bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate Modeling of Surge and Swab Pressures of Yield Power Law Fluids in Concentric Annuli
Authors: Erge O. , Akin S. , Gucuyener I. H.
Published: January 2018

Accurate numerical modeling of surge and swab pressures in concentric annuli is proposed. The numerical scheme is developed for the laminar flow occurring during the drillstring axial movement. The model incorporates Yield Power Law (YPL) fluids, which is a good representation of the most of the drilling fluids. A commercial computational fluid dynamics (CFD) package is used to validate the developed numerical model. Also, the mathematical model and CFD analysis are compared with the existing models from literature.

A high order finite difference numerical model is developed that accurately captures the physics of laminar flow due to surge and swab phenomena in concentric annuli. The numerical scheme is prepared such that it accounts for both Newtonian and non-Newtonian fluids. YPL model is incorporated in the proposed scheme, and it accurately estimates the drilling fluid behavior in both high and low shear rates. CFD analysis is conducted using a commercial software to validate the accuracy of in house developed numerical model. The velocity profiles across the annulus are compared in order to verify the precision of the model.

The proposed model for the surge and swab pressures is more accurate than narrow slot approximation model which is most commonly used in the drilling industry. With this proposed modeling, the physics of surge and swab pressures are better captured, because it accounts for the effect of curvature in annular geometries. The model is well-validated with the CFD analysis and the velocity profile comparison of the numerical solution and CFD analysis yields less than 5% average absolute percent error. With this work, dimensionless velocity profiles are presented which better explain the flow during surge and swab in concentric annuli, while the inner pipe is reciprocating in steady-state.

Pulling out or running tubulars in the vertical section, or running casing with centralizers approximates the position of tubular to concentric. It is very important to accurately calculate these pressure losses to avoid fracturing the formation or having an influx from the formation. Therefore, CFD analysis and mathematical modeling of surge and swab pressures presented in this study has potential to optimize the tripping operations that will help avoid hole problems.
Proppant Performance in Marcellus Shale Fractures Under Experimental In-Situ Stress Conditions
Authors: Elsarawy Ahmed M. , Nasr-El-Din Hisham A.
Published: January 2018

Hydraulic fracturing is a key treatment for economical production from shale formations. High surface pressure is used to fracture the formation, and proppant is pumped to prevent fracture closure after the pressure is removed. The ability of proppant to maintain high fracture width and permeability controls the flow of the hydrocarbon fluids towards the wellbore, and, hence, the behavior of different proppants at in-situ conditions is critical to the success of fracturing operations in shale formations. The objective of this paper is to experimentally evaluate the performance of two widely used proppants in Marcellus shale at elevated stress conditions.

A proppant-crushing test between two samples of Marcellus shale was performed to evaluate the proppant performance at different closure stress values up to 10,000 psia. Two types of proppants were tested: sand and sintered bauxite at different concentrations. This work used a digital microscope to measure the width of the fracture at each closure stress; a series of photographs of the propped fracture were taken, and an image analysis software was used for fracture width measurements. The amount of crushed proppant and induced formation fines due to embedment were also quantified after each test.

The results indicate that with partial monolayer proppant, both proppants experience a significant reduction in the fracture width at elevated closure stresses, reaching as high as 48% at 10,000 psia. Proppant physical properties were found to affect the initial fracture width even though the proppant concentration was the same. The use of multiple layers of bauxite proppant reduced the loss of fracture width to 14% at 10,000 psia closure stress. Results reveal that sand proppant shows a high degree of crushing at 0.05 and 0.25 lb/ft2 proppant concentrations. On the other hand, the use of bauxite results in a higher amount of formation fines due to proppant embedment, which could cause severe damage to the fracture conductivity.

The paper contributes to the understanding of how proppants behave at in-situ conditions of shale hydraulic fractures. Results can be used to optimize proppant and fluid selection, and reduce the sources of damage to fracture conductivity to maximize well productivity.
Drilling Control Rooms of the future
Authors: Botnan Espen
Published: January 2018

The driller, or well execution engineer, as some call it, is now responsible for a bigger part of the overall drilling process as automation and mechanization on rigs increases and the market moves toward performance-based, as opposed to day-rate, contracts. More information must now be absorbed and analyzed; hence, the driller is more important for safe and efficient drilling processes. Due to this, it is more critical than ever to ensure that the well execution engineer has an optimal working environment. This paper outlines several new technologies to help ensure that the working environment and process is more streamlined and comfortable.

Several innovations in the driller's control room (DCR) are outlined, such as new window and display technology, as well as new sophisticated communication systems.

Additionally, new drilling software is developed to ensure constantly high performance through autopiloting.

