Optimize Internal Phase Salinity to Improve Wellbore Stability and Mitigate Lost Circulation

2021 ◽  
Author(s):  
Jianguo Zhang ◽  
Alan Rodgerson ◽  
Stephen Edwards
Keyword(s):  
Water Activity ◽  
Wellbore Stability ◽  
Chemical Effect ◽  
Wellbore Instability ◽  
Lost Circulation ◽  
Main Challenge ◽  
Internal Phase ◽  
Naturally Fractured ◽  
Drilling Operations ◽  
Shale Formation

Abstract Wellbore instability and lost circulation are two major sources of non-productive time (NPT) in drilling operations worldwide. Non-aqueous fluid (NAF) is often chosen to mitigate this and minimize the chemical effect on wellbore instability in reactive shales. However, it may inadvertently increase the risk of losses. A simple method to optimize internal phase salinity (IPS) of NAF is presented to improve wellbore stability and mitigate the increased possibility of losses. Field cases are used to demonstrate the effects of salinity on wellbore instability and losses, and the application of the proposed method. IPS is optimized by managing bidirectional water movement between the NAF and shale formation via semi-permeable membrane. Typically, higher shale dehydration is designed for shallow reactive shale formation with high water content. Whereas, low or no dehydration is desired for deep naturally fractured or faulted formation by balancing osmotic pressure with hydrostatic pressure difference between mud pressure and pore pressure. The simple approach to managing this is as follows: The water activity profile for the shale formation (aw,shale) is developed based on geomechanical and geothermal information The water activity of drilling fluid (aw,mud) is defined through considering IPS and thermal effects The IPS of NAF is manipulated to manage whether shale dehydration is a requirement or should be avoided If the main challenge is wellbore instability in a chemically reactive shale, then the IPS should be higher than the equivalent salinity of shale formation (or aw,shale > aw, mud) If the main challenge is losses into non-reactive, competent but naturally fractured or faulted shale, then IPS should be at near balance with the formation equivalent salinity (or aw, shale ≈ aw, mud) It is important that salt (e.g. calcium chloride – CaCl2) addition during drilling operations is done judiciously. The real time monitoring of salinity variations, CaCl2 addition, water evaporation, electric stability (ES), cuttings/cavings etc. will help determine if extra salt is required. The myth of the negative effects of IPS on wellbore instability and lost circulation is dispelled by analyzing the field data. The traditional Chinese philosophy: "following Nature is the only criteria to judge if something is right" can be applied in this instance of IPS optimization. A simple and intuitive method to manage IPS is proposed to improve drilling performance.

Managing Wellbore Stability Window and Well Integrity by Adjusting the Tight Margin to Successfully Drill through Naturally Fractured Zone Onshore Niger Delta

2021 ◽  
Author(s):  
Bassey Akong ◽  
Samuel Orimoloye ◽  
Friday Otutu ◽  
Akinwale Ojo ◽  
Goodluck Mfonnom ◽  
...  
Keyword(s):  
Niger Delta ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Failure Behavior ◽  
Natural Fractures ◽  
Gas Well ◽  
Well Integrity ◽  
Trajectory Formation ◽  
Naturally Fractured ◽  
Drilling Operations

