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 Some issues of ensuring the stability of the walls of directional wells and preventing the absorption of process fluids

2021 ◽  
pp. 60-67
Author(s):  
A.N. Popov ◽  
◽  
R.A. Ismakov ◽  
A.R. Yakhin ◽  
I.D. Mukhametgaliev ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Drilling Fluid ◽  
Fluid Pressure ◽  
Polycrystalline Diamond ◽  
Horizontal Wells ◽  
Rotary Drilling ◽  
The Stability ◽  
Diamond Bit ◽  
Hydrodynamic Effects ◽  
The Given

Most of the main types of complications in the process of drilling wells, such as collapses, taluses, collapses of the walls, the formation of caverns, etc., are associated with external mechanical and hydrodynamic effects on the walls of the wellbore. Therefore, ensuring the stability of the borehole walls is one of the urgent and difficult technological formation fluid pressure on mechanical processes in rocks when they are opened with a directional well, especially of horizontal wells. This article provides solutions to problems associated with hydraulic fracturing of a well and the condition of its prevention, calculation of generalized stresses in the rock formation for inclined well. As a result of this calculations, the necessary data are obtained for making a decision on the density of the drilling fluid to drilling the considered interval of rocks, as well as for making other technological decisions. The given calculation formulas make it possible to fully evaluate the effect of the formation fluid pressure on the mechanical processes in the rocks when they are opened by a horizontal well. Keywords: hydraulic fracturing; blade bit; steel ball-shaped toothed bit; polycrystalline diamond bit; laser drilling; impact rope drilling; rotary drilling.

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.

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.

Integrated Multidisciplinary Solution for Improving Wellbore Stability and Drilling Efficiency in a Conglomerate Reservoir, a Case Study from North-West China

2021 ◽  
Author(s):  
Yalin Li ◽  
Jiangang Shi ◽  
Fang Zhang ◽  
Shanshan Wang ◽  
David Wiprut ◽  
...  
Keyword(s):  
Multidisciplinary Approach ◽  
Drilling Fluid ◽  
Junggar Basin ◽  
Wellbore Stability ◽  
Drilling Fluids ◽  
Drilling Process ◽  
Rotary Drilling ◽  
North West ◽  
Field Development ◽  
Weight Window

Abstract Drilling long horizontal development wells in a conglomerate reservoir with strong heterogeneity has been challenging in the Junggar Basin, onshore China. To develop the fields economically, rapid and safe drilling with minimal non-productive time (NPT) is required. However, various drilling problems such as stuck pipe, mud losses have been experienced in the build-up section while the horizontal conglomerate section experienced an extremely low rate of penetration (ROP). To overcome the drilling challenges, a thorough understanding of the subsurface characteristics of the formations is critical to develop effective engineering solutions. To improve drilling efficiency, an integrated multidisciplinary approach was applied to derive an effective drilling solution. Drilling experiences from offset wells were reviewed systematically to identify the possible reasons that have caused the drilling problems. This diagnostic approach helped to identify appropriate drilling solutions for mitigating the different drilling risks. Detailed geomechanical models were also constructed to understand the stress state and rock mechanical properties of the conglomerate reservoir and the overburden formations so that proper mud weights can be defined for each section to control both wellbore collapse and mud losses. Mud weight recommendations and failure mechanism diagnosis also provided the basis for drilling fluids designs. Additionally, in order to achieve a better hole quality as well as increase the reservoir contact and ROP, advanced rotary drilling systems were also used with real time monitoring. The latter enabled the tracking of rock property and ECD changes as well as other drilling parameters during the drilling process. This integrated solution was applied in the drilling of several horizontal wells. One typical case is presented in this paper. In this well, the risk of hole instability was very high because the well was targeting a deeper formation with a few shaly intervals in the build-up section which are known to cause serious wellbore stability problems. The safe mud weight window inferred from geomechanical analyses appears to be very narrow, particularly at the casing shoe where the mud weight required to control borehole collapse is very close or even higher than the fracture gradient. To help with drilling the well cost-effectively, drilling fluid was designed to perform three (3) critical functions - 1) maintaining wellbore stability, 2) increasing ROP and 3) broadening the mud weight window to minimize mud losses. The successful drilling of this well broke the drilling record in the same block. The integrated multidisciplinary approach successfully reduced the occurrence of borehole instability related problems and NPT in the study well. Following the same methodology, the drilling efficiency will improve with more experience and understanding obtained from continuous drilling. This continuous learning process will be the key aspect of this project, eventually contributing to the success of the field development.

