scholarly journals Coupled THM Modelling of Wellbore Stability with Drilling Unloading, Fluid Flow, and Thermal Effects Considered

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Shanpo Jia ◽  
Caoxuan Wen ◽  
Fucheng Deng ◽  
Chuanliang Yan ◽  
Zhiqiang Xiao
Keyword(s):  
Fluid Flow ◽  
Pore Pressure ◽  
Thermal Effects ◽  
Process Analysis ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Deep Well ◽  
Underbalanced Drilling ◽  
The Stability ◽  
Pressure Stress

Both overbalanced drilling and underbalanced drilling will lead to the change of pore pressure around wellbore. Existing research is generally based on hydraulic-mechanical (HM) coupling and assumes that pore pressure near the wellbore is initial formation pressure, which has great limitations. According to the coupled theory of mixtures for rock medium, a coupled thermal-hydraulic-mechanical (THM) model is proposed and derived, which is coded with MATLAB language and ABAQUS software as the solver. Then the wellbore stability is simulated with the proposed model by considering the drilling unloading, fluid flow, and thermal effects between the borehole and the formation. The effect of field coupling on pore pressure, stress redistribution, and temperature around a wellbore has been analyzed in detail. Through the study of wellbore stability in different conditions, it is found that (1) for overbalanced drilling, borehole with impermeable wall is more stable than that of ones with permeable wall and its stability can be improved by reducing the permeable ability of the wellbore wall; (2) for underbalanced drilling, the stability condition of permeable wellbore is much higher than that of impermeable wellbore; (3) the temperature has important influence on wellbore stability due to the variation of pore pressure and thermal stress; the wellbore stability can be improved with cooling drilling fluid for deep well. The present method can provide references for coupled thermal-hydraulic-mechanical-chemical (THMC) process analysis for wellbore.

The Effects of Anisotropic Transport Coefficients on Pore Pressure in Shale Formations

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Vahid Dokhani ◽  
Mengjiao Yu ◽  
Stefan Z. Miska ◽  
James Bloys
Keyword(s):  
Pore Pressure ◽  
Fluid Transport ◽  
Drilling Fluid ◽  
Transport Coefficients ◽  
Electrical Potential ◽  
Three Dimensional ◽  
Bedding Plane ◽  
Wellbore Stability ◽  
Coupled Flow ◽  
In Situ Conditions

This study investigates shale–fluid interactions through experimental approaches under simulated in situ conditions to determine the effects of bedding plane orientation on fluid flow through shale. Current wellbore stability models are developed based on isotropic conditions, where fluid transport coefficients are only considered in the radial direction. This paper also presents a novel mathematical method, which takes into account the three-dimensional coupled flow of water and solutes due to hydraulic, chemical, and electrical potential imposed by the drilling fluid and/or the shale formation. Numerical results indicate that the presence of microfissures can change the pore pressure distribution significantly around the wellbore and thus directly affect the mechanical strength of the shale.

A Geomechanical Model and Workflow for Calibrating Elastic Moduli and Min/Max Horizontal Stress from Well Logs in the Nahr Umr Shale

2021 ◽  
Author(s):  
Michael Alexander Shaver ◽  
Gilles Pierre Michel Segret ◽  
Denya Pratama Yudhia ◽  
Suhail Mohammed Al Ameri ◽  
Erwan Couziqou ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Drilling Fluid ◽  
Well Logging ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Lateral Strain ◽  
Fluid Density ◽  
Geomechanical Model ◽  
Stability Problems ◽  
Stress Models

Abstract Thin layering and micro-fracturing of the thin laminated layers are some possible reasons for the wellbore stability problems of the Nahr Umr shale. If the drilling fluid density is too low, collapsing of the borehole is possible, and if the drilling fluid density is too high, invasion of the shale can occur, weakening the shale, making boreholes prone to instability. These effects can be semi-quantified and assessed through the development of a geomechanical model. The application of a geomechanical model of a reservoir and overlaying formations can be very useful for addressing ways to select a sweet spot and optimize the completion and development of a reservoir. The geomechanical model also provides a sound basis for addressing unforeseen drilling and borehole stability problems that are encountered during the life cycle of a reservoir. Key components of any geomechanical model are the principal stresses at depth: overburden, minimum horizontal principle stress, and maximum horizontal principle stress. These determine the existing tectonic fault regime: normal, strike-slip, and reverse. Additional components of a geomechanical model are pore pressure, unconfined compressive strength (UCS) rock strength, tilted anisotropy, and fracture and faults from image logs and seismic. Unfortunately, models used to make continuous well logging depth-based stress predictions involve some parameters that are derived from laboratory tests, fracture injection tests, and the actual fracturing of a well—all contributing to the uncertainty of the model predictions. This paper addresses ways to obtain these key parameter components of the geomechanical model from well logging data calibrated to ancillary data. It is shown how stress, UCS, and pore pressure prediction and interpretation can be improved by developing and applying models using wellbore acoustic, triple combo, and borehole image data calibrated to laboratory and field measurements. The nahr umr shale and other organic mudstone formations exhibit vertical transverse isotropic (VTI) anisotropy in the sense that rock properties are different in the vertical and horizontal directions (assuming non-tilted flatbed layering), the horizontal acoustic velocity is different from that of vertical velocity. This necessitates the building of anisotropic moduli and stress models. The anisotropic stress models require lateral strain, which as shown in the paper, can be obtained from micro-frac tests and/or borehole breakout data.

