Material Properties Research And Application Of Expandable Screen Base Pipe

Expandable screen for loose sandstone reservior is a new well completion technology, which can prevent the collapse of borehole, reduce the sieve damage of tube, decrease resistance of the flow into the tube, and increase the output. Due to the expandable screen corresponding to different depths underground and different production methods in the oil and gas reservoirs (which may be thermal recovery wells), causing the temperature field of its expansion and deformation is50-350℃. Expandable Screen Completion is such a new technology of sand control method that the base pipes of expandable screen are expanded and deformed by the expansion tools during that temperature, which makes expandable screen fit the wall of a well snugly.Currently,316L stainless steel has been widely used for the base pipes of expandable screen. The results of measured performances of316L stainless steel expanded in the temperature field of50-350℃have proved that the strength of steel decreasing when temperature increasing and this results a decreasing anti-collapse property, which seriously influences the safe of expandable screen.This paper focuses on the existing problems of the base pipe which is made of316L stainless steel. The experiment research about the base pipes of expandable screen is carried out, and15CrMo heat-resistant steel may substitute for316L strainless steel. The sub-critical quenching treatment of double phase for15CrMo and the experiment of structure&mechanical property in the downhole temperature field for the treated base pipes of expandable screen have been carried out. The results demonstrate that, when the metal deformation happens in this kind of temperature field, there are not only the work hardening occuring to metal materials, but also the dynamic recovery and dynamic strain aging. This article also analyzes the impact of dynamic deformation on base pipe and performance of the expandable tube.In the condition of simulating the expansion rate of ε=8.3×10-3mmS-1, the dynamic tensile tests about316L stainless steel and15CrMo steel in the temperature range of50-350℃have been carried out, and the stress-strain curves of the two kinds of steel have been established in the different temperature conditions. The results show as follow:For316L stainless steel, the dynamic tensile stress-strain curve is a typical deformation-recovery curve of the flow metal. The sample is entered the stage of plastic deformation, then stress has shown an upward trend with the increasing strain. The stress-strain curves of different temperatures have been compared and it could be find that the strength of steel decreases with the increasing temperature, at the same time, the elongation δ which characterizes the plasticity also decreases sharply.For15CrMo steel, the dynamic tensile stress-strain curve presents the shape of deformation-recovery curve similarly and the difference is that when the metal is entered the yield stage, the stress-strain curves in different temperature have presented the dynamic strain aging which is of the obvious serrated yield. Moreover, the stress-strain curves in different temperatures have been compared and it could be find that with the increasing temperature of dynamic deformation, the yield strength of15CrMo does not decrease, but increases slightly because of the strain aging.The dynamic stress-strain curves have been established by the dynamic tensile test in the temperature range above. With the arithmetic of nonlinear contact problems in the finite element software ANSYS10, the slot parameters, the slot mode and the thread of the base pipes made of316L stainless steel and15CrMo are analyzed systematically respectively, meanwhile the collapse strength, axial tensile strength, axial compression strength and bending loads are also calculated systematically. The relationships between the different temperature conditions of the two kinds of materials after expanding and the performances of the base pipes are set up.For the base pipes made of15CrMo steel, the macroscopicalµscopical analysis methods of damage mechanics in recent period and fracture mechanics in modern times are adopted, and the stress field, cracking&crack-arresting in slot frontend of base pipes expanded in the underground temperature field are analyzed, and the condition of resulting in cracking and crack-arresting are also been discussed, the relationship between the crack initiation, crack arresting, plasticity in crack tip and structures in the slot frontend of15CrMo steel when being expanded are established.The stress corrosion susceptibility tests on316L and15CrMo in the condition of H2S environment are carried out by SSRT, which provid safe limits to the materials adopted currently for the engineering applications in the high H2S condition.This paper would supply an integrated reference specification of well completion design for the oil and gas engineering, which will have the important theoretical and practical significances for expandable screen to the production of oil and gas wells.In this paper, several key technologies of expandable screen are studied. The optimal design of slotted structure is carried out by using the finite element method. Several base pipe materials of screen are chosen. The slotted thread after expansion has the same diameter as expandable screen. The adjustable expansion tool makes expandable screen close to the wall, which can increase the output.The field application of expandable screen is performed after the success of the ground test and simulation test. The practical results show that expandable screen can obtain better production. After expansion, the screen is closed to the wall of the casing, and the diameter of expandable screen is larger than the diameter of the conventional screen. So, the drain area increases, and the oil production increases accordingly. Currently, the application of expandable screen is only used in tube sand control, the technology need to improve as soon as possible, to achieve the applications in open hole wells.