Search

• A 3D impact dynamic model of the perforated tubing string in curved well is developed. • In the model, the well trajectory, fluid pressure and interaction tool are taken into account comprehensively. • A similar experiment is carried out to demonstrate the accuracy of the model preliminarily. • The feasibility of the impact vibration model used in curved well is investigated through a case analysis. Perforating-test joint operation in oil&gas wells may causes strong impact vibration of downhole tools which can easily lead to buckling of tubing string, falling off of tools and damage of instruments. A 3D impact dynamic model of the perforated tubing string is established by using d'Alembert's principle and microelement method, and solved by the Newton difference method, taking into account the well trajectory, internal/external fluid pressure, interaction forces between the tubing and casing, and the coupling effect of perforating gun-shock absorber-tubing string. Due to the complexity of the verification, firstly, a similar experiment is carried out to test the accuracy of the model preliminarily. Secondly, through a case analysis, the feasibility of the model in the perforation impact dynamic analysis of tubing string in curved wells is further investigated. Both the two tests show that the model proposed in this paper has good calculation accuracy and can meet the needs of perforation shock vibration analysis of tubing string in curved wells perforation. [ABSTRACT FROM AUTHOR]

In the development of oil and gas fields, many wells have a phenomenon of wellhead growth originating in thermal stress of columns and cement sheaths poses severe challenges to shaft safety. Notably, the problem of wellhead growth is more serious in fully sealed oil and gas wells at sea. Therefore, this research on the wellbore cementation force, the wellbore lifting force, and wellhead growth for offshore oil and gas wells was critical. Based the effects on the comprehensive consideration of wellbore temperature change, annulus pressure, and performance parameters of cement sheath and casing, and then established the calculation method of cementing force, lifting force, and wellhead growth. Next, used the measured data and the data in the literature to validate the model. The results show that the calculation results of this model accord with the actual situation in the field. Finally, a gas well in the South China Sea was analyzed. Found that the increasing yield and annulus pressure will increase the height of wellhead growth, but the increasing thermal expansivity and the increasing elastic modulus of the cement sheath will decrease the height of wellhead growth. To avoid the wellhead growth, offshore oil and gas wells should adopt the submarine pipeline method (the height of the mud line relative to the deck was Zero). Thus, to improve the height of wellhead growth, the designed performance of the cement sheath, the management of annulus pressure, and the control of yield shall be introduced into the process of oil and gas field development. [ABSTRACT FROM AUTHOR]

• An orthogonal wear experiment was performed on the 13Cr-L80 tubing string. • The wear patterns of the tubing-casing were primarily abrasive and adhesive wears. • The wear life can be augmented by reducing contact load and vibration displacement. • The vibration frequency of tubing string should be maintained below 1.5 Hz. • The completion fluid should be set as approximately 1.2 g/cm3 on-site. Due to wear failures caused by tubing string vibrations in high-yield gas wells, an orthogonal wear experiment was performed on the 13Cr-L80 tubing string. The influence of contact load, friction frequency, wear time, completion fluid density, and reciprocating stroke length on the wear characteristics of the tubing string were effectively analyzed using range analysis, variance analysis and the control variable methods. The results demonstrate that, the wear patterns of the tubing-casing were primarily abrasive and adhesive wears, with minimal corrosion wear. In-field operations, the service life of the tubing string in high-yield gas wells can be effectively augmented by reducing the contact load and longitudinal vibration displacement of the tubing-casing, maintaining the vibration frequency of the tubing string below 1.5 Hz, and utilizing a completion fluid with a higher density (approximately 1.2 g/cm3). The wear amount and friction coefficient of the tubing string are primarily influenced by the contact load and reciprocating stroke length, respectively. Moreover, the effect significances of the contact load and reciprocating stroke length were particularly significant and significant, respectively. These results provide useful guidance for designing and implementing approaches to improve the service life of tubing strings in high-yield gas wells. [ABSTRACT FROM AUTHOR]

• A nonlinear FIV model of tubing string in HPHT oil&gas wells was established and verified by similar experiment. • The production allocation should be far away from the mutation value which can be determined using the FIV model. • In well trajectory design, the length of vertical section should be reduced, the length of building section and the inclination angle should be increased. • The optimal position of the packer can be determined using the FIV method to guide the design of it. This study has established a nonlinear flow-induced vibration (FIV) model of tubing string by using the micro-element method and energy method with the Hamiltonian variational principle, in order to address the vibration failure problem of the tubing string induced by high-speed fluid flow in the tubing of high temperature and high pressure (HPHT) oil&gas well. This model considered factors such as borehole trajectory changes, wellbore temperature and pressure variations, self-weight of the tubing string, and the contact-impact of the tubing-casing. Based on the structural parameters of the M high-yield gas well in the South China Sea, a simulation experiment of the tubing string vibration was conducted according to the similarity principle. A comparison between the experiment data and theoretical data showed that the calculation accuracy exceeded 84%, which verified the correctness and validity of the nonlinear vibration model established in this study. On this basis, the influence of the production rate, well inclination angle, well section length, and packer position on the vibration response characteristics of the tubing string were analyzed systematically. It was found that: ①with the increase of the production rate, the vibration response of the tubing string became clearer. The production rate interval that showed abrupt changes was from 0.9 ~1.2 million m3/day. Thus, during designing, such production rate intervals with abrupt changes should be avoided to ensure the safe usage of the tubing strings; ②with the increase of the well inclination angle, the vibration response of the tubing string decreased to a certain extent. Regarding the influence of the well section length, the longitudinal vibration response of the tubing string was most sensitive to the length of the vertical section, followed by the steady inclined section, and finally the angle building section. Thus, during designing, the length of the vertical section should be reduced, while the length of the angle building section and the well inclination angle of the steady inclined section should be increased; ③As the position of the production packer moved up, the vibration responses of the lower and middle tubing strings both decreased, and the optimal packer position was between 3,549 and 3,666 m. The research results can serve as an effective analysis tool and provide a theoretical basis for the safety design of the tubing strings in the HPHT oil&gas well site. [ABSTRACT FROM AUTHOR]