Jointed Tubing Injector Snubbing on Extended Reach Wells

OBJECTIVE / SCOPE An injector has been developed that is able to continuously move conventional jointed tubing in and out of wells that may be underbalanced. It is an advantage to use the jointed tubing injector rather than coiled tubing or conventional hydraulic snubbing due to cost, speed of operation, transportation, effectiveness, and safety. The paper will describe the function and application of the jointed pipe injector. METHODS, PROCEDURES, PROCESS An injector has been designed with retractable gripping segments integral to the gripper blocks that are able to function on conventional jointed tubing, over interconnecting couplings and with the advantages of continuously operating injector movement. The description is to include how the geometry of the retractable gripper block system works and how the technical and safety risks of a conventional snubbing system or coiled tubing are overcome. Configurations whereby the jointed tubing injector can be used to provide methods of completing wells that are safer and more efficient than coiled tubing or a conventional hydraulic snubbing jack will be presented. RESULTS, OBSERVATIONS, CONCLUSIONS The biggest limitation of coiled tubing is due to its size and residual bend, it is not capable of reaching the end of the well before the wellbore friction causes helical buckling. The OD of the coiled tubing is limited by the available reel sizes and the difficulty transporting the large reels due to road dimensional and weight limitations. Coiled tubing is not able to be rotated at any time in the well. The use of jointed tubing eliminates those limitations. When a well is being completed with a conventional hydraulic snubbing jack, the length of the stroke that the jack can take is limited by the allowable unsupported length of the tubing to ensure that it will not buckle. It is also forced to stop workstring movement each time the jack is reset therefore the static friction of the workstring must be overcome during each movement of the jacks. The design of the jointed tubing injector minimizes the unsupported length of the tubing and allows the continuous movement of the tubing. The operation is less labor intensive, and the controls can be moved to a position that is less exposed to danger. NOVEL / ADDITIVE INFORMATION The Jointed Tubing Injector can continuously move jointed tubulars in and out of a well. There is no other piece of equipment that will address as many of the problems that have been experienced in the completion of extended reach wells. The paper will describe the injector and control system and how it can be applied to solve the challenges.

Analysis of Critical Buckling Loads For Tool-Jointed Drillstrings in Deviated Wellbores

Excessive torque and drag, buckling and shear forces on downhole strings and tubulars are often encountered in the drilling of longer reach or deviational wells. Buckling of drillstring and BHA occurs in drillstring mainly due to high compressive forces. A point may be reached where these compressive forces rise and exceed the critical buckling loads leading to buckling of the drillstring/BHA or tubulars. This study focuses on the evaluation of the effect of tool-joint on the buckling of drillstrings for highly deviated wells. Tool-joint in pipes changes the pipes geometry in the wellbore thus affecting its hydraulics, orientation and stress distribution. A notable error will arise when straight pipe (with uniform outside diameter (OD) models are used to model pipes with end couplings and connections (such as tool joints). These errors may impact critical buckling loads, buckling initiation points, and post-buckling analysis of the pipe or BHA, thus affecting the success of drilling and completion operations. Torque and drag simulation and analysis was carried out for drillstring and BHA components in 9 5/8 in casing and 8.5 in open-hole sections to determine buckling loads. Two cases were considered; case 1 investigated the modeling and definition of buckling conditions for single straight body drillstrings and case 2 evaluated the buckling conditions for tool-jointed pipes. The result shows that buckling in tool-jointed pipes follows similar trend to that of straight body pipes with sinusoidal or lateral buckling being initiated first, and gradually progresses to helical buckling on increased axial force transfer. Furthermore, from the comparison of the results from two cases considered, it was observed that the presence tool-joint in the pipes led to a critical buckling load of 5.8% for sinusoidal buckling modes. The paper suggests that higher compressive force is needed to buckle the tool-jointed ends of the drillstring than the straight ends.

Design Optimization for Hydraulically Driven Agitation Tool in Extended Coiled Tubing Reach Application

As the boundaries are pushed with increased length of horizontal wells, coiled tubing (CT) well intervention capabilities are challenged requiring new technologies to expand existing capabilities. When utilizing coiled tubing, standard best practice is to first utilize CT modeling software to optimize CT size and weight for maximum reach. After choosing the right CT size, the next and most critical factor to address in extending the reach is, drag and frictional forces between the CT and the wellbore. Reducing friction and delaying helical buckling will significantly increase the reach. Several versions have been created utilizing various pressure pulse tools in the CT bottom hole assemble (BHA) to accomplish this task. These tools work by creating vibration or pressure pulses that allow for a delay in the onset of the helical buckling of CT and are widely utilized and accepted as solutions. However, existing agitation tool limitations have been reached. A newly designed and developed, hydraulically driven agitation tool (HDAT) to extend CT reach delivers continuous frequency pressure waves along the entire length of the CT. The HDAT provides a reduction in static friction and converts that to a dynamic friction form along the CT string. The continuous hydraulic agitation reduces the onset of helical buckling and thus reduces CT helical contact points, resulting in lower resistance force. The development, design, and lab testing for the HDAT has been through extensive development stages resulting in three generations of the tool, with each version providing an incrementally improved performance. The latest generation HDAT has been designed to function at optimum operational frequencies and produce excitation that works on a longer section of the CT. The performance advancement of the newly designed HDAT generation was achieved after extensive lab testing with a field run reaching a total depth of 24,500 ft over a 4,600 ft open hole lateral section. The new HDAT was redesigned to improve performance and reliability to achieve an effective matrix acid stimulation treatment. The lessons learned from previous generations were imbedded to extend the reach of the CT in the most challenging extended reach wells.

