scholarly journals Microcrack Porosity Estimation Based on Rock Physics Templates: A Case Study in Sichuan Basin, China

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7225
Author(s):  
Chuantong Ruan ◽  
Jing Ba ◽  
José M. Carcione ◽  
Tiansheng Chen ◽  
Runfa He
Keyword(s):  
Sichuan Basin ◽  
Rock Physics ◽  
Wave Impedance ◽  
Gas Production ◽  
P Wave ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Amplitude Variation With Offset ◽  
Xujiahe Formation ◽  
Seismic Properties

Low porosity-permeability structures and microcracks, where gas is produced, are the main characteristics of tight sandstone gas reservoirs in the Sichuan Basin, China. In this work, an analysis of amplitude variation with offset (AVO) is performed. Based on the experimental and log data, sensitivity analysis is performed to sort out the rock physics attributes sensitive to microcrack and total porosities. The Biot–Rayleigh poroelasticity theory describes the complexity of the rock and yields the seismic properties, such as Poisson’s ratio and P-wave impedance, which are used to build rock-physics templates calibrated with ultrasonic data at varying effective pressures. The templates are then applied to seismic data of the Xujiahe formation to estimate the total and microcrack porosities, indicating that the results are consistent with actual gas production reports.

Basin-wide rock-physics analysis in Campeche Basin, Gulf of Mexico — Phase II: Reservoir rock and fluid properties

2021 ◽  
Vol 40 (10) ◽  
pp. 716-722
Author(s):  
Yangjun (Kevin) Liu ◽  
Michelle Ellis ◽  
Mohamed El-Toukhy ◽  
Jonathan Hernandez
Keyword(s):  
Oil And Gas ◽  
Rock Physics ◽  
Clay Content ◽  
American Petroleum Institute ◽  
P Wave ◽  
Reservoir Rock ◽  
Gas Oil ◽  
Amplitude Variation With Offset ◽  
Fluid Properties ◽  
The Impact

We present a basin-wide rock-physics analysis of reservoir rocks and fluid properties in Campeche Basin. Reservoir data from discovery wells are analyzed in terms of their relationship between P-wave velocity, density, porosity, clay content, Poisson's ratio (PR), and P-impedance (IP). The fluid properties are computed by using in-situ pressure, temperature, American Petroleum Institute gravity, gas-oil ratio, and volume of gas, oil, and water. Oil- and gas-saturated reservoir sands show strong PR anomalies compared to modeled water sand at equivalent depth. This suggests that PR anomalies can be used as a direct hydrocarbon indicator in the Tertiary sands in Campeche Basin. However, false PR anomalies due to residual gas or oil exist and compose about 30% of the total anomalies. The impact of fluid properties on IP and PR is calibrated using more than 30 discovery wells. These calibrated relationships between fluid properties and PR can be used to guide or constrain amplitude variation with offset inversion for better pore fluid discrimination.

Convolutional neural network for seismic impedance inversion

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. R869-R880 ◽  
Author(s):  
Vishal Das ◽  
Ahinoam Pollack ◽  
Uri Wollner ◽  
Tapan Mukerji
Keyword(s):  
Rock Physics ◽  
Normal Incidence ◽  
Wave Impedance ◽  
Training Data ◽  
P Wave ◽  
Computation Method ◽  
Elastic Model ◽  
Spatial Correlations ◽  
Data Set ◽  
Earth Models

We have addressed the geophysical problem of obtaining an elastic model of the subsurface from recorded normal-incidence seismic data using convolutional neural networks (CNNs). We train the network on synthetic full-waveform seismograms generated using Kennett’s reflectivity method on earth models that were created under rock-physics modeling constraints. We use an approximate Bayesian computation method to estimate the posterior distribution corresponding to the CNN prediction and to quantify the uncertainty related to the predictions. In addition, we test the robustness of the network in predicting impedances of previously unobserved earth models when the input to the network consisted of seismograms generated using: (1) earth models with different spatial correlations (i.e. variograms), (2) earth models with different facies proportions, (3) earth models with different underlying rock-physics relations, and (4) source-wavelet phase and frequency different than in the training data. Results indicate that the predictions of the trained network are susceptible to facies proportions, the rock-physics model, and source-wavelet parameters used in the training data set. Finally, we apply CNN inversion on the Volve field data set from offshore Norway. P-wave impedance [Formula: see text] inverted for the Volve data set using CNN showed a strong correlation (82%) with the [Formula: see text] log at a well.

