scholarly journals INFLUENCING FACTORS OF BOREHOLE FAILURE IN BEDDING PLANE OF A RESERVOIR

2015 ◽  
Vol 45 (1) ◽  
pp. 41-47
Author(s):  
Md. Shamsuzzoha
Keyword(s):  
Bedding Plane ◽  
In Situ Stress ◽  
Attack Angle ◽  
Wellbore Stability ◽  
Borehole Stability ◽  
General Behaviour ◽  
Shale Formation ◽  
Well Data ◽  
3D Effect ◽  
Major Factors

Borehole instability during drilling is common in shale formation. Weak bedding plane in borehole is critical in understanding in-situ stress and borehole instability. Unified decision about the plane of weakness and failure of borehole on shale has yet to be fully realized by the industry, particularly because borehole stability has not been well addressed. This research was based on a linear elastic and isotropic model for stresses around the wellbore with the aim of trying to understand the general behaviour of inclined borehole failure due to bedding plane. Using Aadnoy et. al (2009)’s model, this paper discussed mechanical wellbore stability and plane of weakness of shale formation. This paper investigated three major factors firstly, borehole failure of bedding plane, secondly it introduced optimized well path. Thirdly, it analysed whether well data was present at a safe position or bedding exposed positions. This paper also analysed the 3D effect of attack angle changing azimuth with a constant inclination on bedding plane. This paper argues that bedding exposed does not only depend on inclination but also depend on dip of the formation, attack angle and azimuth. It also found the different value of attack angle of up dip and down dip position of Aadnoy model and addressed way to solve the existing difficulty

scholarly journals Borehole Stability in Shale Formation: Modeling the Effects of Molecular Weight and Concentration of Polymers in the Drilling Fluids Formulation

2014 ◽  
Vol 5 (1) ◽  
pp. 260-270
Author(s):  
Khoshniyat A ◽  
Shojaei M. ◽  
Jarahian K. ◽  
Mirali M. ◽  
Ghorashi S. ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Reflection Coefficient ◽  
Drilling Fluid ◽  
Exchange Capacity ◽  
Oil Field ◽  
Wellbore Stability ◽  
Drilling Fluids ◽  
Drilling Process ◽  
Borehole Stability ◽  
Shale Formation

A new experimental model was developed to predict the role of special polymeric additives, in the drilling fluid formulation, on the wellbore stability in shale formation. The shale formation was regarded as a non-ideal membrane and the effects of various characteristics of the added polymers were studied on the membrane reflection coefficient. The model was applied to unique field data from the oil field in south of Iran, including clay structure, cation exchange capacity (CEC), density and porosity of the shale. The results, using various polyglycols and polyacrylamides as the polymeric additive, showed that the structure of the polymeric chains e.g. type and content of ionic segments had significant effect on their adsorption mechanism and its strength.  It was concluded that increasing the molecular weight of the polymer chains decreased the rate and amount of the adsorption due to the increasing of the entanglements between the chains which in turn limited their mobility. So, adsorption of the polymeric material on the shale had significant impress on its performance as a membrane by increasing the shale reflection coefficient enhancing its stability during drilling process. Finally, the developed model results were in good agreement by experimental test results which was done in a specific shale stability set up.

Analysis of Wellbore Instability in an Offshore Field: A Case Study

2018 ◽  
Author(s):  
Nubia Aurora González Molano ◽  
José Alvarellos Iglesias ◽  
Pablo Enrique Vargas Mendoza ◽  
M. R. Lakshmikantha
Keyword(s):  
Field Effect ◽  
Point Of View ◽  
Wellbore Stability ◽  
Geomechanical Model ◽  
Wellbore Instability ◽  
3D Geomechanical Model ◽  
Shale Formation ◽  
Major Factors ◽  
Offshore Field

Several wellbore instability problems have been encountered during drilling a shale formation in an offshore field, leading to the collapse of the main borehole and resulting in several sidetracks. In this study, an integrated 1D & 3D Geomechanical model was built for the field in order to investigate the major factors that control the instability problems from a Geomechanical point of view and to design an optimum mud window for planned wells in the field. Effect of bedding on wellbore stability was the most important factor to explain the observed drilling events. Optimized well paths for planned wells were proposed based on results of a sensitivity analysis of the effect of bedding orientation on wellbore stability. It has been observed that bedding exposed depends not only on well inclination but also on dip of the formation, attack angle, and azimuth.

