impedance will be exacerbated. We have developed a workflow that uses a 2D continuous wavelet transform to suppress coherent and incoherent noise on poststack seismic data. The method involves decomposing time slices of amplitude and attribute data into voices and magnitudes using 2D wavelets. We exploit the increased seismic attribute sensitivity to the acquisition footprint to design a mask to suppress the footprint on the original amplitude data. The workflow is easy to apply and improves the interpretability of the data and improves the subsequent attribute resolution.

Seismic sedimentology study of braided river — A case study in He8 and Shan1 members of Permian, Sulige western region, Ordos Basin

2018 ◽  
Vol 6 (3) ◽  
pp. T625-T633
Author(s):  
Zhong Hong ◽  
Huaqing Liu ◽  
Ming Sun ◽  
Gai Gao ◽  
Guangmin Hu
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Ordos Basin ◽  
Wave Impedance ◽  
P Wave ◽  
Seismic Survey ◽  
Western Region ◽  
Braided River ◽  
Seismic Sedimentology ◽  
Gas Bearing

The He8 and Shan1 members deposited by braided river are major pay zones of the Sulige western region, Ordos Basin. In these two members, the P-wave impedance ranges of gas-bearing reservoir and the surrounding lithologies are highly overlapped. The gas-bearing reservoir cannot be feasibly recognized by the conventional poststack seismic data. In addition, the seismic reflection of the Shan1 member showing mid-weak amplitude distributes discontinuously within the whole seismic survey, leading to difficulties in tracking seismic events and delineating the plane map of reservoir distribution. To solve the problems above, a seismic sedimentology study was conducted in the study area. First, the seismic reflection characterization of braided river was studied according to its sedimentary model. Also, the amplitude variation with offset (AVO) seismic data were used to identify gas-bearing reservoir because the Poisson’s ratios of gas-bearing reservoir and the surrounding rocks are distinctly different. The AVO attribute volume is therefore converted into the lithologic volume, which is useful for the subsequent lithologic interpretation work. The isochronous surface of the Shan1 member seismic reflection can be achieved with the aid of a stratal slicing technique. The practice indicates the feasibility of lithologic converting of the AVO attribute volume. The gas-bearing reservoir of the He8 and Shan1 members can be precisely predicted, and the evolutional history and plane-distribution character of the gas-bearing reservoir are clearly delineated by the stratal slices with isochronous significance.

scholarly journals No mafic layer in 80 km thick Tibetan crust

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaochun Wang ◽  
Hans Thybo ◽  
Irina M. Artemieva
Keyword(s):  
Seismic Data ◽  
P Wave ◽  
Indian Plate ◽  
Low Velocity ◽  
Crustal Earthquakes ◽  
Tectonic Processes ◽  
P Wave Velocity ◽  
Juvenile Crust ◽  
Mafic Lower Crust ◽  
Thick Crust

AbstractAll models of the magmatic and plate tectonic processes that create continental crust predict the presence of a mafic lower crust. Earlier proposed crustal doubling in Tibet and the Himalayas by underthrusting of the Indian plate requires the presence of a mafic layer with high seismic P-wave velocity (Vp > 7.0 km/s) above the Moho. Our new seismic data demonstrates that some of the thickest crust on Earth in the middle Lhasa Terrane has exceptionally low velocity (Vp < 6.7 km/s) throughout the whole 80 km thick crust. Observed deep crustal earthquakes throughout the crustal column and thick lithosphere from seismic tomography imply low temperature crust. Therefore, the whole crust must consist of felsic rocks as any mafic layer would have high velocity unless the temperature of the crust were high. Our results form basis for alternative models for the formation of extremely thick juvenile crust with predominantly felsic composition in continental collision zones.

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