Rock-physics templates based on seismic Q

Geophysics ◽  
2019 ◽  
Vol 84 (1) ◽  
pp. MR13-MR23 ◽  
Author(s):  
Stefano Picotti ◽  
José M. Carcione ◽  
Jing Ba
Keyword(s):  
Quality Factor ◽  
Acoustic Impedance ◽  
Rock Physics ◽  
P Wave ◽  
Gas Oil ◽  
Seismic Properties ◽  
Gas Saturation ◽  
Seismic Quality Factor ◽  
Porosity And Permeability ◽  
Higher Sensitivity

We build rock-physics templates (RPTs) for reservoir rocks based on seismic quality factors. In these templates, the effects of partial saturation, porosity, and permeability on the seismic properties are described by generalizing the Johnson mesoscopic-loss model to a distribution of gas-patch sizes in brine- and oil-saturated rocks. This model addresses the wave-induced fluid flow attenuation mechanism, by which part of the energy of the fast P-wave is converted into the slow P (Biot) diffusive mode. We consider patch sizes, whose probability density function is defined by a normal (Gaussian) distribution. The complex bulk modulus of the composite medium is obtained with the Voigt-Reuss-Hill average, and we show that the results are close to those obtained with the Hashin-Shtrikman average. The templates represent the seismic dissipation factor (reciprocal of seismic quality factor) as a function of the P-wave velocity, acoustic impedance, and [Formula: see text] (P to S velocity ratio), for isolines of saturation, porosity, and permeability. They differentiate between oil and brine on the basis of the quality factor, with the gas-brine case showing more dissipation than the gas-oil case. We obtain sensitivity maps of the seismic properties to gas saturation and porosity for brine and oil. Unlike the gas-brine case, which shows higher sensitivity of attenuation to gas saturation, the gas-oil case shows higher sensitivity to porosity, and higher acoustic impedance and [Formula: see text] sensitivity values versus saturation. The RPTs can be used for a robust sensitivity analysis, which provides insights on seismic attributes for hydrocarbon detection and reservoir delineation. The templates are also relevant for studies related to [Formula: see text]-storage monitoring.

scholarly journals Modeling of the tight sandstone gas accumulation for the Xujiahe Formation, Hechuan-Tongnan Area, Sichuan Basin

2011 ◽  
Vol 38 (4) ◽  
pp. 409-418 ◽  
Author(s):  
Qiulin Guo ◽  
Jianzhong Li ◽  
Ningsheng Chen ◽  
Junwen Hu ◽  
Hongbing Xie ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Tight Sandstone ◽  
Xujiahe Formation ◽  
Gas Accumulation

scholarly journals Reservoir-forming mechanism and enrichment conditions of the extensive Xujiahe Formation gas reservoirs, central Sichuan Basin

2010 ◽  
Vol 37 (2) ◽  
pp. 146-157 ◽  
Author(s):  
Zhao Wenzhi ◽  
Wang Hongjun ◽  
Xu Chunchun ◽  
Bian Congsheng ◽  
Wang Zecheng ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Gas Reservoirs ◽  
Xujiahe Formation ◽  
Forming Mechanism ◽  
Central Sichuan Basin

Seismic estimation of fluid saturation based on rock physics: A case study of the tight-gas sandstone reservoirs in Ordos Basin

2021 ◽  
pp. 1-47
Author(s):  
Chao Li ◽  
Peng Hu ◽  
Jing Ba ◽  
José M. Carcione ◽  
Tianwen Hu ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Rock Physics ◽  
Gas Production ◽  
P Wave ◽  
Quantitative Prediction ◽  
Rock Fragment ◽  
Tight Gas ◽  
Fluid Saturation ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

Tight-gas sandstone reservoirs of the Ordos Basin of China are characterized by high rock-fragment content, dissimilar pore types and a random distribution of fluids, leading to strong local heterogeneity. We model the seismic properties of these sandstones with the double-double porosity (DDP) theory, which considers water saturation, porosity and the frame characteristics. A generalized seismic wavelet is used to fit the real wavelet and the peak frequency-shift method is combined with the generalized S-transform to estimate attenuation. Then, we establish rock-physics templates (RPTs) based on P-wave attenuation and impedance. We use the log data and related seismic traces to calibrate the RPTs and generate a 3D volume of rock-physics attributes for the quantitative prediction of saturation and porosity. The predicted values are in good agreement with the actual gas production reports, indicating that the method can be effectively applied to heterogeneous tight-gas sandstone reservoirs.

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