East Java Mud Volcano (LUSI): Drilling Facts and Analysis

Nurrochmat Sawolo, Edi Sutriono, Bambang P. Istadi, and Agung B. Darmoyo
Energi Mega Persada, JI. Jend. Gatot Subroto 42, 12710, Jakarta Indonesia

A sudden eruption of ho tmud and steam began on May 29th, 2006, near the Banjarpanji¬1 exploration well in Sidoarjo, East Java, Indonesia. In the early stages, the general public opinion speculated that the mud flows were caused by an underground blowout on the Banjarpanji well. But as the data was studied and analyzed, it quickly became clear that the mud flow was not triggered by the well, that an underground blowout did not occur. Firstly, the well-bore fluid pressure was too low to fracture the well bore. Secondly, there was no sustained pressure to propagate fractures. Thirdly and most importantly, the well bore was open and totally dead whilst mud was erupting at more than 300,000bbl/day only 200 maway.

In the absence of the Underground Blowout, studies (e.g. Mazzini, et al. 2007) suggest that tectonically reactivated faults provide the conduit for the water and overpressured shale to erupt and form the LUSI mud volcano. The presence of over pressured zone due to rapid subsidence and burial in the East Java Basin is evident. The high sedimentation rate of its maturing organic rich sediments makes it an ideal setting for mud volcanism. Other mud volcanoes occur naturally in the area, and are aligned with the LUSI mud volcano on the NNE-SSW Watukosek fault zone.

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