Improving hydrocarbon exploration with pore pressure assisted earth-model building

2018 ◽  
Vol 6 (3) ◽  
pp. SG41-SG47
Author(s):  
Yangjun (Kevin) Liu ◽  
Michael O’Briain ◽  
Cara Hunter ◽  
Laura Jones ◽  
Emmanuel Saragoussi
Keyword(s):  
Pore Pressure ◽  
Initial Velocity ◽  
Model Building ◽  
Rock Physics ◽  
Velocity Model ◽  
Hydrocarbon Exploration ◽  
Earth Model ◽  
Well Control ◽  
Physics Model ◽  
Rock Physics Model

In shale-dominated clastic lithology environments, a rock-physics model relating velocity and pore pressure (PP) can be calibrated and used to convert velocity to PP properties. The crossvalidation between velocity and overpressure, which follows the geology, can be used to better understand the model, help to build an initial velocity model, and allow selecting tomography solutions with more confidence. The velocity model developed using this approach is more plausible and more suitable for subsequent PP analysis. We highlight the application of this method in areas with poor seismic illumination and insufficient well control.

Pore-pressure-constrained, rock-physics-guided velocity model building method: Alternate solution to mitigate subsalt geohazard

2015 ◽  
Vol 3 (1) ◽  
pp. SE1-SE11 ◽  
Author(s):  
Nader Dutta ◽  
Bhaskar Deo ◽  
Yangjun (Kevin) Liu ◽  
Krishna Ramani ◽  
Jerry Kapoor ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Model Building ◽  
Rock Physics ◽  
Velocity Model ◽  
Image Point ◽  
Earth Model ◽  
Velocity Modeling ◽  
Integrated Method ◽  
Fracture Pressure ◽  
Physics Model

We developed an integrated method that can better constrain subsalt tomography using geology, thermal history modeling, and rock-physics principles. This method, called rock-physics-guided velocity modeling for migration uses predicted pore pressure as a guide to improve the quality of the earth model. We first generated a rock-physics model that provided a range of plausible pore pressure that lies between hydrostatic (lowest possible pressure) and fracture pressure (highest possible pressure). The range of plausible pore pressures was then converted into a range of plausible depth varying velocities as a function of pore pressure that is consistent with geology and rock physics. Such a range of plausible velocities is called the rock-physics template. Such a template (constrained by geology) was then used to flatten the seismic gathers. We call this the pore-pressure scan technique. The outcome of the pore-pressure scan process was an “upper” and “lower” bound of pore pressure for a given earth model. Such velocity bounds were then used as constraints on the subsequent tomography, and further iterations were carried out. The integrated method not only flattened the common image point gathers but also limited the velocity field to its physically and geologically plausible range without well control; for example, in the study area it produced a better image and pore-pressure prognosis below salt. We determined that geologic control is essential, and we used it for stratigraphy, structure, and unconformity, etc. The method had several subsalt applications in the Gulf of Mexico and proved that subsalt pore pressure can be reliably predicted.

Elastic mineral facies: Selecting site-specific elastic moduli of clay

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. MR111-MR119
Author(s):  
Uri Wollner ◽  
Jack P. Dvorkin
Keyword(s):  
Elastic Moduli ◽  
Rock Physics ◽  
Data Sets ◽  
Depth Range ◽  
Chemical Formula ◽  
Rock Matrix ◽  
Well Control ◽  
Physics Model ◽  
Well Data ◽  
Rock Physics Model

The elastic moduli of the mineral constituents of the rock matrix are among the principal inputs in all rock-physics velocity-porosity-mineralogy models. Published experimental data indicate that the elastic moduli for essentially any mineral vary. The ranges of these variations are especially wide for clay. The question addressed here is how to select, based on well data, concrete values for clay’s elastic constants where those for other minerals are fixed. The approach is to find a rock-physics model for zero-clay intervals and then adjust the clay’s constants to describe the intervals dominated by clay using the same model. We examine three data sets from clastic environments, each represented by three wells, where the selected constants for clay were different between the fields but stable within each field. These constants can then be used for seismic forward modeling and interpretation in a specific field away from well control and within a depth range represented in the wells. In essence, we introduce the concept of elastic mineral facies where we identify clay as a mineral with certain elastic moduli rather than by its chemical formula.

scholarly journals Rock physical characterisation of microstructural fabrics and elastic anisotropy for a shale oil reservoir

2020 ◽  
Vol 17 (2) ◽  
pp. 377-389
Author(s):  
Xiwu Liu ◽  
Zhiqi Guo ◽  
Qibin Zhang ◽  
Yuwei Liu ◽  
Haifeng Chen
Keyword(s):  
Elastic Anisotropy ◽  
Rock Physics ◽  
Physical Modelling ◽  
Velocity Model ◽  
Solid Matrix ◽  
Seismic Modelling ◽  
Anisotropy Parameters ◽  
Shale Reservoirs ◽  
Physics Model ◽  
Rock Physics Model

