Examples of discriminating the downward depth and downward timing of the velocity string in the water-producing gas well

¹ College of Petroleum Engineering, Xi’an Shiyou University, Xi’an, 710065, China
² The College of Life Sciences, Northwest University, Xi’an, 710069, China
³ Engineering Research Center of Development and Management for Low to Extra-Low Permeability Oil & Gas Reservoirs in West China, Ministry of Education, Xi’an Shiyou University, Xi’an, 710065, Shaanxi, China

^* Corresponding author: 244006468@qq.com

Abstract

The problem of bottom hole effusion is an important reason for the reduction and even shutdown of natural gas wells. Downward velocity string is an important drainage gas recovery process, which can improve the flow rate of gas and discharge more liquid from the wellhead. However, the depth and timing of the velocity string is a technical problem that has been difficult to solve by field engineers. To solve this problem, this paper designs a method to select the depth and timing of the velocity string in the case of highly deviated wells and applies this method to Well X6–2 and Well X2–1 of PCOC in Ordos Basin, China. The optimization results show that when the wellhead pressure is 6.26 MPa, Well X6–2 should lower the 2–1.71 in. or 2.375–1.995 in. velocity string to 3337.9 m before the formation pressure decays to 8.800 MPa, which is most conducive to improve the liquid carrying capacity of gas wells. When the wellhead pressure is 4 MPa, Well X2–1 should lower 2–1.71in. velocity string to 3401.3 m before the formation pressure decays to 5.800 MPa, or lower 2.375–1.995 in. velocity string to 3401.3 m before the formation pressure decays to 5.900 MPa.