bluuebunny/crossref_metadata_2025 huggingface dataset:
Deviated Drilling Through Salt Dome and Horizontalization Across Extremely Heterogeneous Formations: A Case Study in North Abu Dhabi
Authors: Nunez Ygnacio Jesus , Sameer Mohamed , Ruiz Fernando , Al Mutawa Ahmed Abdulla , Al Shamisi Eisa Daban , Hamdy Ibrahim , Al Hendi Mohamed , Al Dhaheri Khaled Hamad , Torres Javier
Published: May 2021

Over the last 60 years, Abu Dhabi, United Arab Emirates (UAE) has been producing oil and gas from different conventional fields. Nowadays, and as part of the State long-term strategy to achieve the nation objective of gas self-sufficiency, it has been decided to explore, appraise and develop unconventional plays in the Northern area including the construction of early production facilities to supply the gas power plants. Three wells were drilled as part of the first phase of the project; consisting of a pilot hole into an extremely heterogeneous formation; two of them were horizontalized into the targeted formations. The first well across the salt represented a tremendous challenge due to limited rig capacity generating hole stability issues that required unplanned remedial jobs. The second well was deviated across the salt as pilot hole, then side-tracked and horizontalized in the targeted reservoirs. The third well was drilled directly as horizontal lateral based on previous lessons learned validating the horizontal concept for the future field development plan.

The exploration phase constituted by these three wells, were drilled and completed successfully. A detailed data gathering program was executed allowing mapping of the area validating the presence of gas. The drilling parameters, such as rate of penetration (ROP) for the horizontal section was enhanced by optimizing the drilling Bit design. The mud logging results have confirmed the extremely heterogeneous formations across this section allowing determining the most fit for purpose bottom hole assembly (BHA); obtained after a detailed optimization process. Multiple lessons learned were captured and immediately applied leading to a significant reduction on total days per well that reflected on an outstanding cost reduction including rig move optimization, incrementing the overall efficiency of the operations. This project has proven the potential of unlocking the development of this field focusing on the targeted untapped reservoirs. Key unprecedented achievements have been fulfilled during the execution of this phase of the project: 1. First time to drill across a salt dome in Abu Dhabi Emirate 2. First time that horizontalization has been applied to the targeted formations. In addition, a better understanding of the optimum drilling parameters for future phases has been obtained.
A Challenging Drilling Campaign Unleashed a Unique Fast Drill String Recovery Methodology Eliminating Utilizing Wireline, CT and Overcome Highly Deviated String Accessibility
Authors: Abdelhalim Khaled , Al Zaabi Mohamed , Al Ali Salim , Abdel Karim Islam khaled , Jadallah Haitham , Al Beshr Abdul Rahman , Endo Shigeru
Published: May 2021

Stuck pipe is one of the biggest challenges in the drilling sector and is a multi-billion-dollar issue. Recovering from stuck pipe absorbs significant cost and time. Durations for stuck pipe events and recovery can be mostly variable from a few days to up to over a month to resolve.

When attempts to release the stuck pipe by jarring or acid fail, the operating company and drilling contractors are left with little option but to sever the drill string and prepare for side-track operations or even abandon the hole. Traditional pipe severance methods in the event of a stuck pipe situation typically take significant time (often days, and sometimes weeks), require specialist tools, Service Hands, and are usually reliant on wireline services to deliver the severance method.

In 2018, a Major Operating Company in UAE faced a challenging high-sticking Formation, which caused massive NPT, stuck of drill strings, and loss of drilled section holes.

Brainstorming within the Drilling Engineering team took the campaign to the next level of pre-planning to reach deep access in the hole to be able to achieve zonal isolation by spotting cement plugs through drilling BHA, find a solution to save the hole and recover the pipes in an efficient, cheap and productive manner.

An environmentally safe pre-planned solution to severe the drill string was proposed to help save the wells and allow an excellent methodology to save the wells/fields from stuck pipe risks.

The engineering solution allows a fast recovery of drill pipes using a downhole tool as a part of drilling BHA, with the option to activate it if required, by dropping a smart dart and circulating with mud for a specific time to apply cut string with two option, either spotting cement with recovered BHA or lift BHA with fish neck to try to fish in the hole.
Best Practices Implementation during 7" Liner Milling Operation
Authors: Iftikhar Choudhry Bilal , Khaled AbdelKarim Islam , Alfonso Mendez Freddy , Ahmed Osman Mohamed , Hassan Youssef Karim , Samir Ismail Ahmed
Published: May 2021

The paper explores the 7" liner milling operations in re - entry well bores, operations that have become fairly common especially at the interface of corrosive effluents or after an extended life time. This however being a time and efficiency driven choice highlights the need for optimization from both the performance as well as the operational time perspective. The flat time endemic to the milling operation execution however, can be reduced and the operations can be optimized with effective mills, fine tuned rheological parameters of the milling fluid, the BHA stabilization and the finger printing of the milling parameters put in place to execute the entire operation. This paper looks into the various facets of optimization that can expand the avenue of flat time reduction and milling operations execution.

