Slim Hole String Dynamics Study

With the coming of inland main oilfield after the middle of exploitation, there are some oilfields can't maintain usual produce and cause that producing of oil and gas get down gradually, because it's not easy to deal with event down hole and other reasons such as down-hole water cone or gas cone, more and more oilfield came to waste well vacant well, these obstructed the development of oilfields. In order to reduce the cost of drilling, especially to make use of potentiality of old oilfield. In this paper, on basis of collecting information in home and oversea, analyzed amount of friction and hook load through deducing the models of calculating friction of completion casing with centralizer and without centralizer; analyzed torque of drilling pipe with Drilling Pipe Protesters; finally, analyzed pipe's orientation, horizontal, and torques fluttering in order to guide field processing.The main characteristics of the research in this paper are as follows:(1) Information about dynamics, mechanics, calculating friction and NRPP is collected in home and overseas.(2) On the basis of analyzing the development trends and technical characteristics, using flexible hose calculated completion pipe with centralizers. Divide all casing into unit casing, funding a local coordinate on every unit, so as to analyze unit pipe simply. Then project the force on unit to total coordinate(3)Consult relevant materials have finished supporting the introduction to centralizers' working mechanics. Project bend pipe to Inclination Plane and Azimuth Plane, so turn complicate 3-D problem to two 2-D bend problem .In every plane, calculated friction of completion pipe with centralizers by gripe string model, on the basis of analyzing mechanical characters of casing which contain some centralizers , used vertically and horizontally distort model ,used vertically and horizontally distort principle and linearity equations that is made up of three distort equation ,then the results are close to actual friction.(4) On the basis of preferring to relative materials, introduced working mechanics of NRPP and a few reducing torque tools, the same to completion pipe with centralizer, project drill string in space to two planes, turn complication problem to two simple level problems, found and completed the mechanic model to calculate reduced torque on string that is used in inside drill in slim hole.(5) On the basis of research on basic theory of string dynamics developed the basic theory of pipe dynamics, used method of unit quality to calculate dynamicsmodel for pipe in slim hole and pipe dynamics of horizontal well. And got vertical, horizontal and turning back the natural frequency of vibration and transformed to the critical rotational speed received, in order to use this result to guide field processing.(6) Programmed calculation program to calculate by "Visual Basic6.0.In the process of programming, made the result be exactitude through symmetric dividing method and catch up method in programs.To sum up, on the basis of analysis of a few mechanics models, created models that is used to calculate friction which is more closed to fact, programmed serial program in order to calculate quickly and conveniently and demonstrated it through examples ,so models was proved to be accord with requirement in engineering.