Effect of pressure depletion on fracture-geometry evolution and productionperformance

A fractured well performance evaluation study, in the Frontier formation of the Moxa Arch area (southwestern Wyoming), revealed pressure depletion due to older 640- and 320-acre-spaced producers along the NE-SW diagonal in 64 0-acre sections. This was confirmed by six buildup tests across these secti ons. Reservoir simulation also showed that the production decline of some o f these old, 320-acre-spaced wells causes enough pore pressure depletion to affect the fracture geometry in the new 160-acre infill offsets on the oth er diagonal in the same section. This paper presents the simulated pore pre ssure distribution in the drainage area of these older wells validated by b uildup tests and their effects on the principal effective stress field and consequent fracture-geometry evolution around the newer wells. The present paper also shows that depending on the location of the new well in the depleted zone and the original azimuth of the induced fractures, th e newly created fracture may be asymmetric with only one wing of the fractu re extending into the depleted area developing significant length and condu ctivity. This happens at the cost of development of the other fracture wing . Such asymmetric development of fracture wings can negatively impact produ ction, in addition to the production loss due to actual reservoir pressure depletion.