Considering the various wells in the database considererd vis – a – vis the milling operations, a baseline ROP of 2 – 6 FPH for liner milling can be established. The baseline reference for this operation averages out an approximate of a couple of weeks from the well duration and has inherent complications both of which can be circumvented with optimization. Albeit the best proponent for mill selection is the existing liner configuration downhole, however this is one luxury that is not available in most cases. More often than not, the maiden mill run is done in a well with the least amount of data available regarding the existing well casing state. Therefore, adequate mill selection and mill cutting structure preparation hold significane for the successful execution, after all each milling run dictates the progress of the successive one. The paper also looks into the proponents of operational optimization and the denominators that drive the successful execution of the job.
Record Length Chrome Liner Run Using Innovative, Low-Marking, Non-Ferrous Dies on a Mechanical Casing Running Tool
Authors: Guzman Marco Cespedes , Ozirny Scott Jason , Smith Douglas Grant
Published: May 2021

Abu Dhabi National Oil Company (ADNOC) has steadily advanced toward the use of a casing running tool (CRT) vs. conventional casing running methods to improve efficiency and safety. This advancement focused mainly on 9 ⅝ in to 20 in diameter casing and utilized internal grip tools. Recently they have searched for an external-grip CRT system that would allow them to effectively run the smaller diameter liners of both ferrous and chrome (Cr) materials, especially in the extended reach drilling (ERD) wells with maximum reservoir contact (MRC).

For 20 years CRT companies manufactured tools with gripping dies that could efficiently run ferrous material liners. Development of gripping mechanisms which can effectively run corrosion resistant alloy (CRA) materials has been met with varying success. Some of the challenges are to manufacture gripping dies from non-ferrous materials that will not contaminate the CRA liner and develop a gripping pattern that does not mark the CRA liner more than is accepted by API 5CRA industry standards, but maintain effective gripping force. In addition to hoisting and making up the string with no slippage it needs to perform fluid circulation at 3,000 psi. Until recently the liners were typically run in a conventional method using power-tongs.

One of the tools chosen for the trial runs was a well-proven, external-grip mechanical CRT designed specifically for smaller diameter casing and liners. It has a 500-ton hoist capacity and a 5,000 psi circulation rating and was packaged with a combination float and cushion tool and a wireless torque turn sub. Dies had been designed to meet the non-contamination and acceptable marking criteria previously mentioned and would be compatible with liners possessing as much as 25% Cr. The dies had been extensively lab-tested, including heavy pull tests and torque application tests, but had not previously been used in field applications.

The ERD-MRC well chosen for this trial was planned to have a record length of 6 ⅝ in, 24 ppf, 13% Cr liner with a wedge thread premium connection. In addition to not contaminating the liner, ADNOC expected an average running speed in joints per hour equivalent to the conventional casing running methods and a reduction in time during circulations.

The result of the trial was 589 connections (25,035 ft liner length) successfully run with an average running speed matching their expectations. The liner displayed very minimal marks and there were no issues when hoisting or torqueing the connections. In addition, there were no rejected connections during the run.

This publication will review the preparation for the run, actual run details, photos of the die marks, torque graphs and conclusions expressed by the operator with recommendations for changes moving forward.
Application of 3D Geomechanical Research for De-Risk and Improve High Pressure and High Temperature Well Drilling
Authors: Yi Ming , Liu Ling , Wei Qiang , Chen Liang , Li Binging , Guo Zhiqi , Xu Yangyang , Huang Xingning
Published: May 2021

Exploration focus is moving into deeper targets of high pressure and high temperature (HPHT) regime due to the ever-increasing energy demand of China. Overpressure and wellbore instability related problems in such setting are mainly associated with narrow drilling margin resulting in severe well control incidents and increased drilling cost. In order to reduce drilling risks and operation costs, an accurate geomechanical model is necessary. The model provides technical support for drilling process and minimum reservoir damage due to optimal mud weight program. Well-scale (1D) Mechanical Earth Model (MEM) is constructed on the offset wells which consist of rock strength properties and stress profile by incorporating all available data including open hole log data, geomechanical core lab results, LOT/FIT, direct pore pressure measurements and drilling events. Furthermore, 3D geomechanics model is generated using available well-scale MEM data in the field and distributed throughout the field which guided by seismic interpretation data as distribution control. The 3D geomechanical model is used to design mud weight and casing program for the upcoming well. The offset wells in the study areas were drilled through complex geological settings with high overpressure (13500 psi) and high temperature (200-220 deg C). Therefore, drilling operations is also risky with different types of drilling events encountered frequently including stuck pipe, inflow, losses and connection gas etc. With 3D geomechanical model as the foundation, the integrated approach helps ultra-deep wells to reduce serious wellbore instability caused by abnormal formation pressure, wellbore collapse and other complex drilling problems. The implementation of systematic and holistic workflow has proven to be extremely successful in supporting the drilling of HPHT wells in China. The integrated solution has been applied in the ultra-deep well, recorded an improvement in ROP by 35.3% and decrease no-productive time (NPT) by 25.3% compared with offset well. The geomechanical approach provides a convenient means to assist field engineers in the optimization of mud weight, risk assessment, and evaluation of HPHT wells drilling performance. The findings will provide reference and guideline for de-risk and performance improvement in HPHT wells drilling.
Drilling System Optimization Leads to Expedited Wells Delivery
Authors: Ovwigho Efe Mulumba , Al Marri Saleh , Al Hajri Abdulaziz
Published: May 2021