Abstract The analysis of wellbore stability in gas wells is vital for effective drilling operations, especially in Brown fields and for modern drilling technologies. Tensile failure mode of Wellbore stability problems usually occur when drilling through hydrocarbon formations such as shale, unconsolidated sandstone, sand units, natural fractured formations and HPHT formations with narrow safety mud window. These problems can significantly affect drilling time, costs and the whole drilling operations. In the case of the candidate onshore gas well Niger Delta, there was severe lost circulation events and gas cut mud while drilling. However, there was need for a consistent adjustment of the tight drilling margin, flow, and mud rheology to allow for effective filter-cake formation around the penetrated natural fractures and traversed depleted intervals without jeopardizing the well integrity. Several assumptions were validly made for formations with voids or natural fractures, because the presence of these geological features influenced rock anisotropic properties, wellbore stress concentration and failure behavior with end point of partial – to-total loss circulation events. This was a complicated phenomenon, because the pre-drilled stress distribution simulation around the candidate wellbore was investigated to be affected by factors such as rock properties, far-field principal stresses, wellbore trajectory, formation pore pressure, reservoir and drilling fluids properties and time without much interest on traversing through voids or naturally fractured layers. This study reviews the major causes of the severe losses encountered, the adopted fractured permeability mid-line mudweight window mitigation process, stress caging strategies and other operational decisions adopted to further salvage and drill through the naturally fractured and depleted intervals, hence regaining the well integrity by reducing NPT and promoting well-early-time-production for the onshore gas well Niger Delta.

Wellbore Geomechanics of Extended Drilling Margin and Engineered Lost-Circulation Solutions

SPE Journal ◽  
2017 ◽  
Vol 22 (04) ◽  
pp. 1178-1188 ◽  
Author(s):  
Amin Mehrabian ◽  
Younane Abousleiman
Keyword(s):  
Mechanical Properties ◽  
Stability Analysis ◽  
Analytical Approach ◽  
Wellbore Stability ◽  
Tensile Failure ◽  
Mechanical Interaction ◽  
Lost Circulation ◽  
Drilling Operations ◽  
Secondary Fractures ◽  
Lost Circulation Materials

Summary Wellbore tensile failure is a known consequence of drilling with excessive mud weight, which can cause costly events of lost circulation. Despite the successful use of lost-circulation materials (LCMs) in treating lost-circulation events of the drilling operations, extensions of wellbore-stability models to the case of a fractured and LCM-treated wellbore have not been published. This paper presents an extension of the conventional wellbore-stability analysis to such circumstances. The proposed wellbore geomechanics solution revisits the criteria for breakdown of a fractured wellbore to identify an extended margin for the equivalent circulation density (ECD) of drilling. An analytical approach is taken to solve for the related multiscale and nonlinear problem of the three-way mechanical interaction between the wellbore, fracture wings, and LCM aggregate. The criteria for unstable propagation of existing near-wellbore fractures, together with those for initiating secondary fractures from the wellbore, are obtained. Results suggest that, in many circumstances, the occurrence of both incidents can be prevented, if the LCM blend is properly engineered to recover certain depositional and mechanical properties at downhole conditions. Under such optimal design conditions, the maximum ECD to which the breakdown limit of a permeable formation could be enhanced is predicted.

Wellbore Shielding Technique Increases Operative Window, Avoiding Formation Instability and Losses, Minimizing NPT, and Optimizing Drilling Operations in the Unconventional Plays

2021 ◽  
Author(s):  
Gaston Lopez ◽  
Gonzalo Vidal ◽  
Claus Hedegaard ◽  
Reinaldo Maldonado
Keyword(s):  
Drilling Fluid ◽  
Drilling Fluids ◽  
Wellbore Instability ◽  
Lost Circulation ◽  
Drilling Performance ◽  
Drilling Parameters ◽  
Vaca Muerta ◽  
Drilling Operations ◽  
Fracture Gradient ◽  
Vaca Muerta Formation

