Analysis of Casing Strength after Casing Wear in Ultra-Deep Rock Salt Formation

2012 ◽  
Vol 616-618 ◽  
pp. 538-542 ◽  
Author(s):  
Fu Xiang Zhang ◽  
Wei Feng Ge ◽  
Xiang Tong Yang ◽  
Wei Zhang ◽  
Jian Xin Peng
Keyword(s):  
Rock Salt ◽  
Coupling Effect ◽  
Equivalent Stress ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Attrition Rate ◽  
Salt Formation ◽  
Salt Creep ◽  
Casing Wear

To alleviate the problems of casing collapse induced by the coupling effect of rock salt creep and casing wear, the effects of salt creep, attrition rate and casing abrasive position on the equivalent stress on casings in non-uniform in-situ stress field is analyzed by finite-difference model with worn casing, cement and salt formation. It indicates that, creep reduces the yield strength of worn casing to a certain extent; Equivalent stress on casings is bigger and more non-uniform when the abrasion is more serious; Wear position obviously changes the distribution of equivalent stress on casing, and when the wear located along the direction of the minimum in-situ stress, equivalent stress on casing could be the largest that leads to the casing being failed more easily. Equivalent stress on casings increases gradually with creep time increasing and will get to balance in one year or so; In addition, new conclusions are obtained which are different from before: the maximum equivalent stress on casings is in the direction of the minimum horizontal stress, only when the attrition rate of the casing is little; otherwise, it is not. This method could help to improve the wear prediction and design of casings.

In Situ Stress Measurement and Surrounding Rock Stability Analysis of the Gaoligong Mountain Tunnel

2014 ◽  
Vol 501-504 ◽  
pp. 1766-1773
Author(s):  
Lin Hai Bao
Keyword(s):  
Large Deformation ◽  
Principal Stress ◽  
Stress Measurement ◽  
Pressure Coefficient ◽  
Horizontal Stress ◽  
Wall Rock ◽  
In Situ Stress ◽  
Rock Stability ◽  
Mountain Tunnel

Gaoligong Mountain tunnel is the key project in the Dali-Ruili Railway. In order to optimize the design and guide construction, In-situ stress has been conducted in five boreholes using hydraulic fracturing method, the current shallow crustal in-situ stress state at the project area are obtained according to the measurements results, and deep in-situ stress is predicted using lateral pressure coefficient. The test results show that at depths ranging from 299-979m, the maximum horizontal principal stress is 5.33-30.12Mpa, the minimum horizontal principal stress is 4.94-23.11Mpa, the horizontal principal stress reach 30Mpa at maximum the depth of burial, indicating that the engineering stress filed is dominated by horizontal stress. Based on the In-situ stress data and different distinguish methods, rockburst and large deformation are predicted. The results show that In-situ stress magnitude in this area is classified as high level, and the direction of the maximum horizontal stress is NEE, In-situ stress orientation is conductive to stable of the tunnel. When the tunnel passes through the deep-burial and hard rock, the wall rock may happen rockburst; and the large deformation may happen when the tunnel pass through the weak rock. In order to avoid the disadvantage conditions, reasonable excavation method and safety support method should be adopted during tunnel excavating.

scholarly journals A Dual Fractal Poroelastic Model for Characterizing Fluid Flow in Fractured Coal Masses

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Guannan Liu ◽  
Dayu Ye ◽  
Feng Gao ◽  
Jishan Liu
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Coalbed Methane ◽  
Coupling Effect ◽  
In Situ Stress ◽  
Permeability Model ◽  
Fracture Length ◽  
Coal Deformation ◽  
Throat Diameter

In the process of coalbed methane exploitation, the fracture and pore structure is the key problem that affects the permeability of coalbed. At present, the coupling effect of fracture and pore structure and in situ stress is seldom considered in the study of coal seam permeability. In this paper, the fractal seepage model is coupled with coal deformation, and the adsorption expansion effect is considered. A multifield coupling model considering the influence of matrix and fracture structure is established. Then, the influence of pore structure parameters of main fracture on macropermeability is analyzed, including (1) fractal dimension of fracture length, (2) maximum fracture length, (3) fractal dimension of throat diameter, and (4) fractal dimension of throat bending. At the same time, the simulation results are compared with the results of Darcy’s uniform permeability model. The results show that the permeability calculated by the proposed model is significantly different from that calculated by the traditional cubic model. Under the action of in situ stress, when the porosity and other parameters remain unchanged, the macropermeability of coal is in direct proportion to the fractal dimension of coal fracture length, the fractal dimension of throat diameter, and the maximum fracture length and in inverse proportion to the fractal dimension of coal throat curvature.

