In the third step the boundary conditions are changed to apply the pore pressure on the face of the. The performance of stochastic designs in wellbore drilling. During drilling, there are other sources which can also contribute to the development of stability problems. The 1dmem is the backbone of every geomechanical workflow for which it provides the stress field, pore pressure, and mechanical properties. Pdf numerical simulations of wellbore stability in under.
In abaqus standard the erosion of material at the external surface is modeled by declaring the surface to be part of an adaptive mesh domain and by prescribing surface mesh motions that recede into the material. Energies free fulltext numerical investigation of the. In 2010, alharthi and alajmi applied risk analysis to wellbore stability. Abaqus example problems manual abaqus example problems manual. Research article fracturing pressure of shallow sediment in. Pdf wellbore instability has been the primary cause of financial losses in boreholes in the. Podio and kamy sepehrnoori for their guidance through this research project. Numerical investigation of the influence of the drill. Application of in situ stress estimation methods in. Additionally, the effects of different wellbore sizes on wellbore stability were successively analyzed.
A best practice will be developed and validated against available rock strength data from core samples, and used to provide consistent inputs to the wellbore stability models. Coupled thm modelling of wellbore stability with drilling unloading. Predrill wellbore stability analysis using rock physical. Casing drilling application spe distinguished lecturer series 9 figure 6. Geomechanical modeling of insitu stresses around a borehole. There was a case study from a deepwater well with the history of wellbore stability and loss circulation problems. Erosion of material sand production in an oil wellbore. Abaqus standard will then remesh the adaptive mesh domain using the same mesh topology but accounting for the new location of the surface. The finite element model along with the generated mesh is illustrated in fig. Based upon this wellbore stability theoretical model of coal, many cleat.
The paper reported the major drilling problems related to wellbore instability and pore pressure in deepwater wells. Geomechanics, wellbore stability, buckling, contact interface. Wellbore instability tensile failure using fracture mechanics approach is the result of investigation carried. In oil industry, wellbore instability is the most costly problem that a well drilling operation may encounter. These methods depend 14 on a proper determination of the drilling fluid density that provides pressure inside the cavity of 15 the wellbore. Research article fracturing pressure of shallow sediment. Application of in situ stress estimation methods in wellbore. Flow rule for the purposes of discussing the flow and hardening behavior, it is useful to divide the meridional plane into the two regions shown in figure 18. Conversion tables, constants, and material properties.
Oct 01, 2018 we used abaqus abaqus 2017 17 to perform 3d thm analysis of the wellbore stability problem. Coupled thm modelling of wellbore stability with drilling. Four wells drilled in gulf of suez and mediterranean sea, offshore egypt, were analyzed for wellbore instability, to improve drilling performance in future wells hassan et al. Guidelines for papers to be presented at the abaqus users. The user subroutines usdfld in abaqusstandard and vusdfld in. Abaqus so ware as the solver, in which di erent parts such as thermal, hydraulic, and mechanical modules can. There is a series of data that provide information about the in situ stresses, pore pressure and the rock strength. Buckling of a coiled wellbore tube occurs when the axial. Geomechanical data and failure criterion can be used to model and control rock mass behavior in response to the stresses imposed upon it.
Gavin baldwin modeling pore pressure and determining a reservoirs mechanical properties are significant factors in reducing drilling risk and maximizing. The key factor to control the wellbore stability is the rate of sanding. Mathematical model for wellbore stability in hydratebearing sediments 2. A third problem considered as wellbore instability, is sanding production in the completion stage. If the induced stresses near the wellbore exceed the strength of rock, wellbore failure occurs. Abaqus standard and abaqus explicit are intended to provide the user with two complementary analysis tools. Conventional wellbore trajectory planning is commonly based on an andersonian state of stress sos and the optimum well azimuth and inclination for a specific depth. The effect of field coupling on pore pressure, stress redistribution, and temperature around a wellbore has been analyzed in detail. Special solution techniques are required for quasistatic analysis. The current wellbore stability analyses for analytical solutions are mostly based on the linear elastic or poroelastic theory.
