The main exploration started officially when a cooperative contract signed on September 17, 2005 with Mobil Cepu Ltd., a subsidiary of ExxonMobil as main operator. A joint operation agreement between state oil company Pertamina was signed in March 2006. Pertamina and ExxonMobil concluded a 30-year production-sharing contract in which each company would share 45 percent interest in the block. The remaining 10 percent would go to the local governments. Foreign companies, mainly from China, have started to invest in Bojonegoro in various projects related with the planned exploration and exploitation of the Cepu Block oil fields with total value of US$8 million. According to the former minister and ambassador to the United States, Dorodjatun Kuntjoro-Jakti, Tuban and Bojonegoro would resemble Texas, because of its gas and oil resources.