Flowback Data Analysis for Evaluating Multi-fractured Horizontal Wells Completed in Unconventional Reservoirs

• Author / Creator

  Fu, Yingkun

• This work aims at characterizing fracture network and evaluating multi-fractured horizontal wells completed in unconventional reservoirs through flowback data analysis. A primary focus of this work is to estimate effective fracture pore-volume using flowback rate and pressure data. This work also studies well communication in multi-well pads through a combined analysis of flowback, tracer, and microseismic data. The key findings from this work are summarized in the following paragraphs.Flowback data from tight oil and gas wells completed in the Woodford Formation show several days of single-phase water production. Diagnostic plots of rate-normalized pressure versus material balance time using single-phase flowback data show a unit slope, which represents pseudo-steady flow in fractures. This study applies an existing flowback tank model on flowback data during pseudo-steady flow to estimate effective fracture pore-volume. A procedure is proposed to estimate fracture compressibility, which is a key input of the tank model. This study further correlates the estimated fracture pore-volume with completion design parameters. The results show that total injected-water volume, gross perforated interval, and the number of clusters are among the key design parameters for an optimal fracturing treatment. Flowback data from shale gas wells completed in the Horn River and Eagle Ford Formations show early multiphase production of gas and water. A similar rate-decline behavior in water production is observed on these wells during multiphase flowback period. This study shows that the water-rate decline can be described by a harmonic model, which can be used to evaluate effective fracture pore-volume and predict water recovery. The results show a relatively good match between water recovery predicted by the harmonic model and the values measured during long-term production. Applying the harmonic-decline model on field data shows that water recovery remains very low after several years of production. Microseismic, pressure interaction (frac-hit and interference), and tracer data are analyzed to investigate well communication among 52 wells completed in the Horn River Basin. The results show that lateral and vertical well communications occur at distances above 1 km and up to 130 m respectively. Tracer data analysis indicates that wells are connected through permeable pathways which allow the flow communication of water, gas, and proppants. These pathways are primarily hydraulic fractures and reactivated natural fractures. Also, this study demonstrates that well communication may last for over 2 years due to proppant flow which prevents fracture closure during flowback and post-flowback production.

• Subjects / Keywords

  • Flowback Data Analysis
  • Unconventional Reservoirs
  • Well Interference
  • Rate-decline Analysis
  • Fracture Characterization

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-newm-wq46

• License

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