Rapid Numerical Simulation and Inversion of Nuclear Borehole Measurements Acquired in Vertical and Deviated Wells

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Total Pages : 380 pages
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Book Synopsis Rapid Numerical Simulation and Inversion of Nuclear Borehole Measurements Acquired in Vertical and Deviated Wells by : Alberto Mendoza Chávez

Download or read book Rapid Numerical Simulation and Inversion of Nuclear Borehole Measurements Acquired in Vertical and Deviated Wells written by Alberto Mendoza Chávez and published by . This book was released on 2009 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: The conventional approach for estimation of in-situ porosity is the combined use of neutron and density logs. These nuclear borehole measurements are influenced by fundamental petrophysical, fluid, and geometrical properties of the probed formation including saturating fluids, matrix composition, mud-filtrate invasion and shoulder beds. Advanced interpretation methods that include numerical modeling and inversion are necessary to reduce environmental effects and non-uniqueness in the estimation of porosity. The objective of this dissertation is two-fold: (1) to develop a numerical procedure to rapidly and accurately simulate nuclear borehole measurements, and (2) to simulate nuclear borehole measurements in conjunction with inversion techniques. Of special interest is the case of composite rock formations of sand-shale laminations penetrated by high-angle and horizontal (HA/HZ) wells. In order to quantify shoulder-bed effects on neutron and density borehole measurements, we perform Monte Carlo simulations across formations of various thicknesses and borehole deviation angles with the multiple-particle transport code MCNP. In so doing, we assume dual-detector tool configurations that are analogous to those of commercial neutron and density wireline measuring devices. Simulations indicate significant variations of vertical (axial) resolution of neutron and density measurements acquired in HA/HZ wells. In addition, combined azimuthal- and dip-angle effects can originate biases on porosity estimation and bed boundary detection, which are critical for the assessment of hydrocarbon reserves. To enable inversion and more quantitative integration with other borehole measurements, we develop and successfully test a linear iterative refinement approximation to rapidly simulate neutron, density, and passive gamma-ray borehole measurements. Linear iterative refinement accounts for spatial variations of Monte Carlo derived flux sensitivity functions (FSFs) used to simulate nuclear measurements acquired in non-homogeneous formations. We use first-order Born approximations to simulate variations of a detector response due to spatial variations of formation energy-dependent cross-section. The method incorporates two- (2D) and three-dimensional (3D) capabilities of FSFs to simulate neutron and density measurements acquired in vertical and HA/HZ wells, respectively. We calculate FSFs for a wide range of formation cross-section variations and for borehole environmental effects to quantify the spatial sensitivity and resolution of neutron and density measurements. Results confirm that the spatial resolution limits of neutron measurements can be significantly influenced by the proximity of layers with large contrasts in porosity. Finally, we implement 2D sector-based inversion of azimuthal logging-while drilling (LWD) density field measurements with the fast simulation technique. Results indicate that inversion improves the petrophysical interpretation of density measurements acquired in HA/HZ wells. Density images constructed with inversion yield improved porosity-feet estimations compared to standard and enhanced compensation techniques used commercially to post-process mono-sensor densities.

Rapid Modeling of LWD Nuclear Measurements Acquired in High-angle and Horizontal Wells for Improved Petrophysical and Geometrical Interpretation

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Total Pages : 122 pages
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Book Synopsis Rapid Modeling of LWD Nuclear Measurements Acquired in High-angle and Horizontal Wells for Improved Petrophysical and Geometrical Interpretation by : Olabode Ijasan

Download or read book Rapid Modeling of LWD Nuclear Measurements Acquired in High-angle and Horizontal Wells for Improved Petrophysical and Geometrical Interpretation written by Olabode Ijasan and published by . This book was released on 2010 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear logging-while-drilling (LWD) measurements acquired in high-angle and horizontal (HA/HZ) wells are influenced by tool, geometrical, and petrophysical effects. Reliable interpretation of petrophysical and geometrical properties from LWD measurements acquired in thinly-bedded formations requires that gamma ray, density, photoelectric (PEF), and neutron measurements be quantitatively integrated with explicit consideration of their effective volume of investigation (EVOI). One of the effects of different tool EVOIs is false gas density-neutron crossovers across thinly-bedded formations. Also, in the presence of tool eccentricity, azimuthally-varying standoff gives rise to an azimuthally-varying effective depth of investigation (EDOI), which introduces errors in the inference of formation dip. Conventional Monte Carlo simulations of nuclear measurements are computationally expensive in reproducing multi-sector LWD responses in HA/HZ wells. Using linear iterative refinement of pre-calculated flux sensitivity functions (FSFs), we introduce a fast method for numerical simulation of LWD nuclear images in the presence of tool eccentricity along any well trajectory. Our investigation of measurement responses from FSFs motivates techniques to explicitly consider the EVOI of LWD nuclear measurements. Simple radial DOI and standoff corrections suffice for interpretation of gamma-gamma images but are inadequate for neutron responses due to larger EVOI and azimuthal aperture. We introduce a new azimuthal deconvolution method of neutron images to improve bed-boundary detection. Neutron DOI varies significantly with porosity, whereby we correct neutron images for penetration length due to changes of porosity along the well trajectory. In addition, we implement a new method of separate linear iterative refinement on neutron thermal group responses to improve the resolution of neutron images across heterogeneous and thinly-bedded formations. The method reduces shoulder-bed effects and false neutron-density gas crossovers. We corroborate these techniques with rigorous Monte Carlo simulations in vertical and deviated wells. A field example of application conclusively indicates that numerical simulation of LWD nuclear measurements is necessary for reliable estimation of petrophysical properties.

