University of Texas at Austin Petrophysical and Well-Log Simulator (UTAPWeLS)
3D Petrophysics and Well-Log Simulation Platform (3D UTAPWeLS)
User-friendly, MATLAB-based integrated platform that combines all previously developed toolboxes (modules) into one single software utility for interactive 3D multi-well formation evaluation. The platform constructs multi-layer static and dynamic petrophysical models (also known as Common Stratigraphic Frameworks, CSF) that can be subject to reservoir and geophysical upscaling and that lend themselves to multiple-hypotheses testing, rock classification, cross-validation and numerical simulation of measurements. It also includes basic and advanced well-logging calculations, layer-boundary detection algorithms, basic digital signal processing routines, simulation of the process of mud-filtrate invasion in vertical wells with water- and oil-base muds, and numerical modeling/inversion of well logs for the estimation of layer-by-layer petrophysical properties. 3D UTAPWeLS interfaces the Borehole Resistivity, Borehole Sonic, Borehole Nuclear, Borehole NMR, Formation Testing, Invasion, and Pore-Level Petrophysics Modules described below. We recently introduced a 3D version of the CSF which allows the interactive construction, display, and management of 3D reservoir models penetrated by multiple wells with arbitrary trajectories. Multiple instances of UTAPWeLS can be spawned to detect and define bed boundaries and simulate well logs to quantify layer-by-layer properties within the 3D CSF.
Status: 3D UTAPWeLS is available as a stand-alone (MATLAB independent) utility as well as a Matlab based program, which allows use of 3D UTAPWeLS through its command window (scripting). Users can upload and plot well logs (LAS, Excel, and DLIS formats), perform basic digital-processing operations on well logs, detect layer boundaries, construct and display multi-layer earth models penetrated by multiple vertical or deviated wells, perform basic petrophysical calculations, perform arbitrary calculations on logs or combinations of logs to produce new logs, and populate layer properties to numerically simulate resistivity, nuclear, NMR, and sonic logs, or to simulate the processes of invasion (oil- and water-base muds) and fluid withdrawal with both point-probe and dual-packer formation testers. Numerical simulation of the process of invasion in vertical wells and horizontal layers can be performed for cases of water- and/or oil-base mud assuming either 1D radial or 2D (radial and vertical) fluid displacement. Spatial distributions of fluid saturation and salt concentration due to invasion can be transformed into spatial distributions of physical properties for simulation of resistivity, sonic, nuclear, and magnetic resonance logs, and to initialize fluid-withdrawal conditions for simulation of dual-packer and point-probe formation-tester measurements. An expanded petrophysical calculator enables the quantification of petrophysical properties from well logs and/or CSF properties and includes most of the shaly-sand description models; it also enables interactive spatial filtering and bulk shifting of well logs, and invokes Matlab scripts to perform arbitrary well-log calculations. The same calculator can be used to quantify layer-by-layer properties. Depth-by-depth NMR T1 and T2 distributions can be uploaded and displayed on a separate track. A multi-purpose sonic-log processing and interpretation module (Sonic Studio) can be used for the numerical simulation, analysis, and interpretation of field sonic waveforms. A fast sonic logging module can also be used to simulate P- and S-wave slowness logs. Well logs can be displayed in TVD, measured depth, and horizontal distance as in so-called curtain sections. There are fast modular algorithms for the numerical simulation of LWD resistivity logs in high-angle and horizontal wells. It is also possible to quantify the effect of dielectric permittivity and magnetic permeability on certain types of resistivity logs. Nuclear logs can be simulated with a fast and accurate algorithm that also permits the rapid simulation of LWD borehole nuclear images. Users can access several options for numerical simulation of sonic logs via effective-medium theories. New magnetic resonance simulation utilities exist which are tightly integrated through the palette with nuclear and elastic properties of rock solid/fluid constituents. These utilities allow rapid simulation of T2, T2-D, and T1-T2 magnetic resonance measurements via multi-Gaussian approximations of pore-size distributions and fluid properties for the matching of field data. The NMR studio module helps to load, visualize, and analyze 1D and 2D NMR distributions. A set of calculations devoted to NMR measurements allows the estimation of echo-decays from T1 or T2 distributions, as well as the inverse calculation.