scholarly journals Stability Analysis in Determining Safety Drilling Fluid Pressure Windows in Ice Drilling Boreholes

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3378
Author(s):  
Han Zhang ◽  
Dongbin Pan ◽  
Lianghao Zhai ◽  
Ying Zhang ◽  
Chen Chen
Keyword(s):  
Stability Analysis ◽  
Oil And Gas ◽  
Drilling Fluid ◽  
Fluid Pressure ◽  
Failure Criteria ◽  
Borehole Wall ◽  
Polar Regions ◽  
Borehole Stability ◽  
Oil And Gas Exploration ◽  
The Stability

Borehole stability analysis has been well studied in oil and gas exploration when drilling through rock formations. However, a related analysis of ice borehole stability has never been conducted. This paper proposes an innovative method for estimating the drilling fluid pressure window for safe and sustainable ice drilling, which has never been put forward before. First, stress concentration on a vertical ice borehole wall was calculated, based on the common elastic theory. Then, three failure criteria, the Mogi–Coulomb, teardrop, and Derradji-Aouat criteria, were used to predict the stability of the ice borehole for an unbroken borehole wall. At the same time, fracture mechanics were used to analyze the stable critical pressure for a fissured wall. Combining with examples, our discussion shows how factors like temperature, strain rate, ice fracture toughness, ice friction coefficient, and fracture/crack length affect the stability of the borehole wall. The results indicate that the three failure criteria have similar critical pressures for unbroken borehole stability and that a fissured borehole could significantly decrease the safety drilling fluid pressure window and reduce the stability of the borehole. The proposed method enriches the theory of borehole stability and allows drillers to adjust the drilling fluid density validly in ice drilling engineering, for potential energy exploration in polar regions.

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.

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.

scholarly journals The Perception of the Generational Assessment of Selected Social Behaviour – A Confirmatory Factor Analysis

2020 ◽  
Vol 20 (2) ◽  
pp. 346-360
Author(s):  
Agnieszka Stanimir
Keyword(s):  
Latent Variables ◽  
Structural Equation ◽  
Structural Equation Models ◽  
Research Problem ◽  
Factors Affecting ◽  
Confirmatory Factor ◽  
The Stability ◽  
The Given

Abstract Research background: The search for stable factors affecting latent variables that reflect the assessment of quality of life in three areas of an individual’s functioning is the background of the study. In the analysis was assumed the existence of the relationships between QoL assessment and subjective factors related to socio-economic aspects. Purpose: The aim of the study was to recognize assessments in given areas of transferring subjective satisfaction with a level of social factors and checking the stability of the assumed relationship between factors describing three areas of functioning: household, country of residence, EU. The next goal was to compare the results obtained in the study of natural relationships between factors with the given systems of these factors in the areas of an individual’s functioning. Characteristics of behaviour were compared in three generations of Europeans. The application objective of the study was to indicate the usefulness of SEM in the research problem. Research methodology: The Standard Eurobarometer, autumn 2018, provided data describing adults from the generations Y, X, and BB. Structural equation models were used. Results: The effect of the used method is the determination of the factors that affect the assessments made by three European Generations in the areas of an individual’s functioning: direct, close and further. Novelty: The analysis showed the usefulness of structural equation models to achieve the goals of the study.

