Orca is the operator of the Songo Songo gas wells and gas processing plant on Songo Songo Island (SSI). Five of the eight wells (SS-3, SS-4, SS-5, SS-7 and SS-9) were drilled by previous operators. The remaining three wells (SS-10, SS-11 and SS-12) were drilled by Orca in 2010, 2012 and 2016 respectively under its Production Sharing Agreement with the Government of Tanzania and Tanzania Petroleum Development Corporation (TPDC). In 2015, SS-5, SS-7 and SS-9 were successfully worked over.
Today, the productive capacity of the wells is approximately 165 MMscfd.
There are two separate infrastructure systems used to process and transport the gas from SSI to the principal markets in Dar es Salaam:
- The Songas facilities; and
- The National Natural Gas Infrastructure (NNGI).
The Songas owned gas processing infrastructure includes two gas processing trains, each originally rated at 35 MMscfd (70 MMscfd in total). To meet increased demand, the throughput capacity was raised (in Q2 2011) when Orca signed a re-rating agreement with Tanzania Electric Supply Company (TANESCO) and Songas to operate the gas processing plant at levels up to 110 MMscfd. However, the pipeline that transports the processed gas to Dar es Salaam, and the gas arrival pressure requirements at the Ubungo power plant, restricts production to a maximum of 102 MMscfd.
Processed gas is transported from Songo Songo to Dar es Salaam via a high pressure 25 km 12” offshore pipeline and a 207 km 16” onshore pipeline, both of which are operated by Songas.
When the gas reaches Dar es Salaam, the majority is delivered directly via the high-pressure line to the Songas and TANESCO power generation plants at Ubungo and further north at Tegeta 45 and to the Tanzania Portland Cement Company. The remainder of the gas enters a low pressure 50 km downstream gas distribution network via two Pressure Reducing Stations (PRS). The low-pressure network was constructed by Orca to deliver gas to industrial customers.
National Natural Gas Infrastructure
In 2015, Tanzania completed the construction of the NNGI, comprising a 210 MMscfd processing plant in Madimba, southern Tanzania, a 140 MMscfd processing plant adjacent to the Songas facilities on SSI, a 25 km 24″ pipeline from SSI to the mainland and a 590 km 36″ pipeline capable of transporting up to 784 MMscfd of gas from Madimba to Dar es Salaam.
In 2018, Orca tied-in the SS-11 and SS-12 wells to the NNGI. In May 2019 Orca concluded a long-term Gas Sales Agreement (GSA) with TPDC for the sale of up to 20 MMscfd, subsequently increased to 30MMscfd. The GSA ensures Orca and TPDC can continue to meet TANESCO’s increased and increasing demand for gas for power generation. It also presents the potential for Orca to utilize the infrastructure’s considerable spare capacity to access new gas markets.
Increasing and Sustaining Production
Orca continues to identify and implement options to increase and sustain production levels through the Songas processing plant and the NNGI. In mid-2019 the Company commissioned refrigeration on the Songas processing plant to overcome the effects of reservoir pressure decline following 15-years of successful production and restore maximum production potential to around 97 MMscfd. The refrigeration project is part of a two-phase initiative and will be followed by the installation of compression. Refrigeration is now operational and compression is expected to be completed in 2021.
In addition to the installation of refrigeration and compression, Orca expects to complete limited reconfiguration of surface flow lines to increase production from several wells and enable incremental increases of supply to the NNGI in line with demand.