Inversion-based Petrophysical Interpretation of Logging-while-drilling Nuclear and Resistivity Measurements

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Total Pages : 0 pages
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Book Synopsis Inversion-based Petrophysical Interpretation of Logging-while-drilling Nuclear and Resistivity Measurements by : Olabode Ijasan

Download or read book Inversion-based Petrophysical Interpretation of Logging-while-drilling Nuclear and Resistivity Measurements written by Olabode Ijasan and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Undulating well trajectories are often drilled to improve length exposure to rock formations, target desirable hydrocarbon-saturated zones, and enhance resolution of borehole measurements. Despite these merits, undulating wells can introduce adverse conditions to the interpretation of borehole measurements which are seldom observed in vertical wells penetrating horizontal layers. Common examples are polarization horns observed across formation bed boundaries in borehole resistivity measurements acquired in highly-deviated wells. Consequently, conventional interpretation practices developed for vertical wells can yield inaccurate results in HA/HZ wells. A reliable approach to account for well trajectory and bed-boundary effects in the petrophysical interpretation of well logs is the application of forward and inverse modeling techniques because of their explicit use of measurement response functions. The main objective of this dissertation is to develop inversion-based petrophysical interpretation methods that quantitatively integrate logging-while-drilling (LWD) multi-sector nuclear (i.e., density, neutron porosity, photoelectric factor, natural gamma ray) and multi-array propagation resistivity measurements. Under the assumption of a multi-layer formation model, the inversion approach estimates formation properties specific to a given measurement domain by numerically reproducing the available measurements. Subsequently, compositional multi-mineral analysis of inverted layer-by-layer properties is implemented for volumetric estimation of rock and fluid constituents. The most important prerequisite for efficient petrophysical inversion is fast and accurate forward models that incorporate specific measurement response functions for numerical simulation of LWD measurements. In the nuclear measurement domain, first-order perturbation theory and flux sensitivity functions (FSFs) are reliable and accurate for rapid numerical simulation. Albeit efficient, these first-order approximations can be inaccurate when modeling neutron porosity logs, especially in the presence of borehole environmental effects (tool standoff or/and invasion) and across highly contrasting beds and complex formation geometries. Accordingly, a secondary thrust of this dissertation is the introduction of two new methods for improving the accuracy of rapid numerical simulation of LWD neutron porosity measurements. The two methods include: (1) a neutron-density petrophysical parameterization approach for describing formation macroscopic cross section, and (2) a one-group neutron diffusion flux-difference method for estimating perturbed spatial neutron porosity fluxes. Both methods are validated with full Monte Carlo (MC) calculations of spatial neutron detector FSFs and subsequent simulations of neutron porosity logs in the presence of LWD azimuthal standoff, invasion, and highly dipping beds. Analysis of field and synthetic verification examples with the combined resistivity-nuclear inversion method confirms that inversion-based estimation of hydrocarbon pore volume in HA/HZ wells is more accurate than conventional well-log analysis. Estimated hydrocarbon pore volume from conventional analysis can give rise to errors as high as 15% in undulating HA/HZ intervals.

Rapid Modeling of Borehole Measurements of Nuclear Magnetic Resonance Via Spatial Sensitivity Functions

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Total Pages : 0 pages
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Book Synopsis Rapid Modeling of Borehole Measurements of Nuclear Magnetic Resonance Via Spatial Sensitivity Functions by : Mohammad Albusairi

