Friction-Induced Wellbore Instability Due to Drill String

Abstract Drilling and completion of the surface and intermediate sections in some fields is extremely challenging due to wellbore instability, especially accomplished with complete losses. Such circumstances lead to several time-consuming stuck pipe events, when existing standard ways of drilling did not lead to a permanent resolution of the problems. After exhausting the available conventional techniques without sustainable success, unorthodox solutions were required to justify the well delivery time and cost. Here comes the Casing While Drilling (CwD), being the most time and cost-effective solution to wellbore instability. CwD is introduced at full throttle aiming at the well cost reduction and well quality improvement. The implementation plan was divided in three phases. The first phase was a remedial solution to surface and intermediate sections drilling and casing off to prevent stuck pipe events and provide smooth well delivery performances. After successful implementation of CwD first phase, CwD was taken to the next level by shifting it from a mitigation to an optimization measure. Each step of CwD shoe-to-shoe operations was analysed to improve its performances: drill-out (D/O) of 18⅝-in shoe track with CwD, optimum drilling parameters per formation and CwD bit design. Implemented in 19 wells, CwD shoe-to-shoe performances have been brought up or even above standard rotary bottom hole assembly (BHA) benchmark. Planning for third phase is undergoing whereby CwD is aiming to optimize a well construction to reduce well delivery time, by combining surface and intermediate sections thus eliminating one casing string. Numerous challenges are being worked on including open hole (OH) isolation packer which conform to and seal with the borehole uneven surface. Special "for purpose built" expandable steel packer and stage tool have been manufactured and qualified for the specific application. A candidate well has been chosen and agreed for first trial. The key areas of improvement include, drilling and casing off the surface and intermediate sections while competing with standard rotary BHA performances and slimming down the well profile towards tremendous time and costs savings. This paper encompasses details of constructions of various wells with sufficient contingencies to combat any expected hole problems without compromising the well quality while keeping the well within budget and planned time. It also provides an analysis of the well trials that were executed during the implementation of first and second phases of CwD implementation and the captured lessons learnt which are being carried forward to the next phase. This paper provides the technique on how CwD can be used to help with three aspects of drilling, successfully mitigating holes problems by reducing OH exposure time and to eliminate drill string tripping and modifying conventional casing design to reduce well time and cost by eliminating one casing string.

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Risk Due to Pipe Sticking

Risk Analysis for Prevention of Hazardous Situations in Petroleum and Natural Gas Engineering - Advances in Environmental Engineering and Green Technologies ◽

10.4018/978-1-4666-4777-0.ch003 ◽

2014 ◽

pp. 47-72

Author(s):

Nediljka Gaurina-Medjimurec ◽

Borivoje Pasic

Keyword(s):

Petroleum Industry ◽

Drill String ◽

Differential Pressure ◽

Factors Affecting ◽

Wellbore Instability ◽

Hole Cleaning ◽

Pressure Pipe ◽

Drilling Parameters ◽

Bottom Hole Assembly ◽

Geometry Deviation

A stuck pipe is a common worldwide drilling problem in terms of time and financial cost. It causes significant increases in non-productive time and losses of millions of dollars each year in the petroleum industry. There are many factors affecting stuck pipe occurrence such as improper mud design, poor hole cleaning, differential pressure, key seating, balling up of bit, accumulation of cuttings, poor bottom hole assembly configuration, etc. The causes of a stuck pipe can be divided into two categories: (a) differential sticking and (b) mechanical sticking. Differential-pressure pipe sticking occurs when a portion of the drill string becomes embedded in a filter cake that forms on the wall of a permeable formation during drilling. Mechanical sticking is connected with key seating, formation-related wellbore instability, wellbore geometry (deviation and ledges), inadequate hole cleaning, junk in hole, collapsed casing, and cement related problems. Stuck pipe risk could be minimized by using available methodologies for stuck pipe prediction and avoiding based on available drilling parameters.

