A Workflow to Derive Rock Mechanics Correlations and Stress Profile by the Integration of Dynamic and Static Formation Evaluation Data

2021 ◽  
Author(s):  
Ammar Qatari
Keyword(s):  
Rock Mechanics ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Earth Model ◽  
Stress Profile ◽  
Formation Evaluation ◽  
Static Data ◽  
Mechanical Earth Model ◽  
Low Uncertainty ◽  
Formation Specific

Abstract Rock mechanics utilizes empirical formulas which are based on studies of certain environments. The shortcoming of such criteria is having estimations of rock physical properties with high uncertainty and not field/formation specific. The objective of this paper is to apply a core-log integration to convert dynamic mechanical properties captured from formation evaluation logs and calibrate them with core static data to generate a continuous profile of data with low uncertainty and generate correlations applicable to the specific physical environment. To obtain proper rock mechanical correlations, building a mechanical earth model (MEM) calibrated with core data and stimulation data is essential. Multiple wells drilled in a certain sandstone field with rock mechanical physical tests are analyzed. Multi-arm caliber data is also put in use to establish knowledge about in-situ stress directions. The procedure starts with gathering and filtering acoustic slowness & shear, formation pressure, density, and oriented multi-arm caliper logs. Next, calibration of dynamic to core static mechanical data collected in the lab is established. The geomechanical analysis includes an understanding of the state of stresses in a chosen reservoir along with rock elastic and failure properties. The complied data is then integrated using different workflows to develop Mechanical Earth Model (MEM). The intended rock mechanics correlations include elastic constants (Young's Modulus and Poisson's ratio), and rock failure parameters. Once Mechanical Earth Model (MEM) is established, dynamic logging data and core static data are correlated to produce key rock mechanics elements that are field and formation specific. The correlations include Young's Modulus, Poisson's Ratio, Unconfined Compressive Strength (UCS) correlation, and Friction Angle (FANG) correlation. A range of each rock mechanic element is also highlighted for the specific environment showcasing the limits expected for collapse and fracture. Ultimately, stress profile is generated with low uncertainty highlighting magnitudes of maximum and minimum horizontal stresses along with the given interval.

Experimental Study of Rock Mechanics Parameters in the Elastic Deformation Stage at Different Strain Rates

2012 ◽  
Vol 170-173 ◽  
pp. 1130-1133 ◽  
Author(s):  
Chang Yu Liang ◽  
Xiao Li ◽  
Shou Ding Li ◽  
Jian Ming He ◽  
Sheng Xing Wang ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Elastic Deformation ◽  
Rock Mechanics ◽  
Poisson’S Ratio ◽  
Strain Curve ◽  
Poisson's Ratio ◽  
Strain Rates ◽  
Deformation Stage ◽  
Engineering Investigation ◽  
Fracture Compression

Rock mechanics parameters are important during engineering investigation, design and construction, especially elastic modulus and Poisson’s ratio. According to the end point of initial fracture compression stage and elastic proportional point of stress-strain curve, the elastic deformation stage was determined; then the modulus and Poisson's ratio of rock at different strain rates were calculated by use of the average method. The results indicate that elastic modulus of rock increases with increasing strain rates; Poisson's ratios are scattered, but also present increasing trend.

An Improved Method for Recovering Residual Stress From Strain Measurements in Cylinders and Rings

2006 ◽  
Author(s):  
Anthony P. Parker
Keyword(s):  
Residual Stress ◽  
Poisson’S Ratio ◽  
Traditional Method ◽  
Radial Stress ◽  
Hoop Stress ◽  
Numerical Solutions ◽  
Axial Stress ◽  
Poisson's Ratio ◽  
Stress Profile ◽  
Residual Stress Field

The traditional method for determining the residual stress from experimental strain readings in axisymmetric configurations can produce large discrepancies in stress predictions, particularly radial stress. By numerical calculation of autofrettage residual stress in a long thick cylinder and subsequent numerical modeling of release of axial stress during the cutting of a short ring sample, a potential preexisting radial and hoop residual stress field is calculated. These stress values are converted to radial and hoop strains at a number of discrete radial locations. Numerical strain values are then randomized to enforce a standard deviation some 25% higher than that for a typical experimental procedure. Pairs of randomized, discrete strain values are used to predict associated residual stresses using the traditional method. This produces wide scattering of predicted stress values, particularly radial stress, and showed high sensitivity to assumed Poisson’s ratio. A simple, alternative strain-stress analysis procedure (ASSAP) is proposed. ASSAP enforces equilibrium requirements and essential stress free boundary conditions at the bore. ASSAP is shown to improve prediction of radial residual stress by around an order of magnitude in the near-bore region, and to effectively eliminate the sensitivity to Poisson’s ratio. The predicted radial stress profile is of sufficient quality to define the associated hoop stress profile. The predicted radial and hoop stress profiles are in close agreement with the original numerical solutions for the ring. Numerical and ‘recovered’ bore hoop stresses are within 1.4%. This work also demonstrates a significant limitation of methods that involve the cutting of axially short ring samples from a long, autofrettaged cylinder. Release of axial stress during cutting creates a reduction in compressive bore hoop stress. Such a discrepancy would be very significant if ring, rather than long-cylinder, values were used in fatigue lifetime calculations.

