Management of H2S in Reservoirs – Biological Effects in Reservoirs Related to Souring
An ongoing JIP into the biological aspects of reservoir souring has focused on introduction, attachment, growth, detachment and control of micro-organisms in oil field reservoirs. Laboratory scale micro-models have been combined with field experience in order to develop predictive methods and control strategies for sweet oilfields, as well as souring and already sour fields.
Limits to bacterial growth (nutrient and sulphide concentrations as well as bactericidal chemicals) are built into the predictive models. These models are built around laboratory and field data and can be applied widely in developing field specific souring models.
In order to understand the mechanisms of reservoir souring and to quantify the degree of the problem, studies were conducted on mesophilic SRB (mSRB), growing at 30ºC and thermophilic SRB (tSRB), growing at 60ºC. In previous work, laboratory tests on typical oilfield additives were carried out to assess the effects of these chemicals on sulphide production.
A wide range of techniques was used and developed for these studies, which culminated in a series of field trials on one oilfield. Field specific studies were undertaken for each of the operator sponsors to identify sources of H2S in their particular reservoir, conduct predictions related to H2S development profiles and model microbiological growth in the reservoir.
A numerical simulator has been developed to enable H2S development profiles to be generated, using basic inputs such as well spacing, H2S generation rates and low characteristics in the formation.
This paper presents the findings from investigations into migration of bacteria in laboratory scale glass micromodels and studies on mathematical simulations of H2S production and distribution in the reservoir. Results of on-going investigations will be presented in future papers.