Overall, these new products improve the working environment and overall efficiency, which also results in more cost-effective well construction and safer operations for the rig crew.
Perforating Vertical Smart Well Completions Using Tubing-Conveyed Perforating Gun Assemblies: Case History
Authors: Wood Stuart , Comb Lachlan , Singh Mandeep Kuldeep , Lavery Joshua , Biddle Matthew , Hyatt Paul
Published: January 2018

Smart well completions include downhole gauges, sliding circulation valves, open/close safety valves, control lines, and fiber cables or a combination of these. One method for deploying this downhole equipment is achieved by affixing it to the outside of the casing and permanently cementing it in place; however, a challenge with external-casing equipment is helping to prevent damaging the installation if perforating is the chosen method to establish effective communication between the wellbore and formation. This challenge is further magnified when the well is drilled near-vertical and run on the outside of a large-diameter casing.

This paper discusses the execution of an engineered design of service to perforate a 7-in. diameter production smart well completion using 4 5/8-in. tubing-conveyed perforating (TCP) gun assemblies. As part of the completion design, the TCP gun assemblies were hung below the bottomhole assembly (BHA). A fiber-optic (FO) package was run external to the casing, and the well had a deviation less than 5°, preventing the use of high-side logging tools.

Various options, discussed later in this paper, were considered to locate the azimuthal orientation of the fiber cables, including a new-to-market technology tool. Ultimately, a method was devised to engineer an ultrasonic logging tool to be deployed in conjunction with a north-finding gyroscope tool to accurately determine the location of the external-casing equipment. TCP guns were then hung below the tubing string, which included a fixed-point orienting sub that could be used to confirm the direction of all the planned perforations. To achieve operational and economic objectives, the TCP assembly was dropped to the bottom of the well so that the well could be immediately placed on production without killing the well or retrieving the spent perforating guns.

The well was successfully perforated without damage to the external-gauge equipment, showcasing that collaborating with the operator, and understanding their value drivers, led to an engineered solution that maximized the asset value of the well.
Curing Losses in Vuggy Carbonate Formations
Authors: Alshubbar G. D. , Nygaard R.
Published: January 2018

Despite the preventive wellbore strengthening (WBS) approach, lost circulation (LC) followed by well control events have been encountered where thousands of barrels of mud were lost to a formation resulting in long periods of shutdowns. The aim of this paper is to identify the LC mechanism in this formation and propose conventional loss circulation materials (LCM) treatments that stand a higher chance of curing the losses based on experimental investigation of irregular shaped openings to mimic vuggy porosity.

A review was conducted to identify the depositional and diagenetic processes for the "A" formation. The study concluded that touching vugs type of porosity, created through massive dissolution, is the main LC mechanism. To propose a treatment, four stainless steel disks with different irregular opening shapes and sizes, to mimic the reported vugs in the "A" formation, have been developed. As vugs reportedly have wider openings than what anticipated in fractures, an equivalent vug diameter was defined as the maximum width along the longest vug axis. As an initial screening stage, these disks were used in a low-pressure LCM apparatus (LPA) with different LCM additives to identify if the concentration and particle size distribution (PSD) are able to form a seal. The integrity of the seal was then investigated using a high-pressure fluid loss apparatus.

Synthetic rubbers and calcium carbonates were specifically sized to meet the needed PSD and effectively initiated a seal. Other commercially available products, such as synthetic & acid soluble fibers and reticulated foam, were successful when mixed with other LCM to meet the need PSD. Several combinations of the LCM additives have been successfully identified to form a seal at high pressure differential reaching up to 3000 psi. Such a seal integrity would make a very good potential candidate treatment for "A" formation.
Improve the Drilling Operations Efficiency by the Big Data Mining of Real-Time Logging
Authors: YIN Qishuai , YANG Jin , ZHOU Bo , JIANG Menglei , CHEN Xiaoliang , FU Chao , YAN Li , LI Lei , LI Yatao , LIU Zhengli
Published: January 2018

Today's data is tomorrow's oil and gas. Only the data can tell us right or wrong, but not the experience or feel. The real-time logging data conforms to the 6V features of the Big Data (Velocity, Variety, Volume, Veracity, Visualization and Validity). As a result, the drilling operations efficiency is significantly improved by the Big Data mining of real-time logging.

The Big Data mining helps recognize the drilling operations automatically and identify the invisible non-production time (INPT). Firstly, the real-time logging data is acquired by the comprehensive logging unit. Secondly, the drilling operations are recognized by applying restrictions to drilling parameters. Thirdly, the daily time and the total time is breakdown based on the above logging data and operations categories. Finally, the INPT is identified by setting the target value based on the Big Data mining and learning curve.

