Abstract: The Cretaceous carbonate reservoirs with the thickness of more than 800 m were developed in piedmont fold zone in T oilfield of Zagros Basin. Due to a variety of controlling factors, these reservoirs show strong heterogeneities, which seriously restricts fine characterization of reservoirs and the development plan. The mainly developed froctured reservoirs in Shiranish and Kometan Formation were clarified on the basis of seismic attributes, core, well logging, well testing, fracture modeling and other data. The dolostones in Qamqucha Formation have intercrystalline dissolved pores, vugs and fractures, which are the most developed reservoir units in this area. As a whole, the three formations show obvious characteristics of strata-controlled, fault-controlled and structural position control. The main causes of reservoir development in this oilfield were proposed. ① The intercrystalline dissolution pores (vugs) of dolostones were closely related to penecontemporaneous dolomitization, karstification, shoal facies and hydrothermal alteration. ② The folding and faulting were the fundamental causes of fracture development in this area, and the degree of fracture development was mainly affected by lithology, shale content and structural position. ③ The degree of fracture development superimposed matrix pores and the difference of vertical and plane connectivity were the key factors of strong heterogeneity in this oilfield. These understandings could provide the basis for well placement and development formulation.