Overseas Mbasin Poil Field Characteristics Of Cretaceous System In Phase Galhak-Ⅳ Deposition And Reservoir Lateral Prediction

As there is no core data of the target zone, based on the study of the regional data. The sequence stratigraphic framework of Cretaceous Galhak-IV was eatablished by fully using well logging data, mud logging data and seismic data in P area of Melut Basin. Galhak formation is a third-order sequence and Galhak-Ⅳ is transgressive system tract.There is a NW-SE trending inherited nose-shaped fault block as a whole study area, segmented by normal faults. Structural differentiation is obvious. The differences of faulting controls the structure and sedimentary differentiationThe conclusions were drawn from the analysis on single well sedimentary facies, seismic attributes and wave impendence inversion under the regional sedimentary background. Galhak formation of Cretaceous in study area is third-order sequence. The set of Galhak formation is forth-order sequence. Galhak I-IV is lacustrine transgressive system tracts. Galhak IV-X is lowstand system tracts. Galhak formation of Cretaceous in study area is mainly delta-lacustrine depositional system of wholly upward-fining sedimentary cycles. Reservoir is delta front subaqueous distributary channel sand bodies. Sedimentary subfaciesvary due to the differences of the fault activity of each fault.Sandstone distribution of Galhak-IV is controlled by structure. The structure was cut by NW trending distributing faults with geosycline and horst interlaced in the study area. Faults controlled the development of geosycline while the development of geosycline controlled the distribution of sandbody. Sandstone is mainly developed along fault-controlled geosycline. With a banding distribution, the sandbody developed along two wings to the centre of nose-shaped fault and pinch-out near to the centre. Near the centre of nose-shaped structure, therefore, fracture controlled slope area is favorable region of lithologic pinch-out and hidden reservoir.It is obvious that structural and sedimentary differentiation of three fault blocks in study area. So the exploration targets should be emphasized. The targets of fault block I (Anbar-1block) and fault block II mainly focus on upthrown of reverse fault. And because of the boundary faults activity, target of fault block Ⅲ focuses on the strata below Galhak-Ⅳ.It’s found that there was favorable geological condition for stratigraphic lithologic traps development via comprehensive analogy analysis on basin type, as well reservoir facies belt type and source-reservoir-caprock association. It’s suggested that P area was taken as the break-through point of lithological trap exploration and then spread to other regions in Cretaceous formation in Melut basin.