Abstract:It is easy for drill string to be cracked when it is subjected to complex forces. Evaluating the corrosion fatigue life of drill string according to the actual situation on site can provide a basis for the safe use of drill string. By calculating the axial force， cyclic stress and fatigue limit of the drill string in the wellbore， the fatigue evaluation methods of drill string based on fatigue coefficient， drill string tension and rotation counting are determined， and the influence of acidic fluids is considered. The results show that the increase of the bending stress and buckling will lead to the fatigue failure of the drill string when drilled with severe dogleg. The remaining service life of the drill string will be greatly reduced when the corresponding ROP is reduced and the rotating speed is increased significantly. When severe acid corrosion occurs， the remaining service life of the drill string will be rapidly reduced. The drill strings in the well section with high tension and large dogleg should be regularly shifted to ensure the safe and normal use of drilling string on site.

Abstract:Tianye-1 well is a geological survey well for shale gas， which deployed in the southern Tianba anticlinal core of the South Daba Mountain curved fold belt， Chongqing. The design purpose is to complete the selection of shale gas favorable target areas in the southern Marine shale area， explore new strata， and collect the basic geological data of shale in the mineral area. In view of the probleums of the design dip angle of the opening rock is changed due to steep dip， the wall spalling instability caused by the strong water sensitivity of shale， the high pressure and H2S and CO gas penetration corrosion in the inner well， and the induced blowout. Technologies are adopted such as the high density drilling fluid technology， CHD127mm wireline coring technology and gyro inclinometer combined with eccentric wedge orientation to increase the thickness of drill pipe joint to improve the strength of drill pipe. The safety hazards such as high pressure overflow， drill pipe fracture， H2S and CO gas penetration， etc. are well solved， the well inclination is controlled， and the geological survey coring task of the well is successfully completed. This paper summarizes some technical experience and problems exist in the drilling process， and provides reference experience for similar projects.

Abstract:In order to predict the corrosion resistance of aluminum alloy drill pipes （ADP） in scientific ultra-deep drilling， COMSOL software was used to establish a multi physical field corrosion analysis model for simulation and analysis of the corrosion law of ADP used in SK-2 well under the action of “stress temperature electrochemistry”. The results show that when the corrosion system reaches equilibrium， the electrolyte potential on one side of the aluminum alloy electrode is higher than the steel joint electrode， and the current density of the aluminum rod near the steel joint electrode is higher. With the increase of stress and temperature， the corrosion rate of ADP is accelerated. Compared with temperature， the influence of stress on corrosion is smaller. It is a positive linear relationship between the corrosion rate and the working time. The closer to the galvanic corrosion site， the higher the interface current density of ADP， exhibiting an exponential relationship. The intensive influence area in the outer wall is about 0~200mm away from galvanic corrosion and that in the inner wall 0~110mm away from. The research results can provide reference for the anti-corrosion of aluminum alloy drill pipes.

Abstract:Corrosion of the aluminum alloy drill pipe in the drilling fluid can affect the drilling performance and even cause serious downhole incidents. In order to improve the corrosion resistance of the aluminum alloy drill pipe, the organic corrosion inhibitor (C18H29NaO3S or SDBS) or rare earth corrosion inhibitor (La2(SO4)3) was added at some ratio to the polysulfonate drilling fluid at 10 pH and 70℃, and its effect on the 7075 aluminum alloy drill pipe corrosion was investigated through the mechanical test. The results show that both corrosion inhibitors can reduce aluminum alloy corrosion in alkaline drilling fluids, and improve the tensile strength of aluminum alloy drill pipe by up to 6.73%. The second phase particles of Cu, Mg, Si and other elements in the alloy are the corrosion-sensitive areas. Corrosion pits are formed where the second phase particles have fell off. The corrosion products mainly consist of Al, C, O and other elements.

Abstract:The high- water jet technology has the superiority of the wide range of working medium and environmental protection, and can be used to break the submarine gas hydrate formations. In this paper, LS-DYNA finite element program is used to simulate the fragmentation process of submarine gas hydrate formations with high-pressure water jet under submerged condition. The effects of four key parameters (jet velocity, nozzle diameter, target distance and incident angle) on the erosion volume of hydrate formations are studied. The following conclusions are drawn: the fragmentation of hydrate sediments needs to meet the requirement that jet velocity is higher than the critical velocity; the erosion volume gradually increases with the increase of jet velocity; the increase of nozzle diameter will lead to the increase of the radial erosion volume of formations, thus increasing the overall erosion volume; the increase of target distance will increase the energy loss of water jet in the process of water movement, leading to the decrease of erosion volume; the erosion volume will increase first and then decrease with the increase of nozzle incidence angle, eventually tending to be stable. When the incident angle is 10°, the erosion volume can reach the maximum value.

