Diagenesis-driven pore fluid discrimination

2019 ◽  
Vol 38 (5) ◽  
pp. 366-373 ◽  
Author(s):  
Jack Dvorkin
Keyword(s):  
Acoustic Impedance ◽  
Rock Physics ◽  
Pore Fluid ◽  
Oil Field ◽  
Poisson's Ratio ◽  
Rock Properties ◽  
Fluid Substitution ◽  
Diagenetic Processes ◽  
Medium Porosity ◽  
Fluid Detection

In order to determine a direct hydrocarbon indicator in an oil field formed by low- to medium-porosity fast sandstone, we examine wireline data from four wells. Fluid substitution indicates that the sensitivity of the acoustic impedance and Poisson's ratio to oil-to-brine changes is very small. It appears, however, that due to diagenetic processes, the porosity in the brine-filled strata is noticeably smaller than that in the oil-saturated intervals. This porosity difference makes the impedance in the presence of oil noticeably smaller than that where brine is present. The respective impedance cutoff can serve as a discriminator for fluid detection in the seismically derived acoustic impedance volumes. The lesson learned is that merely relying on a rock-physics tool, such as fluid substitution, may not necessarily provide a fluid-detection recipe. Instead, we need to examine a plethora of natural events that may affect rock properties and then translate these effects into seismically detectable variables.

scholarly journals Rock Physics Based Interpretation of Seismically Derived Elastic Volumes

2021 ◽  
Vol 8 ◽  
Author(s):  
Abrar Alabbad ◽  
Jack Dvorkin ◽  
Yazeed Altowairqi ◽  
Zhou F. Duan
Keyword(s):  
Water Saturation ◽  
Rock Physics ◽  
Clay Content ◽  
Total Porosity ◽  
Pore Fluid ◽  
Oil Field ◽  
Rock Properties ◽  
Volumetric Properties ◽  
S Wave ◽  
A Site

A rock physics based seismic interpretation workflow has been developed to extract volumetric rock properties from seismically derived P- and S-wave impedances, Ip and Is. This workflow was first tested on a classic rock physics velocity-porosity model. Next, it was applied to two case studies: a carbonate and a clastic oil field. In each case study, we established rock physics models that accurately relate elastic properties to the rock’s volumetric properties, mainly the total porosity, clay content, and pore fluid. To resolve all three volumetric properties from only two inputs, Ip and Is, a site-specific geology driven relation between the pore fluid and porosity was derived as a hydrocarbon identifier. In order to apply this method at the seismic spatial scale, we created a coarse-scale elastic and volumetric variables by using mathematical upscaling at the wells. By using Ip and Is thus upscaled, we arrived at the accurate interpretation of the upscaled porosity, mineralogy, and water saturation both at the wells and in a simulated vertical impedance section generated by interpolation between the wells.

scholarly journals Cross plot Analysis of Rock Properties from Well Log Data for gas detection in Soku Field, Coastal Swamp Depobelt, Niger Delta Basin

2018 ◽  
Vol 3 (4) ◽  
pp. 180
Author(s):  
Okoli Emeka Austin ◽  
Okechukwu Ebuka Agbasi ◽  
Onyekuru Samuel ◽  
Sunday Edet Etuk
Keyword(s):  
Acoustic Impedance ◽  
Niger Delta ◽  
Gamma Ray ◽  
Rock Physics ◽  
Oil Field ◽  
Rock Properties ◽  
High Resistivity ◽  
S Wave ◽  
Lithology Identification ◽  
Well Data

The cross plotting of rock properties for fluid and lithology discrimination was carried out in a Niger Delta oil field using well data X-26 from a given oil field in the coastal swamp depobelt. The data used for the analysis consisted of suites of logs, including gamma ray, resistivity, sonic and density logs only. The reservoir of interest Horizon 1, was identified using the available suite of logs on the interval where we have low gamma ray, high resistivity and low acoustic impedance specifically at depths 10,424ft (3177.24m) to 10 724ft (3268m). We first obtained other rock attributes from the available logs before cross plotting. The inverse of the interval transit times of the sonic logs were used to generate the compressional velocities and the S-wave data was generated from Castagna´s relation. Employing rock physics algorithm on Hampson Russell software (HRS), rock attributes including Vp/Vs ratio, Lambda-Rho and Mu-Rho were also extracted from the well data. Cross plotting was carried out and Lambda Rho (λρ) versus MuRho (μρ) crossplots proved to be more robust for lithology identification than Vp versus Vs crossplots, while λρ Versus Poisson impedance was more robust than Vp/Vs versus Acoustic impedance for fluid discrimination, as well as identification of gas sands. The crossplots were consistent with Rock Physics Templates (RPTs). This implies the possibility of further using the technique on data points of inverted sections of various AVO attributes within the field in areas not penetrated by wells within the area covered by the seismic.

