In-Situ Stress Research Articles

Research on Mechanism of Non-Uniform In-Situ Stress Induced Casing Damage Based on Finite Element Analysis

Casing damage is a common problem encountered during oil and gas field development due to the complex stress state of the casing. Despite the large number of studies focusing on this problem, the mechanism of non-uniform in-situ stress-induced casing damage in a low-permeability reservoir is still unclear. In this study, casing damage due to non-uniform in-situ stress variations was investigated, and then the tectonic stress coefficients in the study area were determined by an in-situ stress inversion technique, which led to the derivation of formulas for calculating the maximum and minimum horizontal in-situ stresses. Subsequently, finite element numerical simulations were performed to assess the stress distribution during the formation of the casing cement sheath in a G155 block, a typical low-permeability reservoir. The results indicate that casing damage is caused not only by non-uniform in-situ stresses but also by various additional creep-induced loads. Subsequent finite element investigations into casing behavior under mudstone creep conditions indicated that immersion of mudstone in water instigated further shearing and deformation of the casing, culminating in premature well failure prior to water inundation. Notably, Von Mises stress levels exhibited a positive correlation with injection production ratios, with values exceeding critical thresholds leading to distinct modes of mechanical failure including shear-induced deformations, longitudinal tensile stress, and localized yielding near water wells. Maintenance of an optimal injection production ratio is identified as a key strategy for prolonging casing longevity in the region. To this end, recommendations include augmenting the casing wall thickness or enhancing the steel pressure specifications to mitigate casing damage progression, thereby extending the operational lifespan. This research serves as a pivotal theoretical framework for informing future development strategies aimed at mitigating and preempting casing failures in a low-permeability reservoir.

Analytical Method Based on Machine Learning (AM-BML) for a Cased Borehole under Anisotropic In-Situ Stresses in Formation

Analytical Method Based on Machine Learning (AM-BML) for a Cased Borehole under Anisotropic In-Situ Stresses in Formation

In-Situ Stress Prediction Model for Tight Sandstone Based on XGBoost Algorithm

In-Situ Stress Prediction Model for Tight Sandstone Based on XGBoost Algorithm

Development of a rock-bit interaction analytical model by considering the in-situ stresses for a bottom-hole element

PDC drill bits are an important part of drilling engineering, but improper selection or design can lead to decreased performance and increased costs. Then, accurate modeling of rock-bit interaction for Oil/gas well drilling is critical. Although several mathematical models are presented for this purpose, they have not been able to present a comprehensive model for the rock-bit interaction. In-situ stresses in real drilling conditions affect the force required for rock failure. However, the models proposed so far either have not considered the effects of in-situ stresses or have assumed that the rock failure angle in the downhole conditions is equal to the one calculated in the atmospheric conditions. In this work, after reviewing the background of studies conducted on the rock and bit interaction, with an analytical method, stresses applied to the bottom hole element are examined, including stresses resulting from bit and in-situ stresses. Based on the principle of superposition, the total stress imposed on the bottom hole element is calculated to determine the angle and force of rock cutting. Finally, a novel mathematical model of rock-bit interaction in vertical and deviated oil/gas wells drilling by Considering In-Situ Stresses is presented. Also, the study compares the current model to the Nishimatsu and Xin Ling models using data from a southwest field in Iran. The results show that the simplifying assumption made by previous models leads to a significant underestimation of the failure angle and the amount of force required to the rock failure, with reductions of up to 21% and 48%, respectively, in the case of a vertical well. In an inclined well, the current model predicts cutting force at about 0.14 of that predicted by the previous model.

Experimental Study on Mechanical, Brittleness, and Fracture Behavior of Deep Shales Subjected to Fracturing Fluid-Shale Interactions at Reservoir Temperature and In-Situ Stress Conditions

Experimental Study on Mechanical, Brittleness, and Fracture Behavior of Deep Shales Subjected to Fracturing Fluid-Shale Interactions at Reservoir Temperature and In-Situ Stress Conditions

In situ stress variation and coal reservoir permeability response of the Jurassic Yan'an formation in the southwestern Ordos basin, China: Its impact on coalbed methane development