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On the Influence of the Equivalent Circulent Density Fluctuations on the Development of the Wellbore Natural Fracture

10.2118/201058-ms ◽

2021 ◽

Author(s):

Arnaud Regis Kamgue Lenwoue ◽

Jingen Deng ◽

Yongcun Feng ◽

Naomie Beolle Songwe Selabi

Keyword(s):

Finite Element ◽

Drill String ◽

Natural Fracture ◽

Cyclic Loads ◽

Fracture Width ◽

Wellbore Instability ◽

Fracture Length ◽

String Vibration ◽

String Vibrations ◽

Drilling Operations

Abstract Wellbore instability is one of the most important causes of Non-Productive Time during drilling operations causing billions of dollars of losses every year. During the drilling stage, the Equivalent Circulent Density (ECD) is subjected to fluctuations caused by some factors such as the drill string vibrations cyclic loads. The fluctuating ECD applied on the fractured formation progressively modifies the initial parameters of the fractured formation such as its length and its width and this process finally results into wellbore instability. In this research, a poroelastic model based on a finite element method has been established to analyze the influence of the drill string vibration cyclic loads on the development of the wellbore natural fracture. The analysis was conducted with a two-dimensional plane strain model. A traction-separation law based on energy has been proposed for the Cohesive Zone Model. A nonlinear finite element software ABAQUS was utilized as the numerical simulator. The numerical results showed that the profiles of the fracture width as a function of time follow a sinusoidal behavior similar to the behavior of the drill string vibration cyclic loads profile. For different values of the Weight On Bit (WOB) and constant drill string Revolution Per Minute (RPM), an increase of the fracture width with the fracture length is observed in the near wellbore region. In the region far away the wellbore, the fracture width globally decreases with an increase of the fracture length for each fracture profile. the investigation of the effect of some drilling operational parameters on the development of the wellbore natural fracture also demonstrated that the drillstring vibration cyclic loads lead to an increase of the fracture length, fracture width, the loss circulation and the Bottom Hole Pressure. This study couples the integration of the fracture rock development with the continuous cyclic load generated by drill string vibrations. This aspect has been rarely discussed in the literature. The study indicates that the cyclic loads significantly affect the development of the wellbore natural fracture during drilling operations, and therefore has an important impact on the wellbore stability analysis.

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Numerical Investigation of the Influence of the Drill String Vibration Cyclic Loads on the Development of the Wellbore Natural Fracture

Energies ◽

10.3390/en14072015 ◽

2021 ◽

Vol 14 (7) ◽

pp. 2015

Author(s):

Arnaud Regis Kamgue Lenwoue ◽

Jingen Deng ◽

Yongcun Feng ◽

Haitao Li ◽

Adefarati Oloruntoba ◽

...

Keyword(s):

Cyclic Load ◽

Drill String ◽

Natural Fracture ◽

Circulation Rate ◽

Cyclic Loads ◽

Percentage Increase ◽

Fracture Width ◽

Wellbore Instability ◽

Fracture Length ◽

String Vibration

Wellbore instability is one of the most serious issues faced in the drilling process. During drilling operations, the cyclic loads applied on the fractured formation progressively modify the initial parameters (i.e., length and width) of the fractured formation, thus resulting into undesirable wellbore instability. In this paper, using a nonlinear finite element software (ABAQUS) as the numerical simulator, a poro-elasto-plastic model has been established which aimed at analyzing the influence of drill string vibration cyclic loads on the development of the wellbore natural fracture. The numerical results showed that the fracture width as a function of time profiles followed a sinusoidal behavior similar to the drill string vibration cyclic load profiles. For different cyclic load magnitudes with constant number of cyclic loads, the highest percentage increase of the fracture width after integration of cyclic loads was 64.77%. Interestingly, the fracture width increased with the fracture length in the near wellbore region while it globally decreased in the region far away from the wellbore. But for constant cyclic load magnitude with different number of cyclic loads, the biggest percentage increase of the fracture width after integration of cyclic loads was slightly lower representing 63.12% while the oscillating period of the fracture width increased with the number of cyclic loads. The parametric study revealed that the drill string vibration cyclic loads were relatively independent of the fracture length and the bottom hole pressure. However, the fracture width and the loss circulation rates were considerably impacted by the drill string vibration and the highest percentage increase of the loss circulation rate after integration of cyclic loads was 14.3%. This study provides an insight into the coupling of the fracture rock development and the continuous cyclic loads generated by drill string vibrations which is an aspect that has been rarely discussed in the literature.

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First Abu Dhabi 9.625in × 12.25in Non-Directional Casing While Drilling CWD Run for Intermediate Hole Section Saves Two Days Rig Time, Enhancing Drilling Efficiency & Improving Well Integrity

10.2118/207565-ms ◽

2021 ◽

Author(s):

Felix Leonardo Castillo ◽

Roswall Enrique Bethancourt ◽

Mohammed Sarhan ◽

Abd Al Sayfi ◽

Imad Al Hamlawi ◽

...