Download or read book Rapid Modeling of Borehole Measurements of Nuclear Magnetic Resonance Via Spatial Sensitivity Functions written by Mohammad Albusairi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Borehole measurements of Nuclear Magnetic Resonance (NMR) are routinely used to estimate in situ rock and fluid properties. Conventional NMR interpretation methods often neglect bed-boundary, mud-filtrate invasion, layer-thickness, and layer-dip effects in the calculation of fluid volumetric concentrations and NMR relaxation-diffusion correlations. Such effects introduce notable spatial averaging of intrinsic rock and fluid properties across thinly-bedded formations or in the vicinity of boundaries between layers exhibiting large property contrasts. Furthermore, the interpretation of NMR measurements entails major technical challenges in horizontal layers penetrated by high-angle and horizontal wells (HAHz) or across dipping layers penetrated by a vertical well. Three-dimensional (3D) geometrical effects, coupled with spatially and petrophysically heterogeneous rocks, may bias petrophysical estimates obtained from borehole NMR measurements when using interpretation procedures designed for vertical wells and horizontal layers. Forward modeling and inversion methods can mitigate the aforementioned effects and improve the accuracy of true layer properties in the presence of mud-filtrate invasion and borehole environmental and 3D geometrical effects across spatially complex formations. This dissertation introduces a fast and accurate algorithm to simulate borehole NMR measurements using the concept of spatial sensitivity functions (SSFs) that honor NMR physics and explicitly incorporate tool, borehole, and geometrical properties. To that end, a 3D multiphysics forward model is developed that couples NMR tool properties, magnetization time evolution, and electromagnetic propagation to derive the 3D spatial sensitivity maps associated with a specific borehole instrument. Additionally, a multifluid relaxation model based on Brownstein-Tarr’s equation is introduced to estimate layer-by-layer NMR porosity decays and relaxation-diffusion correlations from pore-size-dependent rock and fluid properties. The latter model is convolved with the SSFs to reproduce borehole NMR measurements acquired with advanced pulsing sequences (e.g., diffusion-editing and saturation recovery sequences). Results indicate that the spatial sensitivity of NMR measurements is controlled by porosity, electrical conductivity, excitation pulse duration, and tool geometry. The SSF-derived forward approximation is benchmarked and verified against 3D multiphysics simulations for a series of synthetic cases with variable bed thickness and petrophysical properties, as well as in the presence of mud-filtrate invasion. It is shown that the approximation can be executed in a few seconds of central processing unit (CPU), by a factor of 1000 times faster than rigorous multiphysics calculations, with maximum root-mean- square errors (RMSE) of 1%. On average, the fast approximation via SSFs reproduces borehole NMR measurements in 0.08 seconds of CPU time per logging measurement and can therefore be used for real-time calculations and interpretations. Next, the NMR forward modeling approximation is implemented to simulate measurements acquired across dipping formations penetrated by deviated wells in the presence of mud-filtrate invasion. Borehole NMR measurements are simulated by transforming a dipping layered model penetrated by an arbitrary well trajectory into an apparent layered model probed by a vertical well. This work compares the effect of radial length of investigation (DOI) from the three distinct NMR acquisition shells at 3.81 cm (1 in), 6.35 cm (2.5 in) and 10.16 cm (4 in), to integrate borehole NMR measurements acquired in 3D complex geometries. It is found that thinly-bedded formations and their petrophysical properties can be resolved with limited measurement resolution in HAHz wells and highly dipping formations. In thinly-bedded layers (e.g., thinner than 0.15 m) probed by a vertical well, spatial averaging effects bias the NMR porosity logs acquired with high vertical resolution (e.g., sampling rate equals to 2.54 cm). Conversely, formation geometrical and petrophysical properties can be accurately estimated across high apparent-dip formations. It is found that the shallower NMR acquisition shell (3.81 cm) is the least affected by bed-boundary averaging with increasing apparent dip. Moreover, the increase in apparent dip shifts the location of apparent bed boundaries. The latter phenomenon is more pronounced at deeper radial DOI. Interpretation procedures must mitigate such geometrical effects to accurately detect true bed boundaries and estimate layer-by-layer petrophysical properties

Mechanistic Numerical Simulation and Interpretation of Borehole Measurements of Spontaneous Electrical Potential Acquired in Complex Petrophysical Environments

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Total Pages : 468 pages
Book Rating : 4.:/5 (128 download)

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Book Synopsis Mechanistic Numerical Simulation and Interpretation of Borehole Measurements of Spontaneous Electrical Potential Acquired in Complex Petrophysical Environments by : Joshua Christopher Bautista-Anguiano