Relaxation shift in rocks containing viscoelastic pore fluids

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. M19-M28 ◽  
Author(s):  
Gary Mavko
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Pore Fluid ◽  
Apparent Temperature ◽  
Rock Properties ◽  
Fluid Substitution ◽  
Viscoelastic Relaxation ◽  
Pore Fluids ◽  
Complex Moduli ◽  
Substitution Models

The interaction of pore stiffness with pore fluid moduli leads to shifts in viscoelastic relaxation times of the overall rock relative to those of the fluids alone. Crack-based and fluid substitution models indicate that stiff pores cause little shift, whereas thin, soft cracks can shift relaxation times by several orders of magnitude toward lower frequencies (longer relaxation times). Pore stiffness also causes a shift in apparent temperature dependence of rock viscoelasticity toward higher temperatures when cracks are present. As with more conventional fluid substitution problems, quantifying the effects of pore fluids on rock properties requires information about the crack and pore stiffness distributions in addition to the complex moduli and viscosity of the pure fluid.

Rock physics and AVO analysis for lithofacies and pore fluid prediction in a North Sea oil field

2001 ◽  
Vol 20 (4) ◽  
pp. 429-434 ◽  
Author(s):  
Per Avseth ◽  
Tapan Mukerji ◽  
Gary Mavko ◽  
Jorunn Aune Tyssekvam
Keyword(s):  
North Sea ◽  
Rock Physics ◽  
Pore Fluid ◽  
Oil Field ◽  
Avo Analysis

scholarly journals Characterization of hydrocarbon reservoir by pore fluid and lithology using elastic parameters in an x field, Niger delta, Nigeria

2018 ◽  
Vol 6 (2) ◽  
pp. 173
Author(s):  
Akpabio . ◽  
Idara O ◽  
Ojo . ◽  
Odunayo T
Keyword(s):  
Wave Velocity ◽  
Niger Delta ◽  
Poisson’S Ratio ◽  
Velocity Ratio ◽  
Rock Physics ◽  
Pore Fluid ◽  
Poisson's Ratio ◽  
Oil Sand ◽  
Elastic Parameters ◽  
Hydrocarbon Reservoir

Quantitative rock physics analysis was carried out to determine the lithology and pore fluid of a reservoir in the Niger Delta. Density, compressional wave velocity and shear wave velocity logs were used as input to calculate elastic parameters such as velocity ratio, Poisson’s ratio, and Bulk Modulus, after estimating the hydrocarbon reservoir in the X field. The calculated velocity ratio log was used to differentiate between sand, sandstone and shale. Poisson’s ratio and velocity ratio were used delineate pore fluid content; gas sand, oil sand and sandstone formation from cross plot analysis. The reservoir in the field lies ranges from 9050 - 9426.5ft, (2760.25 – 2874.93m), this confirm what is obtained in the Niger Delta Basin. The Net Pay zones show an economical viable reservoir, it Net pay depth is 39 – 73.5ft. The Porosity and Permeability of the reservoirs suggested a productivity hydrocarbon reservoir. The reservoir lies between Gas sands, Oil sands and Brine sands, reservoir 2 and reservoir 3 are oil sand reservoirs while reservoir 1 lies between an oil sand and a brine sand.   

Seismic Reflections of Rock Properties in a Clastic Environment

2021 ◽  
Author(s):  
Vagif Suleymanov ◽  
Abdulhamid Almumtin ◽  
Guenther Glatz ◽  
Jack Dvorkin
Keyword(s):  
Rock Physics ◽  
Pore Fluid ◽  
Rock Properties ◽  
Petrophysical Properties ◽  
Sound Waves ◽  
Reservoir Properties ◽  
Field Guide ◽  
Physics Model ◽  
Rock Physics Model ◽  
Seismic Reflections

