IMAGE LOG PROCESSING AND INTERPRETATION FOR FRACTURE AND LITHO-FACIES CHARACTERIZATION; CASE STUDY OF UJUNG PANGKAH FIELD, EAST JAVA

摘要

Fractures and faults are commonly found in Pangkah carbonate reservoirs. These geological features have significant impacts in both well operation and completion scenarios; total loss while drilling and early water production were partly suspected to be due to the presence of fractures and faults in combination with vuggy/cavern porosity.Resistivity based image logs were run in most of the wells, mainly in the producing interval most of which were high angle or horizontal wells. Fractures can be identified, characterized and mapped based on these sets of data. The purpose of the study is to focus on image log processing and interpretation workflow used in the Pangkah Field. To reliably image the fractures and rock fabric, it is required to have well processed image logs. There are many factors affecting the quality of image log; major factors include pad contacts, physical properties contrast of formation, mud type, invasion, fluid mobility, borehole deviation, tool speed, tool position in the hole and functionality of buttons. The workflow discussed includes raw image QC, depth alignment, speed correction, pads correlation, static image generation to view the overall borehole structure, and dynamic image generation to enhance small details.The final image products were utilized primarily for two applications. The first is for dip picking, fracture identification and rock fabric characterization; those dips and fracture information are utilized to generate a fracture density map. The second application is for integration with core and sonic log for litho-facies characterization.This paper will also discuss image generation and processing from conventional density log, the result is then compared with the image log; limited features of image log emulated from conventional density logs are well demonstrated.