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Abstract Mechanical Specific Energy (MSE) is a term used by the oilfield drilling industry to describe several formulae quantifying the energy input within a drilling system. MSE mainly describes the Mechanical (WOB and Torque), for a given unit (Length, area or mass), and the energy required to do the work (i.e. force, time, distance). Although several different formulae have been developed in an attempt to quantify this value, the accepted industry standard is as below: Where: Es = Specific Energy (psi) N = Rotary Speed (rpm) W = Weight on Bit (Ibf) T = Drilling Torque (ft-lbf) Ax = Borehole x-sectional area (inA2) R = Rate of Penetration (ft/hr) When using surface parameters such as RPM and Weight, the drill string and BHA frictional losses are the primary source of energy loss in typical drilling systems. As such, introduction of solutions to reducing these frictional losses would have a significant impact on reducing the MSE of the system. This would lead to improved drilling efficiency, thus lower drilling time and reduced costs. The effect of having an axial oscillation tool (AOT) in the drill string has been previously demonstrated to be effective, particularly in applications where sliding with steerable motors has been problematic. Axial oscillation in the drill string is generated through a series of pressure pulses coming from one part of the AOT. The pressure pulses act on the pump open area of a shock tool, generating the axial motion required to reduce friction, improve the weight transfer to the bit, reduce reactive (and thus overall) downhole torque. The hydraulic vibration also enhances the performance through reducing friction. The AOT's influence on reducing friction in a constant axial oscillation helps reduce the total friction significantly. Friction reduction enables the entire suite of drilling parameters to be optimized through proper weight transfer, which in return, reduces the chance of buckling, reduced torque, increases ROP, and increase bit life; all are a source of energy improvement.
- Well Drilling > Drillstring Design > Torque and drag analysis (1.00)
- Well Drilling > Drilling Equipment (1.00)
- Well Drilling > Drilling Operations > Directional drilling (0.88)
Harmonic Vibration Disruption Improves Drilling Performance in Challenging Applications
Bouziane, Chakib (NOV) | Bates, Paul (NOV) | May, Norman (NOV) | Nicholl, Denise (NOV) | Burnett, Timm (NOV) | Minardi, Andrea (Groupmement SONATRACH-AGIP Algeria) | Golin, Mario (Groupmement SONATRACH-AGIP Algeria) | BenMohamed, Mohamed Heidi (Groupmement SONATRACH-AGIP Algeria) | Bennati, Simone (Groupmement SONATRACH-AGIP Algeria) | Angeletti, Paolo (Groupmement SONATRACH-AGIP Algeria)
Abstract The majority of wells drilled in Algeria are vertical with three hole sections 16, 12¼ and 8½ inches. The main challenge in these applications is the ability to manage the drilling system for optimal performance by drilling efficiently minimizing both drill string component and well bore damage. The highly interbedded and variable compressive strength of the formations make the system prone to severe vibrations. Vibrations are generated down hole while drilling. There are three types of vibration modes and they follow in order of severity, axial, torsional, and lateral. Lateral vibration is the most destructive mode and can create large shocks down hole with the Bottom Hole Assembly (BHA) components impacting the wellbore wall. The design of the drilling system should maximize the transfer of all the energy put into the drilling system drilling the hole rather than vibration. The anti-vibration sub is a tool designed to benefit the drilling by mitigating lateral vibration as part of the required energy management for efficient drilling. This has been observed through downhole data as well as Mechanical Specific Energy (MSE) comparisons. Unlike traditional stabilizers, the near bit anti-vibration stabilizer acts more like a stabilizer and a centralizer while not generating point loaded blade friction associated with traditional stabilizers. The system has been introduced successfully on rotary BHAs with all types of drill bits. The cost per meter has been reduced while improving borehole quality thus reducing associated non-productive time required when conditioning the hole prior to setting casing. This paper presents the field data acquired which indicates the importance of choosing the correct type, dimensions, and placements of the anti-vibration stabilizer. This anti-vibration stabilizer has been successfully utilized in several applications and is currently standard equipment for most vertical wells with rotary BHAs in Algeria.
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Drilling Equipment (1.00)
- Well Drilling > Drillstring Design > Drill pipe selection (0.73)
- (2 more...)
