Abstract: Systems, devices, and methods for generating steering instructions to directing the operation of a drilling system are provided. The systems, devices, and methods may include determining an optimized path to navigate a Bottom Hole Assembly (BHA) to a steering target using one or more steering methods, such as straight line projections, rotary drilling projections, True Vertical Depth, Inclination, and Azimuth (TIA) calculations, and three dimensional “J” (3DJ) calculations, and driving the BHA to the steering target using the optimized path.

Abstract: A method includes operating a downhole acquisition tool in a wellbore in a geological formation and performing formation testing to determine at least one measurement associated within the formation, the wellbore, or both. The tool may include sensors to detect measurements including, for example, formation pressure and/or wellbore pressure. The tool may also include a processor to obtain at least one spectral characteristic associated with the measurement, which may include frequencies of oscillation. The processor may also determine one or more parameters, associated with an oscillation suppression process, based on the spectral characteristic and remove oscillations, including noise associated with fluctuations of a fluid level in the wellbore, in the measurement based on the parameters. Petrophysical parameters may be estimated based on the modified measurement.

Abstract: A system and method for facilitating a user to initiate and accept an assistance request through a chat session is disclosed. Controls may be provided in a graphical chat interface to enable the user to specify inputs to request assistance from other users participating in the chat session. An assistance request may be generated and communicated to those users through the chat session. Graphical representation for the assistance request and controls that facilitate the users to accept the assistance request may be provided in the graphical chat interface. Upon an acceptance to the assistance request by a responding user through the graphical chat interface, an assistance command may be generated and executed in the virtual space.

Abstract: A method and system for detecting an anomaly in measurement data captured by a downhole tool is disclosed provided. In the method and system, measurement data comprising a plurality of measurement channels is obtained and reference data including healthy reference data and faulty reference data is also obtained. The measurement data is preprocessed by modeling at least one measurement channel of the plurality of measurement channels using modeling parameters to produce pre-processed measurement data. Further, a first distance between the pre-processed measurement data and the healthy reference data is obtained and determined to exceed a first threshold for the first distance. A report is generated in response to determining that the first distance exceeds the first threshold. The report indicates detection of the anomaly in the measurement data.

Abstract: The proposed method relates to hydrocarbon production, particularly to the monitoring of well operations by way of data analysis based on the cepstral analysis of the well pressure data recorded at the wellhead. The method assumes the detection of a hydraulic signal-reflecting object in the well, wherein: a fluid-filled well is provided with fluid enabling propagation of a hydraulic signal; a hydraulic signal source is provided, said source being in fluid communication with the well and designed to generate a hydraulic signal; a pressure sensor is provided, said pressure sensor records the hydraulic signal and being in fluid communication with the well and at least one hydraulic signal source. The hydraulic signal is recorded with the pressure sensor during well operations, and a pressure cepstrogram is obtained and an intense signal is found on the pressure cepstrogram. Then the position of object reflecting the hydraulic signal is detected in the well.

Abstract: An x-ray-based reservoir evaluation tool for the measurement of the shale density anticipated at shale-creep barrier within a cased borehole is disclosed, wherein the tool includes an internal length comprising a sonde section, wherein the sonde section further includes an x-ray source; a plurality of radiation measuring detectors; sonde-dependent electronics; and a plurality of tool logic electronics and PSUs. A method of using an x-ray-based shale-seal evaluation tool for measuring the shale density anticipated at shale-creep barrier within a cased borehole is also disclosed, the method including: using x-rays to illuminate the formation surrounding the cased borehole; using detectors to directly measure the density of the formation; using detectors to directly measure the effects on the measurement from tool stand-off or production liner attenuation; and compensating for the production liner and liner-annular region when computing the saturated formation density within the production interval.

Abstract: An illustrative hydraulic fracture mapping method includes: collecting microseismic signals during a multistage hydraulic fracturing operation; deriving microseismic event locations from the microseismic signals to create a microseismic event map for each stage of the operation; fitting a set of fracture planes to the microseismic event maps; determining a stimulated reservoir volume (“SRV”) region for each said stage; identifying where SRV regions overlap to form an overlap region; partitioning the overlap region to eliminate any overlap between the SRV regions; truncating the set of fracture planes for the SRV regions to discard any portion outside the revised SRV regions; and storing or displaying the truncated set of fracture planes for the first revised SRV region.

