Lessons Learned in Permian Gas-Lift Shale Wells: Dynamic Production Analysis With Downhole Gauge

Abstract

Unconventional shale wells involve dynamic flow environments, which can be challenging to artificial lift systems required to produce these wells. Early-stage production from these wells is characterized by rapid production declines. Additionally, these wells experience significant production rate and phase fluctuations. Gas lift is a method of choice for producing gas-dominant assets, and it is commonly used early in the life cycle of liquid-dominant assets when production rates are higher. The design, the operation, and the general production management for shale wells requires a completely different approach and mindset than for conventional wells.

Production systems analysis, usually referred to as nodal analysis3, is a design and optimization technique used to evaluate a variety of current and future production scenarios under the assumption of steady state. Well test data, downhole gradient surveys, or production logging surveys are periodically sampled and provided as boundary conditions for the production systems analysis. The future reservoir conditions, typically obtained from reservoir simulations, are also used as boundary conditions. After performing the systems analysis, operators validate outcomes and determine the correct actions to take by using sporadic measurements. Operators are recognizing that the lower measurement frequency and resulting slower and offline analysis techniques provide incomplete, if not inaccurate, snapshots of the dynamic production environments of shale assets. To address that situation, several operators have started deploying downhole pressure/temperature gauges to understand and manage dynamic production behavior. There is a need for dynamic production modeling tools that analyze field conditions with realtime data and that provide real-time suggestions for corrective production improvement. This paper presents a dynamic production analysis methodology using real-time downhole measurements and its implementation in a software tool.

The presentation provides results from two shale wells produced using gas-lift technology in a Permian asset. Both wells are instrumented with permanent electronic downhole gauges below the operating orifice valve to measure pressure and temperature in the casing-tubing annulus and in the tubing. The real-time data from gauges is visualized and analyzed in real time to diagnose artificial lift performance, including gas-lift valve behavior. More importantly, the analysis-inferred reservoir static pressure and instantaneous productivity index can be compared to the numerical reservoir simulations.

Real-time downhole data coupled to dynamic production analysis is presented for the first time. This approach leads to more accurate production forecasting as well as optimization of highly dynamic shale wells.