On a Deep Gas Project in the Middle East, it is required to drill 3500 ft of 8-3/8" deviated section and land the well across highly interbedded and abrasive sandstone formations with compressive strength of 15 - 35 kpsi. While drilling this section, the drill string was constantly stalling and as such could not optimize drilling parameters. Due to the resulting low ROP, it was necessary to optimize the Drill string in order to enhance performance.

Performed dynamic BHA modelling which showed current drill string was not optimized for drilling long curved sections. Simulation showed high buckling levels across the 4" drill pipe and not all the weight applied on surface was transmitted to the bit. The drilling torque, flowrate and standpipe pressures were limited by the 4" drill pipe. This impacted the ROP and overall drilling performance. Proposed to replace the 4" drill pipe with 5-1/2" drill pipe. Ran the simulations and the model predicted improved drill string stability, better transmission of weights to the bit and increased ROP. One well was assigned for the implementation.

Ran the optimized BHA solution, able to apply the maximum surface weight on bit recommended by the bit manufacturer, while drilling did not observe string stalling or erratic torque. There was also low levels of shocks and vibrations and stick-slip. Doubled the on-bottom ROP while drilling this section with the same bit. Unlike wells drilled with the previous BHA, on this run, observed high BHA stability while drilling, hole was in great shape while POOH to the shoe after drilling the section, there were no tight spots recorded while tripping and this resulted in the elimination of the planned wiper trip. Decision taken to perform open hole logging operation on cable and subsequently run 7-in liner without performing a reaming trip. This BHA has been adopted on the Project and subsequent wells drilled with this single string showed similar performance. This solution has led to average savings of approximately 120 hours per well drilled subsequently on this field. This consist of 80 hours due to improved ROP, 10 hrs due to the elimination of wiper trip and a further 30 hrs from optimized logging operation on cable. In addition, wells are now delivered earlier due to this innovative solution.

This paper will show how simple changes in drill string design can lead to huge savings in this current climate where there is a constant push for reduction in well times, well costs and improved well delivery. It will explain the step-by-step process that was followed prior to implementing this innovative solution.
Mitigating Twist-Offs While Drilling with the Help of BHA Dynamics Software
Authors: Rivas Mario A. , Ramirez Andres A. , Al-Zahrani Bader S. , Abouelnaaj Khaled K.
Published: May 2021

One of the major challenges the Oil and Gas Industry faces nowadays during drilling operations is the twist-offs on Bottom Hole Assembly (BHA) components such as Drilling Jars, Shock Tools, Mud Motors, Roller Reamers, Stabilizers, Drill Collars, PBLs, Heavy Weight Drill Pipe (HWDP), Drill Pipe (DP), etc. To overcome this challenge, an initiative was proposed by performing a study based on twist-offs experienced on BHA components while drilling operations and recommendations are provided to reduce and eliminate twist-offs related to drilling with suboptimal drilling parameters.

The statistical data for the twist-off events was collected coming from Daily Drilling Reports, and the analysis was limited to all wells which presented twist-offs on the drillstring and BHA components. Three examples of twist-offs due to drilling with erratic torque are discussed as well as a successful example of drilling parameters optimization.

The three examples which presented drillstring and BHA twist-offs were analyzed using available BHA Dynamics and vibrations software and it was discovered that the parameters utilized (operational RPM) fell within the critical zone shearing force peaks (resonance vibrations). The components with the most twist-offs were identified. The hole size where we have the most twist-offs were also identified, which will help in focusing on these areas for the recommendations provided.

This analysis will help Drilling Engineers and Foremen to foresee vibration dysfunctions and act accordingly by the use of available BHA Dynamics software in order to optimize drilling parameters before and during drilling. By drilling within a safe operating RPM window (away from resonant RPM), there will be reduction in the number of twist-offs and associated lost time.
Packer-Setting Methodology with Auto-Fill Capability and Interventionless Valve Reduces Completion Cost
Authors: Md Noor Mohd Nazri , Abreu Javier , Demyanov Alexandr , Batita Nabil
Published: May 2021

A new valve has been designed and qualified to reduce interventions during packer-setting operations. In a typical well, completion with a hydraulic-production packer, the tubing string must be plugged to create the required pressure differential for packer actuation. At desired depth, delivering a preselected circulation rate actuates the tool and converts the string to a closed system, enabling the packer to be set hydraulically.