The savings potential, which is determined by the average and target, is critical to improve the operations efficiency. On one hand, the Normal Distribution is established by setting the specific operation time (such as slips connection time, etc.) to the X-axis and the operation count to the Y-axis. The average and covariance of the Normal Distribution is calculated. On the other hand, the target value is based on the Big Data mining by the Bayesian network model and the total-time learning curve of batch wells. As a result, the real-time drilling efficiency can identify the best-performing operations, crews and rigs. The crew-based operational performance comparisons are effective to identify the best-performing crews and to indicate where best to focus training and crew supervision efforts in the future. And the real-time drilling efficiency can measure the rig performance in order to make INPT visible. At last, the real-time drilling efficiency yields cost and time savings on both deep-water and complex wells. The method is successfully applied to BD gas field in Indonesia which is HTHP and LW oil field in South China Sea which is in deep-water. Application shows the INPT represents about 32%.

The Big Data mining of real-time logging significantly improve the drilling operations efficiency, detect and minimize the INPT. As a result, the Big Data mining yields cost and time savings for tomorrow's market.
Optimization of Tripping Speed to Minimize Surge & Swab Pressure
Authors: Al-Abduljabbar A. M. , Hossain M. Enamul , Gharbi S. Al , Al-Rubaii M.
Published: January 2018

Pressure changes due to surge and swab has been a concern in the drilling industry for many years. The fast and sudden movement of the drill string while pulling out of hole causes the wellbore pressure to decrease. This is due to the frictional forces between the pipe moving upward and the drilling mud that is stationary, which is known as the swab pressure. The opposite is also true, moving quickly inside wellbore will cause the pressure to increase, and this is known as the surge pressure. If these pressure changes become very high, the formation might get fractured which introduces influx leading to a kick. In severe cases, this kick might lead to a blowout which endangers human lives and environment.

This article focuses on the fundamental theory of surge and swab in addition to the maximum pipe running speed that avoids surging and swabbing the well. Further, calculations are carried out to optimizing the maximum pipe tripping speed by employing different parameters as input values. Both laminar and turbulent flows are considered in addition to closed ended pipes since it is the most critical one. The objective of this study is to optimize the drilling parameters that specify the maximum pipe tripping speed with different hole's sizes and pipe dimensions. Moreover, this research offers the optimized values to identify the factors that heavily affect surge and swab pressures. The results show that annular space and bottom-hole assembly (BHA) length have significant effects on surge and swab pressure values. Sensitivity analysis shows that pipe size and mud rheology impacts surge and swab values, but not significant. In fact, it is the annular velocity which is heavily affected by BHA length and size. When it comes to casing, the size was not an issue because the annular space is larger compared to smaller casing sizes. In addition, study shows that depth plays vital roles that can be seen with smaller casing sized. This study will enhance the understanding of drilling problems while drilling due to surge or swab pressures.
Use of Managed Pressure Drilling Paved the Way to a Massive Gas Field Discovery in Egypt Western Desert: Case History
Authors: Emam S. S. , Brand P. R. , Gabaldon O. R. , Vityk M. , Leithy A. El , Shanab M. Abou , Hamdy B. , Abdel-Moniem M. , El-Desouky W. , El-Azm H. Abo
Published: January 2018

The BTE – 2 was planned as a land based deep vertical exploration well in Egypt (the deepest ever drilled by Bapetco), designed to evaluate the Abu Roash, Bahariya and Kharita formations, testing the Kharita gas reservoirs and leading into the development of the entire BTE prospect. The complexities included HT classification, formation pressures uncertainties, deep total depth, and introducing a new technology, Managed Pressure Drilling (MPD), to the rig.

MPD played a pivotal role in the major discovery of the exploratory "BTE – 2" well, which led to initial estimated in place volumes of 0.8 TCF for the BTE prospect. MPD allowed the operator to reach the reservoir section by successfully navigating the 0.45 ppg operating window in the upper section. MPD also created a wide range of benefits throughout drilling the 1080 meters section, including managing the BHP through the narrow drilling window, real time prognosis of the pore pressure and fracture gradients incorporating the use of Pressure While Drilling technology, efficiently managing drilling through severe conditions, optimizing logging operations and MPD running and cementing of the 7 inches liner.

A high Intensity kick was detected by the MPD system in Abu Roash "G" formation. Implementing the MPD assisted shut in method helped minimizing influx size. The kick was initially circulated conventionally and the MPD system was engaged during the second circulation while slightly increasing the Mud Weight.

Using the MPD system helped to control the annular pressure profile during multiple rig pump problems and motor stalling events. Due to the small operating window, running the 7 inches liner was a major challenge, even while using the MPD system. Non homogeneous drilling fluid, high loss rates and high PP added complexity to the process. Establishing a closed loop system created a safer and better monitoring and controlling system for the 7 inches liner running operations.

Managed Pressure Cementing was the only valid and reliable method to cement the 7 inches liner in place. The MPD system was used to manage the slim drilling window, and the Coriolis flow meter helped to identify the required pressure values to minimize associated losses.

