Mikhail Y. Gelfgat

Method of Dynamic Analysis for Rod-in-Hole Buckling

The problem of a postbuckling dynamic behavior of weighted rod, which is inserted into an arbitrary profile hole with some clearance, under the axial compression load is considered. In practice, this analysis is important for calculation of the friction drag of the drillstring in inclined and horizontal wellbores. The mathematical model and numerical method of the rod-in-hole contact interaction are developed. The contact model is based on a nonlinear dependence of the normal-directed contact force on the depth of interpenetration of rod in hole. The tangential interaction of bodies with the contact surfaces is described using a model of “elastic-plastic” friction. The developed system of substantially nonlinear differential equations with partial derivatives of 3-D rod dynamics is approximated by the finite differences and integrated by the Runge-Kutta method. A simplified model for axial motion of rod is suggested to make the process of numerical integration faster. The results of numerical simulation of stress-deformed state of rod in horizontal, inclined and curved holes are presented. The results of numerical simulation are compared with the results of experiment. The effect of the friction factor on the rod buckling has been studied. The effect of local outside bulges of the drillstring on a postbuckling behavior of the drillstring is considered.© 2006 ASME

Aluminum Catenary Production Riser: Design, Testing Results, Ways to Improvement

One of the widely used systems for offshore oil production in water depths up to 500–2500 meters is a steel catenary riser (SCR). Requirements for long-term corrosion resistance of SCR are very stringent, that obliges to manufacture it from expensive steels. Still, the increased water depth leads to increased riser tension, grown pressure, aggravated buckling and oscillation problems. Among alternative materials to manufacture catenary risers, i.e., steel, titanium and aluminum alloys, the aluminum is the best from the “Strength/Weight/Cost” aspects with its high corrosion strength.Design of an aluminum catenary production riser (ACPR) was developed in Russia; and comprehensive tests were performed on mechanical characteristics and corrosion resistance properties of ACPR tubes and their connections. Two possible connections of riser sections were considered, i.e., welded and threaded. Strength analysis of threaded connection was performed by FEM.Mechanical testing included: testing of small samples of pipe material and welded connection cut out of riser section, testing of full-scale specimens of connection prototypes, and measurement of residual stresses. Structural and corrosion tests of samples consist of investigation of standard metallographic characteristics of pipe material and welded connection, and assessment of effects of different types of corrosion in seawater and oil fluid. The results of performed work have led to the conclusion that welded connection is most prospective for ACPR manufacturing. At the same time, the testing revealed certain improvements need to be done in the course of further work on this project.Copyright

Aluminium Pipes - a Viable Solution to Boost Drilling and Completion Technology

The modern Ultra Extended Reach Drilling projects become more and more challenging. Some of the lately drilled ERD’s probably reached or came close to the edge of available drilling technology. The most breathtaking well was Maersk BD-04A completed by May 2008 offshore Qatar with 12 290 m (40 320 ft) TMD and 11 569 m (37 956 ft) departure [1]. Other wells with less TMD are as much complicated as BD-04A.

Comparative Strength Analysis of Aluminum Drill Pipes With Steel Connectors Assembled by Different Methods

Aluminum alloys continue to be among the promising materials for manufacture of drill pipes and risers for deepwater and ultra-deepwater environment. Steel tool-joints attached to aluminum alloy pipes increase the number of make-ups and break-outs. Currently, aluminum drill pipes (ADP) are assembled by “cold” or “hot” methods. By the first method, the pin and box are screwed on the pipe with a “sufficiently” high specified make-up torque. By the second method, the pin and box of the tool joint are heated and screwed on the ends of the pipe without effort. After cooling, the shrinkage of the tool joint units creates a reliable permanent threaded “pipe – tool joint” connection. The first method is easier than the second one; however the comparative strength of these ADP connections has not been enough clear. The paper presents the results of comparative strength analysis of both types of connection after assembly at applying tensile load and alternating bending load. The theoretical aspect of the study includes a detailed FEA of “hot” and “cold” assembly connections at applying tensile load and alternating bending load with SCF evaluation. The experimental data are presented as the results of tensile testing of small-scale specimens, removed from different aluminum pipe sections that were heated during “hot” assembly. Finally, full-scale specimens of both types of connections were tested for tensile capacity and fatigue. The comparative strength of both types of connections is concluded.Copyright

Application, Calculation and Experimental Evaluation of SCF for Aluminum Drill Pipe With Steel Connector

Aluminum alloys are among the most promising materials for manufacture of drill pipes for deepwater and ultra-deepwater drilling in corrosive environment. Aluminum drill pipes are made with steel tool-joints to increase the number of connection makings-and-breakings. One of the major concerns of aluminum drill pipe operation in deepwater complex profile wells is the fatigue of their connection. This paper presents the results of study of fatigue properties of aluminum alloy 1953T1 Light Alloy Drill Pipes of Improved Dependability (LAIDP) 147×13 mm that are most extensively used in Russia. During assembly, the pin and box of steel tool-joint are heated and screwed on the tubular ends. After cooling, this assembly provides a reliable permanent connection. The study includes experimental determination of the S-N curve of small-scale specimens of aluminum tubular, FEA of the connection with the SCF determined and fatigue testing of the full-scale LAIDP connection. FEA is based on 3D model. The material properties of tubular are modeled as elastic-plastic. The distribution of hot-assembly stresses is considered in detail. Alternating bending load is applied by several semi-cycles. The results of analysis of Stress Concentration Factor (SCF) at various axial loads, bending moment ranges, friction factors of contact surfaces and interference of connection are given. Full-scale fatigue testing of connection specimen is carried out to verify the results of analysis.Copyright

Dynamic Model of Pipeline During Pulling in Directionally Drilled Hole

The most important problem in pulling pipeline in the directionally drilled hole is overcoming of the soil resistance. This paper presents the 2-D model of contact interaction between the pipeline and soil as well as a numerical method of calculation of the pipeline vertical displacement and drag while pulling. The model is based on dynamic equation of lateral forces. Using this model it is quite easy to take into account nonlinear contact interaction of pipeline and soil in terms of both contact force and friction drag as well as a convective nature of the lateral load propagation at an axial motion of pipeline. Based on the suggested numerical model, a computer program was developed to improve an accuracy of pulling process analysis with moderate computer time needed. The developed program was applied to analyze and select parameters of the Lisichansk-Tikhoretsk oil pipeline in the tunnel under the river of Don. Calculations provided the updating of pulling process parameters and identification of those tunnel intervals, which might be challenging with pipelining.Copyright