Laboratory evaluation of K0 for overconsolidated clays

1991 ◽  
Vol 28 (5) ◽  
pp. 650-659 ◽  
Author(s):  
Vinod K. Garga ◽  
Mahbubul A. Khan
Keyword(s):  
Axial Stress ◽  
Axial Strain ◽  
Stress Path ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Laboratory Method ◽  
Laboratory Evaluation ◽  
Triaxial Apparatus ◽  
Overconsolidated Clays

Most of the laboratory testing methods available for the evaluation of in situ horizontal stresses are applicable to normally consolidated or lightly overconsolidated clays. This paper describes a new laboratory method for the determination of in situ horizontal stresses of heavily overconsolidated clays using a stress-path triaxial apparatus. The proposed method is based on the concept that if the radial stress exceeds the in situ horizontal stress, while maintaining the axial stress constant and equal to the in situ vertical effective stress, only then will the sample experience significant axial strain. The results obtained for undisturbed samples of an overconsolidated clay crust are found to be in agreement with some available methods. For verification of the applicability of the proposed method, K0 was determined for artificially prepared samples that had been subjected to known stress paths simulating field stress history. Key words: K0, overconsolidation, in situ stress, in situ test, clay crust, laboratory test.

scholarly journals In Situ Stress Prediction in Subsurface Rocks: An Overview and a New Method

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yushuai Zhang ◽  
Shangxian Yin ◽  
Jincai Zhang
Keyword(s):  
Horizontal Stress ◽  
In Situ Stress ◽  
New Method ◽  
Alternative Methods ◽  
Tensile Fracture ◽  
In Situ Stresses ◽  
Stress Estimation ◽  
Minimum Horizontal Stress ◽  
Polygon Method

Methods for determining in situ stresses are reviewed, and a new approach is proposed for a better prediction of the in situ stresses. For theoretically calculating horizontal stresses, horizontal strains are needed; however, these strains are very difficult to be obtained. Alternative methods are presented in this paper to allow an easier way for determining horizontal stresses. The uniaxial strain method is oversimplified for the minimum horizontal stress determination; however, it is the lower bound minimum horizontal stress. Based on this concept, a modified stress polygon method is proposed to obtain the minimum and maximum horizontal stresses. This new stress polygon is easier to implement and is more accurate to determine in situ stresses by narrowing the area of the conventional stress polygon when drilling-induced tensile fracture and wellbore breakout data are available. Using the generalized Hooke’s law and coupling pore pressure and in situ stresses, a new method for estimating the maximum horizontal stress is proposed. Combined it to the stress polygon method, a reliable in situ stress estimation can be obtained. The field measurement method, such as minifrac test, is also analyzed in different stress regimes to determine horizontal stress magnitudes and calibrate the proposed theoretical method. The proposed workflow combined theoretical methods to field measurements provides an integrated approach for horizontal stress estimation.

scholarly journals Evaluation of the Influence of In Situ Stress on the Stability of Mine Pit Walls: A Case Study of Songwe Mine

2021 ◽  
Vol 4 (2) ◽  
pp. p1
Author(s):  
Dyson Moses ◽  
Hideki Shimada ◽  
Takashi Sasaoka ◽  
Akihiro Hamanaka ◽  
Tumelo K. M Dintwe ◽  
...  
Keyword(s):  
Active Regions ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Slope Instability ◽  
Open Pit ◽  
Stress Regime ◽  
Tectonically Active ◽  
The Stability ◽  
The Impact

