bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Different Approaches of 1D Mechanical Earth Model Used in Geomechanics
Authors: Su K. , Onaisi A. , Vidal-Gilbert S. 
Published: September 2022

ABSTRACT:
1D Mechanical Earth Model (1DMEM) is the base of many petroleum related works: drilling, completion, prediction of subsidence and cap rock integrity study etc. It provides the profiles of in situ stresses and mechanical properties of geological formations crossed through by a well. The requirement of 1DMEM becomes almost systematic from exploration to development and later to plugging and abandon phases, for both conventional and unconventional fields. There are three types of 1DMEM model based on three distinct assumptions to compute the profile of in situ horizontal stresses: (a) the fault stability model, (b) the poro-elastic model, c) the poro-elasto-plastic compaction model using the Modified Cam-Clay or Mohr-Coulomb model. This paper presents a comparison of the above three types 1DMEM. The assumptions used by each model are examined and their limits of applicability are discussed. The key parameters controlling the in-situ stress contrast regarding to the vertical stress are discussed. Although all these models need well data to calibrate the stress profiles, the stress contrast and the vertical variability of the horizontal stress profiles could be very different between the models. The poro-elasto-plastic approach with eventual consideration of thermal and tectonic stress has high capacity to provide the horizontal stresses profiles consistent with well data in many geological contexts.

1. INTRODUCTION
Mechanical Earth Model (MEM) refers to the numerical representation of the magnitude of in-situ stress in geological formations and their thermo-poro-mechanical properties. It can be elaborated at various scales, 3D or 2D at field scale, or 1D at wellbore scale. Today in the petroleum industry, the request of 1DMEM at wellbore scale is almost systematic over the life of a well, from well preparation, drilling & completion, production phase, infill wells, to plugging-abandon works. Such systematic request of geomechanical model comes from the need to guarantee the well integrity and subsurface integrity of the operations, a need accentuated after the accident of Deepwater Horizon happened in 20th April 2010.
Gas Huff-N-Puff with Pressure Containment Strategy Design for the Bakken Wells
Authors: Song Xueling , Wan Xincheng , Rasouli Vamegh , Yu Wei 
Published: September 2022

ABSTRACT:
Horizontal well drilling and multistage hydraulic fracturing have been widely applied in the Bakken tight oil reservoir to enhance its recovery. However, the primary oil recovery was low due to the majority of oil being remained in the rock matrix. Gas huff-n-puff (HnP), as an enhanced oil recovery (EOR) method, has been applied to the Bakken wells. However, fracture interference among wells leads to fast pressure decline during the gas injection period and slow recovery during the production period. By designing strategies that combine water injection in the offset wells with gas HnP, the pressure of the gas HnP well can be maintained during the production period. Therefore, the effectiveness of gas HnP can potentially be improved. A five-well reservoir model was built using a third-party reservoir simulator with an embedded discrete fracture modeling method. The simulated production data obtained from the reservoir model was successfully matched with the field data. Multiple natural gas HnP strategies were designed and simulated to compare the EOR performances. The results showed that a larger volume of the injected natural gas contributes to more incremental oil production. Higher water injection pressure provided better pressure containment for the gas HnP well, but high water cut presented a detrimental effect on oil production.

1. INTRODUCTION
The Bakken Formation has witnessed a boost in oil production since 2008. By the end of March 2022, the oil production of the Bakken region was approximately 1.2 million barrels per day (U.S. Energy Information Administration, 2022). Although the Bakken formation is tight with ultra-low reservoir permeability, the applications of horizontal well drilling and multi-stage hydraulic fracturing have contributed to the success of Bakken. A typical Bakken well has 50 stages of hydraulic fractures in the 10,000 ft lateral section. These hydraulic fractures serve as the "channels" that connect the well with the tight Bakken reservoir, thus the oil that was originally locked in the formation could easily flow to the wellbore. The interaction between hydraulic fractures and pre-existing natural fractures also contributes to larger stimulated reservoir volume and promotes incremental oil production (Aoun et al., 2022; Kolawole and Ispas, 2020; Wan et al., 2020a). Currently, the new Bakken wells have an average initial oil production of 1963 barrels per day (U.S. Energy Information Administration, 2022). With the current oil price of $115 per barrel, a new well could generate an average revenue of $225,745 per day. Despite a large amount of oil that has been produced, the oil recovery of the Bakken Formation remains close to 10% (Hoffman and Evans, 2016). Alternative enhanced oil recovery (EOR) strategies are needed to fully recover the shale oil locked in the tight reservoir matrix.
A Case Study on Trim Blast Fragmentation Optimization Using MBF and MSW Models at an Open Pit Mine in Canada
Authors: Yang R. , Pratt L. , Zhao Q. C. 
Published: September 2022