Abstract Losses, wellbore instability, and influxes during drillings operations in unconventional fields result from continuous reactivity to the drilling fluid causing instability in the microfractured limestone of the Quintuco Formation in Argentina. This volatile situation becomes more critical when drilling operations are navigating horizontally through the Vaca Muerta Formation, a bituminous marlstone with a higher density than the Quintuco Formation. Controlling drilling fluids invasion between the communicating microfractures and connecting pores helps to minimize seepage losses, total losses, wellbore fluid influxes, and instabilities, reducing the non-productive time (NPT) caused by these problems during drilling operations. The use of conventional sealants – like calcium carbonate, graphite, asphalt, and other bridging materials – does not guarantee problem-free drilling operations. Also, lost circulation material (LCM) is restricted because the MWD-LWD tools clearances are very narrow in these slim holes. The challenge is to generate a strong and resistant seal separating the drilling fluid and the formation. Using an ultra-low-invasion technology will increase the operative fracture gradient window, avoid fluid invasion to the formation, minimize losses, and stop the cycle of fluid invasion and instability, allowing operations to maintain the designed drilling parameters and objectives safely. The ultra-low-invasion wellbore shielding technology has been applied in various fields, resulting in significantly improved drilling efficiencies compared to offset wells. The operator has benefited from the minimization of drilling fluids costs and optimization in drilling operations, including reducing the volume of oil-based drilling fluids used per well, fewer casing sections, and fewer requirements for cementing intervals to solve lost circulation problems. This paper will discuss the design of the ultra-low-invasion technology in an oil-based drilling fluid, the strategy for determining the technical limits for application, the evaluation of the operative window with an increase in the fracture gradient, the optimized drilling performance, and reduction in costs, including the elimination of NPT caused by wellbore instability.

scholarly journals New insight on studying the effect of both chemical sensitivity and rock mechanical properties in shale formation to minimize wellbore instability problems

2020 ◽  
Vol 205 ◽  
pp. 03012
Author(s):  
Mohammad H. Alqam ◽  
Hazim H. Abass ◽  
Abdullah M. Shebatalhmad
Keyword(s):  
Drilling Fluid ◽  
Wellbore Stability ◽  
High Porosity ◽  
Shale Formations ◽  
Wellbore Instability ◽  
Testing Procedures ◽  
Shale Formation ◽  
Rock Mechanical Properties ◽  
Core Volume ◽  
Shale Permeability

Historically, many of the wells drilled in in shale formations have experienced a significant rig downtime due to wellbore instabilities. Most of the instability problems originated from the encountered shale formations. The objectives of this study include (1) to measure the properties governing shale strength and drilling fluid/shale interaction, and (2) to establish a reliable and efficient rock mechanical testing procedures related to wellbore stability. Preserved shale core has been recovered from shale formation and special core handling procedure was implemented. Mineral oil was used for plugging and core preservation. Rock mechanical characterization was conducted on core samples using both XRD/SEM techniques to study the core mineralogy. In addition, shale permeability was determined by two methods: flow testing and pressure transition methods. The results indicated that shale has high percentage of quartz (30-40%) which causes the shale to have high porosity and high permeability. The unconfined compressive strength of shale is very low which any drilling fluid that contains water phase further reduces. The Young’s modulus is very low which makes near wellbore deformation high. Based on the shale swelling testing, the all-oil fluid show no volume change occurred to the shale. When the same shale was exposed to the 7% KCl, about 16% increase in core volume occurred in 48 hours. This means that all samples allowed the water to flow into the shale formation.

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.

Integration of Neural Networks and Wellbore Stability, a Modern Approach to Recognize Drilling Problems Through Computer Vision

2021 ◽  
Author(s):  
Luis Alejandro Rocha Vargas ◽  
Carlos Andres Izurieta
Keyword(s):  
Neural Networks ◽  
Computer Vision ◽  
Data Augmentation ◽  
Wellbore Stability ◽  
Causal Mechanism ◽  
Modern Approach ◽  
Wellbore Instability ◽  
Multiple Parameters ◽  
Drilling Operations ◽  
Multiple Data Sets

