UNDERSTANDING DRBLING HAZARDS THROUGH THE USE LWD RESISTIVITY CASE STUDY: RESISTIVITY INVERSION

摘要

The rock characteristics of Pertamina fields in West Java, South Sumatra, and North Sumatra presents drilling hazards mainly in the upper layers (overburden) of reservoirs. It is so much so that we need to have a new approach in viewing and solving these drilling hazards. Knowing and understanding the nature and characteristics of rock properties will help to develop the field by drilling process. Models of this formation will become the information source in drilling planning to safely reach reservoir. We have to listen to what the hole is telling us. The array of resistivity measurements from LWD resistivity modern propagation not only provides rich information about the formation resistivity but also the environment surrounding the tool, it can yield useful information about the borehole and formation response to drilling disruption. The idea of automated interpretation through an integrated model selection method is that the information contained in the array resistivity measurement should be sufficient to provide a unique identification of the dominant environment responsible for the log curve separations. The whole log is inverted for different prebuilt formation models that may apply, and then the most consistent with the measurement of the tool is selected, under certain petrophysical constraints, as the dominant effect for that part of the log. When a dominant effect is identified, the correction is applied automatically and the relevant environmentally corrected data are generated with the confidence of the interpretation assigned. Seven typical cases from different wells have been studied and presented that have identified a drilling hazard relationship with formation properties. There are identified as: over pressured shale, lateral rock property changes, high permeable zones (thief zones), fractured basement, Deep invasion profile in carbonate, reactive shale, and high gas shale. The method is to use the inverted LWD array resistivity data to understand the drilling effect and the formation property. This should identify the hazard and its drilling process remedy. The result will enhance the drilling plan by knowing and understanding the nature and characteristics of rock properties, and it will help to develop ways to safely reach the reservoir. It is better to analyze a problem based on identifying the cause rather than just drilling by parameters only.