A Predictive Model for the H2S Distribution in Kuwait

摘要

KOC and SGS performed a regional scale study to assess and forecast the H2S risk in the onshore sector of Kuwait. Based on KOC's comprehensive data base of H2S measurements, fluid chemistry, geochemical and lithological data, the H2S concentrations in the various hydrocarbon systems in Kuwait were mapped. The origin of the H2S in the Mesozoic reservoirs were analyzed and four major H2S systems were identified. The origin of the H2S in the Lower Jurassic is the TSR process with a pronounced regional trend of H2S concentrations increasing from 0.5% in the south up to 40% towards the north. The H2S encountered in the Upper Jurassic and Lower Cretaceous reservoirs originates from the cracking of sulfur in the Najmah source rock occurring during the early maturation process. The maximum H2S concentrations recorded in these systems does not exceed 5% and no regional trend of the concentrations is observed. The exceptions are overpressured carbonate stringers in the Upper Jurassic Gotnia and Hith formation which have local occurrences of more than 10% H2S. The Upper Cretaceous reservoirs in several oil fields show distinct H2S anomalies up to 5 %. Some of the anomalies possibly are related to field operation activities (e.g. injection) but also evidence for H2S migrated from deeper strata was found. Also indications for H2S scavenging in the Upper Cretaceous reservoirs was observed but could not be quantified. Some of the Tertiary heavy oil accumulations in the north which show high H2S concentrations could be related to the BSR process, however not all heavy oil reservoirs seem to be affected. A forecast of the future development of the H2S concentrations of each H2S system was performed.