| Along with the advance of human civilization and the rapid development of social economy,national demand for energy is increasing sharply.As the important energy base of national economic development,oil becoming more and more important.When new oil region has not been explored out before,a new energy that can replace petroleum has not been found out,in this case,whether we can improve oil production technology in order to improve the problems of the current oil region oil recovery factor and production that will directly affect the future economic development of our country.Just as the underground oil and gas resources are limited,even for the whole world,after all,it’s hard to find a large oil and gas reservoir when the consumption of oil and gas is continuing in mining,then the available oil and gas resources will be less slowly in the future. In recent years,many domestic oil and gas is in the middle and late old oil region, not only the oil and gas wells water cut have rised, but also the major reservoirs have entered the high water-cut stage.So in the future,the exploitation of oil and gas is gradually pointing to the thin oil layer, deep well, ultra deep well, high temperature well, thermal recovery well and shale gas well so on.Our work center will be shifted to the oil and gas resources of small and medium-sized oil fields, difficult well of development and the reform on the later period of oilfield in order to improve oil recovery factor and production,and obtain enough oil energy to meet the needs of social production and life.For old well, however, in order to improve the recovery factor and production,needing a series of measures to increase production like the perforation,acidizing,fracturing and high pressure water injection and so on to meet the cementing quality of high demands.Especially in high temperature well and thermal recovery well,the downhole temperature is higher,and the cementing quality is a serious challenge.If the cementing quality is not good,in the complex underground geological conditions,it will have a big impact on mining of oil and gas,mainly including:(1) lead to oil, gas, water outside, make the downhole pressure escape out, downhole pressure balance is broken, decrease the oil and gas production, even stop production for a long time;(2) destroy the borehole wall, then hole sloughing is occurred;(3) damage formation, and the interfere between layers may be appearing;(4) if the cementing quality is poor, existing wells could be discarded, thus need to make new Wells, so increase the investment in drilling.The problems of the cementing quality mainly focus on on the cementing quality of two interfaces.The first interface cementation quality is influenced by many factors,and outside surface of casing is one of the important factors.In order to improve the quality of cementing,predecessors have done a lot of research work for the second interface of cementing.the,cement slurry properties and improving the slurry displacement,etc.but the research for the first interface of cementing,especially the external surface of the casing affecting the cementing quality is less.For the outside casing surface condition research,only proposed the cementing of surface adhering sand casing.That is to say coating outside surface of the casing with a layer of cementing agent,and then put a layer of sand on cementing agent again to make the outer surface of the casing rough,so that it not only can increase the area of outside surface of the casing,but also can increase to bite each other between cement and sand.Thus it can increase cohesive force and shear force between casing and cement ring.However,in high temperature well and thermal recovery well,the cementing agent will be melt and the sand bonded on the surface of the casing will appear degumming phenomenon,and unable to achieve the purpose of improving the bonding strength between casing and cement ring.Therefore,to propose a kind of casing with surface roughness,which is less affected by temperature treatment of casing,is very important.Expeting that using this outer surface roughness casing for cementing can compensate the adhering sand casing cementing technology in case of high temperature,so as to achieve the aim of improving cementing quality,offer a way for difficult mining oil and gas well like heavy oil, shale gas and production of old oil region.According to this phenomenon,the study in the article from the bond force source and influence factors of the cementing force on,and on talking overr some of the methods of improving first interface bond force of casing and cement ring,put forward the theoretical basis and solutions of roughing the surface of casing:smooth surface casing model (as contrast test),adhered half spherical casing model, thread casing model, grind arenaceous model,the concave and convex casing model.In order to ensure that casing strength of the surface roughness was not affected,and can still meet the needs of production, so analysis the effect of roughening treatment on casing strength:tensile strength analysis of casing, collapsing strength analysis of casing, yield strength analysis of casing.Finally, the experimental study was used to demonstrate.Among the indoor experimental study,by using the wall up packer test machine,YAW-300c type pressure test machine and surface tensile test machine,on surface smooth casing (as a contrast test), thread casing,frosted grind arenaceous casing,concave and convex casing,having hydraulic cementing strength test,shear bond strength test and the adhesive bond strength test,then recording test data.Among the simulation experimental study,on the smooth surface casing (as a contrast test) and adhered half hemisphere casing,by using the finite element analysis method, establishing finite element analysis consolidation model between casing and cement ring,having adhesive bond strength test and shear bond strength test,then export cementing displacement nephogram and strain nephogram.Laboratory test results show that:that hydraulic cementing strength,shear bonding strength and bonding cementation strength of surface roughness casing is bigger than smooth surface casing’s.Simulation test results show that:shear bonding strength and bonding cementation strength of surface roughness casing is bigger than smooth surface casing’s while cementing interface displacement of the surface roughness casing is litter than smooth surface casing’s.This explains that casing of surface roughness treatment can effectively improve the cementing cementation force of the first interface,and improve the cementing quality.It is beneficial to solve the problem of difficult mining well cementing quality,and prolong the life of mining development well, and ensure that every big oilfield long-term, stable and efficient production.But this kind of surface roughness casing weather has the field application value,and how thread shape and distribution of roughness casing affect on the cementation force,even weathe rough texture affect casing water mud displacement efficiency and so on,in this article,don’t make a analysis on,and also don’t involve in the test.In this study,it is necessary to make further analysis,design a reasonable test scheme at the same time to solve the above problems.In addition,in some laboratory test,we may need some expensive equipment instrument,mock-up casing design and processing,in this case,the cost is quite high. If you can strengthen the study of finite element analysis,in the future,all simulation test is used to do.So all kinds of work will be simple and convenient. |
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