Casing Shear Deformation Based on Micro Seismic Data

2019 ◽  
Vol 944 ◽  
pp. 1011-1019
Author(s):  
Yi Jin Zeng ◽  
Yan Xi ◽  
Shi Dong Ding ◽  
Jun Li ◽  
Xin Yu Hao ◽  
...  
Keyword(s):  
Shear Deformation ◽  
Seismic Data ◽  
Influential Factors ◽  
Natural Fracture ◽  
Well Trajectory ◽  
Cement Sheath ◽  
Dip Angle ◽  
Casing Deformation ◽  
And Control ◽  
Slip Distance

Casing shear deformation, which is caused by fault slipping, is the main morphology of casing deformation occurred during multistage fracturing. In order to determine the relationship between fault slipping and casing shear deformation, the micro seismic data collected from engineering field which can reflect the reality of the formations was analyzed. A new numerical model was developed, and the influential factors on casing shear deformation were studied, including the fault slip distance of lower and upper interface, fault dip angle, the thickness of cement sheath and casing. The results of research shows that: (1) Fault is easily activated by fracturing, which was the main reason of casing shear deformation; (2) The greater the fault dip angel, the slip distance, the greater the casing shear deformation; (3) Increasing the wall thickness of casing or cement sheath is beneficial to decrease the degree of the shear deformation; (4) Two ways can be used to avoid and control the casing shear deformation, one is keeping the designed horizontal segment of well trajectory keep away from fracture-developed area, or be parallel to natural fracture, the other is using stage cementing technology. Research results can provide important reference for design and control of casing integrity during multistage fracturing in shale gas wells.

scholarly journals Mechanisms and Influence of Casing Shear Deformation near the Casing Shoe, Based on MFC Surveys during Multistage Fracturing in Shale Gas Wells in Canada

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 372 ◽  
Author(s):  
Yan Xi ◽  
Jun Li ◽  
Gonghui Liu ◽  
Jianping Li ◽  
Jiwei Jiang
Keyword(s):  
Shear Deformation ◽  
Shale Gas ◽  
Coupling Effect ◽  
Poisson Ratio ◽  
Constitutive Relations ◽  
Prediction Method ◽  
Measurement Results ◽  
Inner Diameter ◽  
Cement Sheath ◽  
Slip Distance

Casing shear deformation has become a serious problem in the development of shale gas fields, which is believed to be related to fault slipping caused by multistage fracturing, and the evaluation of the reduction of a casing’s inner diameter is key. Although many fault slipping models have been published, most of them have not taken the fluid-solid-heat coupling effect into account, and none of the models could be used to calculate the reduction of a casing’s inner diameter. In this paper, a new 3D finite element model was developed to simulate the progress of fault slipping, taking the fluid-solid-heat coupling effect during fracturing into account. For the purpose of increasing calculation accuracy, the elastoplastic constitutive relations of materials were considered, and the solid-shell elements technique was used. The reduction of the casing’s inner diameter along the axis was calculated and the calculation results were compared with the measurement results of multi-finger caliper (MFC) surveys. A sensitivity analysis was conducted, and the influences of slip distance, casing internal pressure, thickness of production and intermediate casing, and the mechanical parameters of cement sheath on the reduction of a casing’s inner diameter in the deformed segment were analyzed. The numerical analysis results showed that decreasing the slip distance, maintaining high pressure, decreasing the Poisson ratio of cement sheath, and increasing casing thickness were beneficial to protect the integrity of the casing. The numerical simulation results were verified by comparison to the shape of MFC measurement results, and had an accuracy up to 90.17%. Results from this study are expected to provide a better understanding of casing shear deformation, and a prediction method of a casing’s inner diameter after fault slipping in multistage fracturing wells.