Download or read book Mechanistic Numerical Simulation and Interpretation of Borehole Measurements of Spontaneous Electrical Potential Acquired in Complex Petrophysical Environments written by Joshua Christopher Bautista-Anguiano and published by . This book was released on 2021 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: Borehole measurements of spontaneous electrical potential (SP) are routinely acquired in wells drilled with water-based mud. However, to this day, the interpretation of borehole SP measurements is chiefly limited to imprecise calculations of formation water resistivity and qualitative assessments of volumetric concentration of shale and permeability. This dissertation develops new methods to numerically simulate borehole SP measurements and improve their quantitative interpretation. Interpretation products are water saturation, water resistivity, and radius of invasion of mud-filtrate invasion in permeable rocks, together with their uncertainty. The calculation of formation water resistivity from borehole SP measurements is commonly performed via Nernst’s equation under the assumptions of shallow mud-filtrate invasion, negligible streaming potentials, and water as the only rock-saturating fluid. To circumvent these limitations while honoring the governing physics of coupled mass transport associated with SP phenomena, a three-dimensional finite-difference algorithm is developed to incorporate electrochemical, membrane, and electrokinetic SP phenomena in the simulation of borehole SP measurements. The algorithm implements a mechanistic description of non-equilibrium thermodynamics, which is coupled to a fluid-flow simulator to quantify the effects of time-varying conditions within permeable formations due to mud-filtrate invasion. Simulations indicate that the best spatial resolution of rock properties possible with SP borehole measurements occurs when rock beds are perpendicular to the well; deviated wells or dipping beds give rise to extended and pronounced shoulder-bed effects on SP measurements. It is also found that the simplifying assumption of perpendicular beds relative to the borehole does not cause significant errors in the numerical simulation of borehole SP measurements acquired in well trajectories with a relative dip less than 30°, thereby reducing CPU time by a factor of at least 1.76. Furthermore, electrokinetic effects on SP measurements become negligible for commonly used pressure overbalance ranges. For the interpretation of borehole SP measurements acquired in hydrocarbon-bearing rocks, this dissertation explores whether the difference between borehole SP measurements and Nernst-equation predictions enables the estimation of in situ hydrocarbon saturation of porous rocks. A new petrophysical model is advanced and successfully verified to establish the limits of detectability of hydrocarbon saturation solely from borehole SP measurements. It is found that optimal conditions for the quantification of hydrocarbon saturation from borehole SP measurements take place when (1) capillary forces dominate the process of mud-filtrate invasion, (2) the matrix-pore interface region, known as the electrical double layer, has a relevant impact on the diffusion of counter-ions, and (3) the electrolyte concentration of drilling mud is greater than that of formation water. Three blind tests show that the developed petrophysical model and the mechanistic SP simulation algorithm enable the estimation of hydrocarbon saturation from SP borehole measurements without the need of electrical resistivity measurements or porosity calculations. The estimation is reliable when (a) the volumetric concentration of shale is negligible, (b) the pore network structure is constant throughout the reservoir, and (c) radial invasion profiles are similar to those observed in calibration key wells used to adjust the parameters of the new petrophysical model. Finally, this dissertation develops a new inversion-based method for the interpretation of borehole SP measurements, which concomitantly mitigates shoulder-bed and mud-filtrate invasion effects on SP logs via fast numerical simulations based on Green’s functions. The method delivers layer-by-layer estimates of (a) equivalent NaCl concentration, (b) radius of mud-filtrate invasion, and (c) sodium macroscopic transport number, together with their uncertainty, by progressively matching borehole SP measurements with their numerical simulations. Successful examples of implementation include noisy borehole SP measurements acquired in aquifers with various degrees of petrophysical complexity. Results confirm the possibility of accurately and reliably estimating the electrical resistivity of formation water resistivity solely from borehole SP measurements, i.e., without the need of porosity calculations or fitting parameters from independent core measurements (as is the case with borehole resistivity measurements). Inversion-based interpretation results (a) compare well to those obtained from resistivity and nuclear porosity logs, (b) provide estimates of uncertainty, and (c) can assimilate a priori knowledge of aquifer petrophysical properties in the estimation

New Methods for the Interpretation of Borehole Geophysical Measurements and Core Data Acquired in Spatially Complex Rocks

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Total Pages : 0 pages
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Book Synopsis New Methods for the Interpretation of Borehole Geophysical Measurements and Core Data Acquired in Spatially Complex Rocks by : Mohamed Bennis

Download or read book New Methods for the Interpretation of Borehole Geophysical Measurements and Core Data Acquired in Spatially Complex Rocks written by Mohamed Bennis and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reliable assessment of in situ storage and flow properties of rocks from borehole geophysical measurements and core data is crucial for appraising subsurface fluid resources. Well-log analysis in the presence of thin beds, mud-filtrate invasion, and/or electrical anisotropy remains a challenge in formation evaluation. Conventional interpretation methods rarely consider shoulder-bed effects on well logs, spatial distributions of fluid saturation around the borehole due to invasion, and differences in the volume of investigation of the different borehole instruments involved in the interpretation. This dissertation develops new quantitative methods for the interpretation of borehole geophysical measurements and core data acquired in spatially complex rocks. First, analytical and Bayesian methods are developed to assess horizontal and vertical resistivities from logging-while-drilling resistivity measurements in the presence of electrical anisotropy, noise, and well deviation effects. Borehole measurements (e.g., resistivity, density) are deconvolved into layer-by-layer physical properties with their associated uncertainty. Additionally, a new method is developed to calibrate and verify the reliability of core data and borehole measurements acquired under adverse geometrical conditions in formations with complex solid composition and thin beds. Numerical simulation of well logs based on high-resolution core data combined with rock typing and multi-well measurement analysis enable the detection of inconsistent, noisy, and inaccurate measurements, including cases of abnormal borehole environmental conditions causing biases in petrophysical interpretations. Finally, a new method is developed to quantify water saturation, residual hydrocarbon saturation, and permeability in the presence of deep mud-filtrate invasion, i.e., when the radial length of invasion is greater than the depth of investigation of borehole instruments. This method combines the numerical simulation of well logs with the physics of mud-filtrate invasion to quantify the effect of petrophysical properties and drilling conditions on nuclear and resistivity logs. Based on core-calibrated petrophysical models, thousands of invasion conditions were numerically simulated for a wide range of petrophysical properties and drilling conditions, including time of invasion and overbalance pressure. Then, analytical and machine-learning (ML) models were combined to infer unknown rock properties. Synthetic examples verify the accuracy and reliability of the introduced interpretation methods and quantify the uncertainty of estimated rock properties due to noisy measurements. Successful field applications are also documented for (a) the estimation of water saturation in an electrically anisotropic sandstone formation offshore Australia penetrated by high-angle and horizontal wells, (b) assessment of the quality of well logs acquired in a shaly-sandstone formation in the North Sea, and (c) estimation of water saturation, residual hydrocarbon saturation, and permeability in a tight-gas sandstone formation invaded with water-base mud in the Middle East. Comparison of interpretation results against those obtained using conventional petrophysical methods confirm the effectiveness of the new quantification techniques introduced in this dissertation for the quantification of petrophysical properties across a variety of rock formations

