Santos, Hugo (Petrobras) | Perondi, Eduardo (UFRGS) | Wentz, André (Senai-SC) | Silva, Anselmo (Senai-SC) | Barone, Dante (UFRGS) | Basso, Eduardo (UFRGS) | Reis, Ney (Petrobras) | Galassi, Maurício (Petrobras) | Pinto, Hardy (Petrobras) | Castro, Bruno (Petrobras) | Ferreira, André (Petrobras) | Ferreira, Lincoln (Petrobras) | Krettli, Igor (Petrobras)
Methane Hydrates and Paraffin Plugs in flexible lines are concerns in offshore production. They may stop wells for months, causing high financial losses. Sometimes, operators use depressurization techniques for hydrate removal. Other strategy is using coiled tubing or a similar unit in order to perform local heating or solvent injection. However, frequently these strategies are not successful. In those cases, a rig may perform the operation or the line may be lost.
This project developed a robotic system in order to perform a controlled local heating and remove obstructions. The robotic system developed is able to access the line from the production platform. It uses a self-locking system in order to exert high traction forces. An umbilical with neutral buoyancy and low friction coefficient allows significant drag reduction. It allows moving upwards and in pipes with a large number of curves. Coiled tubing and similar units cannot do that. Carbon fiber vessels and compact circuits give flexibility to move inside 4-inch flexible pipes. A novel theoretical model allows the cable traction calculation using an evolution of the Euler-Eytelwein equation.
Experimental tests validated this model using curved pipes, both empty and filled with a fluid and using different loads. Experimental tests also validated the external layer traction resistance. Furthermore, the carbon fiber vessels were pressure tested, indicating a collapse resistance of more than 550 bar (8.000 psi). In addition, exhaustive tests of the onboard electronics and of the surface control system guarantee the communication reliability.
Additionally, the 25 kN (5.6 kip) traction system was modeled theoretically considering the self-locking system, the contact with the wall and a diameter range. Four prototypes allowed to: a) compare hydraulic and electric drive systems, b) validate the self-locking mechanism up to its limit, c) analyze the hydraulic system for leg opening and translation and d) prove the traction capacity. Finally, a theoretical model for the local heating system was developed. The system experimental validation on a cooled environment demonstrated its capacity of increasing temperature. Furthermore, it allows the obstruction removal in a controlled manner, avoiding damage to the polymeric layer of the flexible line.
Donadel Basso, Eduardo (UFRGS – Universidade Federal do Rio Grande do Sul) | André Perondi, Eduardo (UFRGS – Universidade Federal do Rio Grande do Sul) | Francisco Lisboa Santos, Hugo (Petrobras – Petróleo Brasileiro S/A) | Augusto Couto Barone, Dante (UFRGS – Universidade Federal do Rio Grande do Sul) | Luis da Silva Júnior, Anselmo (Instituto SENAI de Inovação em Sistemas Embarcados) | Viegas Wentz, André (Instituto SENAI de Inovação em Polímeros) | Mendel, Henrique (Mendel Serviços de Engenharia)
The obstruction inside flexible lines with hydrates or paraffins is quite common in offshore production systems. In these cases, in order to perform the clearance of the pipes, many different techniques, usually time consuming and expensive, are currently used. This article presents the development of a new self-propelled robot that is under design to become an alternative solution for this problem, which has been a research challenge by decades.
The use of robots with umbilical cables inside long obstructed pipes with several curves and bends is currently an important challenge in the robotic field, especially due to the increased traction forces that may occur. The main challenge is the force in the umbilical cable caused by the friction between the cable and the inner pipe surface. This force can be theoretically outlined by the capstan Euler-Etelwein equation (usually applied to the case of rounding a capstan with a rope). In an early study, a theoretical model for cable traction was developed and experimentally validated. This model was used to calculate a typical friction force in a standard pipeline. Several in-pipe movement strategies were analyzed and a suitable mechanism was defined as the main element for the robot traction mechanism. Therefore, we show in this study that the traction challenge can be surpassed by a properly cable materials selection composed with a suitable traction system design. A mechanism base in an inchworm-like movement was selected due to its high traction capacity and, based in an extensive study, a hybrid (electric-hydraulic) system was developed. The electric power transmission is provided through the umbilical, and electric motors drive pumps which supply hydraulic power to linear pistons that execute the movement of the mechanical elements, moving the entire system. Previous analysis and tests indicate that the designed system will be suitable to perform the necessary missions.
