| Wire-line coring drilling technology introduced into our country in the 1970s is one of the very effective exploration methods of geo-drilling,and since the research and application it has been widely used in the drilling industries such as hydrogeology,petroleum geological drilling,and solid mineral geological drilling.Compared with other core drilling technology,the advantages such as high efficiency,high core recovery,long bit life,low drilling costs and low labor intensity feature the wire-line coring drilling technology.Though it poses relatively high efficiency when drilling in the strata with weak natural oblique strength,if any corresponding measures are not taken,the borehole may be prone to bending because of most of strata with the large stratigraphic dip,the hard and soft interbedded rock or serious stratum breaking,causing severe hole deviation accident.With the growing demand for mineral resources,a lot of problems about borehole deviation in drilling engineering make the research of anti-deviation technology of wire-line coring assembly extremely urgent.Aiming at resolving problems of borehole deviation,nowadays a few measures have been taken to prevent deviation.A handful of scientific drillings adopt the self-developed advanced three-in-one technology-"PDM+ hydro-hammer+ wire-line coring" or the two-in-one technology-"hydro-hammer + wire-line coring",which have proved to be very effective in anti-deviation,but in the short term it's difficult to be popularized in a large scale in our country because of its high cost.Most of the geo-drilling has taken the measure that one group or more groups of stabilizers should be joined onto the bottom hole assembly(BHA)to play a positive role in guiding the drilling tools rightly,nevertheless this is not either systematic or scientific just because the measure is not much involved in the further research about the influence of the size,amount and placement of stabilizer on the lateral force of the bit.In addition,some people resort to the method to achieve the purpose of the anti-deviation by change the material,for example,reinforce the intensity to increase the stiffness of the drill pipe or change the structure of the bit and so on,but the effect is not obvious.In order to solve the severe problem of borehole deviation,in this dissertation an innovative application of the vertical and horizontal bending theory which is usually used in oil-gas well engineering has been put forward to the research of anti-deviation technology of wire-line coring assembly.The technology is involved in placing packed hole stabilizers onto the BHA,building mechanical model of crossbar bent continuous beam,theoretically analyzing the force and deformation of BHA based on the superposition principle of vertical and horizontal bending method,finally getting the mathematical model of wire-line coring assembly with packed hole stabilizers for anti-deviation,that is,the three-moment equations,and selecting the appropriate coring drill combinations of anti-deviation according to anti-deviation design principles.Compared to the current techniques for preventing borehole deviation,this technology have the features of low cost,being easily popularized,being systematic,good effect on anti-deviation and so on.The main purpose of the paper is to study suitable technology and design principles of wire-line coring assembly for borehole deviation prevention with packed hole stabilizers so as to effectively solve problems of borehole deviation of wire-line core drilling in exploration engineering of our country and promote to establish better passive anti-deviation system of wire-line core drilling.And it's of high value in improving economic efficiency and widespread use.This dissertation is divided into six chapters,the main contents of each chapter are as follows:The first chapter is introduction.The state of the short supply of mineral resources in our country and the importance of drilling and borehole anti-deviation in mineral resources exploration are briefly discussed,and the urgency of studying the anti-deviation technology of wire-line coring drilling is clarified.Then the research situation of deviation control and anti-deviation in drilling engineering at home and abroad is summarized,and some inadequacies of anti-deviation technology of wire-line coring drilling are pointed out.Finally,an overview of the main research contents and technical route of this article is given.The second chapter is the research on the borehole deviation and its mechanism of wire-line coring assembly based on the vertical and horizontal bending theory.The main factors that lead to the borehole deviation are analyzed,and the superposition principle suitable for wire-line core BHA is derived and its mechanical model is established.Combined with the actual work situation of wire-line coring drilling,small transmogrification assumption of wire-line core BHA based on vertical and horizontal bending theory is set up and some parameters were properly simplified with the subsequent establishment of three-moment equations of the BHA.Finally based on the influence and change laws of the bit lateral forces of none-stabilizer BHA and single-stabilizer BHA with the change of structural and drilling parameters,the qualitative and quantitative study of the reason why the conventional wire-line coring drilling is prone to borehole deviation is elaborately made.The