Earth Model Construction Module
Dedicated to all processes intended to specify properties of the earth model. It includes: (a) Compositional Palette, where the composition of a layer is specified in detail, as well as its internal structure based on the sand-shale laminated system model described in the Thomas-Stieber diagram. (b) Petrophysical Calculator, to set earth-model properties through petrophysical calculations (c) Detect Bed Boundaries, to identify boundaries crossing the well trajectory based on well logs. (d) Populate Properties, to set earth-model properties based on well logs. (e) Well Geometry, to specify the geometry of the well trajectory and the crossings of bed boundaries. (f) 3D Geometry, to visualize the well in a full 3D context with the aid of interactive 2D projection plots of the 3D geometry (slides or curtain, along the well trajectory).
Log Studio Module
Comprehensive set of sub-modules intended to manipulate and calculate logs. It includes: (a) Log Petrophysical Calculator, to perform pre-defined petrophysical calculations using well logs as input and output. (b) Custom Log Calculator, to perform user defined calculations using well logs as input and output. (c) Depth Shift, to bulk shift, stretch, or squeeze well logs along their measured depth. (d) Filters, to apply signal processing filters to well logs.
Borehole Resistivity Module (BRM)
3D UTAPWeLS graphical interface for the processing, interpretation, numerical simulation, and inversion of borehole resistivity logs. The software allows vertical and deviated wells, arbitrary layers, and multiple radial zones of invasion, presence of resistivity anisotropy, electrical permittivity, and magnetic permeability.
Status: Users can define radial profiles of electrical conductivity within each layer. In addition, users can simulate dual-induction, dual-laterolog measurements, SP measurements, Schlumberger’s AIT†, ARC† (LWD), dual laterolog, dual induction, EcoScope†, HRLA†, HALS†, and MSFL† resistivity measurements, Baker-Hughes’ DI††, HDIL††, DLL††, 3DEX††, Rt eXplorer††, and MPR†† (LWD) resistivity logs, Weatherford’s STI†††, MAI†††, MDL†††, and MFR††† resistivity tools, Halliburton’s ACRt†††† array induction tool, EWR-M5†††† tool, and the recently-added Xaminer-MCI†††† tool, Pathfinder’s AWR†††† tool, and GE Oil and Gas’s Centerfire†† tool. The module also includes the possibility of simulating generic induction and laterolog tools. Thanks to Schlumberger, the module includes the most general version of their 1D resistivity code ANISBEDS to be used for simulation and inversion of both wireline and LWD resistivity logs in the presence of transversely isotropic media and deviated wells. For the case of inversion, users can enter raw, borehole-corrected AIT conductivity data to estimate Rxo, Rt, and radius of invasion. In addition, users can simulate array-induction resistivity measurements acquired in arbitrarily deviated wells penetrating horizontal homogeneous, uninvaded, and anisotropic layers. We recently implemented faster semi-analytical and modular resistivity modeling algorithms for the numerical simulation of a wider range of LWD resistivity measurements. Likewise, we enabled the possibility of assessing the effect of dielectric permittivity and magnetic permeability on various types of resistivity measurements.
†Mark of Schlumberger
††Mark of BakerHugheGE
†††Mark of Weatherford
††††Mark of Halliburton
Borehole Sonic Module (BSM)
UTAPWeLS graphical interface for the display, processing, interpretation, simulation, and inversion of time-domain sonic waveforms. The simulation software assumes a vertical well, either point sonic sources/receivers or specific cylindrical tools, horizontal layers, and multiple radial zones of invasion.
Status: Users can define radial profiles of P-wave velocity, S-wave velocity, and density within each layer. Sonic waveforms can be processed with several STC and slowness frequency-dispersion algorithms to detect propagating waves and estimate their corresponding slowness. Users can simulate sonic waveforms in 1D (radial) isotropic or TI media and 2D isotropic or TI media, each in the presence of point sources/receivers and/or a cylindrical tool, for monopole, dipole, or quadrupole sources. Sonic simulations are fully integrated with the simulation of mud-filtrate invasion to assess invasion effects on sonic logs via fluid-substitution and effective-medium equations. Furthermore, sonic simulations are fully integrated with the simulation of nuclear and magnetic resonance logs. Options are available to upload, display, process, and interpret field sonic waveforms to detect and quantify propagating waves and their corresponding slowness based on STC or dispersion processing. The module allows interactive quality control, processing, interpretation, and numerical simulation of field sonic waveforms. It is also possible to numerically simulate sonic-slowness logs based on several effective-medium models. We have recently added a fast sonic logging simulator that can output P- and S-wave sonic slowness logs within seconds for a typical 20 m modeling segment.