The Marine regions represent a significant portion of the total oil production in México. Sustaining oil production at current levels is a constant challenge; thus a large local operator is exploring unconventional methods in their quest to optimize rig utilization by implementing novel rigless work-over interventions.
One of the Marine Region most common interventions is production tubing clean-out. The objective of these interventions is the removal of deposits layers, asphaltenes and scale bridges in order to regain access to the producing intervals, and in some cases to eliminate the detrimental effect in production caused by reduced flow in scaled areas. Traditional clean-out methodology includes tubing conveyance, pumping of cleaning fluids and the operation of hydraulic or mechanical downhole tools.
E-line conveyed technology enables rigless clean-outs by mechanical removal of debris from production tubing, safety devices like SSSV and plug seats, saving deferred production and allowing the operator to optimize rig utilization. The cleaning tool run on a well tractor and e-line has proved to be a reliable and effective solution for clean-out applications.
E-line tractor assisted clean-out technology induces zero damage to the produced zone. The ability of removing debris from the wellbore without pumping a single drop of fluid into the well represents a major turnover into traditional workover approach. E-line conveyed clean-out enables operators to perform environmental friendly interventions, with reduced personnel and carbon footprint, enabling logistics optimization.
This paper examines these recent applications of through-tubing e-line conveyed well intervention solutions in Mexico's marine regions and presents the relevant well conditions and criteria used for selection. It provides case histories with operational challenges as well as the results of several successful, rig-less cleaning operations on an important producing wells.
Since the concept of milling obstructions on electric line (e-line) was introduced in 2005, operators around the world have applied this technique successfully removing downhole valves, plugs, scales, cement and nipple profiles achieving cost-effective and time-efficient interventions.
Recently, a series of e-line milling operations were performed to remove repeater-sub and ball-seat restrictions in oil producing horizontal wellbores located in Southeast Saskatchewan. The low pressure reservoirs favored intervention technologies that did not require excessive hydrostatic head. Operators have traditionally used nitrogen mixed with water to prevent damage to the reservoir and to maintain circulation; however, this reduces the amount of torque that can be achieved at the bit, and causes stalling and sticking issues.
Using a combination of tractor and milling technology on e-line in these wells provided the required torque for milling with a steady and constant weight on bit throughout the wellbore for removal of ball seat restrictions.
This paper presents the latest achievements within e-line milling in Canada. The paper will discuss best practices of date as well as a discussion of e-line milling challenges through three case studies in Canada.
The Business Case for E-Line Milling Ball Seats
Operators typically install a ball drop completion system which requires a ballseat in each stage of a multi-stage frac completion. As fraccing occurs, a ball is dropped and seats into this profile to isolate the frac interval below. Pressure exerted against the ball forces a sleeve to open the next frac stage, and so forth until the frac job is completed. There are a variety of sound reasons to remove balls and even mill out the ball seats; for instance, to increase the production flow area, to remove blockages/potential debris, to enable future interventions like production logging, perforating, diagnostic camera services, or installing a casing patch. Traditionally, the balls and/or ball seats were removed with a milling bit on coiled tubing or jointed pipe; however, service units or drilling rigs are heavy and costly equipment better used for other services such as drilling/ stimulating wells, and the bits are fluid-driven and thus problematic in low pressure or fluid-sensitive reservoirs. The business case for using e-line is to reduce intervention costs, prevent damage to low pressure and fluid-sensitive formations, maximize the utility of the limited inventory of coil/rigs, and provide multiple intervention solutions such as those listed above while onsite.