The in situ stress (ISS) and permeability determine the coalbed methane (CBM) development method and extraction efficiency to a certain extent. Based on the data of the CBM well test and microseismic monitoring in the Jurassic Yan'an Formation, a prediction model of the ISS is established, and its influence on permeability and CBM development in the southwestern Ordos Basin, China, is discussed. The results show that the orientations of maximum principal stresses (Shmax) in the study area's eastern, central, and western parts are NE–SW, SEE–NWW, and NNW–SSE, respectively. With the increased burial depth, the main ISS parameters show an S-shaped variation. The study area's ISS state can be divided into Shmax > vertical stress (Sv) > horizontal minimum principal stress (Shmin) (<420 m), Sv > Shmax > Shmin (420 m–800 m), and Shmax ≈ Sv > Shmin (>800 m), and the transformation depth of the ISS field is 550 m and 1000 m. The lateral pressure coefficients (λ) ranged from 0.30 to 1.19, with an average of 0.69. The λ, Shmax/Shmin and Shmin/Sυ of the stress field are small, which indicates that the horizontal tectonic stress is weak. The coal reservoir's permeability is distributed between 0.0084 and 6.84 mD (av. 1.13 mD). Affected by the variation of the ISS state in the vertical direction, the coal reservoir permeability shows obvious zoning. The tensile stress field is beneficial to high-permeability coal reservoir formation, but it is constrained by the coupling constraints of a coal reservoir's confining pressure and effective stress. The coal reservoirs are in a normal fault stress state, which is beneficial for improving their hydraulic fracturing effect. Since the Shmin in the study area is always smaller than the Sυ, the height of the fracturing fracture should be controlled in the fracturing of the coal reservoir to avoid the overlying aquifer being connected by fracturing fractures. The above new insights have important guiding significance for the hyperpermeability CBM reservoir prediction, well-bore structure and hydraulic fracturing design in the Ordos Basin.

(Invited) In-Situ Stress Measurement during Electrochemical Processing

The electrochemical community often uses in situ wafer curvature and cantilever bending techniques to examine stress development during electrochemical processing. These techniques have been used to examine and quantify surface stress induced by surface charge (electrocapillarity), adsorption processes, and growth stress associated with underpotential deposition (UPD) and electrodeposition. The sensitivity of the stress measurement to surface processes makes this technique particularly relevant for electrochemical studies. For example, we have used in situ surface stress measurements to examine the underpotential deposition of a variety of metals (M) onto (111)-textured Au cantilever electrodes. The stress response clearly shows regions of anion desorption, M–Au bond formation, and in some cases, stress relaxation that can be attributed to surface alloying. This talk will focus on the surface and growth stress that develops during a variety of electrochemical processes, including metal deposition, the formation of elastically strained Pt films for electrocatalysis, and adsorbate-induced surface stress, such as carbon monoxide (CO) on Pt.

Influence of the Xianshuihe Fault Zone on In-Situ Stress Field of a Deep Tunnel and its Engineering Effect

The in-situ stress distribution near a fault zone is affected by factors such as tectonic movement and rock mass property deterioration, and it often shows unique characteristics and further affects the mechanical response of the rock mass and the safety of underground engineering construction. The Xianshuihe fault zone is one of the most active fault zones in the world. To understand the impact of the Xianshuihe fault zone on a tunnel under construction in southwestern China, the in-situ stress measured near the tunnel site at different distances from the faults of the Xianshuihe fault zone is obtained. Furthermore, the characteristics of the in-situ stress at the tunnel site and its engineering influence effect are analyzed. The results indicate the following: 1) Around the Xianshuihe fault zone, the fault mainly affects the maximum horizontal principal stress and the minimum horizontal principal stress in the shallow strata, and the in-situ stress closer to the fault is more greatly affected. 2) In the shallow area near the Selaha-Kangding fault, the maximum horizontal principal stress, minimum horizontal principal stress and lateral pressure coefficient at a borehole increase with increasing distance from the fault. Greater than 600 m from the fault, the horizontal stress plays a dominant role. In the deeper strata, the maximum horizontal principal stress, the minimum horizontal principal stress and the lateral pressure coefficient exhibit no obvious change with distance from the fault. 3) According to the inversion of the in-situ stress field and the stress in the tunnel site, the in-situ stress in the tunnel barrel is affected by the depth and the fault. The in-situ stress is higher at greater depths. The in-situ stress is partially released at the fault so that the in-situ stress is relatively low, and the degree of stress decline at different faults is different. 4) Tunnel rockbursts tend to occur in surrounding rock sections with high stress, which are usually located in the middle of a rock mass between two faults. Large deformation mainly occurs in the fault and its influence zone.

Analysis of in-Situ stress and well trajectory (critical Inclination and drilling Azimuth) for the West Qurna-1 oilfield, Southern Iraq. A comparison study between Mishrif and Zubair Formations.

Analysis of in-Situ stress and well trajectory (critical Inclination and drilling Azimuth) for the West Qurna-1 oilfield, Southern Iraq. A comparison study between Mishrif and Zubair Formations.

