Empirical estimation of viscoelastic seismic parameters from petrophysical properties of sandstone

Geophysics ◽  
2001 ◽  
Vol 66 (5) ◽  
pp. 1457-1470 ◽  
Author(s):  
Adam P. Koesoemadinata ◽  
George A. McMechan
Keyword(s):  
Shear Wave ◽  
Water Saturation ◽  
Clay Content ◽  
Published Data ◽  
Effective Pressure ◽  
Petrophysical Properties ◽  
Quality Factors ◽  
Empirical Estimation ◽  
Reservoir Properties ◽  
Seismic Parameters

Viscoelastic seismic parameters are expressions of underlying petrophysical properties. Theoretical and empirically derived petrophysical/seismic relations exist, but each is limited in the number and the range of values of the variables used. To provide a more comprehensive empirical model, we combined lab measurements from 18 published data sets and well log data for sandstone samples, and determined least‐squares coefficients across them all. The dependent variables are the seismic parameters of bulk density (ρ), compressional and shear wave velocities ([Formula: see text] and [Formula: see text]), and compressional and shear wave quality factors ([Formula: see text] and [Formula: see text]). The independent variables are effective pressure, porosity, clay content, water saturation, permeability, and frequency. As the derived expressions are empirical correlations, no causal relations should be inferred. Prediction of ρ is based on volumetric mixing of the constituents. For [Formula: see text] and [Formula: see text] predictions, separate sets of coefficients are fitted for three water saturation conditions: dry, partially saturated, and fully saturated. Predictions of [Formula: see text] and [Formula: see text] are fitted as functions of porosity, clay content, effective pressure, saturation, and frequency. Predictions of [Formula: see text] are fitted as a function of porosity, clay content, permeability, saturation, frequency, and pressure. Interactions between effective pressure, saturation, and frequency are included. Predictions of [Formula: see text] are obtained from [Formula: see text] and [Formula: see text]. The result is a composite model that is more comprehensive than previous models and that predicts seismic properties from the petrophysical properties. Empirically estimated values of ρ, [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] for the composite data over all saturations predict the measurements with correlation coefficients [Formula: see text] that range from a low of 0.65 (for [Formula: see text],) to a high of 0.90 (for [Formula: see text]). As the fitted relations have been derived from data with limited parameter ranges, extrapolation is not advised, and they are not intended to substitute for locally derived relations based on site‐specific data. Nevertheless, the derived expressions produce representative values that will be useful when approximate, internally consistent predictions are sufficient. Potential future applications include building of seismic reservoir models from petrophysical data and analysis of the sensitivity of seismic data to changes in reservoir properties.

Petro‐seismic inversion for sandstone properties

Geophysics ◽  
2003 ◽  
Vol 68 (5) ◽  
pp. 1611-1625 ◽  
Author(s):  
Adam P. Koesoemadinata ◽  
George A. McMechan
Keyword(s):  
Shear Wave ◽  
Water Saturation ◽  
Correlation Coefficients ◽  
Clay Content ◽  
Seismic Inversion ◽  
Grid Search ◽  
Quality Factors ◽  
Unknown Parameters ◽  
Seismic Parameters ◽  
Input Variables

We use empirical relations derived from laboratory and log data for sandstones to estimate unknown parameters from given parameters. The known and unknown parameters may be any of the following: compressional and shear wave velocities (Vp and Vs), density (ρ), compressional and shear wave quality factors (Qp and Qs), effective pressure (P), frequency (f), water saturation (S), porosity (φ), clay content (C), fluid permeability (k), and Vp/Vs and Qs/Qp ratios. The goal is to obtain estimates of all thirteen of these petro‐seismic variables from subsets of these as input; whether this is achievable depends on the particular combination of input variables. The inversion typically proceeds through a hierarchy of three levels of parameter estimation, in order of the expected reliability of the estimates. First, we solve for the parameters that can be obtained directly from the fitted empirical equations. Then, a grid search is performed to simultanously fit more than one unknown parameter by finding values that best predict the known parameters. Finally, various approximations are invoked to predict values when the inputs are insufficient to use the direct equations or a grid search. These three procedures can be initiated in any desired order and any number of times. Even if the complete set of seismic parameters (Vp, and Vs, ρ, Qp, Qs, and f) are given, it is not possible to uniquely obtain any of the remaining petrophysical variables (S, φ, C, P, or k) directly from the fitted equations without constraints on (or assumptions about) some of the other variables. There is a trade‐off between porosity and clay content that can be resolved by simultaneous fitting of multiple seismic parameters (i.e., Vp, Vs, and Vp/Vs). The predictability of the parameters from various combinations of the available data is expressed using correlation coefficients (R2) and standard deviations. With optimal input combinations, parameters with R2 ≥ 0.8 are (in order from best to worst) Vp, 100/Qp, ρ, Vs, and S. Other parameters with 0.63 ≥ R2 ≤, 0.79 are (in order from best to worst) φ, Qs/Qp, Vp/Vs, ln k, 100/Qs, and C. P and f are the least reliably estimated. All of the seismic parameters can be accurately estimated if all of the petrophysical parameters are known.

