scholarly journals Estimation of the Pore Microstructure of Tight-Gas Sandstone Reservoirs with Seismic Data

2021 ◽  
Vol 9 ◽  
Author(s):  
Wei Cheng ◽  
Jing Ba ◽  
José M. Carcione ◽  
Mengqiang Pang ◽  
Chunfang Wu
Keyword(s):  
Seismic Data ◽  
Velocity Ratio ◽  
P Wave ◽  
Seismic Exploration ◽  
Variable Pressure ◽  
Well Log ◽  
Tight Gas ◽  
Tight Sandstone ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

Tight-sandstone reservoirs have a complex pore structure with microcracks and intergranular pores, which have a significant impact on the seismic properties. We have performed ultrasonic measurements at different confining pressures for 15 tight-gas sandstone samples of the Xujiahe formation in Western Sichuan Basin, and have available well-log and seismic data of this area. The aim of this work is to estimate the porosity and crack properties for variable pressure conditions. The EIAS (equivalent inclusion-average stress) model is adopted to compute the high- and low-frequency bulk and shear moduli as a function of crack aspect ratio and (soft) and (stiff) porosities. Then, we use the EIAS-Zener anelastic model to obtain the wave properties as a function of frequency, and compare results with those of the constant Q (Kjartansson) one for verification of the robustness of the approach. The corresponding P-wave impedance, density and phase velocity ratio (VP/VS) are computed in order to built 3D rock‐physics templates (RPTs) at the ultrasonic, well-log and seismic frequency bands. The methodology is applied to a survey line crossing two wells, which together with the laboratory experiments, provide calibration suitable data. The estimated stiff porosity and crack porosity and density are consistent with the available data and actual production records, indicating that 3D RPTs provide a useful interpretation tool in seismic exploration and prospect evaluation.

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.

scholarly journals Rock Physical Modeling and Seismic Dispersion Attribute Inversion for the Characterization of a Tight Gas Sandstone Reservoir

2021 ◽  
Vol 9 ◽  
Author(s):  
Han Jin ◽  
Cai Liu ◽  
Zhiqi Guo ◽  
Yiming Zhang ◽  
Cong Niu ◽  
...  
Keyword(s):  
Rock Physics ◽  
Wave Dispersion ◽  
P Wave ◽  
Tight Gas ◽  
Tight Sandstone ◽  
P Wave Dispersion ◽  
Frequency Dependent ◽  
Gas Saturation ◽  
Avo Inversion ◽  
Tight Gas Sandstone

Gas identification using seismic data is challenging for tight gas reservoirs with low porosity and permeability due to the complicated poroelastic behaviors of tight sandstone. In this study, the Chapman theory was used to simulate the dispersion and attenuation caused by the squirt flow of fluids in the complex pore spaces, which are assumed to consist of high aspect-ratio pores (stiff pores) and low aspect-ratio microcracks (soft pores). The rock physics modeling revealed that as the gas saturation varies, P-wave velocity dispersion and attenuation occurs at seismic frequencies, and it tends to move to high frequencies as the gas saturation increases. The velocity dispersion of the tight gas sandstone causes a frequency-dependent contrast in the P-wave impedance between the tight sandstone and the overlying mudstone, which consequently leads to frequency-dependent incidence reflection coefficients across the interface. In the synthetic seismic AVO modeling conducted by integrating the rock physics model and the propagator matrix method, the variations in the amplitudes and phases of the PP reflections can be observed for various gas saturations. The tests of the frequency-dependent AVO inversion of these synthetic data revealed that the magnitude of the inverted P-wave dispersion attribute can be used to indicate gas saturation in tight sandstone reservoirs. The applications of the frequency-dependent AVO inversion to the field pre-stacked seismic data revealed that the obtained P-wave dispersion attribute is positively correlated with the gas production from the pay zone at the well locations. Thus, the methods of the rock physics modeling and the frequency-dependent AVO inversion conducted in this study have good potential for the evaluation of the gas saturation in tight gas sandstone reservoirs.

