MODEL PENGENDAPAN DAN DIAGENESIS BATUPASIR 7700 DAN 8420“FORMASI” BROWN SHALE KELOMPOK PEMATANG UNTUK PENGEMBANGANLAPANGAN PUTIH DAN JINGGA SUB-CEKUNGAN KIRI, CEKUNGANSUMATRA TENGAH

• Main Author: Hayati Amlan, Milla
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/77636
• Institution: Institut Teknologi Bandung

Putih and Jingga are gas fields, located at the Kiri Trough, approximately 100 miles northwest city of Pekanbaru, the capital of Riau Province. The northern part of these fields is bounded by the Rangau Trough, the southern by Dalu-dalu thrust belt, the west by major faults trending north-south and the east by the altitude of the final boundary precipitate the development of Brown Shale "Formation" toward the hinge margin. Objectives of this thesis are 7700 Sandstone at Putih-1 well and 8420 Sandstone at Jingga-1 well. Both sandstone reservoirs are located at the Brown Shale "Formation" of Pematang Group, its contain gas reserves that have not fully developed yet. The integration of cutting data, well log data, and interpretation of 2D/3D seismic data with deductive reasoning methods used in reconstructing the depositional model and study the reservoir characteristics and diagenesis processes of 7700 Sandstone and 8420 Sandstone on Brown Shale the "Formation" to determine these sandstones distribution, continuity, and reservoir quality. Integrated and comprehensive understanding of continuity and distribution as well as the quality of the reservoir is intended to help the development plan of Putih and Jingga Fields in the future. The analysis of gamma ray log character in Putih-1 and Jingga-1 are interpreted 2 (two) cycles of deposition, they are: Brown Shale interval of depositional cycle and Upper Red Bed interval of depositional cycle. The entire cycles of precipitation are controlled by the rate of subsidence and sediment supply in Kiri Trough. Analysis is then tied around the 2D and 3D seismic data in the study area, resulting 4 (four) interpretation of depositional sequences in syn rift, they are: early syn-rift system, (Pematang-1 depositional sequence), early middle syn-rift system (Pematang 2 depositional sequence), late middle syn-rift system (Pematang-3 depositional sequences), and late syn-rift system (Pematang-4 depositional sequence). The 7700 and 8420 Sandstones are part of early middle syn-rift system (Pematang-2 depositional sequence). The analysis of RMS amplitude on the Pematang-2 depositional sequence by using 3D seismic data is known that the 8420 Sandstone scattered in the western and south-western part of Jingga Field, while the 7700 Sandstone are scattered in the south of Putih Field. Petrographic analysis of drill cutting data on 7700 and 8420 sandstones by using sandstones classification by Dott (1964) and Folk (1974), states that the 7700 sandstone is quartzarenite sandstone, while 8420 sandstone are consist of sublitharenite sandstones at the upper part and lithic greywacke at the lower part. Based on provenance analysis using diagrams Dickinson (1985), then at the Well of the White Sandstone 7700-1 derived from intra cratonic, while at the Well Orange Sandstone 8420-1 derived from quartz recrystallize. Both sandstones are from a different provenance. Referring to the petrography and provenance analysis above summarize that both of these sandstones are 2 (two) different sandstone bodies. Characteristic of log data and the content of the carbonaceous material in the sandstones indicate that those sandstones are associated with channel facies on lacustrine environment. The rate of subsidence was influenced by extensional force at Kiri Trough. It produced topographic with fault-block relief. So the precipitation that occurred at the Kiri Trough is in the form of axial sedimentation from Rangau High that is located in the northern part of the Kiri Trough and footwall sedimentation from Dalu-dalu High that is located on the western part of Kiri Trough. The 7700 and 8420 sandstones at the Brown Shale "Formation" are syn-rift sediment with Mesodiagenesis stage, they are: compacting, cementation, and dissolution. Compaction and cementation processes are reduced porosity of sandstone reservoir, whereas the leaching process produced secondary porosity that makes 7700 and 8420 sandstones as good enough reservoir quality. From the above analysis, Jingga Field has 12.89 BCF of gas reserves. It is equivalent to add 10 (ten) proposed wells. And analysis from data availability, Putih Field keeps 4.2 BCF of gas reserves, and it will be more if Putih Field covered by 3D seismic data.