3500m_Acid_Frac酸压案例分析.docVIP

Acid Fracture Case History 2500m Limestone The following discussion looks at creating a StimPlan data set for a fracture acidizing application, simultaneously reviewing the considerations that went into selecting acid fracturing as the appropriate stimulation procedure, and the considerations that led to the final design. A basic formation description includes: Lithology “0” Porosity, “Tight” Limestone “Pay” – 20+m vuggy Limestone Shale Permeability 5+ md Reservoir Temperature 280 ?F (138? C) Porosity 20+ % Natural Fracturing Moderate to None Thickness 20m Depth 3,500m Reservoir Fluid Oil – ? ? 5 cp Detail wellbore data is included in the StimPlan file – 3500m_Acid_Frac_Start.STP (and log data is included in 3500m_Acid_Frac.LAS). General Design Considerations First, since the formation is carbonate, possibly with some natural fracturing – acidizing should automatically be considered. This is particularly true given a moderate permeability of 5+ md. Based on this permeability, the StimPlan FOI (Folds-of-Increase)/PI calculations (Figure?15) show a relative short fracture of 20 to 30m significantly increases production. However, if sufficient conductivity can be achieved, then a longer fracture of maybe 80 to 100m (? length) can increase PI by another factor of 1.7X. Also, since the overlying formation is limestone (thus, not shale), there may be less potential for height confinement. Finally, there is some concern about a water productive zone about 18m below the pay, thus downward fracture growth is a major concern. This formation appears to be a candidate for acid fracturing due to: A “Long” fracture is NOT required, Some potential for significant natural fracture permeability, Formation is 100% limestone, and Some concern about downward height growth. Geomechanical Input The basic geomechanical data is input in the Geologic Layering dialog (Figure?16). The shale/shaly layers are expected to have slightly higher stress, with little str