scholarly journals An Integrated Microfacies and Well Logs-Based Reservoir Characterization of Yamama Formation, Southern Iraq

2021 ◽  
pp. 3570-3586
Author(s):  
Mohanad M. Al-Ghuribawi ◽  
Rasha F. Faisal
Keyword(s):  
Reservoir Characterization ◽  
Water Saturation ◽  
Effective Porosity ◽  
Well Logs ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Porosity And Permeability ◽  
South Of Iraq ◽  
Southern Iraq

     The Yamama Formation includes important carbonates reservoir that belongs to the Lower Cretaceous sequence in Southern Iraq. This study covers two oil fields (Sindbad and Siba) that are distributed Southeastern Basrah Governorate, South of Iraq. Yamama reservoir units were determined based on the study of cores, well logs, and petrographic examination of thin sections that required a detailed integration of geological data and petrophysical properties. These parameters were integrated in order to divide the Yamama Formation into six reservoir units (YA0, YA1, YA2, YB1, YB2 and YC), located between five cap rock units. The best facies association and petrophysical properties were found in the shoal environment, where the most common porosity types were the primary (interparticle) and secondary (moldic and vugs) . The main diagenetic process that occurred in YA0, YA2, and YB1 is cementation, which led to the filling of pore spaces by cement and subsequently decreased the reservoir quality (porosity and permeability). Based on the results of the final digital  computer interpretation and processing (CPI) performed by using the Techlog software, the units YA1 and YB2 have the best reservoir properties. The unit YB2 is characterized by a good effective porosity average, low water saturation, good permeability, and large thickness that distinguish it from other reservoir units.

scholarly journals Experimental Study About Water Saturation Influence on Changes in Reservoirs Petrophysical Properties

2021 ◽  
Vol 18 (13) ◽  
Author(s):  
Sudad Hameed AL-OBAIDI ◽  
Victoria SMIRNOV ◽  
Hiba Hussein ALWAN
Keyword(s):  
Physical Properties ◽  
Effective Permeability ◽  
Water Saturation ◽  
Residual Water ◽  
Effective Pressure ◽  
Petrophysical Properties ◽  
Reservoir Conditions ◽  
Water Saturated

Experimental determination of the physical properties of rocks under conditions simulating in situ reservoir conditions is of great importance both for the calculation of reserves and for the interpretation of well logging data. In addition, it is also important for the preparation of hydrocarbon field development projects. The study of the processes of changes in the petrophysical properties of the reservoir under controlled conditions allows not only to determine their reliability but also to evaluate the dynamics of these changes depending on the temperature and pressure conditions of the reservoir and the water saturation of the rocks. In this work, an evaluation of the dependence of the physical properties of hydrocarbon reservoirs on their water saturation (Sw) was carried out. Residual water saturation (Swr) was created in the rocks and the properties of these rocks were compared at the states of partial (25 %) and complete water saturation (100 %). The changes in petrophysical parameters of partially water saturated rocks during the increase in effective pressure were studied and estimates of these changes were obtained. The results showed that when the effective pressure is increased, the Swr increases by an average of 6 % compared to atmospheric conditions. This is accompanied by an increase in the velocity of longitudinal (by 51.9 % on average) and lateral waves (by 37.1 % on average). As residual water saturation increases, effective permeability decreases for both standard and reservoir conditions, with, gas permeability decreasing for both dry samples (by 23 % on average) and samples with residual water saturation (effective permeability decreases by 27 % on average). HIGHLIGHTS Changes in physical properties of hydrocarbon reservoirs by determining physical properties (permeability, porosity, elastic, electrical, deformation strength) under the standard conditions and in physical modelling of reservoir conditions and processes Assessment of the effectiveness of water saturation on the physical properties of the reservoir Comparisons between the petrophysical properties of reservoir core samples in which the pore space is fully saturated with the reservoir fluid model and samples with residual water saturation Experimental determination of the physical properties of rocks under conditions simulating in situ reservoir conditions Estimation of the changes in petrophysical parameters of partial water-saturated rocks during the increase in effective formation pressure GRAPHICAL ABSTRACT