Effect of Pore Type on Porosity, Permeability and Pore Volume Compressibility of Geological Formations Due to In-Situ Stress Change

Effect of Pore Type on Porosity, Permeability and Pore Volume Compressibility of Geological Formations Due to In-Situ Stress Change

Research on Deep-Hole Cutting Blasting Efficiency in Blind Shafting with High In-Situ Stress Environment Using the Method of SPH

This article aiming at the lack of research on the influence of rock clamp production on cutting blasting under high in-situ stress conditions and the lack of rock damage criteria for RHT constitution in numerical simulation. Combined with the critical rock damage criterion and the embedded function of RHT constitution, the criterion for determining the critical damage of rock in RHT constitutive was studied, and the mechanical parameters of Metamorphic sodium lava were substituted to obtain the critical damage threshold of rock in numerical simulation. The smooth particle hydrodynamics (SPH) method was used to numerically simulate and analyze the influence of different rock clamping coefficients on the rock damage range and the cavity area in the cutting blasting. The stress state applied by the numerical simulation was inversely deduced by the field test scanning results to simulate the rock clamping coefficient Kr at the corresponding depth. The relationship between the cavity area Sc and the free surface distance Df is analyzed and established. The results show that the rock clip production has an inhibitory effect on the development and propagation of blast-induced cracks. The stress applied in the numerical simulation affects the range and development degree of cracks, and the cracks generated by the explosion are mainly circumferential cracks. The larger coefficient of rock clip production, the more obvious the inhibitory effect on cut blasting, the less the blast-induced cracks and the smaller the rock damage circle. The fitting results show that the curve fitting degree is about 0.94, which proves the accuracy of Sc-Df curve, and provides important reference value for the design of one-time completion blasting of upward blind shaft.

Evaluation of the Diametrical Core Deformation and Discing Analyses for In-Situ Stress Estimation and Application to the 4.9\xa0km Deep Rock Core from the Basel Geothermal Borehole, Switzerland

The in situ state of rock mass stresses is a key design parameter, e.g., for deep engineered geothermal systems. However, knowledge of the stress state at great depths is sparse mostly because of the lack of possible in situ tests in deep boreholes. Among different options, core-based in situ stress estimation may provide valuable stress information though core-based techniques have not yet become a standard. In this study we focus on the Diametrical Core Deformation Analysis (DCDA) technique using monzogranitic to monzonitic rock drill cores from 4.9 km depth of the Basel-1 borehole in Switzerland. With DCDA the maximum and minimum horizontal stress (SHmax and Shmin) directions, and the horizontal differential stress magnitudes (∆S) can be estimated from rock cores extracted from vertical boreholes. Our study has three goals: first, to assess photogrammetric core scanning to conduct DCDA; second, to compare DCDA results with borehole breakout and stress-induced core discing fracture (CDF) data sets; and third, to investigate the impact of rock elastic anisotropy on ∆S. Our study reveals that photogrammetric scanning can be used to extract reliable core diametrical data and CDF traces. Locally aligned core pieces showed similar SHmax orientations, conform to borehole breakout results. However, the variability of core diametrical differences was large for the Basel-1 core pieces, which leads to a large spread of ∆S. Finally, we demonstrate that core elastic anisotropy must be considered, requiring robust estimates of rock elastic moduli, to receive valuable stress information from DCDA analyses.

Effects of in-situ stress and elastic parameters of cement sheath in salt rock formation of underground gas storage on seal integrity of cement sheath

The cement sheath seal integrity is crucial for a safe operation of underground gas storage. Owing to its creep characteristics, the salt formation squeezes the cement sheath, which may cause failure of the cement sheath’s seal integrity and pose risks to the safe operation of underground gas storage. In this study, the experimentally obtained salt rock creep law and finite-element software ABAQUS were used to verify the adaptability of the salt rock creep in ABAQUS. In addition, a model of casing–cement sheath formation combination under creep formation conditions was developed. The effects of the in-situ stress (ISS) and cement sheath’s elastic parameters on the seal integrity of the cement sheath were studied in the salt rock layer. The creep of the salt rock increased the stress acting on the cement sheath over time and caused shear failure of the cement sheath. A larger uniform horizontal ISS led to a shorter time period for shear failure of the cement sheath, larger equivalent plastic strain (PEEQ), and larger yield area. A larger maximum horizontal ISS led to a shorter time period for shear failure of the cement sheath, larger PEEQ, and larger yield area. The yield area was concentrated in the direction of the maximum and minimum horizontal ISSs. Uniform and non-uniform horizontal ISS creeps did not cause tensile failure of the cement sheath. The reduction in the elastic modulus of the cement sheath and increase in the Poisson’s ratio of the cement sheath could reduce the shear failure risk of the cement sheath in salt rock formation. The influences of the ISS and cement sheath elastic parameters in the salt rock layer on the seal integrity of the cement sheath obtained in this study can provide references for the seal integrity failure of the cement sheath in the creep formation.

