The Study Of Fracture-Cave Reservoir Characterization Of The Middle Permian In The South Of Sichuan Basin

The past two years, the south of Sichuan gradually optimized large duty,large capacity targets in the middle Permian drilling to retrieve declining production in old bases and complete the task of the new wells: In 2008, a new well Bao 003-2 see natural gas in maokou formation drilling, the measurement of 4.6 / day; Si 005-1 maokou formation well drilled big fracture-cavity system and produced the gas and the water simultaneously. The success of these new wells illustrate that still has large remaining reserves in the middle Permian. Therefore, the recognition of fracture-cave reservoir characterization and controlling factors of The Middle Permian in the south of sichuan basin is of great significance.This paper concentrates on the principal reservoir storage space type, cracks-caves of space collocation relation, setting basic geological model of Fracture-Cavity System that is based on dates of core, log, well logging and physical properties. Using thickness of remaining strata reveal carst developmental Characterization and the relationship between depletion section,distribution of the proven reserves and fossil erosion surface generalize the cave reservoir characterization and controlling factors.Research results show that carbonate reservoir matrix block of The Middle Permian is very low porosity and poor permeability. Cave system is the main reservoir and flow space, fracture mainly to provide some filtration channels and expand the scope of connectivity. Himalayan tectonic difficult to form many larger caves, Dongwu Age of ancient karst cave system is the main cause; In the region, the overall erosion thickness is little disparity, central erosion strongest, Mao 4 duan all been eroded, leaving only Mao 3 duan; Using the distribution of depletion wells and proven reserves demonstrate that cave system mainly is situated west of Pinch edge of karst highland - karst slopes in work area. monoclinic and syncline in the karst area can find natural gas as an important block. Based on the previous study, the Himalayan tectonic movement created folds and faults that make underground independent cave system part with the relative uplift of Anticline, partly with the relative decline syncline.Gas-Water differentiation mainly happen in Fracture-cave system that is combined by fracture networks and ancient cave system.Whether the high parts of anticlines or synclines low parts, gas and water must coexist in Fracture-cave system, wherefore gas finding by water withdrawal theory is of universal adaptability.