Abstract Generated by the propagation of sound waves, seismic reflections are essentially the reflections at the interface between various subsurface formations. Traditionally, these reflections are interpreted in a qualitative way by mapping subsurface geology without quantifying the rock properties inside the strata, namely the porosity, mineralogy, and pore fluid. This study aims to conduct the needed quantitative interpretation by the means of rock physics to establish the relation between rock elastic and petrophysical properties for reservoir characterization. We conduct rock physics diagnostics to find a theoretical rock physics model relevant to the data by examining the wireline data from a clastic depositional environment associated with a tight gas sandstone in the Continental US. First, we conduct the rock physics diagnostics by using theoretical fluid substitution to establish the relevant rock physics models. Once these models are determined, we theoretically vary the thickness of the intervals, the pore fluid, as well as the porosity and mineralogy to generate geologically plausible pseudo-scenarios. Finally, Zoeppritz (1919) equations are exploited to obtain the expected amplitude versus offset (AVO) and the gradient versus intercept curves of these scenarios. The relationship between elastic and petrophysical properties was established using forward seismic modeling. Several theoretical rock physics models, namely Raymer-Dvorkin, soft-sand, stiff-sand, and constant-cement models were applied to the wireline data under examination. The modeling assumes that only two minerals are present: quartz and clay. The appropriate rock physics model appears to be constant-cement model with a high coordination number. The result is a seismic reflection catalogue that can serve as a field guide for interpreting real seismic reflections, as well as to determine the seismic visibility of the variations in the reservoir geometry, the pore fluid, and the porosity. The obtained reservoir properties may be extrapolated to prospects away from the well control to consider certain what-if scenarios like plausible lithology or fluid variations. This enables building of a catalogue of synthetic seismic reflections of rock properties to be used by the interpreter as a field guide relating seismic data to volumetric reservoir properties.

A rock physics strategy for quantifying uncertainty in common hydrocarbon indicators

Geophysics ◽  
1998 ◽  
Vol 63 (6) ◽  
pp. 1997-2008 ◽  
Author(s):  
Gary Mavko ◽  
Tapan Mukerji
Keyword(s):  
Seismic Data ◽  
Rock Physics ◽  
Pore Fluid ◽  
Fluid Substitution ◽  
Seismic Velocities ◽  
S Wave ◽  
Seismic Attribute ◽  
The Impact ◽  
Quantifying Uncertainty ◽  
Range Of Values

We present a strategy for quantifying uncertainties in rock physics interpretations by combining statistical techniques with deterministic rock physics relations derived from the laboratory and theory. A simple example combines Gassmann’s deterministic equation for fluid substitution with statistics inferred from log, core, and seismic data to detect hydrocarbons from observed seismic velocities. The formulation identifies the most likely pore fluid modulus corresponding to each observed seismic attribute and the uncertainty that arises because of natural variability in formation properties, in addition to the measurement uncertainties. We quantify the measure of information in terms of entropy and show the impact of additional data about S-wave velocity on the uncertainty of the hydrocarbon indicator. In some cases, noisy S data along with noisy P data can convey more information than perfect P data alone, while in other cases S data do not reduce the uncertainty. We apply the formulation to a well log example for detecting the most likely pore fluid and quantifying the associated uncertainty from observed sonic and density logs. The formulation offers a convenient way to implement deterministic fluid substitution equations in the realistic case when natural geologic variations cause the reference porosity and velocity to span a range of values.

scholarly journals Estimation of Rock Physical Parameters Based on Digital Rock Physics Image, Case Study: Blok Cepu Oil Field, Central Java, Indonesia

2018 ◽  
Vol 16 (1) ◽  
pp. 21
Author(s):  
Handoyo Handoyo ◽  
Fatkhan Fatkhan ◽  
Fourier D. E. Latief ◽  
Harnanti Y. Putri
Keyword(s):  
Digital Image ◽  
Digital Simulation ◽  
Rock Physics ◽  
Elastic Parameter ◽  
Oil Field ◽  
P Wave ◽  
Rock Properties ◽  
Physical Parameters ◽  
Digital Rock Physics ◽  
Digital Rock