Employing the MPD Constant Bottom Hole Pressure (CBHP) technique resulted in numerous learnings, especially when the MPD technique is a first use for the drilling rig crews. This paper highlights and emphasizes the distinguished learnings (not specific to a particular project) that could help in planning and implementation of future MPD wells.
Pioneering the First Hydraulic Fracturing in Iraq's Complex Reservoir
Authors: Syed I. Hussein , Ahmed A. Raheem , Abd Hatem R. , Alabdali S. Adnan , Yandong C. , Wenxin C. , Xinmin Z. , Zhaowei L. , Jin O. , Mingyue C. , Ding Y. , Zhu D. , Liang C. , Theseira K. , Mohd Faiz M. , Ab Murad M.
Published: January 2018

X reservoir in one of Iraq's field, is a medium pore, low permeability and small pore throat limestone oil reservoir with poor petrophysical characteristics. This reservoir group in which X reservoir is in constitutes to about 20% of the total resource in place. Conventional development allows only about 0.3% of reserves to be developed and this needed to be improved further. The mixed results of various stimulation campaigns (for example matrix acidising and acid fracturing) carried out earlier for this reservoir has prompted the Operator to evaluate the hydraulic fracturing stimulation, first of its kind in Iraq to further gauge its effectiveness and feasibility for field implementation.

This paper will discuss the steps undertaken before, during and after the hydraulic fracturing execution. In planning for this campaign, steps were taken to analyse the rock properties and mechanics of the formation to understand the challenges for the hydraulic fracturing and to enable optimisation of the fracturing parameters. Fracture fluid design, proppant optimisation and treatment design were proposed to systematically optimise the process of the hydraulic fracturing. As a deduction, the principles and recommendations of design optimisation for hydraulic fracturing in carbonate reservoirs will be presented in this paper.

The preliminary production gain from this pilot hydraulic fracturing exceeded the pre-job stimulation more than 10 times, showing promise of a new way of developing this challenging reservoir in the future. Comprehensive analysis of the reservoir characteristics and suitable fracturing design are key to this achievement. This approach will be the benchmark for future hydraulic fracturing jobs planned in the field. The optimisation study in this paper could serve as a reference to improve hydraulic fracturing efficiency and success in other similar carbonate reservoirs.

Being the first ever hydraulic fracturing campaign ever performed in Iraq, this paper will focus on the challenges, execution and preliminary results.
Understanding Cement Quality in Intermediate Casing Against Aquifers Using Cement Bond Logs: A Case Study of Cementing Against Aquifers in UAE
Authors: Hanif R. , Ashour S. H. , Yee S. , Hay M. Abdel
Published: January 2018

Cement and Casing integrity across the surface aquifers is as imperative as against the reservoir section, to avoid ground water communication. Zonal isolation among aquifers is obligatory as per local regulations. Understanding the expected cement quality in the intermediate casing across aquifers is desirable. It is essential to understand why there are wells with good cement across aquifers while some wells exhibit poor cementing, keeping the procedures and parameters identical.

A study was conducted to understand the aquifer pressures and overburden geologic features in the entire field and understand how they impact cement quality. Aquifer pressures are incorporated with seismic features to anticipate the aquifer behavior. Representative Wells were selected in different field areas encountering either different aquifer pressures or geological features. The cement bond logs (CBL) were interpreted in these wells, along with the information from drilling, and established the link between cement quality and aquifer behavior in the specific area.

It is observed that poor cement is present where either aquifer pressure is low or there are aquifers channels, sinkholes or other geological features derived from seismic interpretation.

To perform better cementation across the aquifers it is essential to understand the aquifer behavior in specific area of the field, address the issues in the well prognosis to the cement team, plan and perform cementing operations accordingly.
Design and Implementation of the Well Delivery Project Gate System
Authors: Al-Salem Mohammad , Al-Shehab Nawaf , Decena Jose
Published: January 2018

Kuwait Oil Company (KOC) launched a Project Gate System (PGS) program in 2010, which resulted in the development of the KOC PGS Process. The PGS Process was implemented in 2012, and has been applied to surface facility capital projects only. However, subsurface projects were excluded from the PGS, at that time.

In order to also improve the drilling of wells and facilitate the attainment of forecasted production targets efficiently and on time, a study of the development and implementation of a similar PGS Process for the delivery of wells was requested, in 2013. The study concluded that a parallel Well Delivery PGS (WD PGS) Process should be developed based on IOCs’ and NOCs’ best practices for well delivery, KOC's experience with the PGS Process, and the fit-for-purpose requirements of the concerned KOC stakeholders in all business Directorates.
Enhancing Jack-Up Performance Using Spudcan Extensions
Authors: van der List Remco H. , Akkermans Richard A. , Blaauw Floris W. , Baan Rutger C.
Published: January 2018

Jack-ups are designed to withstand specific environmental conditions at a defined water depth in combination with certain types of soil conditions. A balanced design results in an almost full utilization of the design elements under such conditions. Typical design elements used are the holding system (either the leg fixation system if present, or the jacking system), leg chord elements or the preload capacity. This means that if an owner wants to use the jack-up beyond the original design conditions, for example to operate in deeper water or in harsher conditions or with bearing pressure limitations, some of these elements would have to be upgraded. However, these elements are fully integrated into the overall design of the jack-up and thus an upgrade is always a very costly and often also a time-consuming affair.

