Experimental testing of helical buckling of tubulars, using three different test facilities, is presented and discussed. The tests provide information to better understand the buckling behavior of circumferentially restrained tubulars. The finite element method is used in the analysis of helical buckling, allowing inclusion of friction during the development of the helix. There was an excellent agreement between the finite element solution and the experimental results. Introduction Buckling of tubulars (casing, drillstring, tubing and coil tubing) is a critical problem that has been present in oil/gas field operations for many years. Some of the associated problems are: casing failure, drillstring failure, casing wear, increase in drillstring drag and torque, and limiting coil tubing applications and extended reach drilling. The inability of a tubular to achieve its intended function is often attributed to a lack of understanding of its buckling behavior. HELICAL BUCKLING TEST FACILITIES Three test facilities were built to carry out experimental research in helical buckling of tubulars in confined geometry. These are: vertical test facility horizontal test facility variable inclination test facilty Figure 1 shows a general schematic of these facilities. The operational parameters are given in Table 1. The test facilities were designed such that it allows human observation for characterization of modes of buckling and general behavior of the pipe. Data acquisition system An automated data acquisition system was utilized throughout the test program. It consisted of the following: two load cells with capacity of 1000 lb (compression), horizontal and variable inclination test facilities two load cells with capacity of 25 lb (tension / compression), vertical test facility one LVDT with a maximum displacement of 6", all three facilities P. 433^
This paper presents results from experimental data for sinusoidal buckling of tubulars in vertical wells and discusses some analytical solutions presented in the literature. An experimental apparatus 55 feet long was used in the tests. Several tests have been conducted and the results are presented and analyzed. The following aspects of sinusoidal buckling were observed during the tests: critical sinusoidal buckling force, contact point between pipe and wellbore, further buckling modes, effect of friction in the post buckling behavior. Introduction An ideal (weightless) pipe, subjected to an axial force F as shown in Fig. 1, will buckle in an approximately sinusoidal shape provided that is satisfied the following inequality (1) where: L: Length of the string B: Bending stiffness Since a weightless pipe does not exist in practice, the buckled shape will not be a true sinusoidal but rather of the shape shown in Fig. 2. REVIEW OF THE LITERATURE The first rigorous treatment of drill string stability was presented by Lubinski in 1950. In that pioneer work an analysis of two dimensional buckling of pipes in vertical wells and its effects on bit inclination, shape of the string, wall contact force, bending moments, etc., was presented and thoroughly discussed. Using power series Lubinski has solved the differential equation governing the instability problem. His solution, given by Eq. (53) in Ref. 2, is not straightforward, but gives very precise results. As an approximation, for practical purposes, Lubinski proposed the critical force for first mode of buckling as: (2) where m is the length, in feet, of one dimensionless unit (3) Equation (2) is in fact the solution for a string with a length equivalent to 7.94 dimensionless units. Although Eq. (2) gives a very good approximation, it will be shown later that, for strings with length greater than 7.94 dimensionless units, the critical force is less than that predicted by Eq. (2). To determine the exact critical force one must find the result solving Eq. (53) from Ref. 2. P. 77^
Drilling and completion in Campos Basin have been in constant evolution, from the first subsea wells and fixed platforms to latest horizontal wells in deepwater. This paper will first present the lessons learned with drilling and completion in shallow water to latest wells drilled and completed in Roncador in the range of 1,800 meters of water depth. Exploratory drilling will be also addressed. The main points to be presented are: well design, horizontal and multi lateral wells, well head design, well control, operations with dynamic positioning vessels, completion and sand control techniques and their evolution. Second, this paper will address some challenges presenting the problems as PETROBRAS see them, what are the solutions that we are adopting and what do we expect from the industry. The issues that will be presented are: well design for production of heavy oil, dual gradient drilling, intelligent completion systems for monitoring and controlling multiple zones, production or injection from or into a single well, isolation inside horizontal gravel-packed wells, gravel packing long horizontal sections under very low formation fracture gradient. Introduction Campos Basin exploratory activities started in 1971 first with jack ups (Penrod 89) and later with moored drillships that culminated with the discovery of Garoupa field in 1974 at 124 meters of water, soon followed by other shallow water discoveries (Namorado, Enchova, Pargo and others) that came on stream in subsequent years. Petrobras started in 1984 a deepwater exploratory campaign with successful discoveries as Albacora (1984), Marlim (1985), Albacora Leste (1986), Marlim Sul (1987) and Roncador (1996). Campos Basin developments along these 25 years of production have imposed many learnings and challenges in the drilling and completion operations. Several projects were implemented from shallow to ultra deepwater using jack ups, fixed platforms, moored floating rigs and dynamic positioning (DP) rigs in drilling, completion and workover operations. These different projects required different approaches and the key was to use the learnings of each field development in future projects. The most important evolution in drilling and completion operations was seen when we moved towards deeper water. It allowed, in conjunction with the subsea hardware evolution to put the first deepwater well on stream in September 1984 (well 3-PU-2-RJS at 307 meters of WD) and the first ultra deepwater field on stream in 1999 (Roncador). In general, the geological carachteristics in Campos Basin are: shallow reservoirs, no occurrence of shallow gas or HPHT formations. Moreover, the environmental conditions in Campos Basin are mild but with high currents. On the other hand several critical issues have to be still overcome in drilling and completion operations to cope with the challenges of producing in ultra deepwater (2,000 - 3,000 meters) as: steep slope seabed, shallow and unconsolidated reservoirs (Miocene and Oligocene) and expensive operations. Nowadays there are 650 wells drilled in WD up to 1,500 meters and 114 wells drilled in WD deeper than 1,500 meters. Ultra deepwater under going field developments will lead Petrobras domestic production to reach 1.9 million barrels of oil per day by 2005.
For several years, after the Offshore Technology Conference (OTC), I have had the opportunity to address the JPT audience and comment on subsea technologies and field applications that came to the forefront. This year, however, before getting to business, I would like to comment on the major event that hovered over OTC and the questions that could not stop being asked: "What happened?" "What consequences will the industry face?" "How should we get prepared for the day after?" I waited until the day before my review was due to put thoughts on paper. During this period, I closely followed developments and efforts to solve the catastrophe. Nevertheless, more time is necessary to cap the well and much more time will be necessary to recover the environment. How long it will take us to be back in business is another question that we all would like to answer. As we find the answer, our industry will be revisited comprehensively-from regulations and drilling procedures to equipment construction, safety, and environmental response. Time will tell. Now, let us address subsea technology and the papers of this issue. It was pleasing to see new fields implementing subsea boosting in different parts of the world. Three fields particularly caught my attention: Perdido, Parque das Conchas, and Azurite. The Perdido field, in the ultradeepwater Gulf of Mexico, combines a spar with a subsea-boosting system-an engineering master piece. The Parque das Conchas (BC-10) field, in ultradeepwater Brazil, uses a subseaboosting system. The Azurite field, in ultradeepwater West Africa, uses a subseamultiphase-pumping system. Subsea boosting attests that the operators have been looking attentively into this type of solution as the technology evolves into the ultimate subsea-to-shore production systems.I am pleased to suggest a collection of papers that addresses such solutions and their significant benefits to the field. I hope you enjoy it! Subsea Technology additional reading available at OnePetro: www.onepetro.org OTC 20418 • "
This paper was prepared for presentation at the 1999 SPE/IADC Drilling Conference held in Amsterdam, Holland, 9-11 March 1999.
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