The investigation of the influence of in situ stress in Open Pit Mine (OPM) projects has not been accorded a deserved attention despite being a fundamental concern in the design of underground excavations. Hence, its long-term potential adverse impacts on pit slope performance are overly undermined. Nevertheless, in mines located in tectonically active settings with a potential high horizontal stress regime like the Songwe mine, the impact could be considerable. Thus, Using FLAC3D 5.0 software, based on Finite Difference Method (FDM) code, we assessed the role of stress regimes as a potential triggering factor for slope instability in Songwe mine. The results of the evaluated shearing contours and quantified strain rate and displacement values reveal that high horizontal stress can reduce the stability performance of the pit-wall in spite of the minimal change in Factor of Safety (FoS). Since mining projects have a long life span, it would be recommendable to consider “in situ stress-stability analyses” for OPM operations that would be planned to extend to greater depths and those located in tectonically active regions.

scholarly journals In Situ Stress and Stress Regime in the Onshore Part of the Northeast Java Basin

2021 ◽  
Vol 44 (2) ◽  
pp. 95-105
Author(s):  
Agus M. Ramdhan
Keyword(s):  
Petroleum Industry ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Stress Regime ◽  
Severe Erosion ◽  
Tectonically Active ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

In situ stress is importance in the petroleum industry because it will significantly enhance our understanding of present-day deformation in a sedimentary basin. The Northeast Java Basin is an example of a tectonically active basin in Indonesia. However, the in situ stress in this basin is still little known. This study attempts to analyze the regional in situ stress (i.e., vertical stress, minimum and maximum horizontal stresses) magnitude and orientation, and stress regime in the onshore part of the Northeast Java Basin based on twelve wells data, consist of density log, direct/indirect pressure test, and leak-off test (LOT) data. The magnitude of vertical (  and minimum horizontal (  stresses were determined using density log and LOT data, respectively. Meanwhile, the orientation of maximum horizontal stress  (  was determined using image log data, while its magnitude was determined based on pore pressure, mudweight, and the vertical and minimum horizontal stresses. The stress regime was simply analyzed based on the magnitude of in situ stress using Anderson’s faulting theory. The results show that the vertical stress ( ) in wells that experienced less erosion can be determined using the following equation: , where  is in psi, and z is in ft. However, wells that experienced severe erosion have vertical stress gradients higher than one psi/ft ( . The minimum horizontal stress ( ) in the hydrostatic zone can be estimated as, while in the overpressured zone, . The maximum horizontal stress ( ) in the shallow and deep hydrostatic zones can be estimated using equations: and , respectively. While in the overpressured zone, . The orientation of  is ~NE-SW, with a strike-slip faulting stress regime.

scholarly journals Numerical Simulation on Mesoscale Mechanism of Seepage in Coal Fractures by Fluid-Sloid Coupling Method

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Kai Si ◽  
Ruidong Peng ◽  
Leilei Zhao ◽  
Yan Zhao ◽  
Yaheng Zhu ◽  
...  
Keyword(s):  
Coupling Effect ◽  
Numerical Models ◽  
Seepage Flow ◽  
In Situ Stress ◽  
Low Velocity ◽  
Fracture Width ◽  
Gas Seepage ◽  
Fluid Seepage ◽  
Flow Flux

Trying to reveal the mechanism of gas seepage in coal is of significance to both safe mining and methane exploitation. A series of FEM numerical models were built up and studied so as to explore the mesoscale mechanism of seepage in coal fractures. The proposed mesoscale FEM model is a cube with micron fractures along three orthogonal directions. The distribution of velocity and pressure under fluid-solid coupling was obtained, and furthermore, the seepage flow flux and an equivalent permeability of the whole model were calculated. The influences of fracture width, outlet velocity, and in situ stress level on seepage were investigated. The numerical results show that nonlinear Darcy seepage occurs during low velocity zone. The permeability is increased linearly with the increasing of facture width and outlet velocity. A certain change of lateral coefficient of in situ stress also affects seepage. The permeability is increased sharply once deviating the isotropic spherical stress state, but it is no longer changed obviously after the lateral coefficient has been increased or decreased more than 20%. The mesoscale seepage mechanism in coal fractures has been preliminarily revealed by considering fluid-solid coupling effect, and the key factors influencing fluid seepage in coal fractures were demonstrated. The proposed methods and results will be helpful to the further study of seepage behaviour in coal with more complex structures.