scholarly journals The Evaluation of Reservoir Quality of Mishrif Formation in South and North Domes of Buzurgan Oil Field

2019 ◽  
Vol 9 (4) ◽  
pp. 89-106
Author(s):  
Ali Duair Jaafar ◽  
Dr. Medhat E. Nasser
Keyword(s):  
Physical Properties ◽  
Water Saturation ◽  
Oil Field ◽  
Reservoir Quality ◽  
Petrophysical Properties ◽  
The South ◽  
Reservoir Properties ◽  
Formation Evaluation ◽  
The North

Buzurgan field in the most cases regards important Iraqi oilfield, and Mishrif Formation is the main producing reservoir in this field, the necessary of so modern geophysical studies is necessity for description and interpret the petrophysical properties in this field. Formation evaluation has been carried out for Mishrif Formation of the Buzurgan oilfield depending on logs data. The available logs data were digitized by using Neuralog software. A computer processed interpretation (CPI) was done for each one of the studied wells from south and north domes using Techlog software V2015.3 in which the porosity, water saturation, and shale content were calculated. And they show that MB21 reservoir unit has the highest thickness, which ranges between (69) m in north dome to (83) m in south dome, and the highest porosity, between (0.06 - 0.16) in the north dome to (0.05 -0.21) in the south dome. The water saturation of this unit ranges between (25% -60%) in MB21 of north dome. It also appeared that the water saturation in the unit MB21 of south dome has the low value, which is between (16% - 25%). From correlation, the thickness of reservoir unit MB21 increases towards the south dome, while the thickness of the uppermost barrier of Mishrif Formation increases towards the north dome. The reservoir unit MB21 was divided into 9 layers due to its large thickness and its important petrophysical characterization. The distribution of petro physical properties (porosity and water saturation) has shown that MB 21 has good reservoir properties.

scholarly journals Hartha Formation divisions Based on Well Logs Analysis in Majnoon Oil Field, Southern Iraq

2020 ◽  
pp. 1362-1369
Author(s):  
Gheed Chaseb ◽  
Thamer A. Mahdi
Keyword(s):  
Water Saturation ◽  
Effective Porosity ◽  
Oil Field ◽  
Well Logs ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Facies Associations ◽  
Log Interpretation ◽  
Well Logs Interpretation

This study aims to evaluate reservoir characteristics of Hartha Formation in Majnoon oil field based on well logs data for three wells (Mj-1, Mj-3 and Mj-11). Log interpretation was carried out by using a full set of logs to calculate main petrophysical properties such as effective porosity and water saturation, as well as to find the volume of shale. The evaluation of the formation included computer processes interpretation (CPI) using Interactive Petrophysics (IP) software.  Based on the results of CPI, Hartha Formation is divided into five reservoir units (A1, A2, A3, B1, B2), deposited in a ramp setting. Facies associations is added to well logs interpretation of Hartha Formation, and was inferred by a microfacies analysis of thin sections from core and cutting samples. The CPI shows that the A2 is the main oil- bearing unit, which is characterized by good reservoir properties, as indicated by high effective porosity, low water saturation, and low shale volume. Less important units include A1 and A3, because they have low petrophysical properties compared to the unit A2.

scholarly journals Stochastic modelling of spatial variability of petrophysical properties in parts of the Niger Delta Basin, southern Nigeria

