Developing High-Confidence EURs and Optimizing MFHW in Unconventional Formations using PTA and RTA
Maximizing ROI (Return on Investment) is essential in unconventional shale formations. Even when the oil price is high and pay-back periods are shorter, resources may be scarce and logistics challenging, meaning that well productivity remains indispensable. It is therefore important to have consistent key performance indicators, which enable optimization of completion and fracturing design parameters. To this end, PIs (Productivity Index) and the SRVs (Stimulated Reservoir Volumes) were measured on over sixty MFHW (Multi-Fractured Horizontal Wells) Bakken wells, thereby quantifying the impact of horizontal lateral length, fracture spacing, and volumes produced.
To improve inflow characterization, the downhole flowrate was measured directly utilizing ESP (Electrical Submersible Pump) properties to analyze reservoir flow regimes by associating the correct rate change with each flowing pressure change, thereby enabling rate normalization, which is the basis of PTA and RTA (pressure and rate transient analysis).
The PI was measured during BDF (boundary dominated flow) and in undersaturated conditions, thereby eliminating the effect of free gas on inflow productivity and providing a consistent basis for comparing well productivity. EUR forecasting was enabled by equipping rod pumps with downhole permanent gauges, which provided the data to calibrate a material balance model in saturated conditions.
The availability of high-quality real time downhole pressure and liquid rates enabled rapid well performance measurement and workflows for optimization of future completion designs. This also provided a means of evaluating well placement and completion execution practices by comparing achieved well performance against a known historical base line, key to both maintaining and improving the ROI in unconventional wells.
Referenced papers:
1. Optimising MFHW Completion & Fracturing in Shale Formations Utilising High Frequency ESP Real Time Data, URTEC 2790 (URTEC 2020)
2. Free Gas and ESP; Case Studies Illustrating the Difference Between Flow-rate Oscillations, Gas Locking and Instability, SPE 201476 (ATCE 2020)
3. Delivering Pressure Transient Analysis During Drawdown on ESP Wells: Case Studies and Lessons Learned SPE 204567 (MEOS 2021)