scholarly journals Prediction and Early Detection of Karsts—An Overview of Methods and Technologies for Safer Drilling in Carbonates

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6517
Author(s):  
Danil Maksimov ◽  
Alexey Pavlov ◽  
Sigbjørn Sangesland
Keyword(s):  
Early Detection ◽  
The Past ◽  
Diagenetic Processes ◽  
Bottom Hole ◽  
Geological Features ◽  
Carbonate Deposition ◽  
Drilling Data ◽  
Bottom Hole Assembly

The nature of carbonate deposition as well as diagenetic processes can cause the development of unique geological features such as cavities, vugs and fractures. These are called karsts. Encountering karsts while drilling can lead to serious consequences such as severe mud losses, drops of bottom hole assembly and gas kicks. To improve drilling safety in intervals of karstification, it is important to detect karsts as early as possible, preferably in advance. In this paper, we review methods and technologies that can be used for the prediction and early detection of karsts. In particular, we consider acoustic, resistivity, seismic and drilling-data methods. In addition to the inventions and technologies developed and published over the past 40 years, this paper identifies the advantages, limitations and gaps of these existing technologies and discusses the most promising methods for karst detection and prediction.

Bottom Hole Assembly Design Enhancement Successfully Eliminate Hole Problems and Reduce Significant Drilling Time : South S Field Case Study

2020 ◽  
Author(s):  
Y. D. Mulia
Keyword(s):  
Contact Area ◽  
Cost Savings ◽  
Assembly Design ◽  
Drilling Performance ◽  
Bottom Hole ◽  
Unconsolidated Sand ◽  
Bottom Hole Assembly ◽  
Drilling Parameter ◽  
Drilling Time

For S-15 and S-14 wells at South S Field, drilling of the 12-1/4” hole section became the longest tangent hole section interval of both wells. There were several challenges identified where hole problems can occur. The hole problems often occur in the unconsolidated sand layers and porous limestone formation sections of the hole during tripping in/out operations. Most of the hole problems are closely related to the design of the Bottom Hole Assembly (BHA). In many instances, hole problems resulted in significant additional drilling time. As an effort to resolve this issue, a new BHA setup was then designed to enhance the BHA drilling performance and eventually eliminate hole problems while drilling. The basic idea of the enhanced BHA is to provide more annulus clearance and limber BHA. The purpose is to reduce the Equivalent Circulating Density (ECD,) less contact area with formation, and reduce packoff risk while drilling through an unconsolidated section of the rocks. Engineering simulations were conducted to ensure that the enhanced BHA were able to deliver a good drilling performance. As a results, improved drilling performance can be seen on S-14 well which applied the enhanced BHA design. The enhanced BHA was able to drill the 12-1/4” tangent hole section to total depth (TD) with certain drilling parameter. Hole problems were no longer an issue during tripping out/in operation. This improvement led to significant rig time and cost savings of intermediate hole section drilling compared to S-15 well. The new enhanced BHA design has become one of the company’s benchmarks for drilling directional wells in South S Field.

scholarly journals Kinematics and dynamics analysis of new rotary-percussive PDM drilling tool

2021 ◽  
pp. 146134842198915
Author(s):  
Jialin Tian ◽  
Xuehua Hu ◽  
Liming Dai ◽  
Lin Yang ◽  
Yi Yang ◽  
...  
Keyword(s):  
Drill String ◽  
Structure Design ◽  
Drilling Process ◽  
Analysis Model ◽  
Drilling Tool ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
Bottom Hole ◽  
Bottom Hole Assembly ◽  
The Impact

This paper presents a new drilling tool with multidirectional and controllable vibrations for enhancing the drilling rate of penetration and reducing the wellbore friction in complex well structure. Based on the structure design, the working mechanism is analyzed in downhole conditions. Then, combined with the impact theory and the drilling process, the theoretical models including the various impact forces are established. Also, to study the downhole performance, the bottom hole assembly dynamics characteristics in new condition are discussed. Moreover, to study the influence of key parameters on the impact force, the parabolic effect of the tool and the rebound of the drill string were considered, and the kinematics and mechanical properties of the new tool under working conditions were calculated. For the importance of the roller as a vibration generator, the displacement trajectory of the roller under different rotating speed and weight on bit was compared and analyzed. The reliable and accuracy of the theoretical model were verified by comparing the calculation results and experimental test results. The results show that the new design can produce a continuous and stable periodic impact. By adjusting the design parameter matching to the working condition, the bottom hole assembly with the new tool can improve the rate of penetration and reduce the wellbore friction or drilling stick-slip with benign vibration. The analysis model can also be used for a similar method or design just by changing the relative parameters. The research and results can provide references for enhancing drilling efficiency and safe production.

