Design of productivity prediction model of fractured and vuggy carbonate vertical wells after fracturing

Abstract

Fracture-vuggy carbonate reservoir has a unique reservoir structure. It is difficult to form effective seepage channels when natural fractures are not developed, resulting in low natural productivity of oil Wells. Therefore, artificial hydraulic fracturing is needed for reservoir reconstruction. The oil well control area is divided into four seepage zones, namely, fractured fracture zone, reformed zone, natural fissure-cave zone and unreformed zone. According to the different control zones, based on Darcy's law and seepage mechanics theory, and considering the influence of starting pressure gradient, the post-fractured productivity prediction model of fracture-cave carbonate vertical well is derived, and the model is applied to the actual reservoir. The results show that the error between the calculated value and the actual value is small, which indicates that the productivity prediction model is scientific and accurate. Through sensitivity analysis, it can be found that starting pressure gradient, fracturing fracture conductivity, reconstruction zone width, matrix and natural fracture permeability all have an impact on oil well productivity. Among them, starting pressure gradient is inversely proportional to oil well productivity, while fracturing fracture conductivity, reconstruction zone width, matrix and natural fracture permeability are positively proportional to oil well productivity. The effect of natural fracture permeability is greater than that of matrix permeability. The research results provide a reference for post-fracturing productivity prediction and fracturing effect evaluation of fracture-cavity vertical carbonate Wells.