In-Situ Stress Measurements at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) Site

A scientific injection campaign was conducted at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) site in 2017 and 2019. The testing included pump-in/shut-in, pump-in/flowback, and step rate tests. Various methods have been employed to interpret the in-situ stress from the test dataset. This study focuses on methods to interpret the minimum in-situ stress from step rate, pump-in/extended shut-in tests data obtained during the stimulation of two zones in Well 58-32. This well was drilled in low-permeability granitoid. A temperature of 199 °C was recorded at the well’s total depth of 2297 m relative to the rotary Kelly bushing (RKB). The lower zone (Zone 1) consisted of 46 m of the openhole at the toe of the well. Fractures in the upper zone (Zone 2) were stimulated between 2123–2126 m measured depths (MD) behind the casing. The closure stress gradient variation depended on the depth and the injection chronology. The closure stress was found to increase with the pumping rate/volume. This stress variation could indicate that poroelastic effects (“back stress”) and the presence of adjacent natural fractures may play an important role in the interpretation of fracture closure stress. Further, progressively increasing local total stresses may, consequently, have practical applications when moderate volumes of fluid are injected in a naturally fractured or high-temperature reservoir. The alternative techniques that use pump-in/flowback tests and temperature signatures provide a valuable perspective view of the in-situ stress measurements.

Effect of Axial In-Situ Stress in Deep Tunnel Analysis Considering Strain Softening and Dilatancy

In many previous tunnel analyses, the axial in-situ stress was ignored. In this work, its effect on the deformation and failure of the surrounding rock of a deep tunnel was revealed, considering the objective strain softening and dilatancy behavior of the surrounding rock. Analysis based on the incremental plastic flow theory was conducted, and C++ was used to write a constitutive model for numerical simulation to verify and further analyze this effect. Then, the results were validated by the field monitoring data of a coal mine gateway. Results show that the effect of the axial in-situ stress σa0 is more significant when strain softening is considered, compared with the results of a perfectly elastoplastic model. When the axial stress σa is σ1 or σ3 at the initial yield, an increase or decrease in σa0 intensifies the deformation and failure of the surrounding rock. When σa is σ2 at the initial yield, 3D plastic flow partly controlled by σa may occur, and an increase in σa0 intensifies the deformation and failure of the surrounding rock. The effect of σa0 will be amplified by considering dilatancy. Considering both strain softening and dilatancy, when σa0 is close to the tangential in-situ stress σt0 or significantly greater than σt0 (1.5 times), σa will be σ2 or σ1 at the initial yield, and then 3D plastic flow will occur. In the deformation prediction and support design of a deep tunnel, σa0 should not be ignored, and the strain softening and dilatancy behavior of the surrounding rock should be accurately considered.

Effect of Fault on in-Situ Stress Perturbation in Deep Carbonate Reservoir

The existence of faults in deep carbonate reservoirs is characterized by the complex stress field near faults, which has a great influence on the extension of induced fractures and the formation of the fracture network. In this paper a numerical procedure is proposed for the regional boundary stress determination. Fault zone properties were defined by measurement of the samples and were further verified by comparing the calculated stress values with the measured values for the fault zone. The change in the principal stress value and orientation and the perturbation area were quantified. The authors analyzed the boundaries of the areas at the ends of the fault where the horizontal principal stress difference increases and decreases symmetrically. The influence range increases with the increase in the fault length. The stress concentration determined by the fault structure increases or decreases markedly in the area near the fault tip.

In-Situ TEM Stress Induced Martensitic Transformation in Ni50.8Ti49.2 Microwires

In-situ transmission electron microscopy tensile straining is used to study the stress induced martensitic transformation in Ni50.8Ti49.2. Two microwire samples with different heat treatment are investigated from which one single crystal and three polycrystalline TEM specimens, the latter with micro- and nano-size grains, have been produced. The measured Young’s modulus for all TEM specimens is around 70 GPa, considerably higher than the averaged 55 GPa of the original microwire sample. The height of the superelastic stress plateau shows an inverse relationship with the specimen thickness for the polycrystalline specimens. Martensite starts nucleating within the elastic region of the stress–strain curve and on the edges of the specimens while also grain boundaries act as nucleation sites in the polycrystalline specimens. When a martensite plate reaches a grain boundary in the polycrystalline specimen, it initiates the transformation in the neighboring grain at the other side of the grain boundary. In later stages martensite plates coalesce at higher loads in the stress plateau. In highly strained specimens, residual martensite remains after release.