A Novel Method to Determine the Drilling Fluid Density for Gypsum-Salt Layer

2021 ◽  
Author(s):  
Jitong Liu ◽  
Wanjun Li ◽  
Haiqiu Zhou ◽  
Yixin Gu ◽  
Fuhua Jiang ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Shrinkage Rate ◽  
Fluid Density ◽  
Salt Layer ◽  
Rock Creep ◽  
Key Factor ◽  
Well Abandonment

Abstract The reservoir underneath the salt bed usually has high formation pressure and large production rate. However, downhole complexities such as wellbore shrinkage, stuck pipe, casing deformation and brine crystallization prone to occur in the drilling and completion of the salt bed. The drilling safety is affected and may lead to the failure of drilling to the target reservoir. The drilling fluid density is the key factor to maintain the salt bed’s wellbore stability. The in-situ stress of the composite salt bed (gypsum-salt -gypsum-salt-gypsum) is usually uneven distributed. Creep deformation and wellbore shrinkage affect each other within layers. The wellbore stability is difficult to maintain. Limited theorical reference existed for drilling fluid density selection to mitigate the borehole shrinkage in the composite gypsum-salt layers. This paper established a composite gypsum-salt model based on the rock mechanism and experiments, and a safe-drilling density selection layout is formed to solve the borehole shrinkage problem. This study provides fundamental basis for drilling fluid density selection for gypsum-salt layers. The experiment results show that, with the same drilling fluid density, the borehole shrinkage rate of the minimum horizontal in-situ stress azimuth is higher than that of the maximum horizontal in-situ stress azimuth. However, the borehole shrinkage rate of the gypsum layer is higher than salt layer. The hydration expansion of the gypsum is the dominant reason for the shrinkage of the composite salt-gypsum layer. In order to mitigate the borehole diameter reduction, the drilling fluid density is determined that can lower the creep rate less than 0.001, as a result, the borehole shrinkage of salt-gypsum layer is slowed. At the same time, it is necessary to improve the salinity, filter loss and plugging ability of the drilling fluid to inhibit the creep of the soft shale formation. The research results provide technical support for the safe drilling of composite salt-gypsum layers. This achievement has been applied to 135 wells in the Amu Darya, which completely solved the of wellbore shrinkage problem caused by salt rock creep. Complexities such as stuck string and well abandonment due to high-pressure brine crystallization are eliminated. The drilling cycle is shortened by 21% and the drilling costs is reduced by 15%.

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.

scholarly journals Investigation on influence of drilling unloading on wellbore stability in clay shale formation

2020 ◽  
Vol 17 (3) ◽  
pp. 781-796 ◽  
Author(s):  
Yi Ding ◽  
Xiang-Jun Liu ◽  
Ping-Ya Luo
Keyword(s):  
Wellbore Stability ◽  
Clay Shale ◽  
Shale Formation

The in-situ stress state of the Rhine-Ruhr region and its implications for the geothermal energy utilization

2020 ◽  
Author(s):  
Michal Kruszewski ◽  
Giordano Montegrossi ◽  
Tobias Backers ◽  
Erik Saenger
Keyword(s):  
Stress State ◽  
Geothermal Energy ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Energy Utilization ◽  
Natural Fracture ◽  
Electricity Production ◽  
The Future ◽  
Ruhr Region