Abstract Rock physics models are constructed to describe elastic anisotropy of various fabrics in shales. A method is developed to invert elastic properties of the clay mixture in shales. Inversion results indicate that the clay mixture has abnormally low Vs and consequently leads to a very high Vp/Vs ratio, which is related to the presence of the soft interparticle medium in the clay mixture. Accordingly, a model is constructed to describe anisotropy clay mixture that consists of layering distributed illite-smectite particles, and a more compliant interparticle medium that has a bulk modulus similar to that of water and smaller nonzero shear modulus. Rock physical modelling indicates that an increase in the fraction of the soft interparticle medium (f-soft) leads to a dramatic increase in Vp/Vs ratios of the clay mixture. Meanwhile, the fraction of illite (f-illite) also shows a significant impact on elastic anisotropy of the clay mixture. Accordingly, a rock physical inversion scheme is further proposed to estimate the parameters f-soft and f-illite. Finally, based on these inverted parameters, elastic anisotropy values of various fabrics at different scale, including illite-smectite platelet, clay mixture, solid matrix of shale and shale rock, are computed by the constructed rock physics model. The estimated anisotropy parameters reveal lamination textures and can help in the evaluation of mechanical properties of shale reservoirs. Also, the obtained anisotropy parameters can provide an accurate velocity model for seismic modelling, seismic data processing and inversion.

Multivariate probabilistic rock physics models using Kumaraswamy distributions

Geophysics ◽  
2021 ◽  
pp. 1-43
Author(s):  
Dario Grana
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Random Variables ◽  
Rock Physics ◽  
Petrophysical Properties ◽  
Kumaraswamy Distribution ◽  
Model Predictions ◽  
Physics Model ◽  
Rock Physics Model

Rock physics models are physical equations that map petrophysical properties into geophysical variables, such as elastic properties and density. These equations are generally used in quantitative log and seismic interpretation to estimate the properties of interest from measured well logs and seismic data. Such models are generally calibrated using core samples and well log data and result in accurate predictions of the unknown properties. Because the input data are often affected by measurement errors, the model predictions are often uncertain. Instead of applying rock physics models to deterministic measurements, I propose to apply the models to the probability density function of the measurements. This approach has been previously adopted in literature using Gaussian distributions, but for petrophysical properties of porous rocks, such as volumetric fractions of solid and fluid components, the standard probabilistic formulation based on Gaussian assumptions is not applicable due to the bounded nature of the properties, the multimodality, and the non-symmetric behavior. The proposed approach is based on the Kumaraswamy probability density function for continuous random variables, which allows modeling double bounded non-symmetric distributions and is analytically tractable, unlike the Beta or Dirichtlet distributions. I present a probabilistic rock physics model applied to double bounded continuous random variables distributed according to a Kumaraswamy distribution and derive the analytical solution of the posterior distribution of the rock physics model predictions. The method is illustrated for three rock physics models: Raymer’s equation, Dvorkin’s stiff sand model, and Kuster-Toksoz inclusion model.

Porosity estimation based on rock skeleton general formula and comprehensive pore structure parameter – An application to a tight-sand reservoir

2021 ◽  
pp. 1-59
Author(s):  
Kai Lin ◽  
Xilei He ◽  
Bo Zhang ◽  
Xiaotao Wen ◽  
Zhenhua He ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Pore Structure ◽  
Seismic Data ◽  
Rock Physics ◽  
Structure Parameters ◽  
Pore Structure Parameter ◽  
Elastic Parameters ◽  
Physics Model ◽  
Rock Physics Model ◽  
Porosity Estimation

Most of current 3D reservoir’s porosity estimation methods are based on analyzing the elastic parameters inverted from seismic data. It is well-known that elastic parameters vary with pore structure parameters such as pore aspect ratio, consolidate coefficient, critical porosity, etc. Thus, we may obtain inaccurate 3D porosity estimation if the chosen rock physics model fails properly address the effects of pore structure parameters on the elastic parameters. However, most of current rock physics models only consider one pore structure parameter such as pore aspect ratio or consolidation coefficient. To consider the effect of multiple pore structure parameters on the elastic parameters, we propose a comprehensive pore structure (CPS) parameter set that is generalized from the current popular rock physics models. The new CPS set is based on the first order approximation of current rock physics models that consider the effect of pore aspect ratio on elastic parameters. The new CPS set can accurately simulate the behavior of current rock physics models that consider the effect of pore structure parameters on elastic parameters. To demonstrate the effectiveness of proposed parameters in porosity estimation, we use a theoretical model to demonstrate that the proposed CPS parameter set properly addresses the effect of pore aspect ratio on elastic parameters such as velocity and porosity. Then, we obtain a 3D porosity estimation for a tight sand reservoir by applying it seismic data. We also predict the porosity of the tight sand reservoir by using neural network algorithm and a rock physics model that is commonly used in porosity estimation. The comparison demonstrates that predicted porosity has higher correlation with the porosity logs at the blind well locations.

scholarly journals The rock physics model in the unconsolidated methane hydrate bearing sediments

2010 ◽  
Vol 75 (1) ◽  
pp. 59-71 ◽  
Author(s):  
Takao Inamori ◽  
Masami Hato ◽  
Kiyofumi Suzuki ◽  
Tatsuo Saeki
Keyword(s):  
Methane Hydrate ◽  
Rock Physics ◽  
Physics Model ◽  
Rock Physics Model ◽  
Hydrate Bearing Sediments
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