Before designing the valve, an operator's engineering and operational requirements were collected and understood. Then a conceptual design was evaluated, and a prototype device was manufactured. The valve was tested for autofill capability, actuation parameters and pressure integrity. The critical design elements of the valve are the choking and spring mechanisms, which enable circulation without prematurely actuating the valve and then enable tubing autofill. A visual inspection post qualification test was conducted to validate the components’ condition and integrity. During the qualification process, the valve working envelope was developed.

After the successful qualification test, the valve was deployed in a customer well with a production packer that has a blanking device consisting of a ceramic disc. Prior to deployment, hydraulic simulation was done to determine the required flow rate to achieve desired pressure drop across the valve for actuation. During deployment, the tubing was filled automatically, validating the valve autofill capability. Upon reaching setting depth, the completion string was circulated at the required circulation rate to actuate the valve and close the system.

Pressure integrity in the tubing validated the valve functionality. Surface pressure was applied against the blanking device, and the production packer was set hydraulically. Subsequently, before completing the well, the blanking device was broken using a slickline run, and the well was put on production.

The deployment technique using the valve requires only one slickline run whereby in typical operation four slickline runs are required.

This project represented true problem-solving engineering approaches. The operator requirements were properly understood and conceptual design was validated, and product realization phase was initiated. The efficient product development methodology improves the lead time from conceptualization to product realization. During the first well deployment, hydraulic simulation during the prejob planning proved to be critical to understanding the required circulation rates to actuate the valve.
A Novel Water-Based Drilling Fluid Tailored for Challenging Slanted HTHP Wells
Authors: Traboulay Vaughn Reza , Aung Tint Htoo , Manzoleloua Cedric , Panamarathupalayam Balakrishnan , Arena Carmelo , DMello Allwyn , Sebelin Linus , Eyaa Clotaire
Published: May 2021

High-temperature water-based drilling fluid systems hold several advantages over synthetic based systems from financial and environmental viewpoints. However, most conventional water-based systems start to become unstable at temperatures above 300 degF. This paper details the design and implementation of A Novel Water-Based Drilling Fluid that meet these temperature stability requirements.

The newly developed high-temperature water-based system discussed in this paper utilizes a custom-made branched synthetic polymer that exhibits superior rheological properties and fluid loss control as well as long term stability above 400 degF. The branched synthetic polymer is compatible with most oilfield brines and maintains excellent low-end rheology necessary for hole cleaning and solids suspension under high-temperatures and pressures. Under static conditions, the high-temperature fluid shows no gelation resulting in lower swab surge pressures while the stability of the highly branched synthetic polymer and enhanced rheological profile minimize sag.

To drill a challenging exploration well, a Middle East client required a cost-effective drilling fluid system which remains stable under static temperatures expected to exceed 375 degF. The long-term stability of the system was critical for successful wireline logging operations. In addition, the system was required to provide shale inhibition, hydrogen sulfide suppression and sufficient density (above 16.5 lbm/galUS) to maintain well integrity while drilling through anticipated high-pressure zones. The challenging intermediate (12.25-in and 8.375-in) and reservoir (6-in) sections were successfully drilled and evaluated using this new branched synthetic polymer-based system. Fluid property trends and system treatments will be detailed alongside thermal stability data for extended periods required for wireline logging (up to 9 days static).

This paper will discuss how proper laboratory design of the high-temperature water-based system was translated to excellent field performance and will indicate how this technology can be utilized for future campaigns in the region and worldwide.
Nitrogen-Based Back Pressure Unit Modernizes Managed Pressure Drilling Operations
Authors: Al-Hashmy Wamidh Louayd
Published: May 2021

Managed Pressure Drilling (MPD) solutions are no longer the anomaly to Operator strategies, but rather another tool in their belts. With this continual utilization, MPD is evolving to become compact, more effective and safer. The inventive use of a Nitrogen Backup Unit (NBU) has eliminated the reliance of MPD operations on sizable Auxiliary Pumps.

The core function of MPD operations is maintaining the total wellbore pressure by manipulating surface applied back pressure. MPD relies on circulating fluid as back pressure is generated by restricting flow against its choke(s). While drilling, fluid circulation is a given; however, that is not the case during static conditions such as drill string connections. The NBU solves this issue by injecting a small volume of nitrogen into the MPD lines upstream of the choke at a pre-set pressure. This supplements the back pressure control at surface should additional pressure be needed after closing the choke or if pressure diminishes during long static periods.

Prior to the NBU design, the only effective solution was an Auxiliary Pump setup. This solution doubles the choke manifold footprint, relies on mechanical maintenance, and requires additional dedicated personnel at times. Most critically, the Auxiliary Pump lags the operation minutes before each use and is therefore functioned before static conditions when possible. However, unplanned and sudden events are commonplace – such as Rig Pump failures. When drilling formations with narrow pressure margins, unsafe gases, or crucial hole instability pressure limits, a few minutes can result in considerable and costly outcomes. Once installed during initial rig-up, the NBU is capable of injecting nitrogen-sourced back pressure instantaneously at the literal click of a button – avoiding costly and sometimes hazardous conditions.