scholarly journals Study on Wellbore Stability and Instability Mechanism in Piedmont Structures

2015 ◽  
Vol 8 (1) ◽  
pp. 208-213
Author(s):  
Qiang Tan ◽  
Baohua Yu ◽  
Jingen Deng ◽  
Kai Zhao ◽  
Jianguo Chen
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Fluid Pressure ◽  
Tectonic Stress ◽  
Mechanical Analysis ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Instability Mechanism ◽  
Sealing Ability ◽  
Stability And Instability

Piedmont tectonic belts are rich of oil and gas resources, however the intense tectonic stress and broken formation may cause great drilling problems in piedmont structures such as borehole collapse, lost circulation and gas cutting. Through analysis of in situ stress properties, bedding structure and mechanical characteristics, wellbore instability mechanism was expounded from rock mechanics, chemistry of drilling fluid and drilling technology. The high tectonic stress, formation strength decreasing and fluid pressure rising after mud filtrate seepage are main reasons for borehole collapse. The methods of calculating collapse and fracture pressure and determining drilling safety density window were put forward based on mechanical analysis. In order to reduce drilling problems in piedmont structures, some countermeasures should be taken from optimizing well track and casing program, using proper mud density, improving inhibitive and sealing ability of drilling fluid. Good sealing ability can reduce seepage and cut off pressure transmission, enhancing the effective support force. This is the key technology of maintaining wellbore stability in hard brittle shale in piedmont structures.

Sealing Advancements for Rotating Control Devices

2021 ◽  
Author(s):  
Aaron Paul Richie ◽  
Lannie Laroy Dietle
Keyword(s):  
New Technologies ◽  
Drilling Fluid ◽  
High Surface ◽  
Fluid Pressure ◽  
Control Device ◽  
Differential Pressure ◽  
Rotary Drilling ◽  
Critical Elements ◽  
Annular Gap ◽  
Pressurization System

Abstract Some of the most critical elements of a rotating control device (RCD) are the rotary seals that prevent a pressurized abrasive drilling fluid from destroying the rolling element bearings. The rotary seals prevent the drilling fluid from damaging the bearings by sealing the annular gap between the rotating mandrel and the stationary bearing housing. The combination of pressure causing seal material to bulge into the annular gap and the relative runout between the mandrel and housing can cause extrusion damage of the seal. The relative rotation and runout between the seal and mandrel in an abrasive environment leads to abrasive wear of the seal. Finally, the relatively high surface speed and contact pressure between the seal and mandrel leads to adhesive wear of the seal. When the drilling fluid pressure below the RCD is low there are several suitable rotary seal designs that can provide acceptable RCD life at most rotary drilling speeds. To meet higher speed and pressure conditions for the 100 hour minimum duration, established in API 16RCD, many RCD designs employ a sealing approach that splits the sealing tasks across two seals. One seal excludes the abrasive drilling fluid at low differential pressure and another seal, capable of operating at high differential pressure, retains a clean lubricant that is at nearly the same pressure as the drilling fluid. This sealing system generally requires an external lubricant pressurization system to provide the necessary fluid and pressure environment for the seals. Some drilling sites that operate at these conditions cannot accommodate these large, complex, expensive lubricant systems due to space or access constraints, or economic considerations. This paper describes an innovative sealing system that enables an RCD to operate at 1,500 psi and 100 RPM for 200 hours without requiring an external lubricant pressurization system. This claim is based on extensive laboratory testing of three new technologies included in this sealing system. Key results and summaries from the test program are included in this paper. The three key technologies are: A hydrodynamic spring-loaded lip seal that can be used to exclude abrasive drilling fluid at low-differential pressure or retain a clean lubricant at high differential pressure. A direct-compression hydrodynamic seal that can retain a clean lubricant at high differential pressure. A self-actuating miniature valve that replaces the lubricant supply function of an external lubricant pressurization system.

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