A non-isothermal wellbore model for high pressure high temperature natural gas reservoirs and its application in mitigating wax deposition

摘要

Correctly estimate pressure drop and temperature distribution along wellbore is crucial for completion design, production optimization and flow assurance in oil and gas well. In places where wax or paraffin deposits along the wellbore is a concern, a non-isothermal wellbore model is needed to analyze the risks of wellbore plugging under various operational/reservoir conditions and design mitigating approaches accordingly. In this study, a non-isothermal wellbore model for high pressure and high temperature (HPHT) natural gas reservoirs is proposed. The mathematical framework laid out in this article can also be used as a template for modeling gas injection in deep wells. Field cases are used to calibrate and validate the presented model, along with discussions on associated uncertainties. Matain well-head temperature above a desired level is critical for mitigating wax/paraffin deposition, and it is found that the most effective methods to minimize temperature drop along the wellbore are: increasing production rate by hydraulic fracturing; selecting an optimal tubing size and applying thermal insulation coating to the production tubing.