Tight Gas Sandstone Reservoirs, Part 2

2016 ◽  
pp. 429-448 ◽  
Author(s):  
W.R. Moore ◽  
Y. Zee Ma ◽  
I. Pirie ◽  
Y. Zhang
Keyword(s):  
Tight Gas ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

scholarly journals Natural hydraulic fracturing of tight-gas sandstone reservoirs, Piceance Basin, Colorado

2014 ◽  
Vol 127 (1-2) ◽  
pp. 61-75 ◽  
Author(s):  
András Fall ◽  
Peter Eichhubl ◽  
Robert J. Bodnar ◽  
Stephen E. Laubach ◽  
J. Steve Davis
Keyword(s):  
Hydraulic Fracturing ◽  
Piceance Basin ◽  
Tight Gas ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

Reflectivity randomness revisited

Geophysics ◽  
1999 ◽  
Vol 64 (5) ◽  
pp. 1630-1636 ◽  
Author(s):  
Ayon K. Dey ◽  
Larry R. Lines
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Seismic Profile ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Well Log ◽  
Simple Test ◽  
Vertical Seismic Profile ◽  
Seismic Reflectivity

In seismic exploration, statistical wavelet estimation and deconvolution are standard tools. Both of these processes assume randomness in the seismic reflectivity sequence. The validity of this assumption is examined by using well‐log synthetic seismograms and by using a procedure for evaluating the resulting deconvolutions. With real data, we compare our wavelet estimations with the in‐situ recording of the wavelet from a vertical seismic profile (VSP). As a result of our examination of the randomness assumption, we present a fairly simple test that can be used to evaluate the validity of a randomness assumption. From our test of seismic data in Alberta, we conclude that the assumption of reflectivity randomness is less of a problem in deconvolution than other assumptions such as phase and stationarity.

Acidizing Treatments for Tight Gas Sandstone Reservoirs

2009 ◽  
Author(s):  
Hamoud A. Al-Anazi ◽  
Wisam J. Assiri ◽  
Bandar H. Al-Malki ◽  
Adnan A. Al-Kanaan
Keyword(s):  
Tight Gas ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

Depositional Systems and Diagenesis of Travis Peak Tight Gas Sandstone Reservoirs, Sabine Uplift Area, Texas

1988 ◽  
Vol 3 (01) ◽  
pp. 105-115 ◽  
Author(s):  
Michael A. Fracasso ◽  
Shirley R. Dutton ◽  
Robert J. Finley
Keyword(s):  
Tight Gas ◽  
Depositional Systems ◽  
Sandstone Reservoirs ◽  
Tight Gas Sandstone

Identification of gas hydrate dissociation from wireline-log data in the Shenhu area, South China Sea

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. B125-B134 ◽  
Author(s):  
Xiujuan Wang ◽  
Myung Lee ◽  
Shiguo Wu ◽  
Shengxiong Yang
Keyword(s):  
Wave Velocity ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Pore Space ◽  
P Wave ◽  
Well Log ◽  
Hydrate Dissociation ◽  
Free Gas ◽  
P Wave Velocity

Wireline logs were acquired in eight wells during China’s first gas hydrate drilling expedition (GMGS-1) in April–June of 2007. Well logs obtained from site SH3 indicated gas hydrate was present in the depth range of 195–206 m below seafloor with a maximum pore-space gas hydrate saturation, calculated from pore water freshening, of about 26%. Assuming gas hydrate is uniformly distributed in the sediments, resistivity calculations using Archie’s equation yielded hydrate-saturation trends similar to those from chloride concentrations. However, the measured compressional (P-wave) velocities decreased sharply at the depth between 194 and 199 mbsf, dropping as low as [Formula: see text], indicating the presence of free gas in the pore space, possibly caused by the dissociation of gas hydrate during drilling. Because surface seismic data acquired prior to drilling were not influenced by the in situ gas hydrate dissociation, surface seismic data could be used to identify the cause of the low P-wave velocity observed in the well log. To determine whether the low well-log P-wave velocity was caused by in situ free gas or by gas hydrate dissociation, synthetic seismograms were generated using the measured well-log P-wave velocity along with velocities calculated assuming both gas hydrate and free gas in the pore space. Comparing the surface seismic data with various synthetic seismograms suggested that low P-wave velocities were likely caused by the dissociation of in situ gas hydrate during drilling.

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