Keyword(s):

Performance Optimization ◽

Cost Savings ◽

Polycrystalline Diamond ◽

Construction Cost ◽

Drill String ◽

Abu Dhabi ◽

Wellbore Instability ◽

Well Integrity ◽

Well Design ◽

Cement Integrity

Abstract Significant mud losses during drilling often compromises well integrity whenever sustainable annular pressure (SAP), is observed due to poor cement integrity around 9-5/8-in casing in wells requiring gas lift completion. Heavy Casing Design (HCD) is applied as a solution; whereby, two casing strings are used to isolate the aquifers and loss zones, thus ensuring improved cement integrity around the 9 5/8-in intermediate casing. Casing While Drilling (CWD) is a potential solution to mitigate mud losses and wellbore instability enabling an optimized alternative to HCD by ensuring well integrity is maintained while reducing well construction cost. This paper details the first 12 ¼-in × 9-5/8-in non-directional CWD trial accomplished in Abu Dhabi onshore The Non-Directional CWD Technology was tested in a vertical intermediate hole section of a modified heavy casing design (MHCD) aimed at reducing well construction cost over heavy casing design (HCD) as shown in the figure 1. A drillable alloy bit with an optimized polycrystalline diamond cutters (PDC) cutting structure was used to drill with casing through a multi-formation interval with varying hardness and mechanical properties. Drilling dynamics, hydraulics and casing centralization analysis were performed to evaluate the directional tendency of the drill string along with the optimum drilling parameters to address the losses scenario, hole cleaning, vibration, and maximum surface torque. The CWD operation was completed in a single run with zero quality, health, safety, and environment (HSE) events and minimum exposure of personal to manual handling of heavy tubulars. Exceptional cement bonding was observed around the 9 5/8 in casing indicative of good hole quality despite running a significant number of centralizers (with smaller diameter), compared with the conventional drilled wells (cement bond logging was done after the section). CWD implementation saved two days of rig operations time relative to the average of the offset wells with the same casing design. The rate of Penetration (ROP) was slightly lower than the conventional drilling ROP in this application. The cost savings are mainly attributed to the elimination of casing-running flat time and Non-Productive Time (NPT) associated with clearing tight spots, BHA pack-off, wiper trips. The application of CWD in the MHCD wells deliver an estimated saving of USD 0.8MM in well construction cost per well compared to the HCD well design. Additional performance optimization opportunities have been identified for implementation in future applications. The combination of the MHCD and CWD technology enhances cementing quality across heavy loss zones translating into improved well integrity. Implementing this technology on MHCD wells could potentially save up to USD 200MM (considering 250 wells drilled). This is the first application of the technology in Abu Dhabi and brings key learning for future enhancement of drilling efficiency. The CWD technology has potential to enhance the wellbore construction process, which are typically impacted by either circulation losses and wellbore instability issues or a combination of both, it can applied to most of the offshore and onshore fields in Abu Dhabi.

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Numerical Investigation of the Influence of the Drill String Vibration Cyclic Loads on the Time Dependent Wellbore Stability Analysis

10.2118/204774-ms ◽

2021 ◽

Author(s):

Arnaud Regis Kamgue Lenwoue ◽

Jingen Deng ◽

Yongcun Feng ◽

Naomie Beolle Songwe Selabi

Keyword(s):

Cyclic Load ◽

Drill String ◽

Wellbore Stability ◽

Time Dependent ◽

Cyclic Loads ◽

Drilling Mud ◽

Collapse Pressure ◽

Wellbore Instability ◽

String Vibration ◽

Fracture Pressure

Abstract Wellbore instability is one of the most important causes of Non-Productive Time causing billions of dollars of losses every year in the petroleum industry. During the drilling operations, the drilling mud is generally utilized to maintain the wellbore stability. However, the drilling mud is subjected to fluctuations caused by several processes such as the drill string vibration cyclic loads which can result into wellbore instability. In this paper, a nonlinear finite element software ABAQUS is utilized as the numerical simulator to evaluate the time dependent pore pressure and stress distribution around the wellbore after integration of drill string vibration cyclic loads. A MATLAB program is then developed to investigate the wellbore stability by computation of the time dependent wellbore collapse pressure and fracture pressure. The numerical results showed that the safe mud window which was initially constant became narrower with the time after integration of vibration cyclic load. The collapse pressure without vibration cyclic load increased by 14.33 % at the final simulation time while the fracture pressure decreased by 13.80 %. Interestingly, the safe mud windows widened with the increase of the normalized wellbore radius as the wellbore fracture pressure increased and the collapse pressure decreased. This study provides an insight into the coupling of the wellbore stability and the continuous cyclic loads generated by drill string vibrations which is an aspect that has been rarely discussed in the literature.

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