ABSTRACT:
A project for monitoring, analysis, and modelling trim blasting at an open pit copper/molybdenum mine in Canada in 2021 was conducted using Orica’s in house developed proprietary tools, which includes the accelerometer near-field vibration monitoring system, the Multiple Seed Waveform (MSW) near- and far-field blast vibration model, and the Multiple Blasthole Fragmentation (MBF) model. Both MSW and MBF models are built on the fundamentals and empirical aspects of blasting mechanics. The blast vibration at the highwalls from trim blasts was predicted with MSW model. The effects of parameters from the blast design scenarios at the mine site were simulated and optimized designs were proposed based on the MBF and MSW modelling. The MBF model explicitly simulates all blast design parameters. The MSW blast vibration model uses multiple seed waveforms at different distances from a blasthole to a point of interest and is suitable for near-field blast vibration at the highwalls. Through the application of the MBF in conjunction with the MSW, various design scenarios can be explored, and rock fragmentation can be optimized while controlling blast vibration levels. These models have been successfully applied to many open pit mines and quarries around the world.

1. INTRODUCTION
For a large open pit mine, it is of vital importance to optimize trim blasts. A trim blast is next to the presplit. To minimize the negative impact on the highwall, trim blasts are often loaded with a low powder factor that results in much coarser fragmentation than the production blasts. The coarser fragmentation increases the cost of the downstream operations. On the other hand, trim blasts with a high powder factor could impact the highwall causing the highwall instability.
Over the recent years, Orica developed a unique system for blast optimization projects. The system includes near-field blast vibration monitoring using accelerometers, the multiple blasthole fragmentation (MBF) model, and the multiple seed waveform (MSW) blast vibration model. The three components of the system are used together to improve blast performance at a site.
Modeling the Effects of Hydraulic Fracturing on Borehole Acoustic Measurements
Authors: Gallardo-Giozza G. , Espinoza D. N. , Torres-Verdín C. 
Published: September 2022

ABSTRACT:
Borehole acoustic measurements are commonly used to detect and quantify variations in rock elastic properties by comparing measurements acquired before and after fracturing. While shear-waveform slowness variations are routinely recorded in boreholes, analysis of the corresponding attenuation is mostly limited to laboratory experiments. Interpreting the effects of fractures on borehole acoustic measurements often requires numerical modeling. This paper quantifies the effects of hydraulic fractures perpendicular to the well axis on shear and Stoneley borehole acoustic measurements via numerical modeling. Dipole and low frequency monopole acoustic propagation is simulated in 2D models assuming a borehole elastic and viscoelastic model. We vary casing-cement-formation bonding considering models with open hole, perfect-bond cased hole, well-bond cement bonding and unbonded cased hole. Simulation results show that hydraulic fractures perpendicular to the well axis give rise to attenuation and reflected events for both shear and Stoneley propagation modes. For shear waveforms, casing presence obscures the detection of reflected events, but attenuation is still observed. For Stoneley waveforms, the presence of casing enhances the contrast between casing-formation and fluid-filled fractures. Well-bond casing models are the optimal cased-hole models required for fracture interpretation because fracture features can be observed for both shear-wave and Stoneley modes.