Determine In-Situ Stress and Characterize Complex Fractures in Naturally Fractured Reservoirs from Diagnostic Fracture Injection Tests

Estimation of in-situ stresses has significant applications in earth sciences and subsurface engineering, such as fault zone studies, underground CO2 sequestration, nuclear waste repositories, oil and gas reservoir development, and geothermal energy exploitation. Over the past few decades, Diagnostic Fracture Injection Tests (DFIT), which have also been referred to as Injection-Falloff Tests, Fracture Calibration Tests, and Mini-Frac Tests, have evolved into a commonly used and reliable technique to obtain in-situ stress. Simplifying assumptions used in traditional methods often lead to inaccurate estimation of the in-situ stress, even for a planar fracture geometry. When a DFIT is conducted in naturally fractured reservoirs, the stimulated natural fractures can either alter the effective reservoir permeability within the distance of investigation or interact with the hydraulic fracture to form a complex fracture geometry, this further complicates stress estimation. In this study, we present a new pressure transient model for DFIT analysis in naturally fractured reservoirs. By analyzing synthetic, laboratory and field cases, we found that fracture complexity and permeability evolution can be detected from DFIT data. Most importantly, it is shown that using established methods to pick minimum in-situ stress often lead to over or underestimates, regardless of whether the reservoir is heavily fractured or sparsely fractured. Our proposed “variable compliance method” gives a much more accurate and reliable estimation of in-situ stress in both homogenous and naturally fractured reservoirs. By combining the unique pressure signatures associated with the closure of natural fractures, a lower bound on the horizontal stress anisotropy can be estimated.

In-Situ Stress Measurements during Cobalt Electrodeposition

In situ cantilever curvature is used to quantify the growth stress in Co thin films, electrodeposited from an electrolyte consisting of 0.5 mol/L Na2SO4, 0.5 mol/L H3BO3, and 0.1 mol/L CoSO4·7 H20. The average biaxial steady-state stress is measured as a function of the deposition potential and is examined as a function of growth rate. Stresses as low as +85 MPa (tensile) are obtained at small growth rate, increasing to a limiting value of 800 MPa as the growth rate is increased. The data is fit to a kinetic model that appears in the literature and treats the stress as a dynamic competition between coalescence-induced tensile stress and compressive stress due to insertion of atoms into the grain boundary. Kinetic parameters for Co indicate that stress development is dominated by nuclei coalescence and that ad-atom insertion into the grain boundary contributes to the overall stress only at very low growth rates.

Transient Coupling of Swab/Surge Pressure and In-Situ Stress for Wellbore-Stability Evaluation During Tripping

Summary This paper identifies wellbore-stability concerns caused by transient swab/surge pressures during deepwater-drilling tripping and reaming operations. Wellbore-stability analysis that couples transient swab/surge wellbore-pressure oscillations and in-situ-stress field oscillations in the near-wellbore (NWB) zone in deepwater drilling is presented. A transient swab/surge model is developed by considering drillstring components, wellbore structure, formation elasticity, pipe elasticity, fluid compressibility, fluid rheology, and the flow between wellbore and formation. Real-time pressure oscillations during tripping/reaming are obtained. On the basis of geomechanical principles, in-situ stress around the wellbore is calculated by coupling transient wellbore pressure with swab/surge pressure, pore pressure, and original formation-stress status to perform wellbore-stability analysis. By applying the breakout failure and wellbore-fracture failure in the analysis, a work flow is proposed to obtain the safe-operating window for tripping and reaming processes. On the basis of this study, it is determined that the safe drilling-operation window for wellbore stability consists of more than just fluid density. The oscillation magnitude of transient wellbore pressure can be larger than the frictional pressure loss during the normal-circulation process. With the effect of swab/surge pressure, the safe-operating window can become narrower than expected. The induced pore pressure decreases monotonically as the radial distance increases, and it is limited only to the NWB region and dissipates within one to two hole diameters away from the wellbore. This study provides insight into the integration of wellbore-stability analysis and transient swab/surge-pressure analysis, which is discussed rarely in the literature. It indicates that tripping-induced transient-stress and pore-pressure changes can place important impacts on the effective-stress clouds for the NWB region, which affect the wellbore-stability status significantly.