scholarly journals Wellbore stability analysis based on the stress model around boreholes

2018 ◽  
Vol 1 (T5) ◽  
pp. 290-301
Author(s):  
Khanh Quang Do ◽  
Nam Nguyen Hai Le ◽  
Quang Trong Hoang ◽  
Huy Xuan Nguyen
Keyword(s):  
Stability Analysis ◽  
Oil And Gas ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Stress Model ◽  
Gas Drilling ◽  
Wellbore Pressure ◽  
Tensile Fractures ◽  
Matlab Programming

Wellbore stability analysis plays an important role in the oil and gas drilling. Instability problems during the drilling phase are often the results of a combination of both mechanical and chemical effects. This study aims to assess the mechanical wellbore stability based on the stress model around boreholes. The development of the stress model around boreholes, which is associated with the in-situ stresses, rock properties as well as the wellbore pressure and configuration, are presented. It could visualize the stress distribution around an arbitratily orientated wellbore. Next, lower hemisphere diagrams are presented to demonstrate the wellbore pressure required to initiate borehole tensile and compressive failures. A program for the risk analysis of wellbore (RAoWB) is designed and developed by the Matlab programming language to describe and analyse the risk diagrams of the drilling induced tensile fractures (DITFs) and breakouts (BOs). They help to choice the optimum wellbore trajectories for well planning, as well as to predict the wellbore instabilities caused by inappropriate wellbore pressures.

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

SPE Journal ◽  
2018 ◽  
Vol 23 (04) ◽  
pp. 1019-1038 ◽  
Author(s):  
Feifei Zhang ◽  
Yongfeng Kang ◽  
Zhaoyang Wang ◽  
Stefan Miska ◽  
Mengjiao Yu ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Pore Pressure ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Pressure Oscillations ◽  
Deepwater Drilling ◽  
Wellbore Pressure ◽  
Operating Window ◽  
Safe Operating

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.

APPLICATION OF GUIDELINE CHARTS IN DECISIONMAKING ON WELL TRAJECTORY AND MUD WEIGHT PROGRAM

2001 ◽  
Vol 41 (1) ◽  
pp. 609
Author(s):  
X. Chen ◽  
C.P. Tan ◽  
C.M. Haberfield
Keyword(s):  
Stability Analysis ◽  
Case Studies ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Material Strength ◽  
Stress Regime ◽  
Wellbore Instability ◽  
Well Trajectory

To prevent or minimise wellbore instability problems, it is critical to determine the optimum wellbore profile and to design an appropriate mud weight program based on wellbore stability analysis. It is a complex and iterative decisionmaking procedure since various factors, such as in-situ stress regime, material strength and poroelastic properties, strength and poroelastic anisotropies, initial and induced pore pressures, must be considered in the assessment and determination.This paper describes the methodology and procedure for determination of optimum wellbore profile and mud weight program based on rock mechanics consideration. The methodology is presented in the form of guideline charts and the procedure of applying the methodology is described. The application of the methodology and procedure is demonstrated through two field case studies with different in-situ stress regimes in Australia and Indonesia.

Elasto-Plastic Analysis on Wellbore Stability under the Condition of Permeation

2010 ◽  
Vol 156-157 ◽  
pp. 1292-1296
Author(s):  
Jian Bing Sang ◽  
Su Fang Xing ◽  
Chen Hua Lu ◽  
Wen Jia Wang ◽  
Bo Liu
Keyword(s):  
Porous Medium ◽  
Failure Criterion ◽  
Oil And Gas ◽  
Pressure Effect ◽  
Wellbore Stability ◽  
Gas Drilling ◽  
Plastic Analysis ◽  
Key Factor ◽  
Drilling Operations ◽  
Distribution Of Stress

Maintaining the wellbore stability is a key factor for oil and gas drilling operations. In this paper, sock is regarded porous medium. Crevice pressure, effect of permeation and SD effect are considered. The elastic and plastic stresses around the wellbore sock were analysed according to MVM failure criterion. Distribution of stress and displacement was obtained, which can provide theory reference for the wellbore stability.

scholarly journals Experimental Investigation of the Effects of Drilling Fluid Activity on the Hydration Behavior of Shale Reservoirs in Northwestern Hunan, China

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3151 ◽  
Author(s):  
Han Cao ◽  
Zheng Zhang ◽  
Ting Bao ◽  
Pinghe Sun ◽  
Tianyi Wang ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Contact Angles ◽  
Wellbore Stability ◽  
Adsorption Rate ◽  
Drilling Fluids ◽  
Swelling Ratio ◽  
Gas Drilling ◽  
Surface Hydration ◽  
The Relationship

