Logging Evaluation Technology For JZ25-1S Archeozoic Buried Hill Reservoir In Bohai Sea

JZ25-1S field located in the Liaoxi uplift of Bohai Sea area, it is the biggest buried hill oil pool that has been founded till now. The dominated lithology is gneiss and cataclasite, and the reservoir space consist of fracture system and matrix system. The vital factor of buried hill reservoir is fracture effect, it's not only the store space, but also the primary seepage path. Buried hill reservoir has the character with complex lithology, complex store space and strong anisotropism, so it's difficult to interpret and evaluate by conventional logging suite. In logging evaluation of fractured buried hill reservoir in JZ25-1S field, the new logging technology, including borehole imaging logging, multiple array acoustic logging and production logging, play an important role in buried hill reservoir fracture identify, analysis and evaluation.The main lithological and geological characteristics of Archeozoic reservoir in JZ25-1S buried hill were studied by means of observation on core and sidewall core, thin-section analysis, physical property analysis, capillary pressure. Reservoirs can be classified into three types as fractured-porous reservoir, fractured reservoir and porous reservoir. The logging response of various reservoirs was analyzed by integrating mud log, well logging, core observation and analysis.The advanced image logging technology, such as formation micro-imager and multiple array acoustic logging play the important role in fracture evaluation. Combining the traditional logging technology, borehole micro resistivity scan logging can identify the fracture, study the fracture parameter such as direction, inclination, dip angle, fracture width, fracture density. Multiple array acoustic logging can provide information of compressional wave, shear wave, and stonley wave by combining the dipole and monopole technique. It's the effective method for evaluating formation permeability from stonley wave information; the permeability result shows general agreement with production logging result. Anisotropy and crustal stress can be determined by cross-plot dipole log.Based on dual-porosity explanation model, we setup a calculating method of fractured reservoir porosity parameters such as total porosity, basic porosity, fracture porosity. Different pore space should have different saturation models, on the basis of calculating of basic porosity and fracture porosity, we setup the oil saturation models by determining the saturation of matrix and fracture system. We determine the net pay by studying of the production logging. The validation analysis on buried hill reservoir by using the cutoff value proposed in this paper (porosity≥3% and (RD/RS)×DT≥90), agreement with the interpretation result of and full wave logging.