SPE 58750
Microbially Induced Formation Damage in Oilfield Reservoirs
Jonathan M. Wood and Iain S.C. Spark, Corex (UK) Ltd.
Formation damage in terms of physio-chemical reactions such as asphaltene deposition, scale precipitation and fines migration for example, is relatively well understood. In contrast to this the effects of indigenous and introduced microbes and their role in oilfield formation damage is less well understood. Oilfield microbes, especially the S.R.B (sulphate reducing bacteria) have been identified from many oilfields world wide (indigenous) and have been isolated from drilling mud (particularly water based muds) and other downhole chemicals and injection water (introduced microbes). The combination of the various microbial populations often results in the precipitation of insoluble metal sulphides, biopolymer and/or hydrogen sulphide production, with loss in production or injection rates. By utilising bottle tests preformed at a range of temperatures up to actual oilfield reservoir temperature, it is possible to model the microbial formation damage mechanisms using the thermal gradients present in the field. Using this thermal model it is possible to predict where the various microbial formation damage mechanisms, such as hydrogen sulphide production, biopolymer and cell pore blockage, occur in the field area and to predict from the injection water model when the various damage mechanisms will occur in the field. This novel approach using thermal models coupled with microbial bottle and flood tests and geological interpretative techniques is the initial step in predicting microbial formation damage in oilfield reservoirs.