The interaction between drilling fluid and shale has a significant impact on wellbore stability during shale oil and gas drilling operations. This paper investigates the effects of the drilling fluid activity on the surface and osmotic hydration characteristics of shale. Experiments were conducted to measure the influence of drilling fluid activity on surface wettability by monitoring the evolution of fluid-shale contact angles. The relationship between drilling fluid activity and shale swelling ratio was determined to investigate the osmotic hydration behavior. The results indicate that, with increasing drilling fluid activity, the fluid–shale contact angles gradually increase—the higher the activity, the faster the adsorption rate; and the stronger the inhibition ability, the weaker the surface hydration action. The surface adsorption rate of the shale with a KCl drilling fluid was found to be the highest. Regarding the osmotic hydration action on the shale, the negative extreme swelling ratio (b) of the shale was found to be: bKCl < bCTAB < bSDBS. Moreover, based on the relationship between the shale swelling ratio and drilling fluid activity, shale hydration can be divided into complete dehydration, weak dehydration, surface hydration, and osmotic hydration, which contributes to the choice of drilling fluids to improve wellbore stability.

Wellbore-Stability Analysis by Integrating a Modified Hoek-Brown Failure Criterion With Dual-Porochemoelectroelastic Theory (includes associated erratum)

SPE Journal ◽  
2019 ◽  
Vol 24 (05) ◽  
pp. 1957-1981 ◽  
Author(s):  
Chao Liu ◽  
Yanhui Han ◽  
Hui–Hai Liu ◽  
Younane N. Abousleiman
Keyword(s):  
Stability Analysis ◽  
Pore Pressure ◽  
Failure Criterion ◽  
Rock Strength ◽  
Chemical Potential ◽  
Wellbore Stability ◽  
Natural Fracture ◽  
Analysis Tool ◽  
Drilling Mud

Summary When drilling through naturally fractured formations, the existence of natural fractures affects the fluid diffusion and stress distribution around the wellbore and induces degradation of rock strength. For chemically active formations, such as shale, the chemical–potential difference between the drilling mud and the shale–clay matrix further complicates the nonmonotonic coupled pore–pressure processes in and around the wellbore. In this work, we apply a recently formulated theory of dual–porosity/permeability porochemoelectroelasticity to predict the time evolution of mud–weight windows, while calculating stresses and pore pressure around an inclined wellbore drilled in a fractured shale formation. The effects of natural–fracture geometric and spatial distributions coupled with the chemical activity are considered in the wellbore–stability analysis. To account for the degrading effect of the fractured shale matrix on the bulk rock strength, a modified Hoek–Brown (MHB) criterion is developed to more closely describe the in–situ state of stress effects on the compressive shearing strength at great depth. Compared with the original Hoek–Brown (HB) failure criterion, the MHB criterion considers the influence of the intermediate principal stress and thus shows better agreement with true–triaxial data for various rocks at varying stress levels. The MHB criterion converges to the original HB criterion when the confining in–situ stresses are equal. Two field case studies indicate that this novel integrative methodology is capable of predicting the operational drilling–mud–weight windows used in these two cases. Another advantage of this newly developed technique is that it can be used as a back–analysis tool to estimate the fracture–matrix permeability from field operational data.

scholarly journals Probabilistic Approach in Wellbore Stability Analysis during Drilling

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Mahmood R. Al-Khayari ◽  
Adel M. Al-Ajmi ◽  
Yahya Al-Wahaibi
Keyword(s):  
Deterministic Model ◽  
Drilling Fluid ◽  
Probabilistic Approach ◽  
Fluid Pressure ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Well Drilling ◽  
Collapse Pressure ◽  
Wellbore Instability

In oil industry, wellbore instability is the most costly problem that a well drilling operation may encounter. One reason for wellbore failure can be related to ignoring rock mechanics effects. A solution to overcome this problem is to adopt in situ stresses in conjunction with a failure criterion to end up with a deterministic model that calculates collapse pressure. However, the uncertainty in input parameters can make this model misleading and useless. In this paper, a new probabilistic wellbore stability model is presented to predict the critical drilling fluid pressure before the onset of a wellbore collapse. The model runs Monte Carlo simulation to capture the effects of uncertainty in in situ stresses, drilling trajectories, and rock properties. The developed model was applied to different in situ stress regimes: normal faulting, strike slip, and reverse faulting. Sensitivity analysis was applied to all carried out simulations and found that well trajectories have the biggest impact factor in wellbore instability followed by rock properties. The developed model improves risk management of wellbore stability. It helps petroleum engineers and field planners to make right decisions during drilling and fields’ development.

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