Day 4 2 fractures summary

Why fracturing?  10/19/15  2  Hydrocarbon saturation Water cut Gross reservoir height Permeability Reservoir pressure Production system 30 % or more 50 % or less 10 m or more Gas < mD, Oil < 100 mD* Gas: 2x the abandonment pressure Oil 80 % depletion Current production not more than 80 % of max capacity of facilities * Skinfracs can also be applied at higher permeability 10/19/15  3  Productivity Improvement Factor (PIF)?  Inflow Performance of Fractured Well 8  FCD ≥ 10  6  0.5  LCD  re/rw = 2500  0.3  4  0.1  2  Prat’s steady‐state solution  10/19/15  0.7  FCD  4  Material Balance  Total Injected volume The role of fracture model is to determine this split Lost to formation leak-off coefficient, permeability Stored in fracture frac volume (height, length, width)‫‏‬ 10/19/15  5  PAD and Fluid Efficiency  η = Vfp/Vi Vpad = (1- η)/(1+ η)100‫ ‏‬% For instance: η = 33% Pad volume is (0.67/1.33)*100 = 50% In practice 40% Pad is a good starting point 10/19/15  6  Critical Parameters Injected volume = Frac volume + Leak-off volume f(Width, Height, Length)‫‏‬ f(YoungÕs Modulus, PoissonÕs ratio, Net pressure)‫‏‬ f(Time, Height, Length)‫‏‬ f(Fluid-loss coefficient)‫‏‬ f(Stress profile, Net pressure)‫‏‬ 10/19/15  7  Design input data  10/19/15  8  Minifrac  σ3 from shut-in pressure ! Pressure decline trend with frac open is different from decline trend with frac closed ! Identify trend change ! Many different methods !  P vs log Δt P vs log t log P vs Δt log P vs log t P vs log [(t+ Δt)/Δt] G function pseudo plots 10/19/15  9  ¥ Determine frac closure pressure, Pc ! w ¥ Ideally, Pc = σ3 ¥ In reality !  frac geometry dependent !  frac length change !  frac height recession !  multiple closures σ3 Pc BHP " σ3a σ3b σ3c 10/19/15  10  ¥  Widely used by many service companies ¥  Interpretation model dependent ¥  Non-unique solution !  stress and permeability contrasts !  tip screen-out, etc ¥  Assumes accurate BHP data 10/19/15  11  1000 Net pressure (psi)‫‏‬ M=1 restricted height & length M = 1/8 to 1/4 contained height 100 10 M=0 stable height growth 10 M>1 near well restriction M1 near well restriction M