Stochastic discrete fracture network modeling in shale reservoirs via integration of seismic attributes and petrophysical data

2021 ◽  
pp. 1-50
Author(s):  
Yongchae Cho
Keyword(s):  
Seismic Data ◽  
Stochastic Approach ◽  
Fracture Network ◽  
Natural Fracture ◽  
Well Logs ◽  
Fracture Model ◽  
Well Log ◽  
Discrete Fracture ◽  
Discrete Fracture Network Modeling ◽  
Fracture Network Modeling

The prediction of natural fracture networks and their geomechanical properties remains a challenge for unconventional reservoir characterization. Since natural fractures are highly heterogeneous and sub-seismic scale, integrating petrophysical data (i.e., cores, well logs) with seismic data is important for building a reliable natural fracture model. Therefore, I introduce an integrated and stochastic approach for discrete fracture network modeling with field data demonstration. In the proposed method, I first perform a seismic attribute analysis to highlight the discontinuity in the seismic data. Then, I extrapolate the well log data which includes localized but high-confidence information. By using the fracture intensity model including both seismic and well logs, I build the final natural fracture model which can be used as a background model for the subsequent geomechanical analysis such as simulation of hydraulic fractures propagation. As a result, the proposed workflow combining multiscale data in a stochastic approach constructs a reliable natural fracture model. I validate the constructed fracture distribution by its good agreement with the well log data.

Potential Sealing Effects of Permanent Casing Deformation

2020 ◽  
Author(s):  
Sohrab Gheibi ◽  
Sigbjørn Sangesland ◽  
Lucas C. Sevillano ◽  
Martin Horák
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Oil And Gas ◽  
Permanent Deformation ◽  
External Pressure ◽  
Positive Role ◽  
Impermeable Barrier ◽  
Cement Sheath ◽  
Casing Deformation ◽  
Cement Plug

Abstract Permanent plugging and abandonment (P&A) of oil- and gas wells requires proper sealing between the formation and the casing as well as proper sealing inside the casing. The cement sheath in the annulus is intended to function as an “impermeable” barrier. Typically, shrinkage of cement sheath takes place when the cement sets and a microannulus (MA) may be formed. In addition, cyclic pressure and temperature variations may result in cracks and debonding of the cement sheath. This paper investigates the possibility of improved cement sealing imposed by permanent deformation of the casing, thus providing a mechanical compression force to the cement and thus closing the MA when performing P&A. Two experimental setups were designed in this context. The first setup termed casing/cement plug test, where the casing is contracted by an external pressure and simultaneous measurement of the flow rate through the setup. The second setup is termed casing/cement annular test where the casing is internally pressurized while the gas flow rate is measured. Nonlinear finite element analyses were carried out to simulate the two test setups. The numerical results showed an acceptable agreement with the observations in the lab. The second setup was not tested in the lab, but simulated using the FEM code. The numerical analyses indicated that the same concept of casing permanent deformation is also relevant for the annular test. It is shown that the micro-annulus formed due to cycles of pressurization/depressurization as a result of inelastic deformations in the cement can be repaired by inducing permanent deformation in the casing to some extent. Finally, we concluded that permanent casing deformation could play a positive role in favour of closing the micro-annuli in P&A operations.

Can fracture orientation and intensity be detected from seismic data? Woodford Formation, Anadarko Basin, Oklahoma investigation

2019 ◽  
Vol 38 (2) ◽  
pp. 144-150 ◽  
Author(s):  
Marianne Rauch-Davies ◽  
David Langton ◽  
Michael Bradshaw ◽  
Allon Bartana ◽  
Dan Kosloff ◽  
...  
Keyword(s):  
Seismic Data ◽  
Subsurface Layer ◽  
Azimuthal Velocity ◽  
Natural Fracture ◽  
Woodford Shale ◽  
Data Set ◽  
Anadarko Basin ◽  
Fracture Orientation ◽  
Anisotropic Elastic ◽  
Elastic Simulation

With readily available wide-azimuth, onshore, 3D seismic data, the search for attributes utilizing the azimuthal information is ongoing. Theoretically, in the presence of ordered fracturing, the seismic wavefront shape changes from spherical to nonspherical with the propagation velocity being faster parallel to the fracturing and slower perpendicular to the fracture direction. This concept has been adopted and is used to map fracture direction and density within unconventional reservoirs. More specifically, azimuthal variations in normal moveout velocity or migration velocity are often used to infer natural fracture orientation. Analyses of recent results have called into question whether azimuthal velocity linked to intrinsic azimuthal velocity variations can actually be detected from seismic data. By use of 3D orthorhombic anisotropic elastic simulation, we test whether fracture orientation and intensity can be detected from seismic data. We construct two subsurface models based on interpreted subsurface layer structure of the Anadarko Basin in Oklahoma. For the first model, the material parameters in the layers are constant vertically transverse isotropic (VTI) in all intervals. The second model was constructed the same way as the base model for all layers above the Woodford Shale Formation. For the shale layer, orthorhombic properties were introduced. In addition, a thicker wedge layer was added below the shale layer. Using the constructed model, synthetic seismic data were produced by means of 3D anisotropic elastic simulation resulting in two data sets: VTI and orthorhombic. The simulated data set was depth migrated using the VTI subsurface model. After migration, the residual moveouts on the migrated gathers were analyzed. The analysis of the depth-migrated model data indicates that for the typical layer thicknesses of the Woodford Shale layer in the Anadarko Basin, observed and modeled percentage of anisotropy and target depth, the effect of intrinsic anisotropy is too small to be detected in real seismic data.

