pressure and contact changes post production. Compounded by reservoir heterogeneity, uncertainty in the lateral sand connectivity and structural complexity, finding the easy target to drain the remaining reserves often mislead the effort particularly if the resistivity contrast between gas, oil and water are very narrow masking the technical understanding of present-day fluid contact movement. This paper will highlight several case studies in optimizing the horizontal well placement by integrating field wide comprehensive petrophysical evaluation, hydrocarbon mapping and downhole fluid characterization, proactive geosteering to navigate the best reservoir geo-body above the aquifer zone, production logging, pressure transient analysis and also production and surveillance data to address dynamic reservoir changes across the field. Several best practices to enhance technical integrity and overcome operational constraints will be also discussed.
Maximizing production from the horizontal well starts with strategic approach of current fluid contact delineation from the pilot hole data acquisition, production history and reservoir surveillance data from the nearby wells. Extensive downhole fluid characterization validated by compositional analysis on the acquired samples was performed in addition to multiple scenario planning for proactive reservoir navigation incorporating subsurface uncertainties, real time monitoring, pressure build-up transient and production logging to delineate the best reservoir body geometry, assess the producibility and optimize the completion strategy. Enhancing current understanding of gas cap movement through pressure and downhole fluid characterization also provides critical insight for gas injection optimization field wide.
Post drilling results indicate that both gas oil contact and oil water contact had moved up with producible oil trapped in between where long transition zones were observed. Post completion the wells flow average from 500 bopd to 2500 bopd with water cut ranges from 30% to 60% for sand A and almost zero water cut for sand B. Few potential production enhancement initiatives had been identified to be monetized once production declines over time. Rigorous hydrocarbon mapping and compositional analysis had also revealed that both water and oil are the moveable phases across the transition zones which require controlled pressure drawdown to sustain the production.
In a nutshell, strategic data acquisition through real time hydrocarbon mapping and proactive geosteering play a key role in maximizing the reserves in the brown field environment. Integrating reservoir insights at multiple scales brings wealth of information to improve productivity and enhance decision making for future monetization.