1. INTRODUCTION
Borehole acoustic measurements are commonly used to assess the elastic properties of rocks around a well. Rocks can have either natural or hydraulically induced fractures. The presence of fractures often has measurable effects on the acquired borehole acoustic waveforms. Therefore, it is important to understand the role played by fractures on borehole acoustic measurements. Analytical and numerical models enable the estimation of the effect of single and multiple fractures on Stoneley and shear waves (Hornby et al., 1989; Tang and Cheng, 1989; Bakku et al., 2013; Minato and Ghose, 2017, Xu et al., 2021). Numerical modeling represents a technical challenge because analysis of complex geometries is usually required. Two-dimensional (2D) numerical models are powerful tools to understand waveform propagation along the borehole. However, they are limited to only axisymmetric geometries. Three-dimensional (3D) modeling presents technical challenges because it requires a great amount of computational resources. The finite-difference time-domain (FDTD) algorithm is the most extended method for numerical modeling of wave propagation in boreholes (Cheng et al., 1995; Liu et al., 1996; Wang and Tang, 2003; Guan et al., 2009; He et al., 2010). Other methods include finite-element method (FEM) (Michler et al., 2009, Wang et al., 2013, Pardo et al., 2021), frequency-domain hp-adaptative algorithms (Matuszyk et al., 2013), and spectral-element methods (SEM) (Komatitsch and Tromp, 1999; Xu et al., 2021).
Experimental Conditions Affecting Fracturing Research
Authors: Almubarak M. , Germaine J. T. , Einstein H. H. 
Published: September 2022

ABSTRACT:
The fracturing behavior and mechanical characterization of rocks are important for many applications in the fields of civil, mining, geothermal, and petroleum engineering. Laboratory testing of rocks plays a major role in understanding the underlying processes that occur on the larger scale and for predicting rock behavior. Fracturing research, such as producing multiple fractures that follow a particular pattern, requires well-defined and consistent boundary conditions. Consequently, the testing design and setup can greatly influence the results. In this study, a comprehensive experimental program using an artificial material was carried out to systematically evaluate the effects of different parameters in rock testing under uniaxial compression. The parameters include the compression platen type, centering of the specimen, loading control method and rate, specimen size, cross-sectional geometry, and boundary constraints. The results show that these parameters have a significant effect on the mechanical behavior of rocks. Using a fixed compression platen helped reduce bulging of the material. Centering of the specimen played a critical role to avoid buckling and unequal distribution of stress. Slower displacement rates can control the energy being released once failure occurs to prevent the specimen from exploding. Larger specimens generally fail at lower stresses compared to smaller specimens. Also, the frictional end effects were investigated by comparing lubricated and non-lubricated end conditions.

1. INTRODUCTION
The knowledge of mechanical behavior of rocks is relevant and important in rock mechanics, particularly when applied to the fields of civil, mining, geothermal, and petroleum engineering (Isah et al., 2020; Almubarak et al., 2020). Laboratory testing has played an important role in characterizing the strength of rocks and understanding fracture behavior (Xu et al., 2016). As will be explained later, the investigation reported in this paper is conducted with an artificial material.
There has been an interest in using artificial model materials for as long as the mechanical testing of rocks has been performed. Rapid prototyping (RP), additive manufacturing (AM), and three-dimensional printing (3DP) are three interchangeable terms that define a set of methods for the fast, precise, and repeatable production of elements (Zhou and Zhu, 2018). The technology was first introduced in the 1980s and is based on the process of joining materials layer-by-layer to form an object using computer-aided design (CAD). Polymeric, metallic, ceramic, and even complex composite components are among the materials used (Ngo et al., 2018). Various 3DP techniques have been developed, including fused deposition manufacturing (FDM), stereolithography (SLA), and selective laser sintering (SLS).
Stochastic Inversion of Wellbore Stability Models Calibrated with Hard and Soft Data
Authors: Nicolaidou E. , Birchwood R. A. , Prioul R. , Rodriguez-Herrera A. 
Published: September 2022

