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Jin Y.,China University of Petroleum - Beijing | Chen K.P.,China University of Petroleum - Beijing | Chen M.,China University of Petroleum - Beijing | Grapsas N.,Arizona State University | Zhang F.X.,Tarim Oil Field
Physics of Fluids | Year: 2011

The start-up flow of a constant-rate production of a high pressure gas well is studied, with emphasis on the effect of gas acceleration. Gas acceleration is important in the near wellbore region for a high pressure gas in a high permeability formation. It is shown that when gas acceleration is important, the system of governing equations for the porous media flow becomes hyperbolic. In response to an impulsively imposed mass flow-rate, a steep pressure front is created at the wellbore and it propagates into the formation. This steep pressure front is trailed by large amplitude pressure waves. As they travel away from the wellbore, the pressure front becomes less steep and the amplitude of the trailing waves decreases due to viscous damping. It is found that the pressure drawdown experiences a rapid increase followed by an oscillatory behavior in short times before approaching the classical logarithmic rise regime. The pressure gradient at the wellbore wall can grow to a large magnitude in the early times, which can cause a tensile failure of the rock materials near the wellbore. © 2011 American Institute of Physics. Source


He S.,Southwest Petroleum University | Wang W.,Southwest Petroleum University | Shen H.,Petrochina | Tang M.,Southwest Petroleum University | And 2 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Underbalanced drilling (UBD) of horizontal wells has been one of the efficient technologies in the exploration and development of oil and gas fields, while wellbore instability poses a problem during the whole operation process, for fluid seepage induced by the flow of formation fluid into wellbore exerts additional stresses on wellbore. However, the impact of fluid seepage has usually been ignored by conventional analysis of wellbore stability during UBD. This paper, taking the effects from fluid seepage into consideration, introduces a new collapse pressure model for UBD of horizontal wells. A comparison of the new model with the conventional one reveals that maximum equivalent collapse density (MECD) reduces with the decrease of borehole radius and that the wellbore is more stable in a slim hole during UBD of horizontal wells. And with the change of the inclination angle, MECD is higher when fluid seepage is considered under a certain relative azimuthal angle, indicating a narrower mud weight window and a more unstable wellbore; while the variation trend of MECD with the inclination angle are quite different at relative azimuthal angle=90° and 0°. With the change of the relative azimuthal angle, MECD obtained in consideration of fluid seepage is also greater when the inclination angles is fixed, and MECD in both conditions (when fluid seepage is considered and otherwise) decreases with the increase of the relative azimuthal angle; meanwhile, the value of θ where MECD is obtained is also analyzed. © 2015 Elsevier B.V. Source


Lv S.-L.,China University of Petroleum - Beijing | Teng X.-Q.,Tarim Oil Field | Kang Y.-J.,Tarim Oil Field | Yang C.-X.,Tarim Oil Field | And 4 more authors.
Materials Performance | Year: 2012

The 177.8-mm production casing string was run to the depth of 5,456.86 m and the depth of the cement fill top was 1,400 m. The grade of the production casing was V150, and the wall thickness was 11.51 mm. before testing. Production was gas and oil, and the annulus between the casing and tubing contained a mixture of oil and gas during testing. The wider part of the crack was basically along the longitudinal direction, and a thin crack extended in the direction of 75 degrees with a coupling generatrix at the middle of the coupling. There were corrosion pits on the fracture and threads near the crack and away from the crack. The crack may have been caused by corrosion, or brought on by little corrosion pits at the crack origination. There was no corrosion on the pin and the box at the field end of the connection because the threads were protected completely by thread compound. Source


Lv S.-L.,China University of Petroleum - Beijing | Teng X.-Q.,Tarim Oil Field | Zhou J.,Tarim Oil Field | Yang C.-X.,Tarim Oil Field | And 8 more authors.
Materials Performance | Year: 2012

A study was conducted to investigate a pin fracture on a double shoulder tool joint of a S-135 drill pipe in a well. Cracks were found in the pins and an analysis of fracture and pin morphology indicated sulfide stress cracking (SSC). It was demonstrated that the torsion and tensile strength of the tool joint increased and hydraulic loss reduced by increasing the inside diameter and material yield strength, which SSC resistance was reduced. Nondestructive testing (NDT) on more than 170 lengths of drill pipe revealed the lack of defects on the DSTJ40X tool joints. These tests indicated defects on 103 out of a total of 527 lengths of drill pipe with DSTJ40 tool joints, and that 92 lengths of the defective pipe were used during drilling and oil testing operations and 11 lengths of the defective pipe were used only during oil testing operation. Extensive investigations also revealed that two cracks originated from the shoulder root of the pipe, with a maximum crack depth of 1.8 mm. Source


Lv S.-L.,CAS Institute of Electrical Engineering | Yuan P.-B.,Goods Research Institute | Luo F.A.-Q.,Tarim Oil Field | Kang Y.-J.,Tarim Oil Field | And 2 more authors.
Materials Performance | Year: 2010

Solitary and binary inhibition effects of ammonium (NH4NO 3) + A length of S135 drill pipe that broke during pumping from a well that contained hydrogen sulfide was investigated. The drill pipe broke at 950 mm from the box end. There was no obvious plastic deformation at the fracture. Radial lines on the outside surface of the pipe were located on the flat fracture and accounted for 1 2.5% of the whole fracture. Another fracture showed tilted morphology with different orientations. Scanning electron microscopy (SEM) with an energy dispersive analyzer (EDA) showed that the micro-fracture morphology was intergranular and sulfur was identified at the fracture. The microstructure of the drill pipe was tempered Sorbite. Test results led to the conclusion that the macro and micro-fractures and failure were caused by sulfide stress cracking (SSC). The possibility that fracture was due to material defects can be excluded because the composition, microstructure, and mechanical properties of the drill pipe are in accordance with the API Specification 5D standard. Source

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