Application of quantitative risk assessment in wellbore stability analysis

Gholami, Raoof; Rabiei, Minou; Rasouli, Vamegh; Aadnøy, Bernt S.; Fakhari, Nikoo

doi:10.1016/j.petrol.2015.09.013

Cited by 50 publications

(19 citation statements)

References 35 publications

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“…The results obtained are then calibrated against representative core and field data to ensure that the MEM has sufficient accuracy. Further details of a MEM and geomechanical parameters determined for wellbore stability analysis of vertical and deviated wellbores drilled in isotropic and anisotropic formations are comprehensively discussed in the studies carried out by Gholami et al, (2014Gholami et al, ( , 2015aGholami et al, ( , 2015bGholami et al, ( , 2017.…”

Section: Mechanical Earth Modelling (Mem)mentioning

confidence: 99%

“…Regardless of the method used, without calibration against the field scale measurements such as minifrac or leak-off test (LOT), significant uncertainty will be involved in the calculations of in-situ stress magnitudes (Zoback et al, 2003). Poro-elastic equations are perhaps the most commonly used models for estimation of the magnitude of horizontal stresses based on their proven applications in vertical and directional wells (Gholami et al, 2015a, Gholami et al, 2015b, Gholami et al, 2017Rasouli et al, 2011), although the stress polygon approach has also shown its application under many circumstances (Gholami et al, 2015b). However, stress polygon can only be used in the intervals where the magnitude of the minimum horizontal stress is known from LOT, minifrac or hydraulic frac tests.…”

Section: In-situ Stressesmentioning

confidence: 99%

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A methodology for wellbore stability analysis of drilling into presalt formations: A case study from southern Iran

Gholami

Rabiei

Aadnoy

et al. 2018

Journal of Petroleum Science and Engineering

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Drilling into presalt formations has been a long-standing issue due to the rapid changes in the diameter of the borehole during drilling operations either because of creep or wash-out dissolution. There have been many studies on characterization of salts, with many mathematical models being presented to estimate the pressure induced due to the squeezing salt sheets. However, the results of none of these models have been fully validated against real field data and some recommendations have been made based on numerical simulations. In this study, attempts were made to introduce a methodology based on damage mechanics for wellbore stability analysis of a wells drilled in the southern part of Iran. The results obtained indicated that the presence of a thick salt layer in the well has resulted in significant wellbore closure in the intervals above the reservoir section. It was also found that the salt exhibits viscoelastic behaviour during drilling due to the homogeneous temperature which has not reached the threshold limit of viscoplastic boundary. A complicated change in the stress regime was also observed which could be linked to the existence of the thick salt layer or presences of a fault crossing the well. Therefore, it is recommended to further validate this model in other wells using the methodology presented.

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Section: Mechanical Earth Modelling (Mem)mentioning

confidence: 99%

Section: In-situ Stressesmentioning

confidence: 99%

A methodology for wellbore stability analysis of drilling into presalt formations: A case study from southern Iran

Gholami

Rabiei

Aadnoy

et al. 2018

Journal of Petroleum Science and Engineering

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“…For the log based data analysis, dynamic elastic parameters are often used to predict brittleness. Dynamic elastic parameters can be estimated using the density of rocks together with the velocity of P-and S-waves (Fjaer et al, 2008;Gholami et al 2015). However, due to the variation of Young's modulus and Poisson's ratio, the results obtained should be normalized by maintaining the trend of the original data.…”

Section: Well Log Based Brittlenessmentioning

confidence: 99%

“…Aplin et al 1999). Shale anisotropic characteristics are, on the other hand, needed to have an accurate mechanical earth model for the wellbore stability analysis (Gholami et al 2015) and to correct electrical logs for estimation of water saturation (Bang et al 2000;Wei, 2003). Geomechanical parameters of shale reservoirs should also be estimated for the caprock stability analysis, determination of drilling directions and hydraulic fracture initiations (Nygard et al 2004;Dewhurst et al 2008;Delle Piane et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Brittleness of gas shale reservoirs: A case study from the north Perth basin, Australia