The NBU modernizes MPD operations and renders the Auxiliary Pump setup outdated in many applications. This paper details this innovative implementation of maintaining wellbore pressure, highlights several field examples of the NBU maintaining back pressure at critical times and shows how the layout used minimizes the operational footprint.
Design of Horizontal Wellbore in Dadas Shales of Turkey by Considering Wellbore Stability and Reservoir Geomechanics
Authors: Merey Sukru , Polat Can , Eren Tuna
Published: May 2021

Currently, many horizontal wells are being drilled in Dadas shales of Turkey. Dadas shales have both oil (mostly) and gas potentials. Thus, hydraulic fracturing operations are being held to mobilize hydrocarbons. Up to 1000 m length horizontal wells are drilled for this purpose. However, there is not any study analyzing wellbore stability and reservoir geomechanics in the conditions of Dadas shales. In this study, the directions of horizontal wells, wellbore stability and reservoir geomechanics of Dadas shales were designed by using well log data. In this study, the python code developed by using Kirsch equations was developed. With this python code, it is possible to estimate unconfined compressive strength in along wellbore at different deviations. By analyzing caliper log, density and porosity logs of Dadas shales, vertical stress of Dadas shales was estimated and stress polygon for these shale was prepared in this study. Then, optimum direction of horizontal well was suggested to avoid any wellbore stability problems. According to the results of this study, high stresses are seen in horizontal directions. In this study, it was found that the maximum horizontal stress in almost the direction of North-South. The results of this study revealed that direction of maximum horizontal stress and horizontal well direction fluid affect the wellbore stability significantly. Thus, in this study, better horizontal well design was made for Dadas shales. Currently, Dadas shales are popular in Turkey because of its oil and gas potential so horizontal drilling and hydraulic fracturing operations are being held. However, in literature, there is no study about horizontal wellbore designs for Dadas shales. This study will be novel and provide information about the horizontal drilling design of Dadas shales.
Application of Machine Learning Techniques for Real Time Rate of Penetration Optimization
Authors: Elmgerbi Asad Mustafa , Ettinger Clemens Peter , Tekum Peter Mbah , Thonhauser Gerhard , Nascimento Andreas
Published: May 2021

Over the past decade, several models have been generated to predict Rate of Penetration (ROP) in real-time. In general, these models can be classified into two categories, model-driven (analytical models) and data-driven models (based on machine learning techniques), which is considered as cutting-edge technology in terms of predictive accuracy and minimal human interfering. Nevertheless, most existing machine learning models are mainly used for prediction, not optimization. The ROP ahead of the bit for a certain formation layer can be predicted with such methods, but the limitation of the applications of these techniques is to find an optimum set of operating parameters for the optimization of ROP. In this regard, two data-driven models for ROP prediction have been developed and thereafter have been merged into an optimizer model. The purpose of the optimization process is to seek the ideal combinations of drilling parameters that would lead to an improvement in the ROP in real-time for a given formation.

This paper is mainly focused on describing the process of development to create smart data-driven models (built on MATLAB software environment) for real-time rate of penetration prediction and optimization within a sufficient time span and without disturbing the drilling process, as it is typically required by a drill-off test. The used models here can be classified into two groups: two predictive models, Artificial Neural Network (ANN) and Random Forest (RF), in addition to one optimizer, namely genetic algorithm. The process started by developing, optimizing, and validation of the predictive models, which subsequently were linked to the genetic algorithm (GA) for real-time optimization. Automated optimization algorithms were integrated into the process of developing the productive models to improve the model efficiency and to reduce the errors.

In order to validate the functionalities of the developed ROP optimization model, two different cases were studied. For the first case, historical drilling data from different wells were used, and the results confirmed that for the three known controllable surface drilling parameters, weight on bit (WOB) has the highest impact on ROP, followed by flow rate (FR) and finally rotation per minute (RPM), which has the least impact. In the second case, a laboratory scaled drilling rig "CDC miniRig" was utilized to validate the developed model, during the validation only the previous named parameters were used. Several meters were drilled through sandstone cubes at different weights on bit, rotations per minute, and flow rates to develop the productive models; then the optimizer was activated to propose the optimal set of the used parameters, which likely maximize the ROP. The proposed parameters were implemented, and the results showed that ROP improved as expected.
The Hard Case for Whole Drilling Optimization
Authors: Damski Carlos , El Afifi Sameh
Published: May 2021

Today every Oil & Gas company is searching for the elusive drilling optimization process. Authors argue that a global drilling optimization is only achieved calculating the actual ROI – based on money spent in drilling vs total production of the well. As this is impractical, this paper presents a framework to measure engineering and management aspects of this optimization. Engineering approach looks into "doing things right," while managerial attitude is "doing the right things."

Drilling optimization is centered in using existing (and upcoming) data from rig and its analyses. Engineers look into hydraulics, WOB, etc., with the purpose to calculate ideal/best ROP parameters and eventually to avoid problems, such as stuck pipe. This is done by direct calculation and/or running simulated models to spot deviations.