Simulating Drillstring Dynamics Motion and Post-Buckling State with Advanced Transient Dynamics Model

Summary As drilling sections become deeper and longer, transferring more weight downhole to improve rate of penetration is the primary concern for the operator. Drillstring dynamics and buckling are some primary limiters for drilling efficiency. Aggressive drilling parameters may lead to severe downhole dynamics, which leads to cutter breakage and tool damage. When axial compression exceeds a certain threshold, the drillstring buckles sinusoidally inside the wellbore first, followed by helical buckling. Buckling leads to accelerated joint wear, tool fatigue failures, and lower drilling efficiency. To better manage drillstring dynamics and buckling, we propose a method of simulating drillstring dynamics motion and postbuckling state using an advanced transient dynamics model. An analysis methodology was developed on the basis of the finite element transient dynamics model. The model captures the enriched physics of drillstring dynamics and loading: the large deformation of buckled drillstring, the strong nonlinearity of contact and friction forces, and the dynamically triggered instability caused by drilling rotation. Transient dynamics simulations are conducted for drillstring with the actual well trajectory and rotation speed. The weight on bit (WOB) is ramped up gradually, and the drillstring deformation is monitored to detect the onset of buckling or dynamics instability. To conduct the model validation, the buckling inception loads predicted by the model are compared against the analytical equation of critical buckling loads. A field extended reach drilling (ERD) job was simulated by the model. The downhole weight and torque data from the measurement-while-drilling (MWD) tool was used to validate the weight transfer prediction by the model. Most existing buckling theories use the analytical equations of critical buckling load, which were normally derived on the basis of the idealized assumptions, such as perfect wellbore shape and uniform tubular geometry. The proposed method simulates the drillstring behaviors in the field drilling conditions and aims to capture effects of wellbore friction and string rotation. The transient dynamics model is capable of simulating drillstring dynamics movement (whirling and snaking) and weight lockup under severe helical buckling. An automatic method is proposed to interpret the drillstring behaviors from the simulation results. Using the transient dynamics model, the procedure presented in this article can simulate the dynamics and buckling behaviors of drillstring and help mitigate associated risks in well-planning and execution phases.

Rig-Assisted Snubbing: Drillpipe Pressure Control in MPD/UBD

An important pressure control issue during live well work is the expulsion force acting on the drillpipe. Wellhead pressure multiplied by drillpipe sealing area in the blowout preventor must be overcome before entering the well. The highest snubbing force (compression) is applied when running the first joint into the well since pipe weight is at its lowest at this time. Focus of this paper is the mechanical analysis of the drillpipe as a well barrier element during live well entry. We look at normal operation (primary well barrier) and contingency (secondary well barrier). Load cases include critical unsupported buckling, helical buckling inside tubing guide, collapse and burst. In critical unsupported buckling there is no radial confinement of the pipe and the critical buckling limit is determined at the onset of lateral deflection. On the other hand, inside the tubing guide the pipe is allowed to buckle into a helix and the buckling limit is related to permanent corkscrewing of the pipe. Technical contributions in this paper include engineering design formulas for unsupported buckling and helical buckling. Also presented are experimental buckling results from pipe up to 3½ inch (8.9 cm) diameter. Design calculations for primary and secondary well barriers are explained and analyzed using a field case. All load calculations are based on zero neutral axial stress as stress reference datum, which produces a yield circle that is conveniently deployed for three-dimensional well tubular design. The use of the dimensionless yield circle is found to be an efficient method to assess helical buckling loading and the combined effects of pressure and axial stresses.

Combined Effects of Wellbore Curvature, Connector, and Friction Force on Tubular Buckling Behaviors

Summary A tubular buckling model is built, while considering the combined effects of wellbore curvature, tubular connector, and friction force. On the basis of certain assumptions, the expressions of critical helical–buckling loads are deduced with the equivalent beam–column model and energy method and the amendment factors of critical buckling loads because of relevant factors are obtained. The results from the new model are compared with those from previous models and experiments. The roles of relevant factors in tubular mechanical behaviors are discussed. It is indicated that wellbore curvature affects equivalent tubular–string weight, the connectors affect potential energy, and friction force leads to dissipative energy in the buckling–initiation process. Critical helical–buckling loads are most likely underestimated if the combined effects are not considered.