In particular, the orientation of the well has great relevance. We used abaqus abaqus 2017 17 to perform 3d thm analysis of the wellbore stability problem. Wellbore collapse pressure pc is the mud pressure below which the entire wellbore wall becomes unstable, which occurs when zones of compressive wellbore. These measurements would also be restricted as to the depth of acquisition, and generalization of. Hence, wellbore stability methods 12 commonly employed in the design of deep wells are based on assumptions appropriate to the strength and deformation characteristics of welllithified rock formations. Geomechanical and numerical studies of casing damages in a. Prior to drilling, the mechanical stresses in the formation are less than the strength of the. Comprehensive stability analysis of an inclined wellbore. Seismic data available from the berkeley seismology lab suggests that there has been a recent increase in seismic activity in the us midwestern states like oklahoma, and texas among others. Probabilistic approach in wellbore stability analysis.
Program abaqus was chosen for our numerical simulation once that this program is widely employed in the academy and industry. Abaqus standard provides the capability to analyze the followingtypes of problems. Through the study of wellbore stability in different conditions, it is found that for. Pdf finite element analysis for wellbore stability of transversely. Direct techniques conventionally used to determine in situ stresses are indeed very time consuming and expensive. To obtain a more stable algorithm, we write the nonlinear stressstrain law in the form. Surveyed literature has little discussion on fluid injection impact on wellbore, especially casing, responses. Wellbore stability is maintained with drilling fluid density between 0. Tensile failure that can result in fracturing occurs in all depths at 1. Unfortunately, wellbore stability problems, such as unexpected low fracture gradient, are relatively common while drilling close and out of these salt structures. Numerical simulations for wellbore stability and integrity. Maria a nikolinakou, research associate, the university of. Nonetheless, recent researches have revealed that the magnitudes of the loads affecting the wellbore stability are more likely to change over time.
A numerical investigation of wellbore stability problems. Mitigation of wellbore instability in deviated wells by using. Buckling is a mathematical instability that can lead to a failure mode. The finite element code abaqus is applied to analyse the mechanical behaviour of wells with different inclinations and different azimuths.
The production process also changes the effective stresses around the. Basic introduction to wellbore stability analysisdesigned and presented by sam saeed hashemi. The wellbore is regarded as unstable if the determined elasticporoelastic stresses anywhere around the wellbore satisfy some failure criteria for the rock formation. Abaqus so ware as the solver, in which di erent parts such as thermal, hydraulic, and mechanical modules can be called. Wellbore stability analysis acts an important role in the drilling design to avoid stuckpipe. Department coupled analysis draft university of toronto tspace.
Stabilization for general contact in abaqusstandard. 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. Mechanical study on the wellbore stability of horizontal. Buckling analysis for the longterm integrity evaluation of a. The simulation of stability analysis is conducted with a finite element simulator abaqus and consists of two steps. Linear and nonlinear static linear dynamic lowspeed low frequency response nonlinear dynamic nonlinear heat transfer. The default setting of the constant scale factor s c. Jester boulevard houston, texas 770187098 telephone. A history match of the observed field wellbore stability cases with the coupled model was obtained. The plastic poissons ratio, is expected to be less than 0. The importance of geomechanics in problems such as wellbore stability. Based on the wellbore stability simulations, adjusting nyza criteria to 1.
The relationship between the intermediate principle stress and the rate of sanding documented in relevant literatures may. Introduction many major exploration and new field development efforts around the world i. Analysis of wellbore instability in vertical, directional. Wellbore thermal simulation model gtemp1 theory and users manual dea67, phase ii project to develop and evaluate coiledtubing and slimhole technology maurer engineering inc. Wellbore stability problems such as tight hole, packoff, stuck pipe, inflow, and lost circulation are most commonly associated with conventional reservoirs but also occur in unconventional reservoirs. Abaqus technology brief helical buckling of coiled. The most important and the most studied step is wellbore stability analysis, by which the adjustment of wellbore path, casing profile and mud weight and mud type are determined.
Performance by wellbore stability and pore pressure in deepwater exploration. Comprehensive wellbore stability analysis utilizing. The techlog wellbore stability module comprises mechanical earth model 1dmem building, wellbore stability, sand management, and fracture stability computation. Dassault systemes 2011, abaqus user manual version 6. To learn about abaqus the best resource is getting started with abaqus.
