Force Analysis Of High Temperature And High Pressure Deep Well Test

With the exploration and development of nature gas, high-temperature and high-pressure (HTHP) sour gas wells are increasing rapidly. Compared with conventional gas wells, the worst working conditions expose the unconventional ones to higher engineering risk. What’s more, the increasing difficulties in testing process results in higher requirements in gas well testing, which also brings series of problems in safety ground controlling, optimization of testing string and dealing with unexpected emergency. Focused on the difficulties in process of HTHP sour gas wells testing, it is necessary to analyze the reliability of testing string of HTHP sour gas wells.Based on the optimization of HTHP sour gas wells testing string, the differential geometry and string mechanics were employed to construct the stress analysis model of different conditions in HTHP sour gas wells testing process. According to the established model, the reliability of testing pipe string of the HTHP sour gas wells were evaluated, and the following aspects were carried out:1) The scientific design of HTHP sulfur pipe string is the key point to ensure the safety in wellbore testing process. According to the testing purpose, the testing strings were optimized, and the testing strings in different testing process, such as drill stem testing and well completion test, were summarized. The APR combined operation string was recommended for the process of testing in deep wells.2) On the basis of well testing string optimization, the failure mode and the stress of HTHP wells testing strings were analyzed, and the testing strings were simplified as rigid and soft rod models. The three-dimensional describing model for well trajectory and models for rigid and soft rod were established.3) Based on the string mechanics and deformation analysis for testing strings in wellbore, the stress model as well as deformation model, which took the influence of temperature, piston effect, expansion effect and flowing effect into consideration, were established.4) Combined with the engineering practice, the mechanical calculation model for triptych well strings in different testing conditions, such as down-hole process, sealing, seal examination, acid squeezing, acid discharging, testing and well shut-in, was developed.5) For HTHP wells, the failure of testing strings was related to stress as well as temperature distribution of wellbore. The temperature field model of wellbore in different testing process was established, and the temperature field model was calculated in different conditions.6) The developed stress analysis model was applied to evaluate the reliability of testing string of two field cases called well ST1and well YB204. The testing results verified the presented theory and method in this paper can be used to study the string mechanics, deformation analysis and strength checking.