Geomechanical characterization of a caprock-reservoir system in the Northern Appalachian Basin: Estimating spatial variation of in situ stress magnitude and orientation

2018 ◽  
Vol 6 (3) ◽  
pp. T759-T781 ◽  
Author(s):  
Samin Raziperchikolaee ◽  
Mark Kelley ◽  
Neeraj Gupta
Keyword(s):  
Mechanical Properties ◽  
Horizontal Stress ◽  
Appalachian Basin ◽  
In Situ Stress ◽  
Complex Nature ◽  
Well Log ◽  
Reservoir System ◽  
Maximum Horizontal Stress ◽  
Northern Appalachian Basin

Assessing the mechanical integrity of the caprock-reservoir system is necessary to evaluate the practical storage capacity for geologic [Formula: see text] storage. We used a combination of well-log and experimental data to estimate the statistical distribution (mean and variance) of rock mechanical properties of Cambrian-Ordovician strata within the Northern Appalachian region of Ohio and studied their heterogeneity throughout the study area. Empirical correlations between static-dynamic moduli of carbonate and sandstone formations of the Northern Appalachian Basin were developed. The state of stress (the orientation and magnitude of the maximum horizontal stress) for caprock and reservoir formations in the Cambrian-Ordovician sequence was determined at multiple well locations to understand the regional variability of these properties throughout the study area. The maximum horizontal stress ([Formula: see text]) azimuth was estimated from image logs for six wells and S-wave anisotropy data for five wells. The [Formula: see text] magnitude was estimated by analytical and numerical modeling of stresses around the wellbore calibrated to the occurrence of wellbore breakouts and drilling-induced fractures in three wells as a function of depth. The results of assessing the [Formula: see text] magnitude and stress regime in the caprock and reservoirs in the Cambrian-Ordovician sequence using rock mechanical data acquired in this study, well-log data, and drilling data indicate that both parameters vary throughout the study area. In this work, we determined how integrating different types of data from multiple wells allowed us to estimate mechanical properties and characterize the spatial variability (laterally and vertically) of in situ stress for Cambrian-Ordovician caprock and reservoirs throughout the study area. A combination of different methods — numerical, analytical, and stress polygon — is used to estimate the in situ stress magnitude, especially [Formula: see text], regionally on a formation-by-formation basis. The results of this work can be used to improve our understanding the complex nature of stress in the Northern Appalachian Basin.

Relation between coalbed permeability and in-situ stress magnitude for coalbed methane exploration in Jharia and Raniganj coalfields, India

2019 ◽  
Vol 38 (10) ◽  
pp. 800-807 ◽  
Author(s):  
Rima Chatterjee ◽  
Suman Paul ◽  
Prabir Kumar Pal
Keyword(s):  
Coalbed Methane ◽  
History Matching ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Gas Content ◽  
Major Influence ◽  
Reservoir Pressure ◽  
Horizontal Drilling ◽  
Cbm Production

India is among the top five countries in the world in terms of proven coal reserves and coal production. As such, significant potential exists for commercial recovery of coalbed methane (CBM). Two coalfields, Jharia and Raniganj, located in eastern India are currently under development for CBM. This paper describes work done to determine coal seam properties, ambient stress conditions, and effects of depletion at these coalfields that influence CBM production. Coalbed permeability is a parameter that has a major influence on CBM production. Other influences include in-situ stress direction, gas content, and the application of suitable stimulation techniques. A robust methodology is required to determine both initial coalbed permeability and its relation to in-situ horizontal stress magnitudes. Coalbed permeability at the Jharia and Raniganj coalfields was estimated from porosity and known cleat spacing. Initial permeability of major coalbeds was correlated with effective horizontal stress, yielding satisfactory to very good exponential fit using data from Raniganj and Jharia wells. Acoustic televiewer image-logging tool measurements in a single well in the Jharia coalfield were used to infer a maximum horizontal stress orientation between N25°W and N25°E. Reservoir-pressure-dependent permeability models are presented for coalbeds under uniaxial strain condition. The coalbed permeability is dominated by the existing effective horizontal stresses normal to the cleats. Two prospective coal seams from Jharia have been identified through assessment of the response of horizontal stress to the decline of CBM reservoir pressure. Coalbed permeability increases with the drawdown of reservoir pressure and is exponentially related to the change of effective horizontal stress during reservoir depletion. The results of this study are to be used for production history matching for wells in Jharia and to determine optimal horizontal drilling directions for increased CBM production.

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