Study of a model of wellhead growth in offshore oil and gas wells

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.