Abstract: A method and system can include a sensor positioned in a borehole, characteristics of the earthen formation can be measured and logged by the sensor, and an effective permeability can be determined based on the logged characteristics. Multi-component induction (MCI) data can be measured by a logging tool, 3D resistivity components can be determined by inverting the MCI data, and the 3D resistivity components can be logged. Tri-axial permeability components can be determined based on the effective permeability and the 3D resistivity component logs. A permeability of sand in the earthen formation can be determined based on the tri-axial permeability components, the effective permeability, and a laminated shale volume. The sand permeability can be logged and modifications to operation(s) can be initiated based on the sand permeability.

Abstract: The present invention provides a device and a method for measuring overburden of injected gas in cyclic gas injection development of condensate gas reservoir. The device comprises sand packed model and temperature control system. The temperature control system is nested outside the sand packed model. The sand packed model comprises sand pack cell, four gas inlets, four gas outlets, bracket, direction control component, rotating shaft, upper cover, lower cover, fixing bolts, two top pressuring inlets, pressure transmission rods, pressure transfer piston and multiple gas sampling ports. The sand pack cell can be filled with quartz sand of different particle size and composition, and the angle of the whole device is adjusted by the direction control component.

Abstract: A method includes operating a downhole acquisition tool in a wellbore in a geological formation. The wellbore or the geological formation, or both, contains a fluid that includes a native reservoir fluid of the geological formation and a contaminant. The method also includes receiving a portion of the fluid into the downhole acquisition tool, obtaining a measured resistivity, a measured conductivity, or both of the portion of the fluid using the downhole acquisition tool, and using a processor of the downhole acquisition tool to obtain a temperature-corrected resistivity, a temperature-corrected conductivity, or both based on a downhole temperature of the portion of the fluid and the measured resistivity, the measured conductivity, or both.

Abstract: A seismic system that includes a seismic source configured to generate a first seismic signal and a second seismic signal in a formation adjacent the seismic source. A first downhole sensing device disposed in a first borehole configured to detect the first seismic signal and the second seismic signal in the formation; and a first surface acquisition system is in communication with the first downhole sensing device. The first surface acquisition system is configured to: determine a first reference transit time based at least in part on detection of the first seismic signal by the first downhole sensing device; a first subsequent transit time based at least in part on detection of the second seismic signal by the first downhole sensing device; and whether a synchronization variation is expected to be present based at least in part on the first reference transit time and the first subsequent transit time.

Abstract: Methods, computer readable medium, and systems for mapping geologic features are described. In one example, a selection of a template describing a theoretical geologic depositional profile is received. In addition, paleo-elevations and/or paleo-depths of actual geologic facies in an actual geologic depositional profile are received. A graphical map that represents the actual geologic depositional profile is generated by mapping the received paleo-elevations and/or paleo-depths onto the theoretical depositional profile.

Abstract: A system, assembly, module, and method are disclosed for powering a downhole tool in a drilling operation. The system may include a reusable battery module and/or controller to operate multiple batteries.

Abstract: A method includes analyzing a carbonaceous deposit for an asphaltene content from a hydrocarbon-containing fluid located in a well, a wellhead or a production line proximate the wellhead, and applying one or more preventative measures to the hydrocarbon-containing fluid located in the well, the wellhead or the production line proximate the wellhead based on the asphaltene content.

Abstract: A system can include a processor; memory accessible by the processor; a network interface; and processor-executable instructions stored in the memory to instruct the system where the instructions include instructions to receive time series data associated with a borehole; compute a similarity metric for at least a portion of the time series data with respect to other time series data for the borehole; and analyze the similarity metric with respect to at least one operation associated with the borehole.

Abstract: Seismic based fracking fluid disposal can in an example embodiment include selecting a first disposal site of a plurality of disposal sites to receive fracking fluid from a fracking site; measuring, via a seismic sensor, seismic waves associated with the first disposal site; and assigning at least some of the fracking fluid from the first disposal site to a second disposal site of the plurality of disposal sites based on the measured seismic waves.

Abstract: A system and method are provided for automatically correlating geologic tops. The system receives well logs from different well bores and each of the picks is added to a priority queue ordered by each pick's quality measure. User selected picks are assigned the highest level of quality measure. The system performs correlation by selecting a window of well log data about a pick selected from the top of the priority queue and then finding the best optimal match with a corresponding window in a neighboring wellbore.

