This paper presents a process for analyzing production interference and interwell hydraulic fracturing pressure hits for multi-well horizontal pads in unconventional reservoirs. Ten wells with varied spacing in separate formations are evaluated. The analysis determines the degree of connectivity between the wells to help assess the extent and complexity of the stimulated network. Many of these connections persist through flowback and early production. The results of the study impact decisions regarding well spacing, injection rate, perforation design and frac order.
A prescriptive completions program enabled observation of pressure interactions between wells during multi-stage hydraulic fracturing. Wellhead pressures are continuously recorded during all completions and flowback operations. The rate of pressure buildup plus the magnitude and frequency of the inter-well hits are studied. Pressure hits are then compared with production interactions between wells. Connections are mapped to form a comprehensive image of the fracture network.
In the pad studied, all wells had multiple hits with varying degrees of communication across the fracture network. Observations confirm that fractures had significant vertical and lateral growth establishing a highly complex network. Interference analysis indicates the connections between wells often diminish over time. As a final validation, the high degree of interaction and fracture overlap are shown to be consistent with high-resolution microseismic observations.
Establishing the extent of the effective fracture network is fundamental to deciding design variables. Multi-variable pad designs and production results can only be deciphered when viewed in conjunction with fracture interactions. The process discussed provides a simple way to observe and understand these interactions.