Modern technique to estimate of the physical properties of rocks can be done by means of digital imagingand numerical simulation, an approach known as digital rock physics (DRP: Digital Rock Physics). Digital rockphysics modeling is useful to understand microstructural parameters of rocks (pores and rock matrks), quite quickly and in detail. In this paper a study was conducted on sandstone reservoir samples in a rock formation. The core of sandstone samples were calculated porosity, permeability, and elasticity parameters in the laboratory. Then performed digital image processing using CT-Scan that utilizes X-ray tomography. The result of digital image is processed and done by calculation of digital simulation to calculate porosity, permeability, and elastic parameter of sandstones. In addition, there are also predictions of p-wave velocity and wave -S using the empirical equations given by Han (1986), Raymer (1990), and Nur (1998). The results of digital simulation (DRP) in this study provide a higher than the calculations in the laboratory. The digital rock physicsmethod (DRP) combined with rock physics modeling can be a practical and rapid method for determining the rock properties of tiny (microscopic) rock fragments

scholarly journals Lithological Study of Mishrif, Rumaila, Ahmadi and Mauddud Formations Using Vp/ Vs Ratio, Acoustic Impedance and Well Logging at Amara Oil Field, Southern Iraq

2021 ◽  
Vol 54 (2D) ◽  
pp. 39-58
Author(s):  
Hiba Tareq
Keyword(s):  
Acoustic Impedance ◽  
Gamma Ray ◽  
Water Saturation ◽  
Rock Physics ◽  
Shear Velocity ◽  
Oil Field ◽  
High Porosity ◽  
Shale Volume ◽  
Sonic Logs ◽  
Gamma Ray Log

The lithology of four formations from the Cretaceous period (Mishrif, Rumaila, Ahmadi, and Mauddud) was evaluated using the Acoustic Impedance and Vp/Vs ratio cross plot from Rock Physics Templates. Dipole sonic logs in Am-6-Am-10 well log were used to calculate compression velocity then the estimated shear velocity using Greenberg Castagna equations. RHOB and VP logs were used to calculate Acoustic Impedance. The ratio of Vp/Vs was measured then used with Acoustic Impedance colored by shale volume which is measured from gamma ray log, porosity and water saturation to estimate lithology type of the considered formations using cross plots and rock physics chart in the Techlog software. The lithology of the formations found to be of high porosity limestone alternating with hard limestone layers and the shale volume increases in the Ahmadi formation. The water bearing zone was found in all Formations, this zone is indicted by high Vp/ Vs ratio and low AI. The hydrocarbon bearing zones were indicated by low amount of both Acoustic Impedance and Vp/Vs ratio and this observation was shown in Mishrif and Mauddud formations.

scholarly journals Rock property modelling and sensitivity analysis for hydrocarbon exploration in OSSY field, Niger Delta Basin

2021 ◽  
Vol 11 (4) ◽  
pp. 1809-1822
Author(s):  
Alexander Ogbamikhumi ◽  
Osakpolor Marvellous Omorogieva
Keyword(s):  
Wave Velocity ◽  
Structural Complexity ◽  
Rock Physics ◽  
Hydrocarbon Exploration ◽  
P Wave ◽  
Rock Properties ◽  
Fluid Substitution ◽  
Quantitative Interpretation ◽  
S Wave ◽  
Reflection Pattern

AbstractThe application of quantitative interpretation techniques for hydrocarbon prospect evaluation from seismic has become so vital. The effective employment of these techniques is dependent on several factors: the quality of the seismic and well data, sparseness of data, the physics of rock, lithological and structural complexity of the field. This study adopts reflection pattern, amplitude versus offset (AVO), Biot–Gassmann fluid substitution and cross-plot models to understand the physics of the reservoir rocks in the field by examining the sensitivity of the basic rock properties; P-wave velocity, S-wave velocity and density, to variation in lithology and fluid types in the pore spaces of reservoirs. This is to ascertain the applicability of quantitative seismic interpretation techniques to explore hydrocarbon prospect in the studied field. The results of reflection pattern and AVO models revealed that the depth of interest is dominated by Class IV AVO sands with a high negative zero offset reflectivity that reduces with offset. The AVO intercept versus gradient plot indicated that both brine and hydrocarbon bearing sands can be discriminated on seismic. Fluid substitution modelling results revealed that the rock properties will favourably respond to variation in oil saturation, but as little as 5% gas presence will result in huge change in the rock properties, which will remain constant upon further increments of gas saturation, thereby making it difficult to differentiate between economical and sub-economical saturations of gas on seismic data. Rock physics cross-plot models revealed separate cluster points typical of shale presence, brine sands and hydrocarbon bearing sands. Thus, the response of the rock properties to the modelling processes adopted favours the application of quantitative interpretation techniques to evaluate hydrocarbon in the field.

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