Quantitative Prediction of Radon Concentration at Wellhead in Shale Gas Development

SPE Journal ◽  
2016 ◽  
Vol 22 (01) ◽  
pp. 235-243 ◽  
Author(s):  
Wei Tian ◽  
Xingru Wu ◽  
Tong Shen ◽  
Zhenyu Zhang ◽  
Sumeer Kalra
Keyword(s):  
Natural Gas ◽  
Numerical Simulations ◽  
Shale Gas ◽  
Radon Concentration ◽  
Marcellus Shale ◽  
Gas Production ◽  
Influential Factors ◽  
Natural Fracture ◽  
Quantitative Prediction ◽  
Radon Gas

Summary Hydraulic fracturing has been applied as an effective method to increase gas production from shale formations; however, this method has also raised concerns about its adverse impacts on environment. For example, in the Marcellus shale formation, some measured radon-gas concentrations exceeded the safe standard. Therefore, it is important to quantitatively evaluate radon concentration from fractured wells. However, existing researches have not successfully conducted a systematic and predictive study on the relationship between shale gas production and radon concentration at the wellhead of a hydraulically fractured well. To address this issue and quantitatively determine the radon concentration, we present the mechanisms of radon-gas generation and releasing, and conducted numerical simulations on its transport process in the subsurface formation system. The concentration of radon in produced gas is related with the original sources where the natural gas is extracted. Radon, generated from the radium alpha decay process, is trapped in pore spaces before the reservoir development. With the fluid flowing through the subsurface network, released radon will move to surface with the produced streams such as natural gas and flowback water. Our study shows that the radon concentration at wellhead could be significant. Influential factors such as natural-fracture-network properties, formation petrophysical parameters, and fracture dimension are investigated with sensitivity studies through numerical simulations. Analysis results suggest that radon wellhead concentration is strongly related with production rate. Thus, careful production design and protection are necessary to reduce radon hazard regarding the public and environmental impact.

Application of Research of the Relationship between Ground Stress and Fractures in the Trajectory Optimization of Horizontal Wells

2013 ◽  
Vol 765-767 ◽  
pp. 300-306
Author(s):  
Hui Zhang ◽  
Fang Jun Ou ◽  
Guo Qing Yin ◽  
Jing Bing Yi ◽  
Fang Yuan ◽  
...  
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Trajectory Optimization ◽  
Horizontal Wells ◽  
Wellbore Stability ◽  
Natural Fracture ◽  
Fracture System ◽  
Well Trajectory ◽  
The Stability ◽  
The Relationship

From the perspective of improving single well production and wellbore stability, stress field and natural fractures are the factors which have to be taken into account in the development of horizontal wells of the complex carbonate oil and gas fields in Kuqa piedmont and platform-basin transitional area. On the one hand, as the present stress field is the key factor to control fracture permeability, the trajectory of horizontal wells should pass through fracture system with good permeability as much as possible, being conducive to the effective stimulation of the reservoir. On the other hand, at the state of specific stress, the stability of well trajectory varies with directions. Therefore, before drilling horizontal wells, it is necessary to fully analyze the quantitative relationship between the present stress state and natural fracture occurrence and mechanical characteristics, etc., to optimize and determine a well trajectory conducive to high yield and wellbore stability. In this study, firstly, the fundamental principles for evaluating the present stress state and analyzing the relationship between the stress and fractures were described. Then based on the relationship between them, the occurrence and longitudinal positions of permeability fractures were analyzed. Apart from that, the stability index and fracture opening pressure distribution of wells in different directions at given stress state and fracture system were also analyzed. Finally, the optimization scheme for trajectory of horizontal wells under complex conditions was discussed with three aspects taken into account, i.e. best drilling in permeability fractures, wellbore stability and drilled reservoir stimulation.