Assessing wellbore stability with a modified lade failure. Ensuring wellbore stability with geomechanics and pore. Figure 2 shows the work flow of the wellbore stability analysis. Users guide, the yield condition of druckerprager model is expressed as. 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 failure wellbore pressure, borehole closure, plastic zone distribution of different direction wells are given in this paper. The model is described in detail in cast iron plasticity, section 4. Wellbore stability problems classification amoco wellbore stability drilling handbook6 figure 5. As shown in the expressions above for the stabilization pressure and shear stress, the scale factor s c. Workflow carried out for wellbore stability analysis.
The drilling process results in the removal of an already stressed rock material. Mar, 2020 the importance of evaluating wellbore stability in analyzing and estimating the efficiency of drilling directionally into oil and gas reservoirs is well known. Indeed, we illustrate that the evolutionary model yields a narrower safemud window near a salt dome structure. Thus, significant drilling costs could be eliminated if these hazards could be identified and avoided in the well planning process. Jul 01, 2020 additionally, the effects of different wellbore sizes on wellbore stability were successively analyzed. The research results provide a theoretical basis for the design of the well structure during the drilling of hydratebearing strata from a mechanical perspective. Wellbore stability analysis for each of the selected wellbore stability modeling methods, an analytical wellbore. Pdf geomechanical wellbore stability analysis for the reservoir.
Excessive anisotropic and nonuniform stresses, causing shear failure in unconsolidated reservoirs, are one of the main reasons reported for the casing failure. Probabilistic approach in wellbore stability analysis during. The analyses predict critical mud pressure values necessary to maintain wellbore stability at different deviation angles and stress histories. They utilized the mogicoulomb stability model see, 19, and 20 to conduct a sensitivity analysis in vertical wellbores. Buckling analysis for the longterm integrity evaluation. Numerical investigation of the influence of the drill string. For the potential to be welldefined, must be greater than 1. When abaqus cae begins, the start session dialog box appears. Mechanical responses of formation and wellbore induced by. A generalized plane strain model is used in the calculation. The hm coupling module and thermal module in abaqus software is used to. Casings damage is a usually reported incident during production in many fields. Abaqus unified finite element analysis, users manual version 6. In ma and chen 2015, a collapse pressure wellbore stability model for shale.
The geostatic step shows the initial insitu stress conditions before drilling. Excess pore pressure theory insoilmechanicswillbeadoptedin this paper. One reason for wellbore failure can be related to ignoring rock mechanics effects. Wellbore stability in geomechanics nottingham eprints. Introduction to wellbore stability analysis youtube. Formations around the wellbore are divided into elastic zone and plastic zone. Hubbert and willis 1957 developed a mechanical wellbore stability model in which the primary assumption was the linear elastic stress pathway around the borehole. For example, wellbore collapse might happen during drilling andor during production.
Coupled thm modelling of wellbore stability with drilling unloading, fluid flow, and thermal effects considered shanpojia,1,2 caoxuanwen,3 fuchengdeng,3. This incident is conventionally induced by compressional, tensional, burst or collapse forces applied to the casing string. The derived wellbore stability model was calibrated using the drilling information, logging data and geological model. The maintenance technique has many steps to go through the drilling process. The governing equations and assumptions were described in section 2. Geomechanics, wellbore stability, creep, visualization. Special considerations for the marcellus shale julie kowan1,2 and see hong ong1. For the evaluation of the impact that can have the presence of the planes of weakness in the wellbore stability, a numerical modeling with a commercial software called the abaqus, which has a. In this study, an integrated thm coupled model consisting of reservoirlayers, injectionproduction wells and casings, is proposed to predict the mechanical behavior. Jul 26, 2018 wellbore failure can occur at different stages of operations. Probabilistic approach risk analysis in vertical wellbore stability. The main aim of this research is to use new method and theory in geomechanics to conduct the stability analysis of wellbore. Abaqus tends to takes less time for geomechanical and flow simulation. A suite of logs, including dsi sonic, gr, and density were used as input to.
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