| Abstrakt: |
Basin model study that discusses the importance of transforming smectite to illite/kaolinite as a source of changes in the brittleness of shale rock in the North East Java Basin which affect borehole stability in open hole conditions, is a very interesting challenge. The well BJN-004 is a development well located in the North East Java Basin Area where there are hole problems related to borehole stability, namely clay swelling at the upper depth interval, and caving at the lower depth interval. Based on the stratigraphy of the North East Java Basin, the source of shale lithology in the well BJN-004 are Lidah/Mundu, Ledok, Wonocolo, and Ngrayong Formations. Each of these formations has unique mineral characteristics according to its lithological characteristics, especially quartz and clay mineral content. In identifying the transformation of smectite to Illite/Kaolinite (clay diagenesis), mineralogy analysis (XRD) of drill cuttings data is carried out. The results of mineralogy analysis are correlated with lithological depth intervals, and drilling problems that occur. Clay diagenesis occurs due to the influence of high temperature and the presence of potassium in the sand-shale series. The North East Java Basin is generally dominated by shale lithology, and based on data from the drilling of the well BJN-004, it shows the presence of high temperatures starting at a depth of 4000 ft, where BHCT (bottom hole circulating temperature) has reached 1000C. The presence of dominant shale and high temperature allows the clay diagenesis process to occur in the area penetrated by the well BJN-004. From the results of the lithological correlation penetrated by the well BJN-004 with mineralogy analysis, it shows that there is a significant transformation of Smectite to Kaolinite starting at a depth of 4000 ft, which is also confirmed by the results of the MBT which shows that shale with the hard category is close to brittle, so it has the potential to cause caving. This is exacerbated by the presence of dominant Kaolinite, the use of KCl mud will make the shale more brittle. [ABSTRACT FROM AUTHOR] |