Abstract: Herein disclosed are methods and systems related to automatic pressure transient analysis (PTA). More particularly, herein disclosed are methods and systems related to automatic pressure transient analysis (PTA) of continuously measured pressure data associated with production or injection wells which utilizes in part pattern recognition analysis methods to determine key flow regimes in the measured data for more accurate determination of automatic pressure transient analysis (PTA) and determination of reservoir and well characteristic properties.

Abstract: A three-dimensional analog simulation test system for gas-liquid countercurrent in an abandoned mine goaf includes a three-dimensional analog simulation device configured to simulate an analog environment of gas-liquid countercurrent in an abandoned mine goaf, a gas supply system, an automatic water pressure control system and a hydraulic loading system. The three-dimensional analog simulation device includes a reaction frame and a three-dimensional analog simulation chamber. The reaction frame includes a beam, a base and a column for connecting the beam and the base. The three-dimensional analog simulation chamber is arranged inside the reaction frame. The test system can be used to simulate the gas-liquid countercurrent in an abandoned mine goaf so as to study the evolution of water accumulation and gas enrichment in long-term abandonment of closed mines and the migration evolution rules of gas-liquid two-phase in abandoned mines with high gas density.

Abstract: In accordance with presently disclosed embodiments, a method and system for performing real-time evaluation of a restimulation operation using coiled tubing with fiber optics is provided. The method involves performing a restimulation treatment by pumping a slurry with diverter materials through an annulus in the wellbore surrounding the coiled tubing, and using fiber optics in the coiled tubing to identify the order and magnitude of fractures being created during the restimulation treatment. The fiber optics in the coiled tubing may include one or more fiber optic cables designed to collect distributed acoustic sensing (DAS) or distributed temperature sensing (DTS) data. The evaluation of the restimulation operation may be used to validate and/or adjust the restimulation treatment as needed to improve the lateral distribution of transverse fractures through a subterranean formation. The coiled tubing may also be used to remove sand bridges from the wellbore throughout the restimulation treatment.

Abstract: A method for optimizing processes for increasing the load-bearing capacity of foundation grounds includes the following steps: detecting at least one part of a built structure and/or of ground; identifying at least one region to be treated of the foundation ground; and injecting, at least one injection point located substantially within the at least one region to be treated, a cement and/or synthetic mixture. The method further includes at least one second step of detecting at least one part of the built structure and/or of the ground that lies above the injected foundation ground. The method further includes a step of interrupting the injection step, and measuring at least one physical parameter that is susceptible of varying as a consequence of the injection step.

Abstract: Methods and apparatus for evaluating a volume of an earth formation carried out using complex dielectric measurements. Methods include making measurements of complex permittivity at a plurality of frequencies; identifying an optimal frequency by: identifying candidate frequencies having a corresponding measurement with a respective sensitivity to at least one of i) salinity and ii) water-filled porosity, by determining that each respective sensitivity is substantially independent of rock texture; selecting a maximum of the candidate frequencies as the optimal frequency; using a table search method based on a forward model to generate an initial estimate of at least two parameters of the volume; and using the initial estimate as an initial condition for an inversion of other measurements at frequencies other than the optimal frequency to generate a final solution comprising final estimates for formation properties. The at least two parameters may comprise water salinity and water filled porosity.

Abstract: A system and method of hydraulic fracturing a geological formation in Earth's crust, including injecting fracing fluid through a wellbore into the geological formation, measuring pressure associated with the hydraulic fracturing, determining net stress of the geological formation from the hydraulic fracturing, and determining presence of complex shear fracturing or complex shear fractures correlative with the net stress.

Abstract: A method for estimating downhole pressure in wells during a treatment procedure. A pressure head in a treatment well may be determined without requiring downhole sensors. The method for measuring downhole pressure may be used in long horizontal wells. By improving the accuracy of such pressure head estimates and providing the data substantially in real time, the data can also be used to control the treatment being applied to the well. The pressure head may be determined by detecting pump harmonics at a detector, typically positioned outside of the well and/or not in direct contact with the fluid in the well. The detector may be a microseismic array.