ABSTRACT:
Wellbore stability models are used in well-planning to determine the safe mud-weight window for drilling. More generally, calibration of wellbore stability models against observations (such as image logs, caliper measurements, and general drilling observations) is an essential step in constructing reliable 1D and 3D Mechanical Earth Models (MEMs) which are used to design safe drilling, completion, and production strategies. However, such calibration usually produces non-unique results, partly because most common types of calibration data impose only soft (inequality) constraints on wellbore stability models. Such non-uniqueness can be represented using probability density functions (PDFs). In this paper we show the results of stochastic inversion for stress parameters performed by drawing samples from these PDFs using a Markov Chain Monte Carlo procedure. Most types of calibration data (e.g., breakouts, drilling-induced fractures) produce a wide range of possible solutions for the stress parameters. However, the uncertainty reduces dramatically as data from an increasing number of depth locations is simultaneously inverted. The results also illustrate how including depths where breakouts and drilling-induced fractures are absent produces a powerful constraint on inferred stress parameters.

1. INTRODUCTION
Mechanical Earth models (MEMs) encompass the parameters needed to predict deformation and failure of rocks such as rock mechanical properties and in situ stresses. They constitute an essential tool for predicting safe mud weight windows while drilling and are used to inform the well planning process. Traditional methods for calibrating MEMs are tedious, due to their subjective nature, as they rely entirely on the judgement and experience of the analyst. Calibration of MEMs also requires cumbersome and time-consuming fine-tuning of a large number of parameters and computational options.
These problems can potentially be addressed through the implementation of automatic search schemes. To this end, we have developed a Bayesian inversion scheme to search for tectonic strain parameters, εxx, εyy, that control the magnitudes of the minimum (σh), and maximum (σH) horizontal stresses derived from a poroelastic stress model (Thiercelin and Plumb, 1991):
(Equation)
Multiwell DAS Microseismic and Strain Measurements Diagnostics
Authors: Chavarria J. Andres , Oukaci Y. , Laflame L. 
Published: September 2022

ABSTRACT:
Fiber Optic diagnostics are increasingly being used in reservoir development. Traditionally the use of the fiber has focused on either the completion or seismic diagnostics. Here we present how Distributed Acoustic Measurements (DAS) can be processed for joint microseismic (MS) and low frequency strain (LF-DAS). Using a three-dimensional network of fibers during unconventional reservoir development we analyze the dual measurements taken from various vantage points. By using DAS receivers within vertical and horizontal well trajectories we do a full 3D MS mapping. The DAS MS catalog was compared in space and time with respect to the strain data recorded by the same fibers. The significance of this work is that broad band DAS measurements that include MS and LF strain are an effective tool to illuminate the mechanisms for fracture generation. 3D distributions of DAS MS and LF strain events provide the framework for a more accurate description of the injection processes and its reservoir response during stimulation. By combining the two measurements we reveal how these two complimentary, but simultaneously run, measurements illuminate the subsurface and fracturing process. Here we demonstrate how MS and DAS strain respond to different aspects of the fracture generation process within the reservoir.

1. INTRODUCTION
Increasingly fiber optic networks with Distributed Acoustic Sensing (DAS) Interrogator Units (IU) are being used to monitor various processes in the subsurface. Amongst these are aspects of induced seismicity or fracture network generation tied to injection processes for storage purposes or more often, for unconventional reservoir development. DAS measurements provide broad bandwidth measurements. Initially DAS sensing was developed for seismic studies and it was quickly realized that it could be used for monitoring other aspects within the wellbore. In recent years DAS diagnostics within unconventional resources have been used to monitor injection processes with permanent installed fibers. More recently this monitoring has extended to fibers positioned in neighboring wells which allow for a fracture propagation analysis within the reservoir connecting the treatment and sensing well (Jin and Roy, 2017; Ugueto et al 2020). This crosswell monitoring has focused on low frequency strain signals due to high sensitivity of the tools to the opening and closing of developing fracture networks. This has opened the door to various analysis including accurate fracture models that predict the fracture growth in 3D as seen by monitoring fibers (Borne et al., 2021).
Numerical Modeling of Coupled Thermal-Hydro-Mechanical Processes in Salt Formations for Geologic Disposal of Large Nuclear Waste Canisters
Authors: Tounsi H. , Rutqvist J. , Hu M. , Wolters R. , Blanco-Martín L. 
Published: September 2022