Rheological Study of Nanosilica Based Drilling Fluid

2014 ◽  
Vol 575 ◽  
pp. 128-133 ◽  
Author(s):  
Nur Hashimah Alias ◽  
Nuurhani Farhanah Mohd Tahir ◽  
T.A.T. Mohd ◽  
N.A. Ghazali ◽  
E. Yahya ◽  
...  
Keyword(s):  
Xanthan Gum ◽  
Drilling Fluid ◽  
Gel Strength ◽  
Wellbore Stability ◽  
Potential Candidate ◽  
Drilling Mud ◽  
Well Completion ◽  
Strength Tests ◽  
Water Based ◽  
The Stability

In drilling and well completion operations, drilling fluid is a crucial element as it is employed for the purposes of several functions. The main functions of drilling fluid are to control formation pressure, maintain the wellbore stability, transport the cuttings up to surface to clean the borehole bottom as well as to lubricate and cool the drill bit. Moreover, it is used to minimize the drilling damage to reservoir and suspend cuttings when the pumping is stop, hence it will not falling back down the borehole. The purpose of this study is to formulate new drilling mud formulation modified with nanosilica. Six samples of water based mud (WBM) were prepared using three types of polymers, (Xanthan Gum, Hydro Zan Plus and Hydro Star HT), starch and nanosilica. Basic rheological tests such as density, viscosity and pH were carried out. The density test was carried out using mud balance meanwhile the pH test was using pH meter. Theplasticviscosity, yield point and gel strength tests were carried out using viscometer. Besides that, physical observation was also performed for as the stability test. The results concluded that water based mud incorporated with polymer Hydro Zan Plus and nanosilica can be a potential candidate to be commercialized as a smart nanodrilling fluid.

scholarly journals Theoretical preconditions for modeling wellbore stability and predicting hydraulic fracturing

2021 ◽  
pp. 41-49
Author(s):  
A.N. Popov ◽  
◽  
R.A. Ismakov ◽  
F.N. Yangirov ◽  
A.R. Yakhin ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Drilling Fluid ◽  
Fluid Pressure ◽  
Polycrystalline Diamond ◽  
Wellbore Stability ◽  
Rotary Drilling ◽  
Factors Affecting ◽  
The Stability ◽  
Diamond Bit ◽  
The Given

One of the complex technological tasks in the process of drilling is to ensure the stability of the wellbore walls, as well as their modeling for further forecasting the state of the wellbore and the likelihood of hydraulic fracturing. This is due to the fact that most of the complications and factors affecting the equilibrium state of the wall are associated with external influences. The article discusses the mechanical and partially hydraulic aspects of solving the described problems associated with modeling the stability of the wellbore walls and predicting hydraulic fracturing. As a result of calculations, the necessary data are obtained for making a decision on the density of the drilling fluid for drilling the considered interval of rocks. The assumed model of the porous rock and the given calculation formulas make it possible to fully evaluate the influence of the formation fluid pressure on the mechanical processes in the rocks when they are opened by a well. Keywords: hydraulic fracturing; blade bit; steel ball-shaped toothed bit; polycrystalline diamond bit; laser drilling; impact rope drilling; rotary drilling.

scholarly journals Experimental investigation of rheological properties and formation damage of water-based drilling fluids in the presence of Al2O3, Fe3O4, and TiO2 nanoparticles

2020 ◽  
Vol 10 (4) ◽  
pp. 5886-5894
Keyword(s):  
Iron Oxide ◽  
Aluminum Oxide ◽  
Rheological Properties ◽  
Titanium Oxide ◽  
Filtration Rate ◽  
Drilling Fluid ◽  
Gel Strength ◽  
Wellbore Stability ◽  
Formation Damage ◽  
The Stability

The successful drilling of the oil and gas wells almost relies upon the drilling fluid properties. Maintaining wellbore stability, transportation, and releasing cuttings at the surface, and controlling formation pressure are the essential functions of the drilling fluid. Improving the rheological properties of the drilling fluid results in an increase in transport power and also provides better stability. One of the new methods to improve different properties of the drilling mud is the application of nanoparticles. Nanoparticles induce favorable effects on the rheological properties of the fluid. Improvement of mud properties yields in better cleaning of the well, the stability of the wellbore, higher drilling bit efficiency, and, consequently, a lower cost in the long run. Therefore, the present study investigates the effect of adding three different nanoparticles including aluminum oxide, iron oxide, and titanium oxide to the drilling fluid in several experiments by measuring rheological properties (plastic viscosity, yield point, filtration rate, gel strength) and also formation damage and permeability reduction. The number of experiments was determined by the experiment design method. The results of the experiments implied that in nanofluids with the weight of 70 pcf, rheological properties were relatively improved in most of the nanofluids samples concentrations. Samples containing iron oxide exhibited a decreasing filtration rate compare to base drilling fluid that indicates increasing stability in the fluid environment. The gel strength (GS) of titanium oxide and aluminum oxide samples has increased appropriately, which shows improvement in attractive forces in the fluid. For the case of the 80 pcf nanofluid, iron oxide indicates appropriate rheological properties and decreasing of filtration rate that all of them represent nanoparticle caused an increasing and improving the stability of fluid. But titanium oxide and aluminum oxide couldn't show significant effects. This phenomenon can be described by the lack of a uniform and thorough mixing of nanoparticles in the drilling fluid under field conditions. Besides, results obtained from the formation damage test equipment demonstrated the 54% reduction in initial permeability of the iron oxide nanoparticle that is the lowest damage between another nanofluid.