Numerical Simulation and Interpretation of Borehole Fluid-production Measurements

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Total Pages : 0 pages
Book Rating : 4.:/5 (893 download)

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Book Synopsis Numerical Simulation and Interpretation of Borehole Fluid-production Measurements by : Amir Frooqnia

Download or read book Numerical Simulation and Interpretation of Borehole Fluid-production Measurements written by Amir Frooqnia and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Downhole production measurements are periodically acquired in hydrocarbon reservoirs to monitor and diagnose fluid movement in the borehole and the near-borehole region. However, because of the complexity involved with physical modeling and numerical implementation of borehole and formation multiphase flow behavior, inference of near-borehole petrophysical properties from production measurements is limited to simplified single-phase reservoir models. This dissertation develops a new transient coupled borehole-formation fluid flow algorithm to numerically simulate two-phase production logs (PL) acquired across heterogeneous rock formations penetrated by vertical and deviated boreholes. Subsequently, the coupled flow algorithm is used to estimate relevant dynamic petrophysical properties from borehole production measurements. The developed reservoir-borehole fluid flow model is based on an isothermal, one-dimensional (borehole axis) version of two-fluid formulation that simulates simultaneous flow of two fluid phases in oil-water, oil-gas, and gas-water flowing systems. Linkage of borehole and formation fluid flow models is carried out by introducing additional source terms into borehole mass conservation equations. Transient simulation of two-phase production measurements indicates the presence of borehole cross-flow when performing a shut-in test across differentially-depleted multilayer reservoirs. In a two-layer synthetic reservoir model penetrated by a vertical borehole, only two hours of through-the-borehole cross-communication of differentially-depleted layers gives rise to more than 14% increase in volume-averaged oil-phase relative permeability of the low-pressure layer. Simulated borehole fluid properties in the presence of cross-flow are used to estimate formation average pressure from two-phase selective-inflow-performance analysis. A new inversion-based interpretation algorithm is developed to estimate near-borehole absolute permeability and fluid-phase saturation from two-phase production logs. The inversion algorithm integrates production logs acquired in time-lapse mode to construct a near-borehole reservoir model that describes depth variations of skin factor over the elapsed time. Feasibility studies using synthetic reservoir models show that the estimated petrophysical properties are adversely influenced by the large volume of investigation associated with PL measurements. Moreover, undetectable fluid production across low-permeability layers decreases the sensitivity of production logs to layer incremental flow rate, thus increasing estimation uncertainty. Despite these limitations, the estimated fluid saturation and permeability across high-permeability layers are within 25% and 20% of the corresponding actual values, respectively. Oil-water and oil-gas flowing systems are additionally studied to quantify the added value of remedial workover operations (e.g., water and gas shut-off). Simulation of a gas shut-off performed in a gas-oil field example recommends a minimum bottom-hole pressure to prevent high gas production caused by (i) gas coning effects, and (ii) released gas from oil solution. Maintaining bottom-hole pressure above that limit gives rise to more than 60% reduction of downhole gas production.

Simulation and Inversion of Borehole Electromagnetic Measurements for the Estimation of Petrophysical Properties in the Presence of Mud-filtrate Invasion

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Total Pages : 526 pages
Book Rating : 4.:/5 (852 download)

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Book Synopsis Simulation and Inversion of Borehole Electromagnetic Measurements for the Estimation of Petrophysical Properties in the Presence of Mud-filtrate Invasion by : Jesús Mauricio Salazar Luna

