| Frac & pack technique, a combination of hydraulic fracturing and gravel packing, is emerging as an important, and with potentially wide applications, this technique greatly extends the traditional permeability ranges of fracture candidates and has proven to be successful in well completions in the Gulf of Mexico, Prudhoe Bay, North Sea and other fields. The relative popularity and success of the Frac & Pack technique in hydraulic fracturing has resulted in some detailed studies regarding the objective, mechanism of stimulation and sand control, fracture propagation simulation, fracturing fluid volume optimization and field execution & fracture evaluation after fracturing, etc.Based on the research of the predecessors of the pressure decline analysis and the Frac & Pack stimulation, analyzed the present fracturing extending model and fluid leakoff model, this paper developed a new interpretation model of pressure decline. A pressure dependent fluid leakoff model (FE's leakoff model) and 2D fracture propagation model (including KGD model and horizontal fracture model) are incorporated into this new interpretation model. To compare with 2D model, we establish a P-3D interpretation model of pressure decline.To solve this model, an iterative (trial-and-error) method is used to determine the fluidleakoff coefficient C1 before the TSO (for Frac & Pack) or the pump stop (for themin-fracturing test) and then evaluate hydraulic and proppant fracturing geometry, also the efficiency of the fluid. According to this interpretation model, a user-friendly computer software was developed with VB 6.0, using this software, we put up parametric study on the pressure leakoff model and field case studies for both mini-fracturing test and Frac & Pack. It is shown that we can obtain some useful information on the fracture geometry and leakoff behavior with our model; it provides a simple but relatively accurate method of pressure decline analysis for high permeability reservoirs in field applications. |
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