Abstract: A method of generating target-oriented acquisition-imprint-free prestack angle gathers using common focus point (CFP) operators includes receiving a plurality of seismic traces associated with a target point in a reservoir. A first angle domain common image gather (ADCIG) is generated based on the received plurality of seismic traces. A plurality of synthetic traces associated with the target point is generated. A second ADCIG is generated based on the synthetic traces. An enhanced ADCIG is generated using the first ADCIG and the second ADCIG.

Abstract: A method for selecting one or more crude oils from a plurality of crude oils. In some embodiments, a plurality of scenarios may be generated, each scenario comprising a plurality of values corresponding, respectively, to a plurality of uncertain parameters, the plurality of uncertain parameters comprising at least one uncertain parameter relating to a quality of a crude oil of the plurality of crude oils. In some embodiments, a stochastic programming model may be solved to obtain a solution that optimizes an objective function, and one or more crude oils may be procured based on respective procurement amounts in the solution of the stochastic programming model. In some embodiments, a chance-constrained programming model may be solved to obtain a solution that optimizes an objective function, and a plurality of feedstocks may be blended into a final product based on the solution of the chance-constrained programming model.

Abstract: At least some of the disclosed systems and methods obtain a static earth model having a three-dimensional grid with multiple cells. Further, at least some of the disclosed systems and methods determine a plurality of geobodies for the static earth model, each geobody comprising a plurality of connected cells. Further, at least some of the disclosed systems and methods compute one or more tortuosity values for at least one of the plurality of geobodies. Further, at least some of the disclosed systems and methods calibrate the static earth model based on the one or more computed tortuosity values. Further, at least some of the disclosed systems and methods use the calibrated static earth model as input to a flow simulator.

Abstract: Methods may include measuring an interfacial tension (IFT) for a dead oil sample prepared from a fluid within an interval of a formation; calculating a gas:oil ratio for the fluid within the interval of a formation at a specified temperature and pressure; calculating a live oil density for the fluid within the interval of a formation for the specified temperature and pressure; and converting the IFT for the dead oil sample to a corrected IFT measurement for a live oil within the interval of the formation from the calculated gas:oil ratio and the calculated density. Methods may also include constructing a depletion path for the dead oil sample from one or more isobars and one or more isotherms; and converting the IFT for the dead oil sample to a corrected IFT measurement from the calculated gas:oil ratio and the calculated live oil density for a live oil.

Abstract: A method for operating an oil deposit based on a technique of positioning wells to be drilled is disclosed. Based on a grid representative of the petrophysical properties of a subterranean formation through at least one well is drilled, a reservoir simulation is performed up to a time for which production of the formation being studied is to be predicted. Then, attributes are selected that are representative of the flows in the formation and a classification of these attributes is performed. Then, a quality indicator is computed for each of the classes and at least one class is selected such that its quality indicator is greater than a first threshold.

Abstract: Autogrouping is described. An example method includes receiving a data set, building a first partition of subsets of the data set, computing a first subset score for each subset using a scoring function, generating a next partition including at least one subset that includes the elements of two or more subsets of the first partition, computing a second subset score for each subset of the next partition using the scoring function, defining a max score for each particular subset using a max score function, each max score being based on maximal subset scores of that particular subset and at least the subsets of the first partition related to that particular subset, selecting output subsets, selection of each of the output subsets being made using a maximum score of previously computed subset scores, and generating a report indicating an output partition, the output subsets being associated with the received data set.

Abstract: A method for maintaining a well includes receiving production information associated with wells within a field; deriving a field specific model from the production information; receiving initial production information associated with the well; projecting a maintenance schedule associated with the well using a production analysis engine applied to the field specific model, the maintenance schedule including a maintenance event and an associated date; and implementing the maintenance schedule on the well.

Abstract: A method, including: obtaining a scale-depth or scale-time phase image of a continuous wavelet transform of an input signal, the scale-depth or scale-time phase image including oval-shaped circular patterns observed on the mirrored phase image; and extracting, with a computer, hierarchical multiscale intervals from the scale-depth or scale-time phase image, wherein the hierarchical multiscale intervals correspond to the oval-shaped circular patterns observed on the mirrored scale-depth or scale-time phase image of the continuous wavelet transform of the input signal. Another method includes: characterizing, with a computer, curve shapes of intervals of a signal using beta distribution; and visualizing and analyzing, with the computer, shape parameters of the curve shapes on a shape-parameter crossplot.