second chapter is analyzing BHA with packed hole stabilizers.The most of the chapter is analyzing the change laws of the bit lateral forces by change the parameters such as weight on bit(WOB),deviation angle and the placement of stabilizers on the basis of three-moment equations and the relative formulae of bit lateral force of double-stabilizers,three-stabilizers,four-stabilizers and fiver-stabilizers.The fourth chapter is designing the BHA of wire-line coring assembly with packed hole stabilizers.While dividing the process of anti-deviation drilling into two parts,the angle-holding drilling and anti-deviation drilling,the respective designing principles for BHA(involving the angle-holding BHA and anti-deviation BHA)according to the different emphasis between the angle-holding drilling and anti-deviation drilling are confirmed.Then the combining forms and parameters are studied and subsequently designed with the structural features of wire-line BHA and mechanical properties of the BHA with different numbers of stabilizers.The fifth chapter is field application tests.In order to verify the reliability and the scientificity of the vertical and horizontal bending theory in wire-line coring drilling,the designed assemblies involving the angle-holding BHA and anti-deviation BHA are put to tests,and then the practical field effects of the two assemblies are studied with the analyzing of the test results.Finally some suggestions are promoted to improve and perfect the anti-deviation technology of wire-line coring assembly with packed hole stabilizers.The sixth chapter is suggestions and conclusions.In this part,the dissertation summarizes the main innovations and research results and cognition,and then points out the deficiencies and gives some advice about the further study.Aiming at solving serious problems of borehole deviation,the main innovation of this paper is reflected in:(1)The dissertation innovatively applies the vertical and horizontal bending theory to the analyses of borehole deviation of conventional wire-line coring drilling and to the research on anti-deviation BHA of wire-line coring assembly with packed hole stabilizers.Moreover,the equivalent treatment and the corresponding models of some parameters such as the equivalent cross-section shaft moment of inertia I and elasticity modulus E of wire-line coring BHA are provided,which makes the theory suitable for wire-line coring drilling.(2)The research about the anti-deviation BHA of wire-line coring assembly with packed hole stabilizers is based on the vertical and horizontal bending theory,with which the mechanical properties and the influence of corresponding bit lateral forces of different kinds of combinations of BHA are derived,then the dissertation makes the further study about the parameters of the angle-holding BHA and anti-deviation BHA to draw the change laws of the lateral forces with WOB,deviation angle and the placement of stabilizers.Through theoretical study and analysis of test results,the research results are as follows:(1)According to the structural features of wire-line coring BHA,the mathematical model(three-moment equations)and the formulae of bit lateral force are derived on the basis of assumptions and the superposition principle of vertical and horizontal bending theory.In addition,the dissertation has properly simplified the axial load of spans of the mechanical model and reasonably introduced the equivalent cross-section shaft moment of inertia 1 and the bending rigidity EI.(2)The change laws of the bit lateral force of none-stabilizer and single-stabilizer BHA of wire-line coring assembly have been summarized based on which the mechanical reason why conventional wire-line coring drilling is prone to deviation has been found out.The mechanical property of the single-stabilizer BHA is that the buildup force increases when the stabilizer approaches the bit,thus making the conventional wire-line coring drilling prone to borehole deviation.In addition,the bit lateral force of none-stabilizer BHA manifests as the invariable pendulum force when the WOB and deviation angle do not change,which makes it hold angles to some extent in the weak natural strata and with small bit weight at the same time.(3)By analyzing the change laws of lateral force at the bit of double-stabilizer BHA,some conclusions are drawn in terms of the anti-deviation.When WOB and deviation angle don't change and the first and second span of the BHA are shorter(like L1=20 cm,L2 = 100cm),then the bit can get a larger deviation reduction force;when the placement of stabilizers is fixed and the deviation angle is smaller(like ? = 5°),the WOB has less influence on the lateral force,and the larger deviation angle produces larger deviation reduction force when the WOB is under the limit load.A considerable deviation reduction force can be derived from double-stabilizer BHA,for example,when L1=20cm,L2= 100cm,the deviation reduction force Pa=-398N,however,with poor drilling stability.(4)The dissertation has summarized the change laws of deviation reduction force of three-stabilizer BHA.When the drilling parameters and the deviation angle are invariable,then the BHA with relatively large deviation reduction force can be confirmed:the second span is shorter(like L2 = 100cm)and the third span is shorter(such as L3= 100cm)or longer(such as L3=800cm);when the deviation angle is smaller(e.g.a?30°),the first span should be shorter(e.g.L1=20cm),otherwise it should be longer(such as L1=100cm).In addition,when based on the above BHA which,though,can get large deviation reduction force,the increase of WOB can slightly diminish it.Three-stabilizer BHA can not only produce a larger deviation reduction force,but also get good stability.