scholarly journals The Study of the Interaction of Different Arrangements of the Bottom-Hole Assembly with the Bottomhole and the Borehole Wall

2019 ◽  
pp. 58-68
Author(s):  
Ya. M. Kochkodan ◽  
A.I. Vasko
Keyword(s):  
Differential Equations ◽  
Contact Point ◽  
Point Contact ◽  
Drill String ◽  
Borehole Wall ◽  
Deviation Angle ◽  
Technological Parameters ◽  
Bottom Hole ◽  
Anisotropy Index ◽  
Bottom Hole Assembly

The article presents the main factors affecting the buckling when drilling vertical wells. The authors study analytically the effect of the weight on the bit and the force of the interaction of a drill string with a borehole wall using a uniform-sized arrangement of the bottom-hole assembly and the borehole wall which is located in a deviated wellbore when drilling in isotropic rocks in case the drilling direction coincides with the direction of the force acting on the bit. Differential equations of the elastic axis of the drill string are worked out. The solutions of these equations have given nondimensional dependences between the technological parameters. The authors have obtained the graphical dependences of the distance from the bit to the “drill string - borehole wall” contact point and the normal reaction of the bottom to the bit and the “drill string - borehole wall” clearance. The dependence for identifying the drilling anisotropy index in oblique beds is obtained. An interrelation between the anisotropy drilling index, the zenith angle, the bedding angle, the bottom-hole assembly, the borehole dimensions and the axial weight on the bit has been established. The authors have studied analytically the effect of the weight on the bit and the force of the “drill string - borehole wall” interaction, when installing the centralizer to the bottom-hole assembly. The differential equations of the elastic axis of the drill string with the centralizer in the bottom-hole assembly are obtained. It is established that with the increase in the axial weight on the bit and the “drill collars - borehole wall” clearance, the distance from the bit to the contact point of the borehole wall decreases; whereas with the increase of the deviation angle and the clearance, the pressure force of the column on the walls increases. It has also been established that the anisotropy drilling index reduces the distance from the bit to the point contact both in a slick BHA and in the bottom hole assembly with the centralizer. The presence of a centralizer in the bottom hole assembly increases the distance from the bit to the contact point between the string and the borehole wall, makes it possible to increase the weight on the bit without the risk of increasing a deviation angle.

scholarly journals Knowledge, attitudes, and practices of oral cancer prevention among students, interns, and faculty members at the college of dentistry of Jazan University

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mosa A. Shubayr ◽  
Ahmed M. Bokhari ◽  
Afnan A. Essa ◽  
Ali M. Nammazi ◽  
Dania E. Al Agili
Keyword(s):  
Oral Health ◽  
Oral Cancer ◽  
Early Detection ◽  
Cancer Prevention ◽  
Dental Students ◽  
Faculty Members ◽  
Attitudes And Practices ◽  
The Past ◽  
Health Practitioners ◽  
Knowledge Attitudes And Practices

Abstract Background Oral cancer awareness among current and future dental practitioners plays a substantial role in the early detection and prevention of oral cancer. Therefore, this study aimed to assess the knowledge, attitudes, and practices (KAP) of oral cancer prevention (OCP) among oral health practitioners in the College of Dentistry at Jazan University, Saudi Arabia, and to determine factors that facilitate, or limit practices related to oral cancer prevention. Methods A self-administered questionnaire survey was done among dental students (n = 274), interns (n = 81), and faculty members (n = 117) in the College of Dentistry at Jazan University between May 2019 to February 2020. The questionnaire was developed in English and modified from a previously validated and published questionnaire into Arabic. It covered every KAP of oral cancer prevention that was useful in accomplishing the study's objectives. Logistic regression analysis was utilized to determine the factors associated with the practice of oral cancer prevention in the past year. Results Only 29.7% reported having participated in any OCP activities in the past 12 months while about 42% and 53% of participants referred suspected oral cancer patients to the departments of maxillofacial surgery and oral medicine, respectively. Most of the participants had poor knowledge (71.9%), unfavourable attitudes towards OCP (83.6%) and poor levels of practice (62.9%). The study found that the attitude of the participants was significant in influencing their practices of OCP in the previous 12 months, after adjusting for all other factors. Conclusion It was concluded that the level of knowledge, attitudes, and practices of OCP among the sample population was poor. The survey findings suggest that oral health practitioners in Jazan are inexperienced in the methods to adopt for prevention and early detection of oral cancer, despite the high prevalence of oral cancer among province residents. Further research should investigate effective educational strategies and training for improving the participation of students, interns, and faculty members in oral cancer prevention activities.

