Unique Production Conditions of Unconventional Wells in the Appalachian Basin; A Multi-Dimensional Assessment on Recovery

Abstract

This paper delves into the effects of long-term shut-in periods and production cycling on unconventional wet gas wells in the Appalachian Basin, where unique operational circumstances led to a long-term shut-in period. The unconventional Marcellus and Burkett wells were of a variety of production age. Ranging from depleted and operating under artificial lift, while others were recently flowed back and still in wellbore cleanup. A "long-term shut-in" refers to a shut-in period that occurs after a well has been in production for a substantial time period, rather than an intentional delay of production post-stimulation, known as "seasoning." The term "production cycling" refers to turning wells online to production for short periods of time and then shut-in for short periods of time. This was due to pipeline constraints, lease agreements, and/or transient operational conditions. The paper discusses the results of a comprehensive analysis, which included decline curve analysis, statistical analysis, hydraulic fracture modeling, build-up analysis, and rate transient analysis. The study considered many factors, such as inter-well spacing, stimulation, generational effects, wellbore boundaries, and reservoir/geologic characteristics. Overall, the study revealed a wide range of both positive and negative effects from both a reservoir and a production perspective, suggesting that factors such as well age, generation, spacing, and stimulation size were drivers. Near-term improvements were observed in previously damaged parent wells following the shut-in period. Several of the wells experienced a second, higher initial production rate than during flow back due to fluid cleanup effects. However, certain tightly spaced wells experienced negative effects on production in the longer term. In conclusion, this paper provides a comprehensive analysis of the effects of long-term shut-in periods and production cycling on unconventional wet gas wells in the Appalachian Basin. In real-time operations, many unique challenges are presented, gaining a deeper understanding of the downhole reservoir and long-term production effects will aid in more informed operational decisions in the future. The research outcomes emphasize the need for a more nuanced approach to unconventional reservoir development, and a careful consideration of the specific circumstances of each well. This study contributes to the ongoing efforts to improve the recovery of unconventional resources as these assets mature.