Predicting the azimuth of in-situ horizontal stress by integrating multiple discipline data

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.

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Predicting the azimuth of natural fractures and in-situ horizontal stress: A case study from Sichuan Basin, China

Geophysics ◽

10.1190/geo2020-0829.1 ◽

2021 ◽

pp. 1-97

Author(s):

kai lin ◽

Bo Zhang ◽

Jianjun Zhang ◽

Huijing Fang ◽

Kefeng Xi ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Seismic Data ◽

Sichuan Basin ◽

Horizontal Stress ◽

Seismic Attributes ◽

Seismic Events ◽

Natural Fractures ◽

Microseismic Data ◽

Maximum Horizontal Stress

The azimuth of fractures and in-situ horizontal stress are important factors in planning horizontal wells and hydraulic fracturing for unconventional resources plays. The azimuth of natural fractures can be directly obtained by analyzing image logs. The azimuth of the maximum horizontal stress σH can be predicted by analyzing the induced fractures on image logs. The clustering of micro-seismic events can also be used to predict the azimuth of in-situ maximum horizontal stress. However, the azimuth of natural fractures and the in-situ maximum horizontal stress obtained from both image logs and micro-seismic events are limited to the wellbore locations. Wide azimuth seismic data provides an alternative way to predict the azimuth of natural fractures and maximum in-situ horizontal stress if the seismic attributes are properly calibrated with interpretations from well logs and microseismic data. To predict the azimuth of natural fractures and in-situ maximum horizontal stress, we focus our analysis on correlating the seismic attributes computed from pre-stack and post-stack seismic data with the interpreted azimuth obtained from image logs and microseismic data. The application indicates that the strike of the most positive principal curvature k1 can be used as an indicator for the azimuth of natural fractures within our study area. The azimuthal anisotropy of the dominant frequency component if offset vector title (OVT) seismic data can be used to predict the azimuth of maximum in-situ horizontal stress within our study area that is located the southern region of the Sichuan Basin, China. The predicted azimuths provide important information for the following well planning and hydraulic fracturing.

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A Novel Method and its Application to Define Maximum Horizontal Stress and Stress Path

10.2118/204148-ms ◽

2021 ◽

Author(s):

Jianguo Zhang ◽

Karthik Mahadev ◽

Stephen Edwards ◽

Alan Rodgerson

Keyword(s):

Fracture Initiation ◽

Stress Path ◽

Horizontal Stress ◽

Geomechanical Model ◽

Breakdown Pressure ◽

In Situ Stresses ◽

Fracture Closure ◽

Minimum Horizontal Stress ◽

Maximum Horizontal Stress

Abstract Maximum horizontal stress (SH) and stress path (change of SH and minimum horizontal stress with depletion) are the two most difficult parameters to define for an oilfield geomechanical model. Understanding these in-situ stresses is critical to the success of operations and development, especially when production is underway, and the reservoir depletion begins. This paper introduces a method to define them through the analysis of actual minifrac data. Field examples of applications on minifrac failure analysis and operational pressure prediction are also presented. It is commonly accepted that one of the best methods to determine the minimum horizontal stress (Sh) is the use of pressure fall-off analysis of a minifrac test. Unlike Sh, the magnitude of SH cannot be measured directly. Instead it is back calculated by using fracture initiation pressure (FIP) and Sh derived from minifrac data. After non-depleted Sh and SH are defined, their apparent Poisson's Ratios (APR) are calculated using the Eaton equation. These APRs define Sh and SH in virgin sand to encapsulate all other factors that influence in-situ stresses such as tectonic, thermal, osmotic and poro-elastic effects. These values can then be used to estimate stress path through interpretation of additional minifrac data derived from a depleted sand. A geomechanical model is developed based on APRs and stress paths to predict minifrac operation pressures. Three cases are included to show that the margin of error for FIP and fracture closure pressure (FCP) is less than 2%, fracture breakdown pressure (FBP) less than 4%. Two field cases in deep-water wells in the Gulf of Mexico show that the reduction of SH with depletion is lower than that for Sh.

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Interpretation of in situ horizontal stress from self-boring pressuremeter tests in sands via cavity pressure less than limit pressure: a numerical study

Environmental Earth Sciences ◽

10.1007/s12665-017-6660-3 ◽

2017 ◽

Vol 76 (9) ◽

Author(s):

Mohammad Mehdi Ahmadi ◽

Ehsan Keshmiri

Keyword(s):

Numerical Study ◽

Horizontal Stress ◽

Cavity Pressure ◽

Limit Pressure

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.501-504.1766 ◽

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.

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