Download or read book Simulation and Inversion of Borehole Electromagnetic Measurements for the Estimation of Petrophysical Properties in the Presence of Mud-filtrate Invasion written by Jesús Mauricio Salazar Luna and published by . This book was released on 2008 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic, electromagnetic (EM), and nuclear open-hole measurements are affected by fluids saturating near-wellbore porous and permeable rock formations, including hydrocarbons, water, and mud filtrate. Fluid invasion effects can be quantified and advantageously used to estimate petrophysical properties of the invaded rock formations. This dissertation incorporates the physics of water-base mud- (WBM) and oil-base mud- (OBM) filtrate invasion to the simulation and inversion of borehole EM measurements. We assume vertical boreholes penetrating clastic hydrocarbon- or water-bearing formations subject to either WBM- or OBM-filtrate invasion. The simulation of EM measurements in the presence of mud-filtrate invasion considers three different approaches: (1) piston-like invasion profiles, where we solely consider invaded- (flushed) and virgin- (uncontaminated) zones, (2) two-phase immiscible displacement and salt mixing between the invading WBM filtrate and connate water, and (3) invasion of single or multi-component OBM-filtrate into a formation saturated with multiple hydrocarbon components wherein the individual components are first-contact miscible. The last two approaches honor the physics of mudcake growth as well as the petrophysical properties that govern the process of multi-phase, multi-component fluid-flow displacement and include the presence of irreducible, capillary-bound and movable water. Electromagnetic measurements are simulated from spatial distributions of electrical resistivity calculated from the simulations of mud-filtrate invasion using clean- or shaly-sand water-saturationresistivity models. Inversion of petrophysical properties is posed as the nonlinear minimization of quadratic objective functions that quantify the misfit between EM measurements and their simulations. In the case of WBM piston-like invasion profiles in water-bearing formations, combined inversion of array-induction resistivity and spontaneous potential (SP) measurements yields connate water electrical resistivity and Archie's cementation exponent. Permeability is calculated from the inversion of array-induction resistivity measurements assuming immiscible fluid-flow displacement of WBM into hydrocarbonbearing formations. Accurate reconstructions of layer-by-layer permeability are primarily constrained by the availability of a-priori information about time of invasion, rate of mud-filtrate invasion, overbalance pressure, capillary pressure, and relative permeability. This dissertation also quantifies the influence of petrophysical and fluid properties on borehole resistivity measurements acquired in the presence of compositional mixing of OBM filtrate invading partially hydrocarbon-saturated rock formations. Numerical simulations of OBM-filtrate invasion are performed with an adaptive-implicit compositional formulation that allows one to quantify the effects of additional components of mud-filtrate and native fluids on EM measurements. Perturbations of petrophysical and fluid properties enable the quantification of rock wettability changes due to OBM-filtrate invasion and their effect on the simulated induction resistivity measurements. Finally, simulations of induction resistivity measurements in the presence of OBM are compared to the corresponding measurements in the presence of WBMfiltrate invasion. The latter analysis allows us to estimate a realistic flow rate of OBMfiltrate invasion that is responsible for the variation of induction resistivity measurements as a function of their radial length of response. The combined simulation of the physics of mud-filtrate invasion and EM measurements provides reliable estimates of true formation resistivity and hence of water saturation, thereby improving the assessment of in-place hydrocarbons reserves.

Fast Forward Modeling and Inversion of Borehole Sonic Measurements Using Spatial Sensitivity Functions

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Total Pages : 408 pages
Book Rating : 4.:/5 (923 download)

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Book Synopsis Fast Forward Modeling and Inversion of Borehole Sonic Measurements Using Spatial Sensitivity Functions by : Shan Huang (Ph. D.)

Download or read book Fast Forward Modeling and Inversion of Borehole Sonic Measurements Using Spatial Sensitivity Functions written by Shan Huang (Ph. D.) and published by . This book was released on 2015 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Borehole sonic measurements are widely used by petrophysicists to estimate in-situ dynamic elastic properties of rock formations. The estimated formation properties typically guide the interpretation of seismic amplitude measurements in the exploration and development of hydrocarbon reservoirs. Due to limitations in vertical resolution, borehole sonic measurements (sonic logs) provide spatially averaged values of formation properties in thinly bedded rocks. In addition, mud-filtrate invasion and near-wellbore formation damage can bias the elastic properties estimated from sonic logs. The interpretation of sonic logs in high angle (HA) and horizontal (HZ) wells is even more challenging because of three-dimensional geometrical effects and anisotropy. A reliable approach to account for geometrical effects in the interpretation of sonic logs is the implementation of forward modeling and inversion techniques. However, the computation time required to model the direct problem, namely wave propagation in the borehole environment, severely constraints the usage of inversion approaches in sonic-log interpretation. This dissertation develops new methods for the rapid simulation of sonic logs using the concept of spatial sensitivity functions. Sonic spatial sensitivity functions are equivalent to the Green's function of a particular sonic measurement; they also serve as weighting matrices to map formation elastic properties into the respective measurement space. Application of sensitivity functions to challenging synthetic examples verifies that the maximum relative error in the modeled sonic logs is lower than 3% for flexural, Stoneley, and compressional (P-) and shear (S-) modes. Compared to rigorous numerical simulations, the new fast sonic modeling method reduces computation time by 98%. Using the fast sonic simulation algorithm, we develop an inversion method that combines multi-frequency flexural dispersion and P- and S- mode slowness logs to estimate layer-by-layer compressional and shear slownesses of rock formations. Synthetic verification examples as well as interpretation of field cases indicate that the estimated formation compressional and shear slownesses are within 3% of true model properties, exhibiting a maximum uncertainty of 6%. When compared to conventional sonic-log interpretation, the new inversion-based method effectively reduces shoulder-bed effects and relative errors in estimated properties by 15%, while the vertical resolution of sonic logs is improved from 1.83 m to 0.5 m. Finally, we show that multi-mode wave interference in HA/HZ wells makes it difficult to identify the low-frequency slowness asymptote of the flexural mode. We extend the sensitivity method to three dimensions to approach this latter problem and to model high-frequency dispersion logs. Because the calculated P-mode slowness log exhibits strong dependence to processing parameters, conventional waveform semblance-based processing becomes inadequate in HA wells. We introduce a new P-arrival slowness log to circumvent wave mode interference and to avoid semblance calculations. Additionally, we also develop a one-dimensional integration method to rapidly model P-arrival slowness logs when HA/HZ wells penetrate anisotropic thin beds. The fast modeling algorithm generates synthetic logs that match sonic logs simulated with rigorous modeling procedures within 5% while providing a 99% reduction in computation time.