Abstract This paper demonstrates how Forward Synchronous Whirl (FSW), when induced in an underreaming while drilling BHA through the application of an Asymmetric Vibration Damping Tool (AVDT), substantially reduces both stick-slip and lateral vibrations and significantly improves drilling performance. The physics of operation, pre-job planning and modeling, followed by a thorough examination of run data and comparisons to offset wells will be documented and quantified. The performance of underreaming while drilling assemblies in long salt sections, as well as in pre-salt environments around the world has improved considerably in recent years. However, down-hole vibration still limits rates of penetration and overall drilling efficiency. Often, these long salt sections comprise the most challenging intervals of a deepwater well. A major development project in the Green Canyon section of the Gulf of Mexico contains wells with hole sections exceeding 9,000 ft in length through salt, and into the pre-salt. In order to evaluate the potential benefits of FSW, an AVDT has recently been added to the drilling assembly while keeping all other variables constant (rig, bit type, BHA, etc). The results showed that overall penetration rates increased by more than 50% and Stick-Slip (SS) vibration reduced by more than 75%. While there was a substantial across-the-board reduction in vibration and an increase in ROP, the benefits of the AVDT were recognized most in the portion of the hole section where elevated vibration levels typically cause a reduction in ROP as energy is lost to vibration (near the base of salt). With the addition of the AVDT there was little to no increase in SS, and no decrease in ROP. In fact, on one of the wells that used the AVDT, the final 2,500 ft of the 9,000 ft section was drilled 83% faster than the closest offset (178 fph vs. 97 fph), with 90% less SS vibration. Of the five wells analyzed, three were without the AVDT and two were with. All of the runs in question were with a 14 1/2"-16 1/2" underreaming while drilling, rotary steerable drilling assembly. This novel approach has wide-spread application in global deepwater basins, particularly in vibration-prone wells. This paper demonstrates how the technology is being applied effectively, and provides a platform for further application.
- North America > Cuba > Gulf of Mexico (0.89)
- Africa > West Africa (0.89)
Abstract This paper describes the work, on test rigs and full-scale drilling rigs, carried out with respect to placement of an Asymmetric Vibration Damping Tool (AVDT) within drilling while underreaming operations. An AVDT, by virtue of the forward synchronous motion imposed on the drill string, offers benefits in minimizing down hole vibration related tool failures and therefore maximizing ROP. Of interest in using the AVDT is the tendency to minimize stick slip by means of the parasitic torque it generates. This is of particular importance during underreaming operations. While underreaming, stick slip can result in low ROP and potentially an increased incidence of down hole tool failures. The use of an AVDT in these operations has been shown to significantly reduce stick slip. However, due to the forward synchronous motion caused by the AVDT, there is the potential to cause eccentric wear to BHA components in the vicinity of the AVDT. If allowed to progress, this eccentric wear can cause a reduction in down hole tool life and drilling performance. Eliminating eccentric wear would be beneficial in reducing repair costs, extending component life and further improving drilling performance. To minimize eccentric wear and maximize drilling performance, the placement of the AVDT within the bottom hole assembly is critical. This paper describes how the placement of intermediate stabilizers between the AVDT and the underreamer can minimize eccentric wear to the underreamer and the adjacent drill string due to the forward synchronous whirl induced by the AVDT. This approach allows the full benefits of the AVDT to be recognized while reducing the potentially damaging effects of eccentric wear to other BHA components. The work has drawn upon small scale rig testing, full scale testing at the Ullrigg test facility in Norway and from real-world drilling and underreaming operations in the USA.
Abstract Slick-slip (SS) and lateral shocks are harmful to many expensive downhole tools such as rotary steerable systems, and downhole measurement and logging tools. Due to this concern, an asymmetric vibration damping device has been engineered to reduce these specified vibrational modes. This tool is uniquely specialized that, when placed and ran with the recommended drilling parameters, reduces stick-slip tendencies as well as dampen lateral shocks by placing the drill string near the tool in Forward Synchronous Whirl (FSW). As a result of placing the BHA (bottom hole assembly) into FSW, other harmful vibrational modes such as chaotic whirl and backward whirl are prevented from occurring. Stemming from the exclusive geometry of the tool, the tool will interrupt harmonic modes during rotation that can lead to harmful shocks and SS. Extensive research has been performed in laboratory and field testing using the vibration damping tool, and its success has been proven in multiple deep water applications (primarily with hole opening BHA’s), but also on land with bi-center bits. Recently, a new approach was undertaken, utilizing two vibration damping tools in a single BHA. This was intended to control vibrations and reduce shocks that were causing extensive damage to Rotary Steerable System (RSS) horizontal applications in North America. The initial trial wells used the dual placement within the vertical and horizontal sections, drilling into the Cotton Valley formation in North Louisiana. These applications have historically seen very high vibration levels due to both the trajectory and challenging formations.
- North America > United States > Texas > East Texas Salt Basin > Cotton Valley Group Formation (0.99)
- North America > United States > Louisiana > East Texas Salt Basin > Cotton Valley Group Formation (0.99)
- North America > United States > Arkansas > East Texas Salt Basin > Cotton Valley Group Formation (0.99)