Porosity identification using amplitude variations with offset: Examples from South Sumatra

Geophysics ◽  
1989 ◽  
Vol 54 (8) ◽  
pp. 942-951 ◽  
Author(s):  
S. Chacko
Keyword(s):  
Oil And Gas ◽  
Angle Of Incidence ◽  
The South ◽  
Gas Reservoir ◽  
Amplitude Versus Offset ◽  
Variation Patterns ◽  
Reefal Facies ◽  
Highly Porous ◽  
Amplitude Versus ◽  
Good Agreement

Widespread deposition of platform and reefal carbonates of the Baturaja limestone formation occurred during the Miocene epoch in the South Sumatra basin. Although significant oil and gas deposits have been discovered in the porous facies, porosity within the Baturaja limestone has been observed to vary widely between tight platform facies and highly porous reefal facies, making predrill prediction of porosity an important exploration objective. I use amplitude‐versus‐offset seismic modeling to distinguish between porous and tight Baturaja limestone facies. Amplitude variations with offset for reflections from two Baturaja reefs in the South Sumatra basin were studied: one, a proven gas reservoir, the other, an interpreted reef that had not yet been drilled at the time of study. The seismic data were processed judiciously to preserve and enhance amplitude effects, which were then modeled using the Bortfeld approximation for reflection coefficients. A key assumption was that the [Formula: see text] ratio of limestone depends primarily on minerology rather than on porosity or pore‐fluid content. The modeling showed that porous and tight limestone facies have unique and different reflection-coefficient variation patterns with angle of incidence. Good agreement was found between observed data and the modeling results, indicating that the modeling of amplitude variations with offset can be used as a lithology discriminant. In the second case, a predrill prediction of porosity was confirmed by subsequent drilling.

THE JANSZ GAS FIELD, CARNARVON BASIN, AUSTRALIA

2003 ◽  
Vol 43 (1) ◽  
pp. 303 ◽  
Author(s):  
C.C. Jenkins ◽  
D.M. Maughan ◽  
J.H. Acton ◽  
A. Duckett ◽  
B.E. Korn ◽  
...  
Keyword(s):  
Column Height ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Gas Field ◽  
Amplitude Versus Offset ◽  
Gas Markets ◽  
Sandstone Reservoir ◽  
Western Limb ◽  
Amplitude Versus ◽  
Carnarvon Basin

The Jansz gas field is located in permit WA-268-P, 70 km northwest of the Gorgon gas field in the Carnarvon Basin. The Jansz–1 discovery well was drilled in April 2000 and intersected 29 m of net gas pay in an Oxfordian age shallow marine sandstone reservoir. The well drilled a stratigraphic trap on the western limb of the Kangaroo Syncline.The Io–1 well was drilled in January 2001 in the adjacent permit WA-267-P (18 km from Jansz–1) and intersected the same Oxfordian sandstone reservoir penetrated by Jansz–1, with a total of 44 m of net gas pay. The Tithonian and the Upper Triassic Brigadier Sandstone gas reservoirs at Geryon–1 (1999) and Callirhoe–1 (2001) in WA-267-P are in pressure communication with the Oxfordian gas reservoir at Jansz–1 and Io–1. Consequently, the three different age reservoirs comprise a single gas pool, with a common gas/water contact.The Jansz gas field has been delineated by four wells and 2D seismic. The gas sandstones have a prominent amplitude versus offset response, which defines the field limits. The Jansz gas field is confirmed by drilling to be an areally extensive (2,000 km2) gas accumulation with a gross column height of 400 m and an estimated 20 TCF (566 G.m3) recoverable sales gas, which represents 40% of the discovered gas resources in the deepwater Carnarvon Basin. The size of the Jansz gas field and its remoteness from existing pipeline gas markets suggests that an export LNG project will be the basis for its development.

