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A Reseach on the Possible Contributing Factors of Water Breakthrough in Cased-Hole Completed Wells

Abstract

Abstract

Staatsolie Maatschappij Suriname N.V. produces heavy oil with a gravity of 15.6 API (American Petroleum Institute) from shallow unconsolidated sand reservoirs in the coastal plain of Suriname from three oil fields; the Tambaredjo (1982), Calcutta (2006) and Tambaredjo North-West (2010) fields. Currently from these fields with every barrel oil, 6.4 barrels water is co-produced. However in the Tambaredjo North-West (TNW) field, the water oil ratio is 0.5, which is showing an increasing trend since 2013. Since an increase in water production affects the life cycle of a well and finally the oilfield performance, a research is carried out to identify the possible contributing factors of water breakthrough in cased-hole completed wells as observed in the TNW field from 2010 till 2014. Water breakthrough is defined as uncontrollable water production of a well due to changes in reservoir or completion parameters affecting significantly the oil production performance of the well. This research aimed to identify possible contributing factors of water breakthrough based on reservoir and production data evaluation and correlation with surrounding cased-hole completed wells performance on early water breakthrough. A total of 209 cased-hole completed wells have been investigated from which 38 wells showed an early water breakthrough (EWBT) performance while almost 67% of the wells resulted into no water breakthrough performance. Based on the 38 EWBT wells evaluation, water breakthrough due to free water saturation within the oil bearing reservoirs has been identified as the main possible contributing factor in increased water production. In addition an oil-water contact distance less than 20 ft. in the producible reservoir or a subsurface reservoir with poor developed sealing properties, contributed also to water breakthrough. Once the contributing factors of early water breakthrough are identified, proper mitigations can be taken for close monitoring the future wells performances. This will be applicable for the 33 projected development wells of 2016, that was also evaluated based on correlations of surrounded producer's production performance. This evaluation has resulted into a proposal for running the (Magnetic Resonance Imaging Logging) MRIL at 13 wells which will give answers on the free water saturation pattern in mainly the targeted O2, O1 and T3 reservoirs.