2019 ◽  
Vol 10 (2) ◽  
pp. 569-585 ◽  
Author(s):  
Ebong D. Ebong ◽  
Anthony E. Akpan ◽  
Stephen E. Ekwok
Keyword(s):  
Spatial Variability ◽  
Niger Delta ◽  
Water Saturation ◽  
Stochastic Modelling ◽  
Sequential Gaussian Simulation ◽  
Stochastic Methods ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Petrophysical Property ◽  
Niger Delta Basin

Abstract Three-dimensional models of petrophysical properties were constructed using stochastic methods to reduce ambiguities associated with estimates for which data is limited to well locations alone. The aim of this study is to define accurate and efficient petrophysical property models that best characterize reservoirs in the Niger Delta Basin at well locations and predicting their spatial continuities elsewhere within the field. Seismic data and well log data were employed in this study. Petrophysical properties estimated for both reservoirs range between 0.15 and 0.35 for porosity, 0.27 and 0.30 for water saturation, and 0.10 and 0.25 for shale volume. Variogram modelling and calculations were performed to guide the distribution of petrophysical properties outside wells, hence, extending their spatial variability in all directions. Transformation of pillar grids of reservoir properties using sequential Gaussian simulation with collocated cokriging algorithm yielded equiprobable petrophysical models. Uncertainties in petrophysical property predictions were performed and visualized based on three realizations generated for each property. The results obtained show reliable approximations of the geological continuity of petrophysical property estimates over the entire geospace.

scholarly journals Evaluation of Petrophysical Properties Using Well Logs of Yamama Formation in Abu Amood Oil Field, Southern Iraq

2021 ◽  
Vol 54 (1E) ◽  
pp. 67-77
Author(s):  
Buraq Adnan Al-Baldawi
Keyword(s):  
Gamma Ray ◽  
Water Saturation ◽  
Bulk Water ◽  
Carbonate Reservoir ◽  
Oil Field ◽  
Well Logs ◽  
Water Volume ◽  
High Porosity ◽  
Petrophysical Properties ◽  
Reservoir Properties

The petrophysical analysis is very important to understand the factors controlling the reservoir quality and production wells. In the current study, the petrophysical evaluation was accomplished to hydrocarbon assessment based on well log data of four wells of Early Cretaceous carbonate reservoir Yamama Formation in Abu-Amood oil field in the southern part of Iraq. The available well logs such as sonic, density, neutron, gamma ray, SP, and resistivity logs for wells AAm-1, AAm-2, AAm-3, and AAm-5 were used to delineate the reservoir characteristics of the Yamama Formation. Lithologic and mineralogic studies were performed using porosity logs combination cross plots such as density vs. neutron cross plot and M-N mineralogy plot. These cross plots show that the Yamama Formation consists mainly of limestone and the essential mineral components are dominantly calcite with small amounts of dolomite. The petrophysical characteristics such as porosity, water and hydrocarbon saturation and bulk water volume were determined and interpreted using Techlog software to carried out and building the full computer processed interpretation for reservoir properties. Based on the petrophysical properties of studied wells, the Yamama Formation is divided into six units; (YB-1, YB-2, YB-3, YC-1, YC-2 and YC-3) separated by dense non porous units (Barrier beds). The units (YB-1, YB-2, YC-2 and YC-3) represent the most important reservoir units and oil-bearing zones because these reservoir units are characterized by good petrophysical properties due to high porosity and low to moderate water saturation. The other units are not reservoirs and not oil-bearing units due to low porosity and high-water saturation.

The accuracy of estimating Q from seismic data

Geophysics ◽  
1992 ◽  
Vol 57 (11) ◽  
pp. 1508-1511 ◽  
Author(s):  
R. E. White
Keyword(s):  
Seismic Data ◽  
Poisson’S Ratio ◽  
Seismic Velocity ◽  
Clay Content ◽  
Seismic Interpretation ◽  
Poisson's Ratio ◽  
Petrophysical Properties ◽  
Complementary Information ◽  
Seismic Parameters ◽  
Reservoir Rocks

A major aim of seismic interpretation is the inference of petrophysical properties of reservoir rocks. Because the inversion from seismic to petrophysical characteristics is far from unique, this task requires a range of seismic parameters, prominent among which are seismic velocity, impedance, and Poisson’s ratio. The inclusion of seismic absorption in this list could add desirable complementary information. For example, absorption may be more sensitive to clay content than seismic velocity (Klimento and McCann, 1990). However seismic absorption is difficult to measure, particularly over depth intervals as short as most reservoir intervals.