Borehole Nuclear Module (BNM)
3D UTAPWeLS graphical interface for the display, processing, interpretation, numerical simulation, and inversion of borehole nuclear measurements. Numerical modeling is based on new linear iterative refinement approximations developed by the consortium. The software assumes vertical or arbitrarily deviated wells with or without presence of invasion. It includes measurement sensitivity functions calculated with MCNP for specific borehole environmental conditions and provided by oil-service companies. Nuclear properties input to the simulations of nuclear logs can be calculated with either Schlumberger’s SNUPAR†, Weatherford’s WRAPM†††, or our newly developed open-source UTNuPro codes based on pressure, temperature, and chemical compositions and volumetric concentrations of mineral and fluid constituents.
Status: The compositional palette, from the Build Earth Model module, can be used to define classes and volumetric concentrations of solid and fluid constituents of rock formations. Generic rock types are defined based on solid and fluid classes. A library of sensitivity functions (or flux sensitivity functions, FSFs) is invoked to calculate spectral gamma-ray, gamma-ray, density, PEF, and neutron measurements (near- and far-sensing logs whenever applicable), which can be post-processed to simulate commercial depth- and resolution-matched logs for comparison against field logs. The module allows interactive modeling to match field logs, similar to the Borehole Resistivity Module. In addition, the module is fully integrated with the simulation of mud-filtrate invasion to assess invasion effects on nuclear logs. An enlarged library of FSFs allows the simulation of nuclear logs under a wide range of borehole environmental conditions. Likewise, we include a library of FSFs to simulate EcoScope (SLB-LWD) density measurements and Weatherford’s nuclear tools. Numerical simulations can be performed along arbitrarily deviated wells including those acquired with multi-sector LWD tools. We implemented a faster and more accurate algorithm to simulate borehole nuclear logs based on a new library of FSFs with density corrections. The new algorithm enabled the rapid simulation of LWD borehole nuclear images along arbitrary well trajectories, which is now fully implemented in the module.
†Mark of Schlumberger
†††Mark of Weatherford
Borehole SP Simulator
3D UTAPWeLS graphical interface for the 3D simulation of spontaneous potential (SP) logs. The algorithm invokes fundamental physics principles of membrane and diffusion potentials to simulate borehole SP measurements.
Status: The software module is ready to simulate SP logs based on finite differences and using a 3D grid with logarithmic expansion in the radial direction. Simulations can be performed with or without presence of mud-filtrate invasion.
Invasion Module (IM)
3D UTAPWeLS graphical interface for the 1D radial or 2D simulation of water- and oil-base mud-filtrate invasion and corresponding effects on well logs and formation-tester measurements. The software assumes a vertical well, horizontal layers, and constant petrophysical properties within each layer.
Status: This software module performs 1D radial and 2D simulations of invasion for the cases of water- and oil-base muds. Users can invoke the Borehole Resistivity, Borehole Nuclear, Borehole Sonic, magnetic resonance simulation, and Formation Testing Modules to simulate resistivity, nuclear, sonic, magnetic resonance, and formation-tester measurements both before and after invasion. Invasion modeling is performed with an efficient and general algorithm that can seamlessly invoke water- or oil-base muds for the cases of 1D radial and 2D multi-layer formations. Non-permeable layers (e.g. shale) can be excluded from the simulations. Capillary pressure and relative permeability curves can be described using one of the predefined parametric models (Brooks-Corey, Van Genuchten, etc.), or can be entered as arbitrary, user-defined curves. Curves used in different layers or defined for different rock classes can be compared and analyzed in a recently developed module. Modules used for editing, analysis, and comparison of Pc-Kr curves have been consolidated into a Pc-Kr Studio.
Formation Testing Module (FTM)
3D UTAPWeLS graphical interface for the display, processing, numerical simulation, interpretation, and inversion of formation-tester measurements. The software currently assumes a vertical well and horizontal homogeneous and anisotropic layers. Simulations can be performed for the cases of water- and oil-base mud-filtrate invasion. Both dual-packer and point-probe formation testers (including focused point probes) can be invoked when performing the simulations. Custom tool parameters can be saved in a list of predefined tools for easy access.
Status: Users can define time-variable flow rates for fluid withdrawal and buildup with both dual-packer and point-probe formation testers. Invasion can be simulated with both 1D radial and 2D algorithms for the cases of either water- or oil-base muds to subsequently simulate fluid withdrawal with either packer or point probes (including focused point probes). Simulations of pressure transients can be performed at predefined pressure probe locations. Users can compare simulated pressure transients against those predicted with analytical solutions of single-phase fluid flow (radial and spherical flow). In addition, users can simulate the time evolution of water-oil fractional flow rates and salt concentration (electrical conductivity), and can upload field measurements of pressure and flow rate for processing and analysis. Many of the processing and display utilities are the same as those of the Invasion Module. Interactive utilities exist to plot and compare pressure measurements to analytical solutions of single-phase spherical and radial flow for quality control and assessment of formation mobility. We are currently modifying the simulation algorithms to efficiently account for skin and storage effects in pressure transients. Work is also underway to incorporate recently developed algorithms for fast simulation of 3D single-phase pressure transients for arbitrary formation-tester configurations.