Management is concerned with relative efficiency of the process (KPIs) compared to a baseline (offset wells, planned durations, technical limits, etc.). They concentrate at comparisons and focus at how to mitigate operational risks (time, costs, HSE, etc.) while producing the "best well".

Those two intertwined optimization processes are depicted and explained in the next sessions.

Authors' experience has shown that TL (Technical Limit), ILT (Invisible Lost Time) and NPT (Non-Productive time) are façades from the engineering and management efforts in drilling optimization. For example, there is no unique way to describe "Technical Limit" in drilling. We will describe the technical components for it under physics and models, as well as under historical-coaching-KPI approach. Same for ILT and NPT.

Under a unique framework, users can understand and clarify the confusion in the current marketplace to better data and data processing to achieve optimization.

The so called "data analytics" is dissected and formalized so all parties involved: technicians, service providers, operators, equipment suppliers, managers, finances, etc., can fully understand where data can be used (also how they are collected and quality checked) and what processes are needed to achieve each step of the drilling optimization.

Unlike any product or service available today, the framework described in this article looks in the drilling optimization with a holistic view. Efforts so far have been scattered and there is a lack of an overall framework. The best results come from the combination of those two approaches.
Best Practice to Improve Slim Hole Maximum Reservoir Contact Well Drilling Performance
Authors: Antillon Moreira Rodrigo , Jeughale Ramanujan , Takahiro Toki , Motohiro Toma , Andrews Kerron , Fujinaga Ryota , Al Ali Salim Abdalla , Alzaabi Mohamed Abdulrahman
Published: May 2021

Reservoir sections in MRC (Maximum Reservoir Contact) & ERD (Extended Reach Drilling) wells are mainly designed to drill 8 ½" hole, because of drilling limitations with smaller hole size. However, slim hole sizes offer opportunities to revitalize existing wells using re-entry drilling techniques in association with MRC and ERD designs.

This paper discusses the best practices to be implemented in order to mitigate risk, reduce complexity and ensure improved drilling performance.

Re-Entry wells in the field have a risk of well integrity issues such as corroded 9 5/8" casing. In order to mitigate this risk, the corroded 9 5/8" casing should be covered by 7" liner & tied-back to surface before drilling reservoir section. In this situation up to 18,000 ft of 4" DP is used in the wells to drill 6" hole and run 4 ½" lower completion. Offset well analysis, whip stock selection criteria, BHA design, drilling fluid selection, drilling and tripping practices based on torque & drag and hydraulics calculations are most important to achieve the well objective.

The Slim hole MRC well was completed without any issues and achieved good drilling performance. It was observed that the actual drilling parameters such as torque, drag and stand pipe pressure were less than simulated parameters. NAF was selected in the section to reduce the friction factor, while motorized RSS and a reamer stabilizer were used in the BHA to reduce torque, drag and ensure a smooth well profile. A back reaming practice was implemented in hole section to reduce dog leg severity and the open hole was eventually displaced to viscosified brine to minimize the friction factor for running the 4 ½' lower completion. 8500 ft of 6" hole section was drilled and TD was reached at +/- 19,000ft within 50 days including recovering the existing completion, drilling 8 ½" & 6" hole and running completion.

This paper aims to contribute to the oilfield industry by sharing the successfully implemented engineering design and operation execution methodology to overcome the complexities present in Re Entry Wells MRC/ERD wells required to be drilled with slim hole conditions under an optimal cost, time effectiveness and low risk.
Thermochemical-Pulse Fracturing of Tight Gas: Investigation of Pulse Loading on Fracturing Behavior
Authors: Al-Nakhli Ayman , Tariq Zeeshan , Mahmoud Mohamed , Abdulraheem Abdulazeez
Published: May 2021

Unconventional and tight gas reservoirs are located in deep and competent formations, which requires massive fracturing activities to extract hydrocarbons. Some of the persisting challenges faced by operators are either canceled or non-productive fractures. Both challenges force oil companies to drill new substitutional wells, which will increase the development cost of such reservoirs.

A novel fracturing method was developed based on thermochemical pressure pulse. Reactive material of exothermic components are used to generate in-situ pressure pulse, which is sufficient to create fractures. The reaction can vary from low pressure pulse, to a very high loading up to 20,000 psi, with short pressurization time.

In this study, Finite Element Modeling (FEM) was used to investigate the impact of the generated pressure-pulse load, by chemical reaction, on the number of induced fractures and fracture length. Actual tests of pulsed fracturing conducted in lab scale using several block samples compared with modeling work. There was a great relationship between the pressure load and fracturing behavior. The greater the pulse load and pressurization rate, the greater the number of created fractures, and the longer the induced fractures.

