At the early stages of Bakken unconventional development, ConocoPhillips drilled the first fully downspaced DSU with 8 wells staggered in Middle Bakken (MB) and Upper Three Forks (UTF) Formations and completed wells with sliding sleeve technology which resulted in large inter-fracture spacing. We believe this left behind significant undrained resources between perforation clusters along a well and in the far field between wells. With the adoption of plug and perf technology into Bakken, infill drilling and refracturing are two main techniques to recover the inefficiently drained rock volume. This paper will focus on infill and discuss results and key findings from a successful ConocoPhillips Bakken pilot. We will highlight how we use key data types and an integrated modeling workflow to gain insights on parent well depletion, fracture hits, infill fracture geometry, and key drivers of infill well performance.
A typical vintage Drilling Spacing Unit (DSU) was selected for pilot tests. The 8 parent wells had been on production for 6 years before 3 infill wells were drilled in Middle Bakken and Middle Three Forks (MTF) formations. Infill well completion was designed to mitigate asymmetric fracture growth and promote near wellbore fracture complexity. Key data sets collected include diagnostic fracture-injection test (DFIT), offset well bottom hole pressure (BHP) during completion, long-term BHP during production, time-lapse geochemistry, and production interference tests. Comprehensive analyses were performed, and data-driven models were built by a multi-disciplinary team. The model workflow includes a geological model, hydraulic fracture model, parent well and infill well production history matching, geomechanics coupling and production forecast.
The key findings include: 1) Many positive fracture hits were observed in surrounding parent wells during infill well stimulation, resulting in significant parent well production uplifts. 2) The far-field depletion near infill wells was not as high as originally thought, indicating inefficient drainage in-between parent wells. 3) Infill wells outperform parent wells based on the first-year production and long-term forecast shows encouraging infill economic potential. 4) Parent well depletion prior to infill and infill well spacing/stacking are two key factors for infill success. 5) The infill potential of many similar DSUs is unlocked.
The learnings from this data rich pilot can help to improve the understanding of infill well design and parent-child well interaction. The success of this infill pilot will inspire more infill programs to further unlock unconventional reservoir potential. The novel data-driven modeling approach can help to advance the research and development of practical unconventional reservoir analysis tools and workflows.