Simulation and Interpretation of Formation-tester Measurements Acquired in the Presence of Mud-filtrate Invasion, Multiphase Flow, and Deviated Wellbores

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Total Pages : 572 pages
Book Rating : 4.:/5 (436 download)

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Book Synopsis Simulation and Interpretation of Formation-tester Measurements Acquired in the Presence of Mud-filtrate Invasion, Multiphase Flow, and Deviated Wellbores by : Renzo Moisés Angeles Boza

Download or read book Simulation and Interpretation of Formation-tester Measurements Acquired in the Presence of Mud-filtrate Invasion, Multiphase Flow, and Deviated Wellbores written by Renzo Moisés Angeles Boza and published by . This book was released on 2009 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation implements three-dimensional numerical simulation models to interpret formation-tester measurements acquired at arbitrary angles of wellbore deviation. Simulations include the dynamic effects of mud-filtrate invasion and multi-phase flow. Likewise, they explicitly consider the asymmetric spatial distribution of water-base and oil-base mud filtrate in the near-wellbore region due to the interplay of viscous, gravity, and capillary forces. Specific problems considered by the dissertation are: (a) estimation of permeability from formation-tester measurements (pressure and fractional flow) affected by multi-phase flow and mud-filtrate invasion, (b) quantification of the spatial zone of response of transient measurements of pressure and fractional flow rate, (c) prediction of fluid-cleanup times during sampling operations in vertical and deviated wells, (d) joint inversion of formation-tester and resistivity measurements to estimate initial water saturation and permeability of multi-layer models, and (e) estimation of saturation-dependent relative permeability and capillary pressure using selective measurement weighting and Design-of-Experiment (DoE) methods to secure a reliable initial guess for nonlinear inversion. Using realistic tool and formation configurations, field measurements validate the reliability of the proposed methods. In one example, multi-layer rock formations are modeled using electrofacies derived from nuclear magnetic resonance logs, thereby reducing the number of unknown layer permeability values from 22 to 6. In the same example, non-uniqueness in the estimation of permeability is reduced with the quantitative integration of resistivity and formation-tester measurements. A second field example undertakes the estimation of permeability by history matching both pressure and gas-oil ratio (GOR) measurements acquired with a focused-sampling probe in a 27° deviated well. Because the latter measurements are affected by partial miscibility between oil-base mud and in-situ oil, Equation-of-State (EOS) simulations are used to account for variations of fluid viscosity, fluid compressibility, fluid density, and GOR during the processes of invasion and fluid pumpout. Results indicate that gravity-segregation and capillary-pressure effects become significant with increasing angles of wellbore deviation. If not accounted for, such effects could substantially degrade the estimation of permeability. Synthetic and field examples confirm that standard formation-tester interpretation techniques based on single-phase analytical solutions lead to biased estimations of permeability, especially in deviated wells or when complete fluid cleanup is not achieved during sampling. In addition, it is found that gravity-segregated invaded formations strongly affect predictions of fluid sampling time. Reliable and accurate estimations of petrophysical properties are only possible when both the angle of wellbore deviation and the process of mud-filtrate invasion are included in the interpretation methods.

Inversion-based Petrophysical Interpretation of Multi-detector Logging-while-drilling Sigma Measurements

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ISBN 13 :
Total Pages : 742 pages
Book Rating : 4.:/5 (882 download)

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Book Synopsis Inversion-based Petrophysical Interpretation of Multi-detector Logging-while-drilling Sigma Measurements by : Edwin Yamid Ortega