ABSTRACT:
Salt has long been considered as a potential host rock for the geological disposal of radioactive waste because of its favorable properties, including self-sealing, low permeability and high thermal conductivity. The feasibility of nuclear waste disposal within salt formations has been investigated mainly for small-sized canisters, widely considered in many national nuclear waste disposal programs. Direct disposal of larger-sized canisters originally designed for spent nuclear fuel storage and transportation has lately been examined as a promising and cost-effective alternative. However, the amount of decay heat released by large canisters may cause high temperature in the backfill surrounding the canisters and in the host rock. This results in pressure and stress changes that may affect the long-term repository performance. To analyze it, the TOUGH-FLAC simulator is used to conduct fully coupled Thermal-Hydro-Mechanical (THM) simulations of a generic salt repository for large-sized canisters. In this code, large deformation has been considered allowing to accommodate viscous compaction of the crushed salt backfill as well as the long-term stress changes in salt host rock. The simulations show that the peak temperature in the backfill and in the host rock can be reduced by adjusting the distance between the canisters along emplacement tunnels or the spacing between the tunnels themselves. Nevertheless, the thermal pressurization in the salt host rock and in the crushed salt backfill, following the reconsolidation of the backfill, seems to be less sensitive to these spacing adjustments. Consequently, the pore-pressure could potentially exceed the lithostatic stress causing an increase of permeability and a fluid infiltration into the rock mass that may last more than 1000 years after the waste canister emplacement. Thus, it is critically important to analyze and manage these coupled THM processes for a safe and effective disposal of nuclear waste in salt formations.

1 INTRODUCTION
Geologic disposal of large-sized canisters, originally designed for spent nuclear fuel storage and transportation, has lately been examined as a promising and cost-effective alternative to conventional smaller-scale canisters commonly considered in many national nuclear waste disposal programs (Hardin et al., 2015).
Evolutions of Dynamic Elastic Properties of Opalinus Clay Under Varying Stress Paths
Authors: Liu L. , Chalaturnyk R. , Deisman N. , Zambrano G. 
Published: September 2022

ABSTRACT:
Understanding the elastic stiffness evolution of the host rock under stress is important in the prediction of ground deformation during the construction and operation of a radioactive waste repository. The relationship established between dynamic elastic properties and stress also allows for an accurate interpretation of seismic survey and borehole sonic logging data in the field.
In this work, the dynamic elastic properties of Opalinus Clay are determined using axial ultrasonic surveys at varying stress steps in triaxial tests. The evolutions of the P- and S-wave velocities are investigated along different stress paths, respectively with constant mean stress (CMS) and constant radial stress (CRS). For CMS testing, a cycle of triaxial compression and extension is performed. It is shown that P-wave velocity gradually reduced at the stage of triaxial compression and reversing the stress path in triaxial extension does not fully recover the velocity changes. The onset of specimen damage is identified at a deviator stress threshold where the velocity change diverts from its current trend in either triaxial compression or extension. The stress threshold differs between triaxial compression and extension, and it is inversely related to the water saturation of the Opalinus Clay.
Before damage initiation, dynamic Young’s modulus shows a minor degradation under the CMS path, whereas it increases under the CRS path in triaxial compression. Both trends agree with the measured evolutions of static Young’s modulus of argillaceous claystones at similar stress levels. This study provides additional experimental guidance for constitutive modeling of stress-dependent elastic stiffness for this rock type.

1. INTRODUCTION
Opalinus Clay is a shale with low permeability and has self-sealing potential upon the intake of moisture. It is considered as a possible host rock for future radioactive waste disposal in Switzerland (Bossart et al., 2017). Understanding the geomechanical response of the Opalinus Clay allows for the safe construction and operation of a disposal repository (Amann et al., 2017). One of the key geomechanical properties that have been under investigation is elastic stiffness.