The objective of this project was to determine fluid flow and drainage in a reservoir with stacked pay for asset development optimization. The asset is located in the Delaware Basin with multiple prospective benches of the Wolfcamp and Bone Spring and development consisted of 8, 1.5-mile-long wells. A multi-disciplinary workflow incorporating a seismic inversion-based geomodel, completions diagnostics, and time-lapse geochemistry were used to assess: 1) the optimal spacing and stagger pattern; 2) whether multiple benches are needed to properly develop the Avalon; 3) what can be understood from time-lapse geochemistry (TLG) regarding connectivity beyond the typical completions diagnostics timeframe; and 4) whether TLG provides insight into 3BSLM depletion risk.
Prospective zones identified via well correlations, seismic interpretation, and petrophysical analysis were used to construct a geomodel and combined with integrated subsurface modeling to determine the optimal well pattern and completion design. Key diagnostics measured were: hydraulic interactions during stimulation using Sealed Wellbore Pressure Monitoring (SWPM), early-time Chow Pressure Group analysis (CPG) utilizing down-hole pressure gauges upon flowback, and Rate-Transient Analysis to characterize well performance. Fluids were assessed by Ultra High-Res GC (UHRGC), API gravity, water chemistry with extended metal ions, and water isotopes. Methods described by Jones et al., (2021; URTeC-2021-5993) were used to determine end members compositions and allocate produced oil and water TLG samples.
SWPM analysis suggested a hydraulic interference between wells targeted in the 2BSLM and Avalon C, while the Avalon A well saw minimal interference. The CPG analysis confirmed early-time connectivity of the stimulated rock volume based on the magnitude of pressure response during flow back. The Avalon A well saw a lower magnitude of pressure interference, confirming the data from the SWPM analysis. Data show Avalon, 2BSLM, 3BSLM, 3BSSS, and Upper Wolfcamp fluids are distinct, providing robust parameters for allocation. Time-lapse series did not show significant evidence for communication between 2BSLM wells and deeper reservoirs. Results suggest variable degrees of overlap in the stimulated rock volume between the various landing zones.
UHRGC proved to be a useful method to understand variations in oil compositions, especially for lighter species and differences in the relative abundance of compound classes. Geochemical data provide a means to assess parameters related to organic matter source, maturity, early vs. late generation products, oil fractionation through short-distance migration, and in-reservoir cracking. Applying an integrated workflow to a complex flow unit provided valuable insight into asset development. The methods spanning: initial modeling of the test, interference testing to gain insight into communication, time-lapse geochemistry to verify flow unit contribution, and post fracture modeling to validate subsurface understanding, worked to inform and predict optimal development for remaining locations.
A full cycle interdisciplinary approach taken in this appraisal project includes: 1) identification of prospective zones via well correlations, seismic interpretation, and petrophysical analysis to inform the development plan; 2) building a geomodel from mapped reservoir properties as the basis for future analysis; 3) combining the geomodel with offset activity for preliminary integrated subsurface modeling to determine the optimal well pattern and completion design to stimulate and drain the reservoir most economically; and 4) using diagnostics taken during completion and flowback to calibrate the model. The integrated subsurface model is the basis for running case scenarios and assess development options. This multi-disciplinary workflow is iterative and provides a calibrated tool to plan for future developments.