A simpler way of upgrading the overall capacity of a jack-up is through the use of spudcan extensions. Spudcan extensions can be designed to replace the existing spudcan in the form of a new spudcan below the existing one at the bottom of the leg, a so-called add-on spudcan, or as a temporary or permanent extension of the original spudcan. In these cases, the impact of the spudcan extensions on the total jack-up are very limited, where in the best case the jack-up remains as-is and in the worst case only the lower ends of the legs are affected. The purpose of spudcan extensions is generally twofold:

Limit the leg penetration into the seabed, effectively reducing the free leg length below the hull; Move part of the overall leg bending moment from the hull towards the spudcan, effectively reducing the loads acting at hull level;

The first purpose is relatively simple and usually results in just an enlargement of the total horizontal projected area of the spudcan. In this case, the spudcan extension can be a welded permanent structure, or if the owner wants to be able to go back to the original design it will be designed to connect temporarily to the chords of the lower end of the legs or the top plate of the spudcan, fitting around the existing spudcan.

The second purpose is a bit more complicated, as the extension must now be able to attract overall leg bending moments. This usually means that the extension must either be significantly bigger than the original spudcan or equipped with skirts, or a combination of both. The size and type of spudcan required depends heavily on the soil conditions of the intended area of operation. The end result is mostly in the shape of an add-on spudcan, but can also be executed as a permanent extension.

GustoMSC shall present the design considerations of typical spudcan extensions, apply spudcan extension to three well known types of GustoMSC jack-ups and show the influence of spudcan extensions to the capacity of the jack-ups.
Microbial Assessment and Control in Drilling Operations
Authors: Sindi Mohammed E. , Ezzat Abdalla M , Ba Hamdan Abdulaziz A , Subhi Mohammed A , Al-Humaid Ghassan A. , Al-Humam Abdulmohsen A. , Zhu Xiangyang
Published: January 2018

Microbial contamination and extensive growth of bacteria in the drilling mud impact drilling operation and reservoir integrity. To reduce the damaging effect of microbial growth, drilling mud is generally treated with biocides for microbial control and preventing loss of rheological properties from biodegradation. Make-up water and drilling mud samples from reserve tank and mixing tank were collected from three drilling rigs in Saudi Aramco oilfields. The baseline number of general aerobic bacteria (GAB) and sulfate-reducing bacteria (SRB) in make-up water and drilling mud samples were determined using the Most Probable Number (MPN) method. Microbial growth in the drilling mud and microbial control using glutaraldehyde-based biocide were evaluated under the conditions simulating short-term (<24 hours) and long-term (up to 7 days) downtime of drilling operations. In short operational downtime, the current practice in Saudi Aramco with no biocide addition resulted in high number of GAB (105-107/ml) in the mud samples. In long operational downtime, addition of 1500 ppm of biocide (1/3 of normal dosage) at Day 3 was effective in controlling GAB and SRB growth in drilling mud. Biocide performance was significantly affected by sulfide content in the mud; higher dosage and more frequent treatment may be required to control the microbial growth in the drilling mud. The study indicated that biocide treatment is essential for microbial control in drilling operation, especially in the period of operational downtime. Finally, drilling mud operation and field best practice for microbial control were recommended to be implemented in all Saudi Aramco drilling rigs.
Mechanical Specific Energy and Statistical Techniques to Maximizing the Drilling Rates for Production Section of Mishrif Wells in Southern Iraq Fields
Authors: Alsubaih Ahmed , Albadran Firas , Alkanaani Nuhad
Published: January 2018

