A Comprehensive Approach to Water Management: Simulating Surface-To-Subsurface Integration in Pakistan's Mature Gas Field
Authors: Ahmed S. , Sheikh H. M. U. , Jawed Y. , Hammad M. , Nahiyoon S. N. 
Published: November 2024

Effective water management is vital for the smooth operation of oil and gas fields, serving as a cornerstone for their sustained performance. The focus of this study is a field that encompasses four distinct reservoirs: A, B, C, and D. Reservoirs A and B, with extensive histories, house the majority of in-place reserves, accounting for over 90% and still containing approximately 0.6 TCF of gas. Although characterized as traditional dry gas reservoirs, these reservoirs have experienced a gradual increase in water production. In contrast, Reservoirs C and D, relative newcomers to the field, are aquifer-driven reservoirs, where water production is surging at a significantly faster rate. While the current water production in these reservoirs remains manageable, predictive reservoir modeling has foreseen potential challenges on the horizon. Addressing this impending rise in water production necessitates proactive measures.

This paper presents a development strategy for this mature gas giant, leveraging integrated dynamic data to define reservoir performance and optimize hydrocarbon recovery, all while managing water efficiently. Comprehensive simulation models were developed to determine the reservoirs' production capacities for both hydrocarbons and water. The field's current configuration includes dedicated three-phase separators for Reservoirs C and D, while Reservoirs A and B are co-produced using two slug catchers. Water from Reservoirs A, B, and D is directed to flash vessels and settling tanks before being disposed-off through a dedicated well. In contrast, water from Reservoir C is channeled to a water pit, also serving as a contingency should issues arise with the slug catchers or separators.

During this study, simulation models were developed and used to generate the water production forecast for the considered scenarios. To address the impending water management challenges, substantial efforts have been made to expand the field's water handling capacity. While the current water disposal well is equipped to manage the increased water volumes, regular coiled tubing cleanup jobs have been scheduled to maintain the injection pressures within the surface system's limits. Furthermore, a detailed workflow has been defined for significant expansion of the separation facility, along with its emergency backup pit, to ensure efficient water handling and separation as the water production escalates. This enhancement is projected to increase the field reserves by approximately 10 BCF, resulting in a significant NPV for the water handling capacity project.

By taking a forward-thinking approach and integrating the dynamic field data with detailed reservoir interpretation, this field is primed for the future. The study underscores robust engineering models and systematic data analyses that will enable uninterrupted operations and ultimately enhance the field's recovery potential. This strategic approach to water management ensures the field's resilience and longevity in the face of evolving production dynamics.