Analysis Of Concrete Tunnel Frameworks Subject To Fault Removal

Think India ◽  
2019 ◽  
Vol 22 (3) ◽  
pp. 204-211
Author(s):  
Geddam Teja ◽  
A.P.Nagendra Babu
Keyword(s):  
Near Field ◽  
Influential Factors ◽  
Effective Characteristics ◽  
Finite Element Program ◽  
Element Program ◽  
Pulse Type ◽  
Final Response ◽  
Shear Distortion ◽  
Dip Angle ◽  
Earthquake Fault Rupture

An earthquake fault rupture generates two types of ground motion: permanent quasi-static dislocations and dynamic oscillations, characterized by strong pulses. This study investigates tunnel’s response to two different conditions using a 2D finite element program; the first one has a static dislocation corresponding to different earthquake magnitudes, while the second combines near-field seismic motions with three specific peak ground accelerations along with permanent dislocations. The impulsive ground motions affect the lining response further to other influential factors such as fault type and dip angle, making changes in sectional forces, displacement, and shear distortion of the lining. Moreover, pulse intensity, period, and frequency content are effective characteristics of impulsive motions that change in final response of the lining, subjected to subsequent static dislocations. Based on the second condition, at low PGAs, the pulse type is more effective to final response of the lining, due to forward and backward momentum specifications in impulsive motions. For earthquakes with high PGA and larger values in nearfield parameters, both the pulse type and period are effective. The tunnel displacement increases at PGAs as large as 0.7 and 1g, unlike the low PGA as large as 0.35g, because of increasing soil stress and plastic strain, respectively.

Seismic data display and reflection perceptibility

Geophysics ◽  
1981 ◽  
Vol 46 (2) ◽  
pp. 106-120 ◽  
Author(s):  
Frank J. Feagin
Keyword(s):  
Image Enhancement ◽  
Seismic Data ◽  
Random Noise ◽  
Variable Density ◽  
Digital Data ◽  
Gray Scale ◽  
Seismic Section ◽  
Low Contrast ◽  
Wide Range ◽  
Dip Angle

Relatively little attention has been paid to the final output of today’s sophisticated seismic data processing procedures—the seismic section display. We first examine significant factors relating to those displays and then describe a series of experiments that, by varying those factors, let us specify displays that maximize interpreters’ abilities to detect reflections buried in random noise. The study.—From psychology of perception and image enhancement literature and from our own research, these conclusions were reached: (1) Seismic reflection perceptibility is best for time scales in the neighborhood of 1.875 inches/sec because, for common seismic frequencies, the eye‐brain spatial frequency response is a maximum near that value. (2) An optimized gray scale for variable density sections is nonlinearly related to digital data values on a plot tape. The nonlinearity is composed to two parts (a) that which compensates for nonlinearity inherent in human perception, and (b) the nonlinearity required to produce histogram equalization, a modern image enhancement technique. The experiments.—The experiments involved 37 synthetic seismic sections composed of simple reflections embedded in filtered random noise. Reflection signal‐to‐noise (S/N) ratio was varied over a wide range, as were other display parameters, such as scale, plot mode, photographic density contrast, gray scale, and reflection dip angle. Twenty‐nine interpreters took part in the experiments. The sections were presented, one at a time, to each interpreter; the interpreter then proceeded to mark all recognizable events. Marked events were checked against known data and errors recorded. Detectability thresholds in terms of S/N ratios were measured as a function of the various display parameters. Some of the more important conclusions are: (1) With our usual types of displays, interpreters can pick reflections about 6 or 7 dB below noise with a 50 percent probability. (2) Perceptibility varies from one person to another by 2.5 to 3.0 dB. (3) For displays with a 3.75 inch/sec scale and low contrast photographic paper (a common situation), variable density (VD) and variable area‐wiggly trace (VA‐WT) sections are about equally effective from a perceptibility standpoint. (4) However, for displays with small scales and for displays with higher contrast, variable density is significantly superior. A VD section with all parameters optimized shows about 8 dB perceptibility advantage over an optimized VA‐WT section. (5) Detectability drops as dip angle increases. VD is slightly superior to VA‐WT, even at large scales, for steep dip angles. (6) An interpreter gains typically about 2 dB by foreshortening, although there is a wide variation from one individual to another.

Sign in / Sign up

Export Citation Format

Share Document