Nuclear Magnetic Resonance Module (NMRM)
3D UTAPWeLS graphical interface for the display, processing, numerical simulation, interpretation, and inversion of magnetic resonance measurements. The software simulates T2, T2-D, and T1-T2 measurements with a rapid approximation that assumes multi-Gaussian distributions of pore sizes and fluid properties. Solid and fluid properties are fully integrated with the same property palette that controls the simulation of nuclear and elastic properties of rocks. Specific NMR acquisition parameters can be selected on a graphical-user interface.
Status: Users can interactively define Gaussian pore-size distributions and saturating fluids within each Gaussian pore-size distribution. The selection of properties can be manually adjusted to match field measurements. Currently, the module can display simulated T2-D and T1-T2 maps as well as conventional T2 distributions. In addition, T2 distributions can be displayed as typically done in a well track. Likewise, the module can interactively assess the influence of variable fluid saturation (fluid substitution analysis) on T2, T2-D, and T1-T2 measurements. We recently added the capability to read and display field data in T1, T2 distribution, as well as its corresponding echo-decay. We can also perform calculations of echo-decays from distributions, and more importantly invert calculations from raw echo-decays data to T1 or T2 distributions using a fast in-house developed algorithm. We have also expanded the display capabilities to allow for comparison of field and/or earth model data at different measured depths within the same plot.
Inversion Resistivity Module
3D UTAPWeLS module that allows estimation earth-model resistivity values via inversion.
Status: The software module allows selection of a set of well logs for inversion based on measured-depth-segmented 1D simulations of induction-based LWD resistivity tools. Models can be assumed isotropic or transversely isotropic. Users can decide whether regularization (stabilization) is to be invoked in the inversion or not, as well as the type of regularization. The inversion algorithm can be stopped by invoking different criteria: data misfit, data misfit reduction, or maximum number of iterations. Users can examine the evolution of data misfit, data misfit reduction, and model norm as the algorithm performs sequential iterations toward convergence or termination.
Markov-Chain Monte Carlo Inversion Module
3D UTAPWeLS module that allows inversion of various earth-model properties. The user selects an input well log that is to be matched with a numerically simulated log by adjusting the corresponding earth model property via perturbations with a Markov-Chain method.
Status: The software allows the inversion of earth-model’s Resistivity, Gamma Ray, Density, Migration Length or PEF. It works based on a biased Markov Chain that uses the differences between simulated and input logs to reach the right properties. It is currently restricted to 1D forward simulators.
Pore-Level Petrophysics Module (PLPM)
3D UTAPWeLS graphical interface for pore-level petrophysical analysis and quantification of (a) granular porous media, and (b) 3D CT rock images. Granular porous media are constructed by simulating the processes of sedimentation, compaction, and cementation of grain packs.
Status: Users can construct grain packs with variable grain-size distributions, compact, and cement them. Grains are assumed spherical or ellipsoidal and there are several options to replicate the processes of compaction and cement growth. It is also possible to input 3D pore-space images acquired with 3D computer-tomography (CT) scans to perform calculations of effective petrophysical properties. The module is fully integrated with 3D UTAPWeLS. It calculates porosity, permeability, relative permeability, capillary pressure, formation factor, resistivity index, and magnetic-resonance transverse relaxation (with arbitrary pulse sequences in the presence of gradient diffusion). The module also includes an efficient and accurate percolation-invasion algorithm to distribute two-phase immiscible fluids in the pore space. In addition, the module includes a wide range of plotting capabilities for visual inspection of rock/grain-pack samples and for exporting calculations. Fast algorithms can be invoked to construct grain packs composed of arbitrary distributions of variable-size spherical and ellipsoidal grains. Fast simulation algorithms are available to calculate the permeability and electrical conductivity of voxelized 3D pore-scale images. A user-friendly interface enables users to input, analyze, and interpret micro-CT images described with a series of 2D slices (in tiff format). Users can calculate distributions of pore-body size, throat size, and tortuosity based on the concept of streamlines. We are currently developing a new output option to plot NMR T1-T2 and T2-D maps from pore-scale simulations of magnetic resonance.
