Abstract
Conventional gas separators struggle processing and delivering liquid to the pump during a gas slug event due to extremely high concentrations of gas within the separator, as there is little to no liquid to process and deliver to the pump. A special gas separator developed for mitigating the effect of gas slugs replaced a conventional, high flow, tandem gas separator system in a slugging well. The development and initial field trial results are discussed in this paper.
An investigation of the effect of gas slugs on conventional gas separator systems, where fluid entering the separator fluctuates from 97% liquid to 97% gas with varying amounts of time, inspired the creation of a novel gas separator design. A new separator with internal reservoirs, to provide additional liquid to be processed during a gas slug event, was constructed. The prototype was installed in an unconventional well with a severe "toe up" condition creating slugging initially after production started. The inability of a conventional separator to prevent gas locking in this well motivated the operatorto allow a field trial of the new separator.
Extreme interruptions in production in the well began just below 2000psi Pump Intake Pressure (PIP) resulting in severe gas slugging, and a premature failure of the ESP string. The initial gas separator was a tandem gas separator. The operator, having been made aware of a novel separator designed with slug mitigation, suggested a field trial of the concept separator.
The second installation included a new pump (having best efficiency point (BEP) from 3500 BPD to 1750 BPD) due to well conditions and the tandem gas separator was replaced with the new gas separator, a single gas separatorwith an additional liquid reservoir concept.
The field results were very encouraging. The new separator allowed drawdown below 1200 psi PIP with no interruption in production. As the PIP approached 1100 psi the slugs grew in duration and frequency, resulting in operating thedriveinProportional Integral Derivative (PID) mode and eventually gas lock mode. The most important proof of the concept was the operator's ability to operate continually through February of 2023 to a 1000 psi drawdown and an increase of gas production of nearly 20%
Data generated from the field trial has resulted in further development of the concept, including a tandem version and increased liquid storage area for increasing slug duration.
By design, slugging is a problem in most unconventional wells. In the transition from horizontal to vertical, the flow evolves into a type of slugging flow. With the drawdown of pump intake pressure, the gas percentages increase and thereby increase the size or duration of the slugs of gas. The conceptual method of providing reserve liquid within a separator to mitigate this issue has proven successful.
