Unraveling Minimum Liquid Yields from Variable PVT and Production Data in the Woodford using EOS
This paper introduces a novel workflow to map minimum liquid yield (OGR) values of the Woodford unconventional reservoir to generate a trend that indicates a compositional variance from a lean to a rich in-situ gas system.
The objective of the workflow is to estimate the minimum yield based on the initial yield produced from a well. For this purpose a unified Equation of State (EOS) model was generated using the recombined fluid samples of nine Woodford wells. EOS tuning was focused on Constant Composition Expansion (CCE), Constant Volume Depletion (CVD), and flash liberation of separator liquid experiments. Discrepancies between initial producing OGR and reported OGR of recombined surface fluids from the lab reports were resolved by modifying the recombination ratio of the liquid and gas phases. An iterative procedure was used to calculate the appropriate surface recombination ratio utilizing a compositional reservoir simulator.
A compositional depletion simulation study was conducted to replicate the CVD experiments and to calculate the liquid yield values of each well for various abandonment pressures. It was shown that the minimum liquid yield value produced in the field is affected by the critical oil saturation as well as the phase behavior of the fluid. Increasing critical oil saturation decreases the minimum liquid yield. The reported minimum liquid yield values in this study are considered as the minimum liquid values that can be reached theoretically for this particular fluid system.
A correlation between the initial producing OGR and the simulated minimum yield was established. Using the correlation the minimum liquid yield for wells without any fluid sample can be estimated from the initial producing yield and can be mapped. Choosing the well locations with higher liquid yield potential will add economic value to reservoir development project. The engineer can also design the most appropriate operational practices for the expected liquid yields.