OVERCOMING PT.LAPINDO BRANTAS HOT MUD CASE
By: Aditya Rahman Sulaiman
International Undergraduate Programme
Lapindo hot mud flood case or we usually called it “banjir lumpur panas Lapindo” is an event of the unstoppable mud gush in Kecamatan Porong, Kabupaten Sidoarjo, Jawa Timur and this accident have been happened since 29 may 2006. There are 2 views of the cause of this Lapindo hut mud flood case. First, some scholars said that the primary cause of this event was because drilling mistakes and technical problems. Other theory said that it was happened because natural disaster, this theory explaining that sooner or later hot mud gush will be arise, the lapindo’s mining activity is only the trigger. First theory believes that there is an eror in the mining activity, PT.LAPINDO is suspected not doing a proper procedure in using the correct brace and bit (mata bor), they use it within different depth which has different thickness and causing a fault. In the begininning, PT LAPINDO won a drilling well tender called “pengeboran sumur Banjar Panji-1” from PT Medici Citra Nusantara as worth as US$24 million. PT LAPINDO was planning to drill the well until 8500 feet or 2590 meter depth. In order to reach that depth, infiltrate the Kujung layer (lapisan batu gamping), anticipate circulation loss potency (losing mud from the formation cause a high density liquid or mud come up) and kick potency (infiltration of other fluide to the upper layer), normally PT LAPINDO is needed to use a casing for its brace and bit. Running their work, PT LAPINDO has already used 30 inch casing for 150 feet depth, 20 inch casing for 1195 feet, 16 inch casing for 2385 feet and casing 13-3/8 inch for 3580 feet until 9297 feet, they only not yet put the last casing, the 9-5/8 inch casing for reach the Kujung layer in 8500 feet. The fact is, PT LAPINDO has a wrong prognosis a drilling term which briefly means drilling method of some points. They make a prognosis in different areas, they making a research of the Kendeng Zone but they drill at the Rembang Zone they assume such areas has same layers, due to those areas are closed enough . They estimate that in the drilling point, Kujung layer will obstruct them at 8500 feet depth, actually there is no Kujung layer within areas. They used some casing which they are don’t necessary need to use and make an accident. As consequences, an overpressure mud is blow out to the upper layer in mining process, the lower layer had already broken rapidly and not suitable with PT LAPINDO method.
Then, after reaching 9297 feet the brace and bit touches limestone (batu gamping). LAPINDO thought that the target at Kujung formation has been achieved, in fact they only reach Klitik zone (also a limestone formation but has different density and porousity). Commensurate with mining procedure, LAPINDO use a mining pump to prevent the hot mud come up. The porousity of Klitik zone made the covering mud been spread over that zone and circulation loss happen. After the covering mud losing, kick was happened, the hot mud tried to achived upper layer due to density difference. Following the mining procedure, mining process was stopped and the brace and bit has been tried to be lifted up. Unfortunately, the brace and bit was stuck and been cut. A Blow Out Preventer (BOP) on the rig has been closed and another weight mud which has a big number of density was pumped down in order to stopping the kick. Another unexpected mud activity happned, because layer is so porous and the Blow Out Preventer (BOP) was already placed, the hot mud was trying to find other way. Condition and natural fissures of such soil also could be a factor why this kick –ing accident is happen. Since this surface blow out accident happened, the hot mud is not been stopped yet. The odd things is all of the document and mining procedure especially about casing installation is already accepted by BP...