Abstract

In the process of continuous production of natural gas wells, formation pressure and gas flow rate decrease continuously. The ability to carry liquid decreases continuously, thus gradually forming bottom hole liquid. Bottom hole liquid accumulation is an important reason for the decrease of production or shutdown of natural gas wells. How to diagnose whether there is liquid accumulation in natural gas wells and identify the degree of liquid accumulation, to adopt drainage gas recovery operation in time, is the research focus of efficient development of natural gas reservoirs. In this paper, a method for diagnosing bottom hole liquid accumulation combining production performance curve and modified Fernando inclined well critical liquid-carrying model is designed for a large scale double-branch horizontal well used in unconventional reservoirs. The method is applied to the Well X2 of He 8 Member in PCOC. The application results showed that there was no liquid accumulation in the horizontal and vertical sections of the Well X2. The liquid in the wellbore was generated at the bottom of the inclined section and the liquid accumulation is upward along the wellbore from the bottom of the inclined section, with the height of 3 m.

Highlights

  • During natural gas production, condensate oil and water will be carried out of the formation

  • When the gas flow rate is lower than the critical flow rate of carrying liquid, these liquids will deposit at the bottom of the well and produce bottom hole liquid

  • The Well X2 of the double-branch horizontal well of He 8 Member in PCOC is taken as an example for specific analysis, and the conclusions are as follows: (1) For wells with liquid accumulation, the critical gas carrying flow rate model for double-branch horizontal wells can not be determined only by the data of the vertical well section

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Summary

Introduction

Condensate oil and water will be carried out of the formation. Considered that wellbore liquid holdup is an important factor affecting the critical gas flow rate of liquid-carrying gas wells[5,6]. These critical liquid-carrying models are more complex to calculate the bottom hole liquid height, and few of them apply to the calculation of the bottom hole liquid height of doublebranch horizontal wells. Based on the field production data of PCOC, this paper optimized the critical liquid-carrying model suitable for the doublebranch horizontal wells of the He 8 Member. (2) Establish a critical liquid-carrying model to identify the degree of liquid accumulation in the vertical, inclined and horizontal sections, and determine the height of liquid accumulation. The following aspects are studied: (1) Diagnose the liquid accumulation, determine whether there is the liquid accumulation in the wellbore, and determine the beginning time of liquid accumulation. (2) Establish a critical liquid-carrying model to identify the degree of liquid accumulation in the vertical, inclined and horizontal sections, and determine the height of liquid accumulation. (3) Take Well X2 of He 8 Member in PCOC as an example, the bottom hole liquid is diagnosed and the degree of liquid is identified

Critical liquid-carrying model of the vertical well section
Critical liquid-carrying model of the inclined well section
Conclusion

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