Research on Wellbore Stability in Formation with Anisotropic Strength

2013 ◽  
Vol 765-767 ◽  
pp. 3151-3157
Author(s):  
Hui Zhang ◽  
Fang Jun Ou ◽  
Guo Qing Yin ◽  
Jing Bing Yi ◽  
Fang Yuan ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Rock Body ◽  
Collapse Pressure ◽  
Wellbore Instability ◽  
Transversely Isotropic Rock ◽  
Fracture Development ◽  
Anisotropic Formation ◽  
The Impact

As most of sedimentary rocks are anisotropic, it is significant to research the impact of the anisotropy of strength on wellbore stability in drilling engineering. Particularly, in the Kuqa piedmont exploration area, the anisotropy of strength caused by various jointed surfaces, fracture surfaces and fault planes in formation cause the formation of several groups of weak low-intensity planes traversing borehole . These weak planes will become failure earlier than the rock body in the context of strong stress and high pore pressure, causing chipping, breakouts and sticking. If fractures have good permeability and drilling fluid column pressure is greater than pore pressure, loss may occur. The loss pressure would not be controlled by fracturing pressure and horizontal minimum principal stress, but it depends on the relationship between fracture occurrence and triaxial stress state. In the event of loss, the drilling fluid will flow into these weak structural planes, causing the decrease of friction between rocks and increase of wellbore instability. As a result, for strongly anisotropic formation, the collapse pressure and leakage pressure of weak planes are key factors for evaluating well drilling stability. In this study, according to the stability evaluation on the transversely isotropic rock mechanics in Keshen zone of Kuqa piedmont, the impacts of fracture development on wellbore instability is analyzed; relevant suggestions on engineering geology for the special pressure window in strong anisotropic formation are also put forward.

scholarly journals Numerical Investigation of Wellbore Stability in Deepwater Shallow Sediments

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Wei Liu ◽  
Hai Lin ◽  
Hailong Liu ◽  
Chao Luo ◽  
Guiping Wang ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
Horizontal Stress ◽  
Wellbore Stability ◽  
Gas Wells ◽  
Shallow Sediments ◽  
Deformation Stress ◽  
The Stability ◽  
Fluid Penetration ◽  
Mud Pressure ◽  
Oil Gas

An elaborate poro-elastoplastic numerical model has been developed in this paper to explore the stability characteristics of wellbore in shallow sediments of deepwater oil/gas wells. The combined Drucker-Prager/cap plasticity model is employed to characterize the mechanical behavior of the weakly consolidated or unconsolidated shallow sediments, by which both plastic compaction deformation and plastic shear deformation can be considered. Possible penetration of drilling fluid into the formation and its coupling to deformation have also been accounted for in the model. Using this model, deformation, stress evolution, and failure characteristics of the formation around the wellbore are analyzed in detail. Results presented in this paper demonstrate the necessity of considering the plastic compaction capability of the formation during the wellbore stability analysis of shallow sediments in deepwater. For mud pressures lower than the in situ horizontal stress, excessive wellbore shrinkage may occur if the mud pressure is too low, which, however, can be effectively mitigated through properly increasing the mud pressure even fluid penetration into the near-wellbore region may occur. It is also evidenced that, if penetration of drilling fluid into the formation is prevented, fracturing of the wellbore will not occur even the mud pressure is very high. Instead, the wellbore will expand substantially due to plastic compaction, and the deformed wellbore radius could be several times larger than the original value. However, if drilling fluid can penetrate into the formation, high pore pressure will develop within the near-wellbore region, resulting in tensile hoop stress at the wellbore and thus fracturing of the wellbore along the radial direction. The numerical results and implications in this paper are anticipated to be beneficial for the drilling operation in the shallow portion of deepwater oil/gas wells.

MODELING HERSCHEL-BULKELY DRILLING FLUID FLOW IN A VARIABLE RADIAL FRACTURE

2014 ◽  
Vol 17 (3) ◽  
pp. 239-254 ◽  
Author(s):  
Song Li ◽  
Yili Kang ◽  
Daqi Li ◽  
Lijun You ◽  
Chengyuan Xu
Keyword(s):  
Fluid Flow ◽  
Drilling Fluid ◽  
Radial Fracture
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