The Mechanical Specific Energy (MSE) and Statistical Analysis Approach (SAA) have been widely implemented in oil and/or gas well drilling industry to enhance the Rate of Penetration (ROP) and reduce the operation cost. This work focuses on predicting and optimizing the drilling efficiency and performance in the production section of Mishrif reservoir in southern Iraq fields. The drilling data from twenty-five wells has analyzed and examined to improve the drilling productivity relied upon MSE and statistical approaches. By using MSE technique, the minimum required energy to drill unit volume of each formation has determined to improve the drilling speed and avoid unnecessary energy consumption that may come out in the form of bit wearing / balling or vibration. The optimum energy is achieved when the MSE value comes close to the unconfined compressive strength (UCS) value that obtained from the empirical formula for limestone and shale rocks. The flounder and threshold points have recognized to optimize drilling data in the offset wells to enhance ROP in the future wells. In the statistical approach, the regression coefficients have obtained from the screened and filtered fields drilling data then the empirical equations to estimate ROP have constructed by using linear regression analysis through a commercial software. The optimization techniques lead to an impressive increase in the rate of penetration in the production section of the Mishrif reservoir. The MSE surveillance provides a reliable tool to maximize the ROP and reduce some drilling problems by using sufficient energy to drill each formation below the flounder point. An excessive energy consumption throughout drilling can be observed in the majority of wells been investigated. Thus, the non-productive time has mitigated considerably by utilizing drilling variables that have induced MSE equal to the unconfined compressive strength of the rocks. On another hand, the statistical analysis of real-time data for twenty-seven wells revealed a remarkable improvement in drilling performance by suggesting an empirical equation that predicts ROP through changing some key parameters such as Flow Rate (FL), Weight On Bit (WOB), Torque (TQ), Revolution Per Minute (RPM), Mud Weight (MWT) and Total Flow Area (TFA). The recommended drilling parameters resulted from this work can be used to reduce the drilling cost and prevent/mitigate the time-dependent failure in the production section.
Successful Acidizing of an HF Acid Sensitive Formation Using a Protective Ion-Complexing Agent
Authors: Salmi Ahmed Al , Al-Yaaribi Ahmed , Al-Ruzeiqi Saleh
Published: January 2018

Sandstone matrix acidizing is a challenge in most cases. The conventional mud acid system involving hydrochloric acid and hydrofluoric acid (HCl:HF) is widely used in stimulating sandstone formations. The disadvantage of using HCl:HF is in its rapid reaction rate, resulting in insoluble by-products from secondary and tertiary reactions that limit the treatment effectiveness. The system can also limit the acid's performance capability when deep formation stimulation is targeted.

Enhancing HCL:HF acid system has been developed by utilizing of a protective ion-complexing agent. The agent forms a temporary protective film on clay surfaces allowing the acid to react with the remaining parts of the formation. The stimulation treatment fluids can be placed within the open hole reservoir section using two methods. The first utilizes 2-in. by 1-in. concentric coil tubing (CCT) with side-jetting nozzles to achieve uniform placement across the horizontal section and deep penetration inside the matrix. The second method uses a conventional bull heading treatment.

Laboratory testing was performed to qualify the treatment. Different minerals were used to evaluate and understand the retardation of different acid systems. The solubility of clays was lower comparing to normal HF acid systems, indicating the slow reaction of the acid on clays and a sign that improved retardation was achieved. Further testing confirmed the formation of a protective layer on clays, enabling the acid to react more efficiently with the remaining minerals. After successful laboratory testing, field trials were conducted on four oil-producing wells in southern Oman that experienced fines migration issues. The main acid system was squeezed into the matrix, followed by brine post flush, and then flowed back. Treatments with the protective acid systems in the treated wells showed a net oil gain of 30% to 80% sustained for longer than six months.

This paper outlines the technical challenges in the design and application of the proposed acid system and presents the successful lab results indicating the formation of the protective film on the clays minerals and the deep penetration phenomenon.
Reduction of Subsurface Losses and Non-Productive Time During Deepwater Drilling by Application of Wellbore Strengthening Mechanism – A Strategic Approach
Authors: Alimuddin Sultan , Sharma Sunil , Mahadeshwar Sachin , Marinescu Pavel , Raman Chakrapani Venkat , Kumar Yogesh , Velavaraj Nirmaladevi K , Panicker Santosh , Rahim Syed Abdul
Published: January 2018

To maximize oil and gas production, it is paramount to reach the whole reservoir and extract hydrocarbon resources efficiently. Moreover, to reduce the costs in today's market, the well should be drilled in minimum operating time with no operational failures. This paper presents a detailed study and outline of a neoteric practice of using a wellbore strengthening while drilling, to drill a depleted deepwater reservoir and eliminate nonproductive time related to downhole losses. This novel solution has the potential to be used while drilling depleted reservoir sections in all Middle East areas.

In a deepwater block situated on India's east coast, synthetic-based reservoir drilling fluids are used to drill the reservoir section. While drilling depleted reservoir sands, dynamic losses amounting to 300 bbl/hr were encountered that led to nonproductive time and even abandonment of well. To continue the drilling campaign and lessen the downhole losses, fracture sizes of depleted reservoir sands were simulated using proprietary software. Considering the measurement-while-drilling (MWD) tool's limitations and other reservoir behavior, a reservoir drilling fluid with wellbore strengthening material was formulated. Extensive laboratory tests were conducted to confirm the bridge and sealing capability of the solution. Subsequent to laboratory testing, the same reservoir drilling fluid formulation was field trialed. The well was drilled successfully with no hindrance, except minor losses encountered at the top of the sand. Implementing this customized solution, combined with precise running strategy, led to effective results in more than four wells to date.