(5)According to the analyses of the mechanical properties of the four-stabilizer BHA,the law of the deviation reduction force at the bit has been summed up.When WOB and deviation angle don't change and the first three spans of the BHA are shorter and the fourth span is not long(such as L1=20cm,L=2=100cm,L3= 100cm,L4=400cm),then a larger deviation reduction force at the bit can generate.Moreover,the increase of WOB can slowly reduce the deviation reduction force when the BHA identified above is implemented.Four-stabilizer BHA can be very stable in drilling but produce relatively smaller deviation reduction force.(6)Through the analyses of the change laws of the bit lateral force of five-stabilizer BHA with its main influential factors,the dissertation has summarized the optimal law of deviation reduction force.When WOB and deviation angle are constant,then how the BHA can generate larger deviation reduction force is revealed:the first span is shorter(e.g.,L1=20cm),the second span is shorter(such as L2= 100cm),the third span is longer(such as L3=800cm),the fourth span is moderate(e.g.L4=400cm),the fifth span is longer(e.g.L5=600cm).Besides,when the appropriate BHA confirmed above is applied,the deviation reduction force will increase with the WOB rising.The five-stabilizer BHA has more advantages in drilling stability than three-stabilizer and four-stabilizer BHA,and its optimal deviation reduction force is also larger than the four-stabilizer one.(7)According to the design principles of the angle-holding BHA and anti-deviation BHA and the mechanical features of double-stabilizer,three-stabilizer,four-stabilizer,five-stabilizer BHA,the dissertation has designed proper the angle-holding and anti-deviation BHA.The angle-holding BHA is the five-stabilizer one that is most stable in those BHA,the concrete structural parameters of which is the first span L1=14cm,the second span L2=300cm,the third span L3=600cm,the fourth span L4=600cm and the fifth span L5=400cm;the anti-deviation BHA is the three-stabilizer one that has the moderate stability in drilling and relatively large deviation reduction force,the structural parameter is the first span L1=14cm,the second span L2=300cm and the third span L3=800cm.(8)When the wire-line coring angle-holding and anti-deviation BHA were respectively tested in one mine in Anhui and the other mine in Jiangxi,the results proved to be effective and demonstrate the feasibility of guiding the wire-line coring drilling for preventing deviation by the vertical and horizontal bending theory.The angle-holding drilling test guided by vertical and horizontal bending theory was carried out in Anhui,and two kinds of BHA were used in the test,the BHA 1#and BHA 2#,which had been proved to be superior to the conventional wire-line coring BHA,and the BHA 1#was more stable in the test than BHA 2#.In addition,the anti-deviation drilling was tested with the three-stabilizer BHA in Jiangxi,and the drift angle dropped from 3° to 2° and the maximum drift deviation intensity reached 0.99°/100m during the test,which proved that the three-stabilizer BHA had a good effect on anti-deviation.Theoretical and experimental studies have shown that the wire-line coring drilling can maintain its original quality of fast coring and,meanwhile,achieve better anti-deviation effect when the wire-line coring drilling is associated with packed hole stabilizers.It can make up for deficiencies of the existing wire-line coring drilling and enrich the anti-deviation technology of wire-line coring drilling,and obviously the vertical and horizontal bending theory has the guiding significance in the application of wire-line coring drilling technology.The dissertation has the following deficiencies:(1)Since the amount of data for studying the lateral force at the bit is too large,the paper involves only theoretical calculation and analysis,and there are no analyses in the internal mechanical mechanism of change of bit lateral force.(2)During the process of calculating lateral force,the dissertation has adopted the methods by mathematically weighting the cross-section shaft moment of inertia and the lineal weight of the span which is combined with both the coring tube part and drill pipe part,because the variable cross-section algorithm of the vertical and horizontal bending method is very complicated in computation,and nothing herein is derived and discussed.(3)In this paper,the theoretical analyses have considered neither the impact of the formation force nor its influence factors and change law.So as to solve the above deficiencies,further research needs to expand the following tasks:(1)Studying the internal link between lateral force at the bit and the main factors such as WOB,deviation angle and placement of stabilizers;(2)Further study is required to establish the mechanical and mathematical model of crossbar bent beam which has variable cross-sections;(3)Studying the change law of resultant force with the change of its main influence factors such as WOB,deviation angle and stabilizers when considering the formation force. |
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