Abstract Cavings are a valuable source of information when drilling operations are being performed, and multiple parameters can contribute to producing cavings which indicate that failure has occurred or is about to occur downhole. This study will describe a project which is an integrated study of Machine Learning, Computer Vision, Geology, and Photography so that the recognition of cavings in the shaker is possible and how to link the cavings morphology with causal mechanisms related to wellbore instability problems. This study aims to develop a model which can extract caving features such as Shape, Edge Definition, Color, and Size. One of the core aspects of this study was to develop a structured image database of cavings from the Norwegian Continental Shelf which contains important feature information and the application of different algorithms used for automation enabled several opportunities to analyze and identify causal mechanism related to wellbore instability problems in real-time. As a result of that, the drilling operations would experience an improvement in terms of a faster decision-making process to solve operative problems related to wellbore stability which will lead to optimization not only in time and resources but also in safer drilling operations. Different algorithms and artificial intelligence tools were used to investigate the best approach to correctly detect and derive meaningful information about the shape, color size and edge from cavings like supervised learning, unsupervised learning, neural networks and computer vision. A key part of this study was image augmentation which plays a significant role for the detection of the cavings and their features. Multiple data sets can be created, and by using data augmentation, this will enable recognition of more complex patterns that will have on-rig applicability. Also, this new approach can deliver multiple outcomes besides failure mechanism identification such as volume of rocks being drilled, transport of cutting, type of formation being drilled.

Mitigating Lost Circulation Across Permeable Formations of the Gunashli Field in the Caspian Sea with a New Tailored Spacer System

2021 ◽  
Author(s):  
Tom Farrow ◽  
Nurlan Gadimov ◽  
Kyriacos Agapiou ◽  
Mukhtar Safarov
Keyword(s):  
Caspian Sea ◽  
Field Application ◽  
Wellbore Stability ◽  
The Caspian Sea ◽  
Lost Circulation ◽  
History Of ◽  
Drilling Operations ◽  
Zonal Isolation ◽  
Additional Costs ◽  
Loss Control

Abstract Cementing operations seek to minimize non-productive time (NPT) as part of the broad effort to optimize costs. A commonly encountered event that contributes to NPT is lost circulation. Lost circulation may often be associated, and treated, during drilling operations, but can occur during cementing practices, e.g. while running casing in the wellbore and/or circulating cement and treatment fluids. When fluids are lost to the formation and not appropriately cured, cementing objectives may not be met and, ultimately, zonal isolation can be compromised. Additional costs may be incurred to remediate the well construction and achieve a dependable barrier. It is, therefore, of great interest to develop and implement solutions which can facilitate the prevention and treatment of lost circulation. Described herein is the evaluation and use of a new tailored spacer system (TSS) engineered to effectively prevent lost circulation and maintain wellbore stability. The TSS was designed for use in cementing shallow water Caspian Sea wells with permeable formations and a history of losses. The spacer was subjected to conventional spacer tests and simulations including rheological measurements, compatibility assessments and fluid modeling to ensure job requirements would be met. Loss control tests were performed to verify the efficacy of the TSS to effectively prevent losses. All screenings demonstrated the TSS would be well-suited for the intended field application. The spacer system was successfully deployed in Caspian Sea wells and helped meet cementing objectives where conventional treatments failed.

Study and Application of Nanomaterials in Drilling Fluids

2012 ◽  
Vol 535-537 ◽  
pp. 323-328 ◽  
Author(s):  
Long Li ◽  
Jin Sheng Sun ◽  
Xian Guang Xu ◽  
Cha Ma ◽  
Yu Ping Yang ◽  
...  
Keyword(s):  
Potential Application ◽  
Essential Role ◽  
Oil And Gas ◽  
Wellbore Stability ◽  
Drilling Fluids ◽  
Borehole Stability ◽  
Lost Circulation ◽  
Gas Recovery ◽  
Film Forming ◽  
Drilling Operations

Due to their special properties, nanomaterials had potential application value, and they could play an essential role in improving mudcake quality, assisting in film-forming, reducing lost circulation, and enhancing wellbore stability. Some nanomaterials, such as nanocomposite filtration-reducing agent, nanocomposite viscosifier, nanosized emulsion lubricant, nanometer organoclay, and so on, were introduced, and all of them had significantly influence on the process of drilling operations. As a result, the application of nanomaterials in the field of drilling fluids are very useful for cleaning borehole, maintaining borehole stability, protecting reservoir, and enhancing oil and gas recovery. Finally, the further application of nanomaterials in drilling fluids is also prospected.