The developed novel fracturing method will increase stimulated reservoir volume of unconventional gas without introducing a lot of water to formation. Moreover, the new method can reduce formation breakdown pressure by around 70%, which will minimize number of canceled fracturing.
Logging While Tripping - LWT Ensures Data Acquisition in Challenging Interbedded Salt Formation in Abu Dhabi Onshore Exploration Wells
Authors: Nunez Ygnacio , Sameer Mohamed , Abdelaal Atef , Al Mutawa Ahmed Abdulla , Al Shamisi Eisa Daban , Hamdy Ibrahim , Al Hendi Mohamed , Ruiz Fernando , Al Dhaheri Khaled Hamad , Torres Javier , ELWazeer Fathy , Bechir Ilknur , Khalife Bassam , Propper Maarten , Lentz Curtis
Published: May 2021

The understanding of salt beds has been significantly improved over the years; however, certain operational challenges still persist. Conditions encountered during drilling salt formations may lead to stuck Logging While Drilling (LWD) and or wireline tools, which, at times, can contain radioactive sources. As data gathering remains a primary requirement in exploration wells, cost optimization, beside risk mitigation, is a further challenge in today’s economic landscape. A holistic approach is proposed to address these main objectives. The conventional procedure required drilling and formation evaluation (LWD and or wireline) in the section above the interbedded salt formation, followed by rotary steerable (RSS) only in the interbedded salt formation sections of the well. Considering the shallow depths of the well and the proximity to the aquifers, the threat posed by losing radioactive sources in the well is significant, therefore, formation density and neutron porosity logging operation is often compromised due the inherent risk. Logging While Tripping, a method in which tools record open hole data from inside the pipe, resolves this compromise, as the risk of lost in hole (LIH) is virtually eliminated.

The empty LWT collars are run in the last bit trip or reamer run, as they do not affect the drilling operation. Once the well’s total depth is reached, the LWT logging tools are pumped from surface, safely inside of the pipe, and data is acquired while tripping the drill pipe out of the well. If the situation is evaluated as risky, drilling operation may continue without data acquisition. In case the logging tools already were deployed, they can be retrieved at any time by wireline or slickline.

Prior to the introduction of the LWT in the drilling/data acquisition procedure, only gamma ray - sonic data was acquired over the challenging formation sections. Compressional and shear data may be important to improve modelling accuracy; however, they may be negatively affected by various factors such as drilling noise, mud properties, washouts and gas in the formation, particularly reservoir rocks interbedded with thick salt beds. When compared to the Neutron-Density porosity, sonic porosity is noticeably inferior, showing limited formation signature. Neutron-Density porosity correlates well with core data.
A Geomechanical Model and Workflow for Calibrating Elastic Moduli and Min/Max Horizontal Stress from Well Logs in the Nahr Umr Shale
Authors: Shaver Michael Alexander , Segret Gilles Pierre Michel , Yudhia Denya Pratama , Al Ameri Suhail Mohammed , Couziqou Erwan , Al Marzouqi Adel Rahman
Published: May 2021

Thin layering and micro-fracturing of the thin laminated layers are some possible reasons for the wellbore stability problems of the Nahr Umr shale. If the drilling fluid density is too low, collapsing of the borehole is possible, and if the drilling fluid density is too high, invasion of the shale can occur, weakening the shale, making boreholes prone to instability. These effects can be semi-quantified and assessed through the development of a geomechanical model.

The application of a geomechanical model of a reservoir and overlaying formations can be very useful for addressing ways to select a sweet spot and optimize the completion and development of a reservoir. The geomechanical model also provides a sound basis for addressing unforeseen drilling and borehole stability problems that are encountered during the life cycle of a reservoir. Key components of any geomechanical model are the principal stresses at depth: overburden, minimum horizontal principle stress, and maximum horizontal principle stress. These determine the existing tectonic fault regime: normal, strike-slip, and reverse. Additional components of a geomechanical model are pore pressure, unconfined compressive strength (UCS) rock strength, tilted anisotropy, and fracture and faults from image logs and seismic.

Unfortunately, models used to make continuous well logging depth-based stress predictions involve some parameters that are derived from laboratory tests, fracture injection tests, and the actual fracturing of a well—all contributing to the uncertainty of the model predictions. This paper addresses ways to obtain these key parameter components of the geomechanical model from well logging data calibrated to ancillary data. It is shown how stress, UCS, and pore pressure prediction and interpretation can be improved by developing and applying models using wellbore acoustic, triple combo, and borehole image data calibrated to laboratory and field measurements.

The nahr umr shale and other organic mudstone formations exhibit vertical transverse isotropic (VTI) anisotropy in the sense that rock properties are different in the vertical and horizontal directions (assuming non-tilted flatbed layering), the horizontal acoustic velocity is different from that of vertical velocity. This necessitates the building of anisotropic moduli and stress models. The anisotropic stress models require lateral strain, which as shown in the paper, can be obtained from micro-frac tests and/or borehole breakout data.
A Novel Routing Algorithm with Bernoulli Sampling-based Link Quality Estimation in Wireless Sensor Networks
Authors: Meng Chao
Published: May 2021