Download or read book Inversion-based Petrophysical Interpretation of Multi-detector Logging-while-drilling Sigma Measurements written by Edwin Yamid Ortega and published by . This book was released on 2014 with total page 742 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsed-neutron borehole measurements involve a physical process in which a source emits energetic neutrons that lose energy upon collisions with formation nuclei, and are eventually captured by a nucleus to form a heavier, excited state. The excited nucleus decays to its ground state by the emission of gamma rays. Both thermal-neutron and gamma-ray populations decay with time at a rate defined by Sigma, which is a nuclear property that quantifies a material's ability to capture thermal neutrons. The large contrast in Sigma between hydrocarbon and salty connate water enables calculations of water saturation directly from pulsed-neutron measurements. Sigma logs have proven useful in the assessment of thinly bedded formations because they exhibit a small volume of investigation, and have been deemed superior to resistivity logs in the petrophysical evaluation of carbonate formations. The recognized potential of Sigma logs in formation evaluation initiated the development of multi-detector Logging-While-Drilling (LWD) Sigma measurements. These measurements are acquired using one thermal-neutron and two gamma-ray detectors at different spacings from the source. Such a design is aimed at providing distinct radial depths of investigation to detect filtrate invasion in the near-wellbore zone. Despite their formation-evaluation potential, multi-detector time-decay measurements commonly remain affected by invasion, shoulder-bed, and well-deviation effects. The purpose of this dissertation is to develop a fast-forward simulation method to reproduce multi-detector time decays and combine the method with inversion techniques to improve the petrophysical interpretation of LWD Sigma measurements. First-order perturbation theory and a library of pre-calculated Monte Carlo detector-specific sensitivity functions and time decays are used to numerically simulate borehole Sigma measurements in realistic logging environments. The new simulation method is one hundred thousand times faster than rigorous Monte Carlo calculations and remains within two capture units of disparity. Next, the fast-forward simulation method is embedded within inversion algorithms to estimate layer-by-layer radial length of invasion and formation Sigma corrected for shallow invasion, shoulder-bed, and well-deviation effects. Both fast-forward and inverse modeling algorithms are benchmarked against laboratory and synthetic time decays. The improvement of formation Sigma obtained with inversion-based interpretation leads to an improvement in the estimation of Sigma-derived water saturation. Likewise, the estimated radial length of invasion is combined with neutron and density measurements to correct the latter for invasion effects. Results indicate that the inversion-based interpretation method is well suited for the evaluation of high-porosity formations invaded by salty mud filtrate. Inversion-based interpretation of field LWD time decays enables the estimation of lower values of water saturation when compared to conventional Sigma interpretation or resistivity methods. Estimated values of water saturation are as much as fifty percent lower than predicted by conventional interpretation of Sigma logs in the case of measurements affected by shoulder-bed effects, and as much as one hundred percent lower than predicted by the conventional interpretation method for measurements additionally affected by salty filtrate invasion. The key attributes of the combined petrophysical interpretation of multi-detector Sigma, neutron, and density measurements developed in this dissertation are that it explicitly enforces the physics of all nuclear measurements, honors the pressure and temperature dependency of reservoir fluid nuclear properties, and takes into account a-priori information such as mud-filtrate salinity, connate-water salinity, and bed-boundary locations.

Well Seismic Surveying and Acoustic Logging

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ISBN 13 : 9782759822638
Total Pages : 0 pages
Book Rating : 4.8/5 (226 download)

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Book Synopsis Well Seismic Surveying and Acoustic Logging by : Jean-Luc Mari

Download or read book Well Seismic Surveying and Acoustic Logging written by Jean-Luc Mari and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Approaches that are typically applied in deep exploration geophysics, combining different seismic and logging methods, can be technically adapted for certain geotechnical or hydrogeological surveys or some site characterizations in the framework of seismic hazard studies. Currently it is entirely feasible to implement this type of geophysical surveying if the situation requires. After reviewing the current state of knowledge regarding borehole measurements of subsurface shear velocities applied to the geotechnical field, this book illustrates the feasibility of carrying out vertical seismic profiles (VSPs) and logs in this field. This approach also illustrates the value of combining velocity measurements of formations provided by borehole seismic tools (VSP) and acoustic (sonic) tools. An innovative example of the application of borehole seismic and logging methods is then presented in the case study of a relatively near-surface (from 20 to 130 m) karst carbonate aquifer. It shows how a multi-scale description of the reservoir can be carried out by integrating the information provided by different 3D-THR surface seismic methods, full waveform acoustic logging, VSP with hydrophones, borehole optical televiewer and flow measurements. In this book the authors provide readers with guidelines to carry out these operations, in terms of acquisitions as well as processing and interpretation. Thus, users will be able to draw inspiration to continue transferring petroleum techniques and other innovative methods for use in near-surface studies.

Petroleum Abstracts

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ISBN 13 :
Total Pages : 344 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Petroleum Abstracts by :

Download or read book Petroleum Abstracts written by and published by . This book was released on 1996 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

The Log Analyst

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ISBN 13 :
Total Pages : 548 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis The Log Analyst by :

Download or read book The Log Analyst written by and published by . This book was released on 1996 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Well Seismic Surveying

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Publisher : Editions TECHNIP
ISBN 13 : 9782710807766
Total Pages : 262 pages
Book Rating : 4.8/5 (77 download)

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Book Synopsis Well Seismic Surveying by : Jean-Luc Mari

Download or read book Well Seismic Surveying written by Jean-Luc Mari and published by Editions TECHNIP. This book was released on 2003 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: CD-ROM is extracted from the Reservoir and Civil Engineering Geophysics.

Radioactive Waste Management

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ISBN 13 :
Total Pages : 630 pages
Book Rating : 4.X/5 (1 download)

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Book Synopsis Radioactive Waste Management by :

Download or read book Radioactive Waste Management written by and published by . This book was released on 1981 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Geophysics and Geosequestration

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Publisher : Cambridge University Press
ISBN 13 : 1107137497
Total Pages : 391 pages
Book Rating : 4.1/5 (71 download)

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Book Synopsis Geophysics and Geosequestration by : Thomas L. Davis

Download or read book Geophysics and Geosequestration written by Thomas L. Davis and published by Cambridge University Press. This book was released on 2019-05-09 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of the geophysical techniques and analysis methods for monitoring subsurface carbon dioxide storage for researchers and industry practitioners.