This paper presents a comprehensive study of drilling depleted zones using wellbore strengthening while drilling, identifying ideal products, studying reservoir compatibility, calculating cost effectiveness, evaluating overall performance based results, and overcoming challenges while implementing the strategy in deepwater wells. A detailed comparison of all the challenges that occurred while drilling and the proper troubleshooting steps are also discussed. Finally, the paper aims to compare the existing results with previous drilling techniques, which may help operators with the future development of respective fields. In this application, new technology of reservoir-friendly, loss prevention materials of ultra large size were used successfully.
Application of a Wellbore Shield Eliminates NPT in South China Sea Wells
Authors: Bakar Muhammad Aizat , Nasrudin Khairul Anwar , Nor M Abshar , Mclellan Justin , Bradbury Andy , Syrapushchynski Sasha , Wilder Michael , Rockwood Jene
Published: January 2018

Owing to the high depletion and narrow drilling windows characteristic of many wells in the South China Sea, the risks of severe losses increase exponentially. Mud density, sufficient to maintain well control, typically exceeds the fracture gradient of the clastic and coal formations. Thus, operators face a dilemma in balancing the need for mud weight to remain below the fracture gradient to avoid losses, while also providing sufficient density to block influxes into the well.

This paper describes the development and application of a process that essentially stabilized troublesome zones and enabled the wells to be drilled with mud weights higher than the maximum density. The authors will describe the drilling process that stabilizes microfractures in the formations and mitigates many of the issues associated with wellbore instability. The presentation of a case history will illustrate the historical mud weights and properties used to drill offset wells, and the corresponding hole stability problems. The comparative analysis demonstrates how the use of a higher mud weight eliminated well influxes while simultaneously achieving zero mud losses to the formation.

Furthermore, the technology delivered additional wellbore strength to weak formations, allowing the drilling operation to be completed as per plan. Accordingly, the operator significantly reduced the wellbore stability challenges associated with lost circulation, stuck pipe and well instability, thereby facilitating easier logging and delivering a quality, and less costly, producing well.
Overview of Lubrication Regimes and Contact Pressure Distribution in Proprietary Tubular Connections for Special Drilling Environments
Authors: Meza O. Grijalva , Sinaga S.
Published: January 2018

As a significant contributor to Well Integrity, the use of Premium Connections has increased in modern oilfield developments, where combined mechanical loading and a growing need for fluid tightness are becoming more common than before. This type of "specialty connectors" feature a metal-to-metal seal (MTM) which assures enhanced fluid tightness by means of distribution of contact stress generated during the make up process. In applications in which high amounts of torque or where rough field handling are the norm (e.g. Casing Drilling), the risk for damage at the MTM are big enough to put at risk the integrity of the well against leakage events. By means of understanding the mechanical and tribological aspects impacting the performance of such connectors a better understanding of their importance can be given, at the same time well defined areas of opportunity can be identified in the context of challenging drilling processes like drilling with casing.
Synthesis & Evaluation of synthesized PAA/AMPS-g-Sesbania Gum Graft Copolymer in Water Based Drilling Mud System for Mitigation of Borehole Instability in Conventional and Troublesome Formations
Authors: Kumar Saket , Chaurasia Siddharth , Sundriyal Pankaj , Gautam Sandarbh
Published: January 2018

The major problems associated with shale formation when it interacted with water based mud are borehole instability. This Wellbore instability may be due to swelling and dispersion of clay present in shale and also leads to other well problems like pipe sticking, hole enlargement, improper rheological & fluid loss control properties, and additional reaming etc. In this research paper an attempt has been made to evaluate the feasibility of synthesized graft copolymer in the formulation of water based mud system for challenging formations. The microwave irradiation technique has been adopted for synthesizing PAA/AMPS-g-Sesbania gum copolymer. Further, it was processed in the formulation of mud system. The remarkable rheological and filtration properties of the mud system have been seen with synthesized additive. The developed mud has possessed strong pseudoplastic behavior which is a desired property of any mud which has been observed from shear rate vs. shear rate curve. In addition, shale stabilization properties were investigated with shale rotability test on the synthesized core sample prepared in the laboratory. Moreover, percentage reduction in permeability (i.e., formation damage effect) has been found lesser in developed copolymer system co paring to conventionally used PHPA system. Hence, the formulated mud system can be used as a potential drilling mud system for drilling any oil wells.
Operational Performance Improvement Plan: How to Boost the Performance and Reduce the Cost During well Construction
Authors: Ruzhnikov Alexey , Alzate Jose , Singh Rudra , Al-Wahedi Khalid , AL-Kindi Rashid
Published: January 2018

Since the drilling started on the remote artificial islands located in UAE the operator used multiple initiatives to enhance the performance. One of them was the development of Operational Performance Improvement Plan(OPIP) targeting key aspects of the well planning and construction with an aim to improve the performance and reduce cost. The paper describes the thought process and steps taken to implement the OPIP and bring the performance to the new level for the operator.