Abstract: A method of determining the presence of hydrocarbon-filled natural fractures with sufficient lateral extension in a well in which stimulation by hydraulic fracturing is intended to be carried out. Following perforation of an interval, a fluid is pumped into the well and a pressure response trace is collected. The fluid is pumped at a rate which is lower than the pump rate for the intended frac job and the data collection rate is higher than the data collection rate for the intended frac job. Characteristic elements are identified in the pressure response trace whose value and combination indicate the presence or absence of hydrocarbon-filled natural fractures with sufficient lateral extension in the interval.

Abstract: This disclosure is directed to methods and systems to evaluate noise contend of seismic data received during a marine survey. The seismic data includes pressure and particle motion data generated by collocated pressure and particle motion sensors of a seismic data acquisition system. The pressure and particle motion data are cross ghosted and temporal and spatial wavelet transforms are applied to the cross-ghosted pressure and particle motion data in order to compute pressure energies and particle motion energies in temporal and spatial scales of a temporal and spatial scale domain. The pressure and particle motion energies may be compared to evaluate noise content in the pressure and particle motion data, evaluate changes in the noise content during the marine survey, and adjust marine survey parameters to reduce the noise content.

Abstract: The present invention is directed to a method to use nuclear magnetic resonance (“NMR”) to determine the surface relaxivity in a reservoir. The surface relaxivity can be used to calculate the pore size distribution in a reservoir.

Abstract: A method and a device for determining geological facies in subsoil for oil and gas exploration. The method determines a combined proportion cube from a first meshed proportion cube and a second meshed proportion cube. The invention combines some facies models giving vertical probabilities and some facies models giving horizontal probabilities. This determination is particularly efficient in the presence of a zero probability in one of these models and is capable of respecting the mathematical constraint according to which the sum of each row and each column in the final proportion model must be equal to a predetermined maximum value.

Abstract: A method for estimating a property of an earth formation includes: obtaining a sample of rock; scanning the sample to determine internal rock damage; measuring a deformation parameter of the sample; constructing a mathematical model of the sample that replicates the determined and measured internal rock damage distribution; simulating the one or more tests using the mathematical model; obtaining a rock deformation parameter using the one or more simulated tests corresponding to the measured rock deformation parameter; comparing the rock deformation parameter obtained from the one or more simulated tests to the corresponding measured rock deformation parameter; adjusting parameters of the mathematical model based upon the rock parameter obtained from simulation not being within a selected range of the measured rock parameter; and providing the mathematical model as a verified mathematical model based upon the rock parameter obtained from simulation being within a selected range of the measured rock parameter.

Abstract: A location of a fracture can be determined in a wellbore. Micro-electro-mechanical (“MEM”) devices of different sizes and shapes can be included in a sweep and injected into a wellbore. A MEM reader can be positioned within a downhole tool for detecting MEM devices in the wellbore after a sweep returns to the surface of the wellbore. The MEM reader can be disposed in the wellbore for measuring the position of the MEM devices remaining in the wellbore. A location, size, and shape of a fracture in the wellbore can be determined based on the position of the MEM devices in the wellbore.

Abstract: A method includes receiving, via a processor, dielectric measurements of a geological formation and receiving, via the processor, sigma measurements. The sigma measurements include thermal neutron capture cross section of the geological formation. The method also includes jointly inverting to fit the dielectric measurements and the sigma measurements to a petrophysical model, and computing at least water salinity of the geological formation based on the joint inversion.

Abstract: A method including selecting candidate sensors for pooled calibration and determining a multivariate fluid characterization model with the pooled sensors is provided. The method includes determining a virtual master kernel standardization model with the pooled sensors, implementing a calibration result into a processor circuit and determining a value of a fluid characteristic by applying the multivariate fluid composition model to a plurality of responses obtained from a plurality of sensor responses to the fluid sample. The plurality of responses may be obtained from the plurality of sensor responses using the virtual master kernel standardization model. The method includes optimizing a wellbore operation based on the value of the fluid characteristic. A device for implementing the above method is also provided.