Link quality is important and can greatly affect the performance of wireless transmission algorithms and protocols. Currently, researchers have proposed a variety of approaches to implement link quality estimation. However, the estimated result of link quality is not accurate enough and the error is large, so they may lead to the failure of routing algorithm and protocol. In this paper, a novel method is proposed to achieve the more accurate estimation of link quality than before. This method employs Bernoulli sampling-based algorithm to complete the estimation of link quality. The problem is modeled as calculation of estimators based on Bernoulli sampling data. The authors further prove that the calculation results are accurate by probability theory. Furthermore, according to link quality estimation, the authors also provide a centralized routing algorithm and a distributed improvement algorithm in order to switch the data transmission on the better quality link. Finally, the extensive experiment results indicate that the proposed methods obtain high performance in terms of energy consumption and accuracy.
Risk Analysis of Severe Thrombocytopenia in Nasopharyngeal Carcinoma During Concurrent Radio-Chemotherapy
Authors: Xu Jiasheng , Wu Quanli , Tang Luoyong , Liu Anwen , Huang Long
Published: May 2021

Objective:To explore the risk factors and predictive indexes of severe thrombocytopenia during concurrent radio-chemotherapy of nasopharyngeal carcinoma. Methods: Retrospective analysis were performed from the hospitalized patients with nasopharyngeal carcinoma from August 2014 to July 2017 and completed induction chemotherapy and concurrent radio-chemotherapy.Patients were divided into observation and control group according to the lowest platelet count during concurrent chemotherapy. The general information and laboratory examinations were recorded and analyzed by univariate analysis, multivariate regression analysis and ROC curve analysis. Results: Take the factors, including Age, PLT, IBIL, APTT at first visit, WBC, RBC, HGB, PLT, NEUT, APTT,IBIL, FFA, Crea,Urea before radio-chemotherapy, which are significant in univariate analysis into multivariate regression analysis. It turned out that RBC（OR=10.060, 95%CI2.679-37.777, P=0.001）,PLT(OR= 1.020, 95%CI1.006-1.034, P=0.005) and IBIL（OR=0.710,95%CI 0.561-0.898, P= 0.004） are independent predictors of severe TP in NPC. ROC analysis showed that the AUC of RBC, IBIL, PLT, AGE is 0.746(P< 0.001), 0.735（P<0.001）, 0.702(P=0.001), 0.734(P<0.001). New variables called joint predictor was calculated by regression equation (Y=2.309*RBC-0.343*IBIL+0.02*PLT-10.007), the AUC of which is 0.870(P<0.001), best truncation value is＞5.87 mmol/L. Conclusions: Lower RBC, PLT, higher IBIL before concurrent radio-chemotherapy are the independent risk factors causing severe TP during concurrent radio-chemotherapy of NPC. The RBC, PLT, IBIL before concurrent radio-chemotherapy and joint predictor have a good predictive value to evaluate the risk of severe TP during concurrent radio-chemotherapy of NPC.
Thermal- Elastic Waves of Microstretch Semiconductor Medium with Rotation Field during Photothermal Excitation
Authors: lotfy khaled , El-Bary A. A.
Published: May 2021

A mathematical novel model for elastic semiconductor medium with microstretch properties is investigated. The generalized model is studied in the context of photo-thermoelasticity theory when the semiconductor medium is excited. The governing equations describe the coupled between the propagation of the elastic-thermal-plasma waves when the thermo-microstretch elastic semiconductor material is studied during a rotation field. The linear medium has an isotropic properties. The photothermal transport processes occurs during a two dimension (2D) elastic and electronic deformation when the microinertia of microelement is taken into account. The harmonic wave method can be used to obtain the general solutions for the basic physical variables. The complete analytical solutions of the considered variables are obtained when some mechanical-thermal and plasma conditions are applied on the boundary of the semiconductor medium. The numerical simulations of silicon (Si) and Germanium (Ge) media are constructed graphically with many comparisons according to a new parameters with thermal memories and rotation parameter.
Reproductive Ecology of Euglossine Bee-pollinated Orchid Catasetum Integerrimum Hook (Ochidaceae)
Authors: Hernández-Ramírez Angélica María
Published: May 2021

Catasetum is a dimorphic and dioecious genus of orchids with a pollinaria release mechanism triggered by pollinator visitation. The reproductive ecology of Catasetum integerrimum Hook (Orchidaceae) was characterized in Central Veracruz, Mexico. For that, it was determined whether floral senescence and fruit production are resulted of pollination efficiency in the species, and if so, to what extent present reproductive event constraint the investment in subsequent reproductive event. In the sampled population, efficient pollinaria removal/deposition triggered floral senescence. Eulaema polychroma bee visited earlier and with lower frequency the staminate than pistillate flowers. Alleviating pollen limitation increased fruit production but it caused a reduction in flower and fruit production in the subsequent reproductive event. C. integerrimum seemed to exhibit reproductive cost-saving mechanisms linked to the pollinator identity and behavior, whereas pollinator efficiency appeared to be mediated by dioecism and dimorphism in floral traits. This study highlights the importance to understand the adaptive significance of dimorphic floral traits in animal-pollinated plants, stimulating new research avenues on the role of pollinators in maintaining safe reproduction threshold of plants.