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Zhang J.,Xian Shiyou University | Han Y.,Xian Maurer Petroleum Engineering Laboratory | Xiao G.,China National Petroleum Corporation
Natural Gas Industry | Year: 2015

Casing wear is a noticeable issue in the drilling operations of deep and ultra-deep gas wells, so it is remarkably important to investigate the wear resistance of P110 and V140 steel for the casing selection in drilling design. In this paper, the full-scale casing wear tester produced by Moore Industries International, Inc. was used to simulate the actual drilling parameters and drilling fluid formula used in oil and gas fields. Sequentially, full-scale physical wear tests on P110 and V140 steel casings were conducted under three typical low, medium and high lateral contact forces between tool joints and the casing interior wall. Afterwards, associated inspections and a comparative analysis were performed for the depth and width of casing wear groove, wear coefficient, friction coefficient, wear volume, and other parameters which were obtained at different wear stages of casing samples. Finally, the casing friction surface was examined by a scanning electron microscope to further discuss the casing wear mechanism under different working conditions. The study showed that under a low lateral contact force, the wear degrees of two kinds of casings were similar; but under a medium lateral contact force, V140 steel casing was worn more seriously than P110 steel casing, and under a high lateral contact force, P110 steel casing was worn obviously more serious. With the increase in the lateral contact force between tool joints and the casing interior wall, the friction coefficient in a frictional pair increased accordingly, which was in an adhesive wear state. This study will provide valuable reference for the casing selection in the casing string design based on the casing wear resistance considered according to different wellbore curvatures. ©, 2015, Natural Gas Industry Journal Agency. All right reserved.

Zhao G.-X.,Xian Shiyou University | Lu X.-H.,Xian Maurer Petroleum Engineering Laboratory | Han Y.,Xian Maurer Petroleum Engineering Laboratory
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2010

Varying degree of corrosion occurred in internal and outer wall of tubing string. Serious corrosion is found in some well deep. The results of chemical composition analysis, metallurgical structure test, SEM, EDS and XRD show that chemical composition and metallurgical structure of the tubing meet the API Spec 5CT standard requirement. Large corrosion products stack at the bottom of the pitting. Cl- enriches under the corrosion product layer. Corrosion product in internal wall are FeCO3, MgFe(CO3)2, FeO(OH), Mg3Ca(CO3)4 and Fe3O4, that in outer wall are FeCO3, MgFe(CO3)2, CaCO3 and FeO(OH). Internal wall are damaged by CO2 corrosion. Corrosive gas and medium come into the space between casing string and tubing string corrode outer wall of tubing. Tubing around 3279 meter is most hardly affected because it is at the temperature which CO2 corrosion is most seriously. Cl- enrichment is the important reason inducing local corrosion.

Li W.,China Institute of Technology | Zhou Y.,China Institute of Technology | Xue Y.,Xian Maurer Petroleum Engineering Laboratory
Journal Wuhan University of Technology, Materials Science Edition | Year: 2013

The corrosion behavior of C100 steel in simulated environments with high H2S and CO2 content was studied through high-temperature and high-pressure autoclave, and the H2S stress corrosion cracking (SSC) resistance of C100 steel was evaluated by SSC tests. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) technique were employed to characterize the corrosion products and the metal matrix. The results indicate that all of the corrosion products in this investigation are mainly composed of different types of iron sulfide such as Fe0.95S, FeS0.9, Fe0.985S, Fe7S 8 and FeS, and the absence of iron carbonate in the corrosion scales suggests that the corrosion process is governed by H2S corrosion. The corrosion rate decreases in the initial stage and then increases with the enhancement of the temperature. There exists a minimum corrosion rate at about 110 C. Under the partial pressure of H2S lower than 9 MPa, the corrosion rate decreases with the increase of P-{H-2 S} While over 9 MPa, a higher P-{H-2 S} will result in a faster corrosion process. When the applied stress is 72%, 80% and 85% of actual yield strength (AYS), all tested specimens show no crack, which reveals a superior SSC resistance. © 2013 Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.

Liang E.,Tianjin University of Technology and Education | Li Z.,Yanshan University | Han Y.,Xian Maurer Petroleum Engineering Laboratory | Li G.,Tianjin University of Technology and Education | Guo P.,Tianjin University of Technology and Education
Chinese Journal of Mechanical Engineering (English Edition) | Year: 2013

Carrying capacity of the casing will reduce after the casing is worn, which seriously affects the subsequent well drilling, well completion, oil extraction and well repair. A lot of researches on calculation of casing wear collapse strength have been done, but few of them focus on collapsing failure mechanism, and influencing factors and law of collapse strength. So, significant difference between estimated value and actual value of collapse strength comes into being. By theoretical analysis, numerical simulation and actual test, the collapsing failure mechanism of casing wear as well as the influencing factors and laws of collapse strength are investigated, and the investigation results show that collapse of crescent casing wear belongs to "three hinged" instability. The severely-worn position on the casing is yielded into the plastic zone first then deformed greatly, which causes the plastic instability of the whole structure. The casing wear collapse strength presents changes of exponent, power function and linear trend with the residual casing wall thickness, wear radius and axial load, respectively. When the flexibility is less than 10°/30 m, the borehole bending has less impact on casing collapse strength. Thus, the computation model for the casing wear collapsing strength is established by introducing wear radius coefficient and casing equivalent yield strength, at the same time, the model is tested. The test results show that the relative error for the computation model is less than 5%. The research results provide a basis for design of the casing string strength and evaluation of down-hole safety. © Chinese Mechanical Engineering Society and Springer-Verlag Berlin Heidelberg 2013.

Lu X.-H.,Xian Shiyou University | Zhang F.-X.,Petrochina | Yang X.-T.,Petrochina | Xie J.-F.,Petrochina | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2014

High pressure and high temperature corrosion performance of high strength 15Cr martensitic stainless steel was studied in different severe environments-live acid (10% HCl + 1. 5% HF + 3% HAc + 5.1% corrosion inhibitor), spent acid and formation water containing CO2. The results show that the corrosion of high strength 15Cr martensitic stainless steel in live acid is most serious, and the uniform corrosion rate is far greater than those in spent acid and formation water containing CO2 corrosion environments, but all of them can be acceptable for oilfield. Acidizing corrosion inhibitor displays a good matching ability with the high strength 15Cr martensitic stainless steel in terms of decreasing the uniform corrosion rate, which changes mainly the anodic process of high strength 15Cr martensitic stainless steel. The corrosion potential moves to the positive direction, thus the corrosion current density decreases significantly. There arc some different degrees of pitting of high strength 15Cr martensitic stainless steel after corrosion tests in live acid, spent acid and formation water containing CO2, and the pitting density aggravates significantly and the maximum pit depth decreases in the corrosion sequence. © 2014 Central Iron and Steel Research Institute.

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