The main objective in harsh economic conditions was to construct the wells safer, with less cost and more efficiently. To achieve the goal, several well construction optimization workshops were organized aiming to change the drilling processes, operations procedures, tools, equipment and well design, as well as to have a clear plan on smooth expanding the extended reach drilling envelop. As a result, the operational performance improvement planwas developed and joint well engineering, subsurface and operations team was set to ensure the implementation.

The main purpose of the plan was the standardization of all processes between few rigs, elimination of non-necessary activities and utilization of fit-for-purpose tools during execution phase. The OPIP had over80 items, and everyone of them was targeting specific drilling / completion activities. As part of the implementation, the process required a multi-discipline approach including but not limited to drilling, completions, equipment, subsurface, production, rig and service contractors with subsequent small task forces and focal point assigned to each individual action for time delivery, follow up and closure. At the same time not all the initiatives were implemented – some were rejected due to significant increase of operational risks and / or due to HSE associated risks.

The process uses a live tracker and it resulted in significant performance improvements, when time for some operations decreased by 25%(i.e. blow out preventer test time), some activities were eliminated (i.e. wiper trips), drilling practices were completely changed (i.e. use of integral packer) and as a result, the project duration was reduced by one year as of to date.

The manuscript describes a structural approach to the optimization of the well construction process with an objective to improve time and cost associated. The proposed ideas can be used at any project worldwide, especially on high cost, extended reach wells drilling projects.
Advantage of Studying Lithology of Dense Zones Formation to Avoid Well Bore Collapse between Sidetrack and Landing Point - Case Study - Offshore Abu Dhabi
Authors: Khemissa Hocine , Channa Zohaib , Nofal Salman F. , McNeilly Kevin Dean , AL-Felasi Ali , Al-Mazrooqi Laila Sayed , Al Qubaisi Salama Darwish , Al-Shamsi Latifa Ali
Published: January 2018

The company vision development plan to capitalize on oil production, sustainability, maximise recovery and as cost effective to reduce number of wells to be drilled requests to drill extended horizontal drains (Oil producer and water Injector).

Subsurface well location optimisation, focus in detail on targets location and the related risks. The present offshore case study, demonstrate furthermore how important to study in detail all hazards along the well path, such as lithology of side-track formation. The risk of well bore stability, collapse is very high in such formation. Subsequently, in case of collapse or drop of scratched portion of rocks, the horizontal drain will be plugged and cease to produce. This case study, demonstrate how this event happens and adequate solution was successfully applied.

To efficiently perform the proposed plan, and develop multilayer geological units with poor to moderate limestone, a detailed reservoir study was performed including all subsurface team and drilling division. It was proposed to drill and complete wells as extended horizontal drain (+3000 ft.), with several designs: multilateral drains or step down 6″open hole.

The first planned well was dual oil producer, two targets, one deviated and the second 6 inch horizontal 3000 ft. length. Feasibility with drilling engineer was performed to study all drilling parameters, drilling hazards, logging requirement, geosteering, equipment preparation and simulation for acid stimulation was showing easy to be executed with barge.
API 16A 4th Edition Changes in Testing for Drill-Through Equipment
Authors: Berckenhoff Mike , Bieneman Konstantin
Published: January 2018

API Specification 16A defines the requirements for design, testing, and other aspects of drill-through equipment. This includes ram and annular blowout preventers as well as connectors, spools, and adapters. The most recent edition contains changes that will drive a significant amount of rigorous testing to monogram pressure-control equipment going forward. This drill-through equipment will contain many operating system seals that are off-the-shelf but original equipment manufacturers (OEM) must also design custom seal assemblies to contain a flowing wellbore fluid. This requires optimizing the design of the assembly and selecting a compatible elastomer compound. Both steps are critical to meet performance requirements. Once designed, the prototype must undergo a battery of tests to qualify the design to API 16A. Here, formalized test standards divide equipment qualification into performance requirement (PR) levels, either PR1 or PR2. Previous editions of API 16A did not have PR levels.

Laboratory evaluation of elastomer compounds and full-scale component testing may be performed to improve the final product. Lab test results include immersion testing in hydrogen sulfide while product testing at elevated temperature and pressure may be performed in a full-size blowout preventer (BOP). API 16A test standards are used by the industry to monogram the finished product. However, there are limitations in API 16A qualification tests regarding chemical compatibility. Annular and ram BOP packers and seal designs serve as examples of the technological process used to improve performance and extend service life at elevated temperatures and pressures. All testing is tied back to API 16A validation and qualification requirements.