scholarly journals A Practical Method to Calculate and Model the Petrophysical Properties of Reservoir Rock Using Petrel Software: A case Study from Iraq

2020 ◽  
pp. 2640-2650
Author(s):  
Sarah Taboor Wali ◽  
Hussain Ali Baqer
Keyword(s):  
Water Saturation ◽  
Three Dimensional ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Sequential Gaussian Simulation ◽  
Geological Model ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Software Models ◽  
Average Water

Nasiriyah oilfield is located in the southern part of Iraq. It represents one of the promising oilfields. Mishrif Formation is considered as the main oil-bearing carbonate reservoir in Nasiriyah oilfield, containing heavy oil (API 25o(. The study aimed to calculate and model the petrophysical properties and build a three dimensional geological model for Mishrif Formation, thus estimating the oil reserve accurately and detecting the optimum locations for hydrocarbon production. Fourteen vertical oil wells were adopted for constructing the structural and petrophysical models. The available well logs data, including density, neutron, sonic, gamma ray, self-potential, caliper and resistivity logs were used to calculate the petrophysical properties. The interpretations and environmental corrections of these logs were performed by applying Techlog 2015 software. According to the petrophysical properties analysis, Mishrif Formation was divided into five units (Mishrif Top, MA, shale bed, MB1 and MB2).    A three-dimensional geological model, which represents an entrance for the simulation process to predict reservoir behavior under different hydrocarbon recovery scenarios, was carried out by employing Petrel 2016 software. Models for reservoir characteristics (porosity, permeability, net to gross NTG and water saturation) were created using the algorithm of Sequential Gaussian Simulation (SGS), while the variogram analysis was utilized as an aid to distribute petrophysical properties among the wells.      The process showed that the main reservoir unit of Mishrif Formation is MB1 with a high average porosity of 20.88% and a low average water saturation of 16.9%. MB2 unit has good reservoir properties characterized by a high average water saturation of 96.25%, while MA was interpreted as a water-bearing unit. The impermeable shale bed unit is intercalated between MA and MB1 units with a thickness of 5-18 m, whereas Mishrif top was interpreted as a cap unit. The study outcomes demonstrated that the distribution accuracy of the petrophysical properties has a significant impact on the constructed geological model which provided a better understanding of the study area’s geological construction. Thus, the estimated reserve h was calculated to be about 7945 MSTB. This can support future reservoir development plans and performance predictions. 

scholarly journals Viscoelastic Model and Synthetic Seismic Data of Eastern Rub’Al-Khali

2021 ◽  
Vol 11 (4) ◽  
pp. 1401
Author(s):  
Septriandi A. Chan ◽  
Paul Edigbue ◽  
Sikandar Khan ◽  
Abdul L. Ashadi ◽  
Abdullatif A. Al-Shuhail
Keyword(s):  
Shear Wave ◽  
Seismic Data ◽  
Seismic Waves ◽  
Sand Dunes ◽  
Viscoelastic Model ◽  
Specific Area ◽  
Data Availability ◽  
Published Data ◽  
Quality Factors ◽  
Data Set

The Rub’ Al-Khali basin in Saudi Arabia remains unexplored and lacks data availability due to its remoteness and the challenging nature of its terrain. Thus far, there are neither digital geologic models nor synthetic seismic data from this specific area accessible for testing research techniques and analysis. In this study, we build a 2D viscoelastic model of the eastern part of the Rub’ Al-Khali basin and generate a corresponding dual-component seismic data set. We compile high-resolution depth models of compressional- and shear-wave velocities, density, as well as compressional- and shear-wave quality factors from published data. The compiled models span Neoproterozoic basement up to Quaternary sand dunes. We then use the finite-difference technique to model the propagation of seismic waves in the compiled viscoelastic medium of eastern Rub’ Al-Khali desert. In particular, we generate vertical and horizontal components of the shot gathers with accuracy to the fourth and second orders in space and time, respectively. The viscoelastic models and synthetic seismic datasets are made available in an open-source site for prospective re-searchers who desire to use them for their research. Users of these datasets are urged to make their findings also accessible to the geoscience community as a way of keeping track of developments related to the Rub’ Al-Khali desert.

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