Abstract: A method for determining a fracture aperture of a fracture aperture in a wellbore comprises measuring a resistivity of the wellbore with a downhole tool in a wellbore for obtaining an image of the wellbore. Based on the image, the method detects fractures in the wellbore, and calculates a fracture aperture of the detected fracture according to a predetermined model of the wellbore set up based on hypothesis relative to the configuration of the wellbore. Then, the method estimates a correction to the predetermined model when at least one of the hypothesis is not met, and determines an uncertainty range for the fracture aperture also using a measured parameter.

Abstract: A method and system for simulating reservoir recovery include taking into account inaccuracies in well spacing due to wellbore positional uncertainty.

Abstract: In one embodiment, a method includes receiving, via a processor, data from a plurality of imaging buttons disposed on a downhole tool within a borehole, generating, via the processor, a resistivity image, a permittivity image, a standoff curve, a rugosity index curve, a high-resolution image of a relationship between resistivity and permittivity of a section of a geological formation measured by the downhole tool, or some combination thereof based on the data, characterizing, via the processor, one or more vugs, one or more fractures, or some combination thereof based at least on the resistivity image, the permittivity image, the standoff curve, the rugosity index curve, the high-resolution image of the relationship between resistivity and permittivity, or some combination thereof, and identifying, via the processor, one or more rock types based at least on the high-resolution image of the relationship between resistivity and permittivity.

Abstract: A method can include receiving data for a geologic environment where the data include data acquired via different types of borehole tool sensors; based at least in part on the data, determining rock composition of the geologic environment where the rock composition includes depositional components and diagenetic components; and, based at least in part on the rock composition, outputting a stratigraphic model of at least a portion of the geologic environment.

Abstract: Techniques for determining a proppant-area of a hydraulic fracture include identifying a fracture fluid leak-off curve that includes time-dependent pressure signal values of a first fracturing fluid in a monitor wellbore that is in fluid communication with a first hydraulic fracture formed from the monitor wellbore. Each of the time-dependent pressure signal values is a pressure change in the first fracturing fluid induced by a second hydraulic fracture from a treatment wellbore formed by a second fracturing fluid that includes proppant.

Abstract: Disclosed herein is an approach to processing the waveforms measured by a plurality of receivers in a manner that improves signal-detection performance for multiple simultaneously occurring signals, despite disparate signal and noise levels, by applying an waveform pre-processing scheme prior to computing a semblance map therefrom.

Abstract: An embodiment of a method of evaluating fluid trapping in an earth formation includes injecting a water-based fluid into at least one fluid channel fabricated on a substrate, the at least one fluid channel having a pore structure configured to represent a condition of an earth formation. The method also includes injecting oil into an inlet of the at least one fluid channel until at least a selected amount of the injected oil exits the channel, imaging the fluid channel and determining an amount of remaining fluid in the fluid channel after injection of the oil, the remaining fluid being an amount of the oil and/or an amount of the water-based fluid, and estimating a proportion of the total volume of the fluid channel occupied by the remaining fluid to determine an amount of fluid trapping in the pore structure. The method further includes analyzing the amount of fluid trapping.

Abstract: A downhole monitoring system and method that includes a sensor system with a sensor array with a number of sensors and a hub. Data measured by the sensors is processed by the hub and wirelessly communicated to a smart node. The sensor system may be mounted in the annulus formed between a borehole wall and an exterior surface of a well casing. The sensors may be configured to monitor the formation for microseismic events generated during hydraulic fracturing. The fracture growth and propagation may be monitored using the data obtained by the sensors. The data may facilitate real time control of the hydraulic fracturing operation.

Abstract: A method can include receiving data sets where each of the data sets corresponds to one of a plurality of individual emitter-detector arrangements; calculating a multi-dimensional similarity metric for one of the data sets; and, based at least in part on the multi-dimensional similarity metric, assessing the one data set.

Abstract: Systems and methods for determining vector-ratio safety factors for wellbore tubular design are provided. Pressure and temperature data for at least one load point along a tubular component of a wellbore are obtained. An effective failure axial load expected at the load point is calculated during a downhole operation to be performed along one or more sections of the wellbore within a subsurface formation, based on the obtained data. An upper boundary and a lower boundary for the effective failure axial load are determined, based on physical properties of the tubular component at the load point. A midpoint of the effective failure axial load is calculated based on the upper and lower boundaries. A critical failure differential pressure is calculated, based on the midpoint of the effective failure axial load. A vector-ratio safety factor is calculated, based on the critical failure differential pressure relative to the effective failure axial load.