With the goal of extracting the maximum possible recovery from unconventional reservoirs, operators try to place their wells as close as possible. With such well spacing pattern, hydraulic fracture hits among the horizontal wellbores have become norm. The study presented here aims at studying the cause and effect of such fracture hits on wellbore productivity and integrity by numerical simulation and finite element analysis.
Fracture hits have been reported in almost all the unconventional reservoir basins across North America. In some wells, their impact on production is claimed to be positive whereas in others it is claimed to be negative. To further investigate the impact of any fracture hit, advanced modeling workflows were applied to several case studies. The workflows include complex fracture simulation model, coupled numerical reservoir simulation, and finite element geomechanical modeling to evaluate rock deformation due to hydraulic fracturing, the impact on wellbore and casing integrity, deformation of the casing, near-wellbore proppant dislodgement, and the effect of time and distance from the offset wells.
From the study, it is proven that the impact due to a fracture hit on a well is not only dependent on the geomechanical stress alteration arising from stimulation in the offset well and its production, but is also determined by the degree of fluid and proppant dislodged in the near-wellbore area. The offset-well hydraulic fracture propagation, pressures, and fluid and proppant transport are also critical in deciding the future productivity after a fracture hit. A case study demonstrates that the production of the considered parent wellbore can deteriorate by 17% in 1 year when a fracture hit is negatively impacting productivity.
The modeling approach allows operators to improve their strategy of pad development and look at the impacts of fracture hits more closely. Well spacing decisions are streamlined better following the recommendations from this study. Whereas closing-up the well spacing to extract the last drop of oil and gas is important in a pad development mode, the treatment designs must be modified as required to negate the effects of fracture hits. The study allows operators to realize the true benefit of optimizing treatments at the multi-well level for developing an engineered pad development strategy.