Application Of Tandem Rotary Steerable-Positive Displacement Motor Bottom Hole Assembly In Drilling Horizontal Wells: Case Study Of Three East Siberia Wells

2011 ◽  
Author(s):  
Zimuzor Michael Okafor ◽  
Andrew John Buchan ◽  
Dmitry Diyanov ◽  
Sheldon Andre Rawlins ◽  
Grigoriy Zhadan ◽  
...  
Keyword(s):  
Horizontal Wells ◽  
East Siberia ◽  
Positive Displacement ◽  
Bottom Hole ◽  
Bottom Hole Assembly

Optimizing Bottom Hole Assembly Design Criteria to Improve Mechanical Performance in Slim Hole Drilling Environment

2021 ◽  
Author(s):  
Stephen Fleming ◽  
Roberto Ucero ◽  
Yuliya Poltavchenko
Keyword(s):  
Mechanical Performance ◽  
State Of The Art ◽  
Hole Drilling ◽  
Force Analysis ◽  
Software Suite ◽  
Assembly Design ◽  
Positive Displacement ◽  
Drilling Performance ◽  
Bottom Hole ◽  
Bottom Hole Assembly

Abstract After analyzing the historical data of neighboring wells adjacent to the drilling site, 11 bit trips were required due to the low mechanical performance of the bottom hole assembly elements. This observation is based on maximum circulation hours and low helical bucking values that make it uneconomic to drill the sections with a positive displacement motor drive system. A redesign the bottom hole assembly was proposed to achieve an improved mechanical performance which allowed the section to be drilled with a single assembly. With a focus on increasing the mechanical limitations of the downhole elements, the use of 4 ¾" equipment is considered instead of the 3 ½" standard equipment used in this hole size. One of the biggest challenges was modifying the 4 ¾" positive displacement motor (PDM) to fit into the 5 ½" hole given that the mud motor has a maximum unmodified diameter of 5 ½". Using the force analysis module of a State-of-the-art BHA modelling software suite, multiple iterations were performed to simulate and validate an alternative PDM design and accompanying directional assembly. This new design featured modifications to an existing 4 ¾" PDM deploying a long gauge bit in combination with a fit for purpose measurement while drilling system. After numerous runs using this assembly design, it was found that there was no additional or unexpected wear of the modified Mud Motor components or associated elements of the downhole equipment. These observations act to validate the pre-job engineering force analysis. With the improved mechanical specifications of the 4 ¾" Bottom Hole Assembly (BHA) components, circulating hours were increased from 100 hours to 250+ hours in a stepwise process. This enabled drilling of the entire 5 ½" section with a single BHA, comparing favorably to the legacy approach with an average of eleven bit runs. The modified 4 ¾" PDM coupled with long gauge bit technology enabled a reduction in the oriented to rotate drilling ratio and an associated increase in the overall rate of penetration (ROP). It can be concluded that the substitution of 4 ¾" drilling equipment for 3 ½" in the 5 ½" hole section, increased the drilling efficiency between 30-50% according to field data obtained in Ukraine. The modified 4 ¾" PDM combined with long gauge bit technology has the potential to improve 5 ½" hole drilling performance in other locations. Following a structured planning process using State-of-the-art BHA modelling software suite enabling the evaluation of the significant forces that act in the drilling assembly and so significantly reducing the risks associated with exceeding the original design limits of the assembly. By improving the mechanical performance of the drilling assembly in a 5 ½" hole, new territory for drilling engineers and design engineers is now available to increase the drilling performance in slim wellbores.

Enhanced Steel Alloys Outperform Typical Bottom Hole Assembly Chemistries in Sour Service Applications

2007 ◽  
Author(s):  
Alvaro Chan ◽  
Glenn Robert Brown ◽  
Raymond Brett Chandler ◽  
Leianne W. Sanclemente ◽  
Danijel Hinger
Keyword(s):  
Steel Alloys ◽  
Bottom Hole ◽  
Bottom Hole Assembly ◽  
Sour Service
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