<p>The Rhine-Ruhr region is one of the largest metropolitan areas in Europe, with more than 10 million inhabitants, located in western Germany. The region is defined by the rich coal-bearing layers from the upper Carboniferous period, extracted as early as the 13<sup>th</sup> century and belonging to the sub-Variscan Trough. In 2018, after more than 700 years of exploration, the last black coal mine was closed in the area. One of the most promising re-uses of the abandoned coal mines is the exploitation of geothermal energy sources. Additionally, to the geothermal energy extracted from existing mines, potential deep geothermal reservoirs within the Rhine-Ruhr, may exist at depths between 4.5 and 6 km, where Devonian limestones were found. Based on the available temperature profiles from deep exploration wells in the area, geothermal gradient amounts to 36.8<sup>o</sup>C/km and results in reservoir temperatures between 170<sup>o</sup>C and 220<sup>o</sup>C, which will enable not only heat but even electricity production. This study provides a comprehensive investigation of the full in-situ stress state tensor with its anisotropy and presents crucial physical formation and natural fracture properties. The data for this investigation was acquired from the extensive borehole logging and geomechanical campaigns carried out in deep coal exploration wells throughout the 1980s as well as from the recent shallow geothermal research wells. Acquired data allowed assessing critically-stressed, i.e. hydraulically active, fractures undergoing shear displacement, being primarily responsible for the future geothermal reservoir permeability. Extensive sets of microseismic, subsidence and drilling data were used to confirm the results of the analysis. Additionally, wellbore stability analysis and potential drill paths for the future medium-to-deep geothermal wells in the region were assessed. This study is a part of the 3D-RuhrMarie project, which aims to assess the intrinsic seismic risk within the Rhine-Ruhr region to promote safer and economically more efficient exploration and exploitation of the future geothermal resources.</p>

The Effect of Anisotropy of Medium on the Stress State around a Borehole

2011 ◽  
Vol 291-294 ◽  
pp. 2139-2144
Author(s):  
Yong Shu Jiao ◽  
Mu Hui Fan ◽  
Li Juan Li ◽  
Zong Xi Cai
Keyword(s):  
Maximum Shear Stress ◽  
Bedding Plane ◽  
Fracture Analysis ◽  
In Situ Stress ◽  
Stress Changes ◽  
Degree Of Anisotropy ◽  
Inclined Boreholes ◽  
Collapse Failure ◽  
Inclined Borehole

Based on the analytical solution for the stress field around an inclined borehole in an anisotropic medium, a computer program was developed and a serial parametric study was conducted. The effects of parameters such as degree of anisotropy, borehole inclination, bedding plane inclination and in-situ stress conditions on the stress distribution around a borehole were evaluated. The results showed that medium anisotropy has little effect on borehole fracture analysis at low borehole inclinations, but its influence becomes significant for highly inclined boreholes. As the degree of anisotropy varies the maximum shear stress changes remarkably. This indicates that the degree of anisotropy plays a role in the collapse failure of a borehole. The information generated in these studies can be used in predicting the fracture or collapse-initiating pressures.

Mechanical-Thermal-Chemical Coupled Research of Wellbore Stability in Jabung Oil Field, Indonesia

2011 ◽  
Vol 402 ◽  
pp. 709-714 ◽  
Author(s):  
Pei Yang ◽  
Mian Chen ◽  
Yan Jin ◽  
Bing Hou ◽  
Kang Qiu ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Drilling Fluid ◽  
Great Influence ◽  
Chemical Properties ◽  
Oil Field ◽  
Wellbore Stability ◽  
Additional Stress ◽  
Borehole Stability ◽  
Well Trajectory ◽  
The Impact

The Jabung oilfield in Indonesia is characterized by complex geological structural movement, large tectonic stress and high temperature gradient. Accidents such as borehole collapse and sticking were frequently encountered when drilling shale formations, which often result in serious damage. In this paper, a series of experiments were conducted to evaluate the performance of shale in drilling fluid, including linear expansion rate evaluation tests and rolling recovery evaluation tests. Also X-ray diffraction was used to analyze the mineral composition of shale. The mechanical parameters of shale were obtained through statistical analysis. By using ABAQUS software, the temperature difference induced by thermal stress distribution was analyzed. After that, the borehole stress distribution was determined by coupling the additional stress with in-situ stress. Finally, based on borehole stability mechanical models, the effects of well trajectory on borehole stability were analyzed. We found that the chemical properties of drilling fluid, wellbore trajectory and temperature has a great influence on wellbore stability, and the impact of temperature changes and of well trajectory are the largest factor.

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