The CO 2 is regarded to be an excellent solvent for miscible flooding. However, it is still facing a main problem which is the high mobility. Microbubbles with their unique characters offer some advantages for CO 2 EOR application. Different pore throat size filters were used to generate different dominant sizes of microbubbles that were injected into sandpacks under tertiary condition. Microscopic analysis was carried out to visualize the presence, stability and behavior of microbubbles inside the solution and porous media. The microbubbles with a dominant size of 10-50 µm showed additional 26.38% of oil recovery, showing their advantages over a larger dominant size of microbubbles up to 5.28% of oil recovery. The injection with larger microbubbles with a dominant size of 70-150 µm showed 27.5% of higher injection pressure than with a smaller dominant size of microbubbles, showing their advantage in gas blocking ability. In the heterogeneous porous media experiment, the recovery volume ratio between low-and high-permeability sandpacks was increased from 1:57 during water flooding to 1:4 during the CO 2 microbubble injection with 74.65% of additional recovery from a low-permeability zone, showing the microbubble gas blocking capability to change the flow pattern inside heterogeneous porous media.
Jambaran Field was discovered in 2001 by J-1ST1 exploration well. The discovery well encountered steep-flanked carbonate build-up structure (Kujung Fm) that contain thick gas column and thin oil rim. To date six more wells have been drilled to unravel the geometry of the carbonate build up reservoir type. The carbonate build up which is up to 10 km length and 1 km width was deposited during Oligo-Early Miocene and sealed cap by very thick Tuban shale. This stratigraphic configuration has caused several drilling risks. First, there is a huge drop in pore pressure value between Tuban Shale and Kujung Carbonate; of up to 12.6 ppg in Tuban Shale and 8.1-11 ppg in Kujung Carbonate. Second, shale instability commonly happened during drilling Tuban shale. Third, total loss circulation, which can lead to H2S gas kick, potentially happened once penetrating Kujung Carbonate. To reduce those drilling risks, the casing ought to cover as much as Tuban Shale and as close as possible to Kujung Carbonate. During the exploration wells drilling, conventional methods such as; cutting observation, wetness-balance gas ratio, calcimetry, and mud losses have been applied to hunt the casing point as close as possible to Kujung Carbonate. Those conventional methods were successful in several well but also failed in the others. There are many other sophisticated tools developed by Service Company to serve the purpose of set casing, such as resistivity at bit. However, in our ongoing development wells drilling campaign, we utilized the combination of those conventional methods successfully to set 9-5/8” casing point as close as possible without entering Kujung Carbonate.
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