The Round will cover eight offshore blocks in waters between 2,000m and 3,000m deep and which vary in size from 2,545 km2 to over 3,600 km2. They lie east of and close to areas which have already been found to be prospective, with estimated reserves of 5 Tcfg in Block 1, close to the southern border with Mozambique, and a similar volume in the adjacent Block 2, which includes the promising Zafarani discovery, made in February this year. Of the six wells drilled offshore in 2011–2012, five found commercial quantities of gas.
This will be the fourth offshore bid round for Tanzania. The first took place between June 2000 and April 2001, when only one of the six offered blocks was taken up, by Petrobras. Things improved in the 2nd Round, in July 2002, when four out of 11 blocks were awarded, all to Shell. A 3rd Round in 2005 resulted in take-up of three blocks, and two further blocks were directly awarded to Ophir Energy a year later. The remaining two blocks were awarded to Dominion Petroleum and Petrobras in 2007 and 2011 respectively. Since then, there have been a number of relinquishments and these, plus areas never offered before, are included in the new bid blocks.
A number of plays, both stratigraphic and structural, have been identified from seismic in the offshore area. Reservoirs ranging from Tertiary to Upper Cretaceous have been tested, with channels, fans and turbidite systems all expected to be present. Source rocks are thought to be Jurassic and Cretaceous, and there are ample supplies of shales and siltstones to act as cap rocks. To date, seven wells have been drilled in the deepwater offshore, resulting in five discoveries: Pweza, Chewa, Zafarani, Chaza and the most recent one, Jodari, found in March 2012. This last is considered to have recoverable reserves in the region of 5 Tcfg, and proved the viability of the outboard basin fan play, so productive in neighbouring Mozambique. None of these offshore fields are yet in production, but the cumulative discovered gas resource in Blocks 1, 2 and 4 is now about 10 Tcf, approaching the minimum required for a two-train LNG development.
With this in mind, Tanzania has been looking to improve its hydrocarbon infrastructure. The processing plant at Mnazi Bay, one of only two onshore producing fields in the country, near the Mozambique border, has been expanded to increase capacity from 10 MMcfgpd to 21 MMcfgpd. Mtwara Base Supply Port, close to the discoveries in south-eastern Tanzania, has also been upgraded as an oil and gas supply and logistics base. In addition, a 580 km long 36” gas pipeline from Mtwara to the capital, Dar es Salaam, the longest in the country, is currently under construction.
Plenty of Data Available
The Tanzania Petroleum Development Corporation (TPDC) is working with seismic company ION/GX Technology in preparing a data room for the duration of the Round, and data packages will be available to interested companies. In recent years ION/GXT has acquired and processed a significant amount of regional 2D seismic offshore Tanzania as part of its multiclient East AfricaSPAN project, which includes about 5,000 line kilometres across the offered area. In addition, ION are about to commence infill lines to help map leads, and a refraction survey is underway in order to attempt to delineate the limit of ocean crust. Piston coring of the seabed in the vicinity of known oil seeps will also be undertaken in the next few months. About 11,000 line km of good regional PSTM and PSDM 2D seismic dataset will also be available. The data is being re-processed from Post-Stack Time Migration to Pre-Stack Time and Depth Migration.
The 4th Tanzania Licensing Round will be officially launched on 13 September during the HGS/PESGB Africa Conference in Houston, which will be followed by road shows at AAPG ICE in Singapore, in London in October and at the East African EAPC conference in Arusha, Tanzania in March 2013. Further information can be obtained from TPDC website, www.tpdc-tz.com and on www.tz-licensing-round.com.