massamabala

Attached is an Extract from Wikipedia in regard to oil extraction from Massambala. I looks like the 20% extraction figure being touted is extremely conservative!



Cyclic Steam Stimulation
This method, also known as the Huff and Puff method, consists of 3 stages: injection, soaking and production. Steam is first injected into a well for a certain amount of time to heat the oil in the surrounding reservoir to a temperature at which it flows. After it is decided enough steam has been injected, the steam is usually left to "soak" for some time after (typically not more than a few days). Then oil is produced out of the same well, at first by natural flow (since the steam injection will have increased the reservoir pressure) and then by artificial lift. Production will decrease as the oil cools down, and once production reaches an economically determined level the steps are repeated again.

The process can be quite effective, especially in the first few cycles. However, it is typically only able to retrieve approximately 20% of the Original Oil in Place (OOIP), compared to steam flooding which has been reported to retrieve over 50% of OOIP. It is quite common for wells to be produced in the cyclic steam manner for a few cycles before being put on a steam flooding regime with other wells.

The mechanism was accidentally discovered by Shell while it was doing a steam flood in Venezuela and one of its steam injectors blew out and ended up producing oil at much higher rates than a conventional production well in a similar environment.