ResFrac lends itself particularly well to the optimization of hydraulically stimulated geothermal wells. ResFrac not only computes fracturing and reservoir flow simultaneously, but also calculates thermal stress changes and supercritical fluid properties. Fowler and McClure (2021) evaluate three geothermal designs: a closed-loop, a closed-loop with thermally conductive fractures, and an open-loop multi-lateral.
HFTS 2 is one of the highly measured hydraulic fracturing pads in the world. In 2021, the HFTS 2 consortia and ResFrac collaborated on a modeling study to incorporate all the advanced diagnostics in HFTS 2 into a single, comprehensive model. This model was then employed in an automated optimization workflow to assess opportunities to improve NPV by adjusting well spacing, proppant loading, fluid loading, cluster spacing, and landing zone. Pudugramam et al. presented the ResFrac model calibration and optimization in URTeC 3723620 in 2022, showing a 60% possible improvement in NPV by optimization of well placement and completion design.
Parent-child interactions have been a continual challenge for the unconventional oil and gas industry in recent years. At HFTC 2022, Devon and ResFrac co-authored a study on modeling parent-child interactions in the STACK in Oklahoma (SPE 209152). The parent well, two generations of children wells, and a remediation treatment in the parent well are modeled in a single, continuous ResFrac model. The continuous nature of the ResFrac modeling allowed for fluid exchanges between parent and children wells to be captured, while also requiring a holistic explanation for performance degradation in parent well post-hit. The model quantitatively described all historical observations (including damage to parent and subsequent recovery after remediation treatments) and is now suited for optimization of child well design and parent remediation programs.
The main parameters of interest derived from a diagnostic fracture injection test (DFIT) are minimum in-situ stress, reservoir pressure, and permeability. The latter two can only be obtained uniquely from the transient reservoir responses, often requiring days to weeks of test time. The DFIT flowback analysis (DFIT-FBA) method, a sequence of pump-in/flowback (PIFB), is a fast alternative to the pump-in/falloff (conventional) DFIT for estimating minimum in-situ stress and reservoir pressure.
The problem of a plane strain hydraulic fracture propagating in a layered formation is considered. Fracture toughness, in-situ stress, and leak-off coefficient are assumed to vary by layer, while the elastic properties are kept constant throughout the domain for simplicity. The purpose of this study is to develop a numerical algorithm based on a fixed mesh approach, which is capable to solve the above problem accurately using elements which can even be larger than the layer size.
Well spacing and hydraulic fracture design optimization are among the most important challenges confronting companies operating in unconventional reservoirs. Field trials are time-consuming and expensive. Reservoir simulation and/or rate transient analysis can help guide development decisions, but these calculations can be affected by non-uniqueness. This work demonstrates that tracers can be used to reduce non-uniqueness.
This paper demonstrates how geochemical production allocations can be used to calibrate reservoir simulation models and improve the optimization of well spacing and hydraulic fracture design in unconventional assets. Geochemical analyses provide quantitative assessments of flow by layer over time. This allows numerical models to be fine-tuned to realistically capture the productive fracture height for wells landed in different stratigraphic layers.
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