Seismic data analysis by adaptive sparse time-frequency decomposition

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. V207-V217 ◽  
Author(s):  
Hamid Sattari ◽  
Ali Gholami ◽  
Hamid R. Siahkoohi
Keyword(s):  
Data Analysis ◽  
Seismic Data ◽  
Mixed Norm ◽  
Gas Reservoir ◽  
Efficient Tool ◽  
Time Frequency ◽  
Frequency Decomposition ◽  
Amplitude Versus Offset ◽  
The Difference ◽  
Amplitude Versus

The variation of frequency content of a seismic trace with time carries information about the properties of the subsurface reflectivity sequence. Time-frequency (TF) analysis is a significant tool to extract such information for seismostratigraphic interpretation purposes. However, several TF transforms have been reported in the literature; higher resolution and sensitivity to local changes of the signal have always mattered. We have developed an adaptive high-resolution TF transform that is performed in two sequential steps: First, the window length is adaptively determined for each sample of the signal such that it leads to maximum compactness of energy in the resulting TF plane. Second, the generated nonstationary windows are used to inversely decompose the signal under study via a convex constrained sparse optimization, where a mixed norm of the TF coefficients is minimized subject to invertibility of the transform. Later on, the optimized transform is used as an efficient tool for seismic data analysis such as thin-bed characterization and thin-bedded gas reservoir detection. In the case of gas reservoir detection, based on amplitude versus offset analysis in the TF domain, a simple new method called the difference section was evaluated. The results of various numerical examples from synthetic and field data revealed a remarkable performance of the proposed method compared with the state-of-the-art TF transforms.

Pipeline Politics in Iran, Turkey, and the South Caucasus

2017 ◽  
Author(s):  
Mahmood Monshipouri
Keyword(s):  
Local Governments ◽  
Oil And Gas ◽  
Complex Dynamics ◽  
The South ◽  
South Caucasus ◽  
The Caspian Sea ◽  
Economic Interests ◽  
Oil Companies ◽  
Caucasus Region ◽  
Territorial Conflicts

The relationship between Iran, Turkey and the South Caucasus states have been influenced by an array of geopolitical, strategic, cultural, and economic factors. The competition between Iran and Turkey and their roles in the South Caucasus are best defined by traditional balance-of-power relations and the broader context of the post-Soviet era. This chapter unpacks the complex dynamics of pipeline politics in the South Caucasus region by underlying the need to understand the “Great Power Game” involving geostrategic and geo-economic interests of local governments, regional actors, global powers, and international oil companies. The larger focus turns on underscoring the importance of the region’s large oil and gas reserves; its land connection between the Caspian Sea, South Caucasus, and Europe; and its long-standing territorial conflicts in the post-Soviet era. Iran and Turkey have fought for influence in the South Caucasus while maintaining relatively good bilateral relationships in the region.

Incomplete AVO near salt structures

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 543-553 ◽  
Author(s):  
Christopher P. Ross
Keyword(s):  
Seismic Profiles ◽  
Spectral Modeling ◽  
Signal Degradation ◽  
Amplitude Versus Offset ◽  
Bright Spots ◽  
Close Proximity ◽  
Pseudo Spectral ◽  
Amplitude Versus ◽  
Structure Class ◽  
Made In

Amplitude versus offset (AVO) measurements for deep hydrocarbon‐bearing sands can be compromised when made in close proximity to a shallow salt piercement structure. Anomalous responses are observed, particularly on low acoustic impedance bright spots. CMP data from key seismic profiles traversing the bright spots do not show the expected Class 3 offset responses. On these CMPs, significant decrease of far trace energy is observed. CMP data from other seismic profiles off‐structure do exhibit the Class 3 offset responses, implying that structural complications may be interfering with the offset response. A synthetic AVO gather was generated using well log data, which supports the off‐structure Class 3 responses, further reinforcing the concept of structurally‐biased AVO responses. Acoustic, pseudo‐spectral modeling of the structure substantiates the misleading AVO response. Pseudo‐spectral modeling results suggest that signal degradation observed on the far offsets is caused by wavefield refraction—a shadow zone, where the known hydrocarbon‐bearing sands are not completely illuminated. Such shadow zones obscure the correct AVO response, which may have bearing on exploration and development.

Sign in / Sign up

Export Citation Format

Share Document