Noble Energy's investments in West Africa began in the early 1990s and now represent a significant component of our international portfolio. Our production activities began with our 34 percent working interest in the Alba field, offshore Equatorial Guinea. In addition to natural gas and crude oil production, related operations include an LPG processing plant where liquids are recovered and a methanol plant. Recent exploration success on Block O and I is driving liquid production and cash flow increases for Noble Energy.
We are actively engaged in additional development programs offshore Equatorial Guinea, with operated working interests of 45 percent in Block O and 40 percent in Block I. We also have a 50 percent interest offshore Cameroon in the YoYo mining concession and Tilapia exploration block. Over the last few years, we have achieved tremendous exploration success in the region, discovering multiple oil and gas-condensate reservoirs, and major project developments for Noble Energy.
In 2009, we sanctioned the Aseng oil project (formerly Benita) in Block I and brought it to production in November 2011, seven months ahead of schedule. Our major project development success continued with Alen, a condensate gas-cycling project (formerly known as Belinda) sanctioned in 2010, which commenced production late in the second quarter of 2013. We are also progressing additional liquid discoveries and integrated gas monetization efforts for our natural gas discoveries.
Further exploration is planned with a Cameroon well planned for 2014. The Company recently expanded its footprint in West Africa with an agreement to explore two blocks offshore Sierra Leone, and is currently conducting seismic acquisition and processing to determine future activity.