Abstract:The development of earth sciences is more and more depending on the deep earth exploration data, the scientific ultra-deep drilling, known as “the telescope into the crust”, becomes an indispensable method for the research on deep geology. Compared with the steel drill pipe, the aluminum alloy drill pipe, with its unique superiorities (lighter weight, high specific strength, deep drilling depth and less energy consumption), has become the essential scheme for drill string design used in difficult to enter area, extended reach wells and scientific ultra-deep well and so on. From the perspective of popular science, this article describes the differences between drill string and drill pipe, the limit use length of drill string, the technical advantages of aluminum alloy drill pipe and the existing deficiencies, so as to improve our understanding of aluminum alloy drill pipe and promote the research and development of the aluminum alloy drill pipe.

Abstract:In order to explore the process and mechanism of high pressure water jet cutting and breaking natural gas hydrate reservoir of the South China Sea, LS—DYNA3D code had been used to simulate the process of water jet breakup of hydrates in submerged state. The effect of different jet velocities on the crushing effect of hydrate bearing sediments under high pressure water jet was studied. The erosion depth increases linearly with the jet velocity. The erosion volume of hydrates sediment is the result of axial erosion and radial erosion. The greater the jet velocity is, the axial and radial erosion of hydrate deposits are enhanced, and the increasing rate of the erosion volume of the hydrate deposits is increased.

Abstract:Hydrogeological and water well drilling are important parts of exploration engineering. With the increasing demand of underground water resources and requirement intensification of ecology and environment protection, the hydrogeological and water well drilling engineering become more important. In the well completion process, corrosion and scaling of the filter are often encountered, which directly affect the wellbore influent amount and pumping effect, and even lead to the filter being scrapped and water well abandoned. Prof. Третьяк А.Я., who works in National University of Technology in Southern Russia, and some others have invented a new automatic scale-handling water filter and resolved the filter corrosion and scaling in the drilling process.

Abstract:Freservoir in Y Oilfield is characterized with high temperature, high pressure and high yield with corrosive fluids. In order to ensure a long term, efficient and safe production, it is necessary to study the well completion technology and anticorrosion for string protection. The completion string with packer is run downhole, and the annulus between tubing and casing above packer is then filled with anticorrosion packer fluid. Two introduced annulus packer fluid systems are tested at lab to evaluate the physical and chemical properties of , high temperature stability, and the corrosion of pipe downhole. Test results show that CaCl2 annulus packer fluid has poor high temperature stability, the high values of immersion corrosion rate values and galvanic corrosion rate values are 0.062 mm/a and 0.078 mm/a respectively, larger than the set corrosion rate of 0.05 mm/a. While the introduced NaCl KCl annulus packer fluid has better high temperature stability with high values of immersion corrosion rate values and galvanic corrosion rate values 0.014 mm/a and 0.037 mm/a respectively, lower than the set corrosion rate of 0.05 mm/a. In view of this situation, the improvement and optimizing design are made on this introduced CaCl2 annulus packer fluid to determine the proper system. The optimizing designed CaCl2 annulus packer fluid shows good high temperature stability, the immersion corrosion and galvanic corrosion rate values are below the set corrosion rate, and the overall performance have reached the field application requirements.

Abstract:In view of the service conditions of aluminum drill pipe in complex ultra-deep well drilling engineering, the main external drilling engineering factors of the corrosion behavior of aluminum alloy drill pipe are analyzed, the test and analysis on corrosion degree of the aluminum drill pipe engineering sample of Songke-2 well in the project of deep drilling of resources and environment in Songliao basin. The results show that the structure of drill pipe, wear and stress, drilling fluid medium as well as high temperature and high pressure are the main factors of corrosion; the corrosion at the connection point of aluminum rod and steel joint is the most serious and the aluminum rod body is the next; the corrosion resistance of pipe upsetting end is the best, the main components of the corrosion products are Al2O3 and Al (OH)3 phase.