Abstract:With the increase of well depth and recovery difficulty in oil and gas development, the downhole temperature and pressure rise unceasingly. The wellbore is simultaneously subjected on the non-uniform in-situ stress and high temperature and high pressure (HT&HP) under this complicated operation environment, which will seriously threat the wellbore integrity and bring huge economy loss. So, give a comprehensive analysis of wellbore integrity and propose corresponding prevention measures are of important sign… Show more
“…With the continuous increase in energy demand, the focus of oil and gas exploration has gradually shifted to high-temperature and high-pressure wells with complex formations. Compared with normal temperature and normal pressure wells, the distribution of wellbore temperature and pressure at different times when high-temperature and high-pressure gas wells are on and off is more complex and dynamic monitoring is also more difficult (Huan et al, 2021; Wang et al, 2020). Many existing conventional monitoring process methods and interpretation techniques often cannot meet monitoring needs (Wang et al, 2019; Galvao et al, 2019), and theoretical analysis must be used to predict the distribution of wellbore temperature and pressure.…”
Switching wells in high-temperature and high-pressure gas wells will affect parameters such as the temperature and pressure of the fluid in the wellbore. Dynamic monitoring of temperature and pressure is difficult, and wellbore temperature, pressure, and fluid physical parameters are coupled to each other. Obtaining them separately will lead to large calculation errors. In order to improve the prediction accuracy of temperature and pressure in high-temperature and high-pressure gas wells, Based on the temperature–pressure coupling algorithm, this study compares the advantages and disadvantages of nine classic algorithms based on the temperature–pressure coupling algorithm, considers the impact of high temperature and high pressure on the temperature and pressure of the gas wellbore fluid, and establishes an unsteady temperature–pressure coupling model for high-temperature and high-pressure gas wells under on–off well conditions. Comparing with the measured data, it is proved that the prediction accuracy of the unsteady temperature–pressure coupling model of high-temperature and high-pressure gas wells meets the construction requirements of switch wells. The established model is used to simulate the temperature and pressure distribution of two high-temperature and high-pressure gas wells under switching conditions. The analysis shows that the distribution of wellbore temperature and pressure under the switch on and off conditions is affected by the gas–water ratio, heat transfer coefficient, tube size, and gas well production. Among them, the gas–water ratio increased by 1.5 times, the wellhead temperature increased by 25%, and the wellhead pressure decreased is 7.68%; When the heat transfer coefficient is increased by 1.5 times, the wellhead temperature drops to 34.38% and the wellhead pressure drops to 2.29%. When the tube size is increased by 1.125 times, the wellhead temperature is reduced by 44.20% and the pressure is increased by 6.09%. When the production of gas well is doubled, the wellhead temperature increases by 40.79% and the wellhead pressure decreases by 2.29%. The results can be used as a basis for the construction of high-temperature and high-pressure gas wells.
“…With the continuous increase in energy demand, the focus of oil and gas exploration has gradually shifted to high-temperature and high-pressure wells with complex formations. Compared with normal temperature and normal pressure wells, the distribution of wellbore temperature and pressure at different times when high-temperature and high-pressure gas wells are on and off is more complex and dynamic monitoring is also more difficult (Huan et al, 2021; Wang et al, 2020). Many existing conventional monitoring process methods and interpretation techniques often cannot meet monitoring needs (Wang et al, 2019; Galvao et al, 2019), and theoretical analysis must be used to predict the distribution of wellbore temperature and pressure.…”
Switching wells in high-temperature and high-pressure gas wells will affect parameters such as the temperature and pressure of the fluid in the wellbore. Dynamic monitoring of temperature and pressure is difficult, and wellbore temperature, pressure, and fluid physical parameters are coupled to each other. Obtaining them separately will lead to large calculation errors. In order to improve the prediction accuracy of temperature and pressure in high-temperature and high-pressure gas wells, Based on the temperature–pressure coupling algorithm, this study compares the advantages and disadvantages of nine classic algorithms based on the temperature–pressure coupling algorithm, considers the impact of high temperature and high pressure on the temperature and pressure of the gas wellbore fluid, and establishes an unsteady temperature–pressure coupling model for high-temperature and high-pressure gas wells under on–off well conditions. Comparing with the measured data, it is proved that the prediction accuracy of the unsteady temperature–pressure coupling model of high-temperature and high-pressure gas wells meets the construction requirements of switch wells. The established model is used to simulate the temperature and pressure distribution of two high-temperature and high-pressure gas wells under switching conditions. The analysis shows that the distribution of wellbore temperature and pressure under the switch on and off conditions is affected by the gas–water ratio, heat transfer coefficient, tube size, and gas well production. Among them, the gas–water ratio increased by 1.5 times, the wellhead temperature increased by 25%, and the wellhead pressure decreased is 7.68%; When the heat transfer coefficient is increased by 1.5 times, the wellhead temperature drops to 34.38% and the wellhead pressure drops to 2.29%. When the tube size is increased by 1.125 times, the wellhead temperature is reduced by 44.20% and the pressure is increased by 6.09%. When the production of gas well is doubled, the wellhead temperature increases by 40.79% and the wellhead pressure decreases by 2.29%. The results can be used as a basis for the construction of high-temperature and high-pressure gas wells.
Well sustained casing pressure signifies failure in the barrier envelop of any well and results in situations where pressure is observed or recorded in the annuli of a well and this pressure usually rebounds after bleed down. This phenomenon is a precursor to environmental and safety risk to the global oil and gas industry and presents a challenging situation that requires monitoring to understand the severity and management strategy. It is assessed to be a well integrity issue due to noncompliance to well barrier concept. It has become increasingly critical to address wells with sustained casing pressure (SCP) in view of the regulations guiding the industry and the operating environment which is experiencing an escalation of third-party activities. A bridge of well safety portends serious safety, health, environmental, operational, and integrity risks. Well PO-21 was completed as a single string, horizontal completion in the Q-10/PO-20 reservoir in 2004. Although, the well exceeded the production targets, it was subsequently shut-in in 2007 due to SCP. The initial well work attempts were carried out but were ineffective in resolving the SCP concerns: the well works carried out to isolate the casing pressure include tubing hole finding and setting of pack-off to isolate the holes. These activities could not resolve the sustained casing pressure issues with the well until a comprehensive analysis of the well, using a production logging tool comprising of noise and temperature log was deployed which gave a better understanding of the challenges of the well. A Major Rig Work Over (MRWO) was subsequently carried out on well and production was restored.
The well has continued to produce. This paper sets out to explore the holistic study of well PO-21: the initial well construction – drilling (casing, cementing, etc.,) and completion (lower and upper) design and operations. It will also showcase the production and nature of the problem observed during the production, the evaluations, and diagnostics carried out to isolate the source of SCP. The step-by-step solution approach in eliminating possible sources will be discussed based on the identified issues with the well using acquired data. The paper will also focus on the MRWO operations, and the several challenging situations encountered which necessitated a management of change from the planned recompletion strategy in response to the observed well condition. The well was successfully recompleted with no loss of containment and several lessons were learnt.
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