Types of Interlayers and Log Interpretation Methods of Cretaceous Carbonate Rocks in the Middle East

The interlayers had an important impact on the development of carbonate reservoirs. Due to the diverse genesis and concealment, it was difficult to identify by the logging curve in uncored well. This paper aimed to establish an effective method for applying logs to identify different genetic interlayers. Based on core, physical property data, cast thin section and mercury injection data, the interlayers in cored well of the Cretaceous Mishrif Formation in M oilfield were identified. The distribution interval of logs values of different types of interlayers was defined by the fine calibration between rock and electric. The radar chart were used to compare the logs difference of each interlayer, and the “mistaken identification rate” was used to characterize the ability of different logs to distinguish the reservoirs and the interlayers, and then the most representative logs for each interlayers was selected. The results showed that there were five types of interlayers, named IT1, IT2, IT3, IT4 and IT5. The reservoir and interlayers could be effectively separated by the Density log except the IT4. The IT1 and IT2 had similar logs characteristics which were difficult to distinguish. The IT3 had the highest Gamma value and could be used as a feature to identify the IT3. The IT5 had the highest Density value and could be distinguished from other type. It concluded that under the control of facies and strata, each interlayers could be sequential identified.