A microbial enhanced oil recovery (MEOR) technology for optimisation of waterflood sweep efficiency was studied using a transparent pore micro model and a recently developed cybernetic image processing method (Automated Microscope Observation Reaction System = AMORS). Indigenous seawater microbes were stimulated with a nutrient package and allowed to develop inside the once through flow cell; a replica of the pore structure of a North Sea sandstone reservoir.
Microbial growth, as a result of subsequent controlled addition of nutrient and minerals, was observed in the automated microscope observation /reaction system. This novel integrated software/hardware cybernetic design allows approximated real-time, essentially simultaneous observation of several critical sites in the network and facilitates selective recording and compilation of observations as a function of the biological activity at each particular site. Local in-pore flow velocity measurement was possible to carry out by measuring the velocity of the particulate matter in pores/pore throats of different sizes. Sensitive, automated monitoring of the micro model pressure gave additional information of the degree of blockage.
Attachment of bacteria and development of bio mass, slime and extra cellular polymeric material was found to be most pronounced in channels of preferential water flow. The growth and subsequent narrowing of the pore network was not following a homogenous pattern, The possibility of predicting the blocking phenomenon as a function of growth rate of bacteria and/or concentration of nutrients (flow rate) is discussed with reference to the data collected with the AMORS system.
The use of micro models fitted with the AMORS package is an important step in revealing the nature of microbial blocking phenomena in porous matrices. Reservoir potential evaluation and consideration of MEOR process logistics, as compared to alternative treatment methods indicates that selective biological diversion may be a highly cost-effective and controllable way of optimising waterflood sweep efficiency in many North Sea reservoirs.
AMORS is a flexible tool recommended for investigating processes that take place on a micro/macro scale.