Multiparameter 𝓁1 norm waveform fitting: Interpretation of Gulf of Mexico reflection seismograms

Geophysics ◽  
1999 ◽  
Vol 64 (4) ◽  
pp. 1023-1035 ◽  
Author(s):  
Hugues A. Djikpéssé ◽  
Albert Tarantola
Keyword(s):  
Gulf Of Mexico ◽  
Poisson’S Ratio ◽  
Seismic Refraction ◽  
Synthetic Seismograms ◽  
Poisson's Ratio ◽  
Inversion Method ◽  
Earth Model ◽  
Additional Parameter ◽  
Shear Properties ◽  
Waveform Fitting

Estimation of the elastic properties of the crust from surface seismic recordings is of great importance for the understanding of lithology and for the detection of mineral resources. Although in marine reflection experiments only P-waves are recorded, information on shear properties of the medium is contained in multioffset reflection seismograms. Being able to retrieve both dilatational and shear properties gives stronger constraints on the lithology. It is therefore desirable to recover isotropic elastic parameters from multioffset seismograms. Unfortunately, most classical waveform fitting methods used for extracting shear properties of the subsurface are based on a 1-D earth model assumption and on linear approximations of the wave equations. In this paper, a 2.5-D elastic waveform inversion method is used to extract the variations of acoustic impedance and Poisson’s ratio from marine multioffset reflection seismograms collected in the Gulf of Mexico area. A complete seismic profile is interpreted, including complex physical phenomena apparent in the data, such as unconsolidated sediment reflections and seismic refraction events. The amplitude of the reflections cannot be explained by one parameter related to the dilatational properties (P-impedance) only, when trying to minimize the least absolute fit between observed and synthetic seismograms. When adding an additional parameter related to shear properties (Poisson’s ratio), the fit between observed and synthetic seismograms improves. The resulting 2-D models of P-impedance and Poisson’s ratio contrasts are anticorrelated almost everywhere in depth, except where hydrocarbons are present. The estimation of physical P-impedance and Poisson’s ratio models by a full waveform fitting allows lithology characterization and, therefore, the delineation of a shale‐over‐gas sand reservoir.

scholarly journals Experimental Study on Rock Mechanics Parameters-A Case of the Sand Conglomerate Reservoir in M2 Well Area

2018 ◽  
Vol 53 ◽  
pp. 03067 ◽  
Author(s):  
Shi Shanzhi ◽  
Zhao Chaoneng ◽  
Liu Hai ◽  
Ding Kun ◽  
Li Jie ◽  
...  
Keyword(s):  
Rock Mechanics ◽  
Modulus Of Elasticity ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Poor Correlation ◽  
S Wave ◽  
Rock Samples ◽  
Static Modulus ◽  
Static Mechanical ◽  
Static Modulus Of Elasticity

This paper presents the acoustic characteristics tested on 20 groups of cores (20 vertical samples and 60 horizontal samples) from the sand conglomerate reservoir in Baikouquan and lower Wuerhe Formation (two wells in the M2 well area). The average values of dynamic modulus of elasticity and Poisson's ratio of rocks from Baikouquan Formation are 32.1 GPa and 0.2055 respectively, and those of lower Wuerhe Formation are 28.4 GPa and 0.2425 respectively. The three axis rock mechanics test device is used to test the stress-strain curves of the corresponding rock samples. The sand-conglomerate samples in this area generally have good brittleness characteristics; the static modulus of elasticity and Poisson's ratio of the corresponding rock samples are 13.7GPa and 0.2858 respectively, and those of rocks from lower Wuerhe Formation are 14.9GPa and 0.2565, respectively. In general, there is a good correlation between P&S wave velocity, and poor correlation in the dynamic and static mechanical parameters.

The Model for Calculating Elastic Modulus and Poisson's Ratio of Coal Body

2013 ◽  
Vol 6 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Ai Chi ◽  
Li Yuwei
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Fractured Rock ◽  
Rock Block ◽  
Poisson's Ratio ◽  
Linear Elastic ◽  
Study Results ◽  
The Face ◽  
Block Face ◽  
Coal Rock

Coal body is a type of fractured rock mass in which lots of cleat fractures developed. Its mechanical properties vary with the parametric variation of coal rock block, face cleat and butt cleat. Based on the linear elastic theory and displacement equivalent principle and simplifying the face cleat and butt cleat as multi-bank penetrating and intermittent cracks, the model was established to calculate the elastic modulus and Poisson's ratio of coal body combined with cleat. By analyzing the model, it also obtained the influence of the parameter variation of coal rock block, face cleat and butt cleat on the elastic modulus and Poisson's ratio of the coal body. Study results showed that the connectivity rate of butt cleat and the distance between face cleats had a weak influence on elastic modulus of coal body. When the inclination of face cleat was 90°, the elastic modulus of coal body reached the maximal value and it equaled to the elastic modulus of coal rock block. When the inclination of face cleat was 0°, the elastic modulus of coal body was exclusively dependent on the elastic modulus of coal rock block, the normal stiffness of face cleat and the distance between them. When the distance between butt cleats or the connectivity rate of butt cleat was fixed, the Poisson's ratio of the coal body initially increased and then decreased with increasing of the face cleat inclination.

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