CO2 transport and injection using CO2 extracted from natural gas field developments can be applied to store the CO2 and/or can be used to enhance oil or gas recovery. CO2 can be stored in saline formations or depleted or producing oil or gas fields. Storage in saline formations is achieved by one or more of several trapping mechanisms, namely stratigraphic, structural, hydrodynamic and/or geochemical trapping. Storage in depleted oil or gas fields has similar features, but the pressure regime in depletedis likely to be different to that in saline formations and this will have a significant effect on the design of the injection system.
Storage in producing oil or gas fields is likely to have the added advantage of improving oil or gas recovery. As regardsusing CO2 (CO2 EOR), the additional recovery might occur through miscible or immiscible flooding. The suitability of a reservoir for EOR depends on the characteristics of that reservoir and properties of the oil it hosts.
Some geological basins have reservoir characteristics that might be more suited to CO2 EOR than others. Our preliminary filtering suggests that the Malay and N.W. Java basins might be suitable candidates for CO2 EOR. However, this does not mean that other basins in South-East Asia are not worthy of consideration. Our preliminary ranking of formations for CO2 EOR is given below. This is a first-pass approximate ranking using rock properties only. The best formation has a rank of 1. The tabulation is intended to prioritise those formations that might be worthy of further investigation.
First pass ranking of formations for CO2 EOR based on rock properties only
|H Group||Malay B.||Malaysia &||1|
|Talang Akar Fm||N.W. Java B.||Indonesia||2|
|Batu Raja Fm||N.W. Java B.||Indonesia||3|
|D, E, F & G Group||Malay B.||Malaysia||4|
|Terumbu Fm||E. Natuna B.||Indonesia||5|
|Cycle V||Baram Delta B.||Brunei||6|
|Nam Con Son Fm||Nam Con Son B.||Vietnam||7|
|Peutu Fm||N. Sumatra B.||Indonesia||8|
|Pattani Trough||G. ofB.||Thailand||9|
|Miocene Delta Sst||Kutei B.||Indonesia||10|
|Lower Kembelangan Gp||Bintuni B.||Indonesia||11|
|Sihapas Gp Sst||C. Sumatra B.||Indonesia||12|
|J Group||Malay B.||Vietnam||13|
|I Group||Malay B.||Vietnam||14|
|K Group||Malay B.||Malaysia &||15|
|L Group||Malay B.||Vietnam||16|
|Pematang Fm||C. Sumatra B.||Indonesia||17|
Therefore, CO2 EOR works better with particular reservoir conditions. In addition, it is typically applied to depleting reservoirs with relatively low production. Finally, the economics of CO2 EOR depends on favourable oil and CO2 prices. These factors imply that, while some CO2 EOR projects might be economically viable, such projects might not in total require volumes of CO2 that are significant when compared to the volumes emitted from South-East Asian gas developments.
As regardsusing CO2 (CO2 EGR), the technology has not been applied extensively and is in its infancy. To our knowledge, it has not been applied to enhance gas production in South-East Asian reservoirs.
Gas-to-liquids (GTL) conversion might be an appropriate means of using the CO2 co-produced with natural gas from high-CO2 reservoirs.
From the perspective of reducing CO2 emissions, CO2 EOR, CO2 EGR and GTL are not strictly comparable to CO2 storage. Enhanced recovery produces additional hydrocarbons and GTL combines methane and CO2 into different hydrocarbons. These hydrocarbons are ultimately burned and therefore cause additional CO2 emissions to the atmosphere unless the emissions are captured and stored.