Seismogeology Of Karst Carbonate Reservoir In 2^th Block Of Ordovician Tahe Oil Field

Tahe Oil field is located in the southwest of Akekule uplift, The main target layer is Ordovician carbonate reservoir, the depth is 5300-6000 m, The wave velocity of carbonate reservoir is 5500-6000m/s, the resolution and signal to noise ratio of seismic waves are very low. Work area higher in the north, the distribution of strata in north-south exit have differences, YiJianFang and YingShan Formation are exposed in the northern,LiangLiTaGe and QiaEr BaKe Formation are Denudated. By multiple tectogenesis, fracture characteristics are very complex, large differences in topography between the north and south. The Reservoir spaces are dissolution caves, cracks, and solution pores, heterogeneity is very strong. Seismic reservoir prediction is difficult, the distribution of fractured reservoirs is strongly variegated, the key factors are also varitaions. Aiming at the characteristics of Tahe Oilfield, this paper studied development characteristics of paleokarst, proceeding from fracture research. By utilizing various seismic measures, the paper conducted predictions of fracture-hole reservoir. Also the paper researched karst distribution regularities of this area from many aspects, such as distribution characteristics of fracture-hole reservoir, distribution characteristics of fault, palaeogeomormorphic shape, distribution regularities of palaeodrainage pattern. The main outcomes are as follows: Well point geological stratification as constraint, and bonding with well-seism, this paper determined accurately the distributions of three unconformity surfaces at the work area and the outcropping conditions of four sets of strata. Applying multiple methods and techniques, for example instantaneous phase, cosine phase, curvature, coherence along the layer, the sub-order fault of work area was discriminated. By means of structural evolution and stress analysis, this paper confirmed that the work area mainly developed four groups of faults with NW, NNW, near SN and near EW as their directions, controlling the reservoir. The fault has an important influence on karst reservoir. Through moulage method, the paper restored the ancient landscape of this area, and depicted the palaeodrainage pattern, based on the reservoir and combined with features of fault, geomorphology, paleo-monadnock. Geomorphology and drainage have important roles on reservoir development. Applying a variety of seismic technology, carbonate fracture-hole reservoir was identified. On basis of fracture-hole reservoir distribution regularities, and combined with fault features, palaeogeomormorphic shape, and distribution regularities of palaeodrainage pattern, the paper divided the work area into four zones and analyzed them respectively. Each zone has different main controlling factors. Finally, the karst distribution pattern of second area was summarized in Tahe Oilfield.