Gholami

Rasouli

Sarmadivaleh

et al. 2016

Journal of Natural Gas Science and Engineering

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Shale reservoirs have gained the attention of many in recent years due to their potential as a major gas resource. Production from this kind of formation, however, requires an accurate estimation of brittleness and employments of hydraulic fracturing. There have been many studies as to how brittleness can be estimated, but few research works were carried out so far indicating how brittleness indices vary in gas shale formations. The aim of this paper is to evaluate the variation of brittleness in one of the gas shale reservoirs located in the north Perth Basin of Australia. The results obtained indicated that the lower part of the Carynginia shale should be selected for a hydraulic fracturing job due to a high brittleness index, although a careful analysis of Total Organic Content (TOC) might be required before initiating any plans. The mineralogical report and interpretations revealed that the space created by cross-plotting the elastic parameters is able to identify dominant minerals contributing into brittleness. Performing a series of true triaxial tests, which are capable of simulating the real field condition by applying three independent principal stresses, implied that as the stress anisotropy increases, a transition takes place from brittle towards the ductile behaviours. However, when this anisotropy becomes significant, samples regain their strength. This study, therefore, recommends more studies to get a practical conclusion on brittleness under true triaxial conditions.

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“…However, due to the uncertainty of formation lithology, the uncertainty of formation pressure, the uncertainty of mechanical properties of rocks, and the unstable wellbore pressure, the input parameters of wellbore stability analysis never can be known precisely. In other words, the input parameters are often uncertain, which might cause an incorrect result [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In order to quantify the influence of uncertain parameters on wellbore stability and SMWW, it's necessary to utilize reliability assessment method.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Tang

Chen

et al. 2019

Energies

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Due to the uncertainty of formation properties and improper wellbore stability analysis methods, the input parameters are often uncertain and the required mud weight to prevent wellbore collapse is too large, which might cause an incorrect result. However, the uncertainty evaluation of input parameters and their influence on safe mud weight window (SMWW) is seldom investigated. Therefore, the present paper aims to propose an uncertain evaluation method to evaluate the uncertainty of SMWW. The reliability assessment theory was introduced, and the uncertain SMWW model was proposed by involving the tolerable breakout, the Mogi-Coulomb (MG-C) criterion and the reliability assessment theory. The influence of uncertain parameters on wellbore collapse, wellbore fracture and SMWW were systematically simulated and investigated by utilizing Monte Carlo simulation. Finally, the field observation of well SC-101X was reported and discussed. The results indicated that the MG-C criterion and tolerable breakout is recommended for wellbore stability analysis. The higher the coefficient of variance is, the higher the level of uncertainty is, the larger the impact on SMWW will be, and the higher the risk of well kick, wellbore collapse and fracture will be. The uncertainty of basic parameters has a very significant impact on SMWW, and it cannot be ignored. For well SC-101X, the SMWW predicted by analytical solution is 0.9921–1.6020 g/cm3, compared to the SMWW estimated by the reliability assessment method, the reliability assessment method tends to give a very narrow SMWW of 1.0756–1.0935 g/cm3 and its probability is only 80%, and the field observation for well kick and wellbore fracture verified the analysis results. For narrow SMWW formation drilling, some kinds of advanced technology, such as the underbalanced drilling (UBD), managed pressure drilling (MPD), micro-flow drilling (MFD) and wider the SMWW, can be utilized to maintain drilling safety.

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Application of quantitative risk assessment in wellbore stability analysis

Cited by 50 publications

References 35 publications

A methodology for wellbore stability analysis of drilling into presalt formations: A case study from southern Iran

A methodology for wellbore stability analysis of drilling into presalt formations: A case study from southern Iran

Brittleness of gas shale reservoirs: A case study from the north Perth basin, Australia

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

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