The Impact of Diagenesis and Compaction on Drilling Failure Detection

2017 ◽  
Author(s):  
Nur Suriani Mamat
Keyword(s):  
Failure Detection ◽  
Complex Problem ◽  
Wellbore Stability ◽  
Related Factors ◽  
Wellbore Instability ◽  
Lost Circulation ◽  
Drilling Parameters ◽  
Sensitive Clay ◽  
A Chain ◽  
The Impact

An important problem during drilling operation is wellbore instability; a complex problem caused by mechanical and chemical related factors. Even the best drilling practice could evade small instability problems that later may become irreparable. The risk of wellbore stability is mostly related to drilling, tripping and reaming activity with, including lost circulation, sloughing repair and loss of penetration. In this paper, the impact of historical and state of diagenesis and compaction on borehole instability has been studied, systematized, and used for general modelling. All the concepts are presented as symbolic concepts in a hierarchical order and linked in a chain of cause-effect relationships to wellbore failures. Through surveillance of drilling parameters, diagenesis and compaction were identified through formation hardness, well depth, shale type, and cuttings/cavings characteristic. From the analysis, kaolinite, which normally exists in intermediate diagenesis, is most likely to cause bit balling when hydrated. Smectite, which is water-sensitive clay, would cause chemical wellbore instability in water-based mud. Carbonates formation such as dolomite and limestone is more likely to result in lost circulation as compared to shale. Our work demonstrates how state of diagenesis and compaction could influence wellbore instability condition. This knowledge could be applied to understand the behavior of rock formation being drilled and would influence the prediction of probable failures as an end result. The method presented here integrates theoretical knowledge and real-time drilling data to envisage the most likely failure.

scholarly journals An Assessment of the Causes of Wellbore Instability and Stuck Pipe Occurrences in an Offshore Field, Niger Delta, Nigeria

2020 ◽  
Vol 1 (1) ◽  
Keyword(s):  
Cation Exchange ◽  
Niger Delta ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Swelling Potential ◽  
Offshore Drilling ◽  
Wellbore Instability ◽  
Clay Swelling ◽  
Drilling Operations ◽  
Cationic Exchange

Wellbore instability and consequential stuck pipe issues are a common challenge associated with offshore drilling. Usually, the effect of wellbore instability is an increase in nonproductive time, possible loss of tools and costly drilling operations. Hence, there is a need for wellbore stability analyses before and during drilling operations. In “Agaza Field”, offshore Niger Delta, wellbore instability problems were encountered at various depths between 3,696-4,270 ft.; 5,000-5,425 ft. and 7,600-8000 ft. intervals. Sixty-five ditch-cutting samples and composite log plots obtained from both wells were and analyzed to determine the clay swelling potential and the cationic exchange between the formation and the drilling fluid as well as causes of formation instability. Agaza-1 well showed evidence of tight hole at intervals between 4,200 and 7,600 ft. In Agaza-2, there were indications of wellbore stresses from 1,908 ft. to 2,030 ft. However, deeper than 4,225ft depth, high fluctuation of pore pressure coincided with wellbore instability between 4,810 ft. and 5,200 ft. The principal clay minerals present within the formations are Illite, Smectite and Smectite/Illite interlayered types. Result of the cation exchange analysis showed that high concentration of calcium and sodium in the shale is responsible for high dissociation of the constituent minerals hence making the shales unstable. Analysis has shown that samples at some intervals from both wells are associated with high swelling potential while average cation exchange value is 40 meq/100g. Therefore, the primary cause of wellbore instability and stuck pipe within the studied intervals are attributed to high swelling and reactivity over time due to fluidformation interaction. Keywords: Clay cationic exchange, Clay swelling potential, Offshore drilling challenges, Reactive shales. African

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