--> The Cardium Formation Production and Injection Database. Gas to Oil Ratios, Production Forecasting and GOR Risk Assessment

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The Cardium Formation Production and Injection Database. Gas to Oil Ratios, Production Forecasting and GOR Risk Assessment

Abstract

The Cardium Formation has been one of the most important Cretaceous hydrocarbon exploration and production targets in the Province of Alberta for the last 60 years. Most fields reached maturity in the early 1970's; however with the debut of multi-stage horizontal drilling and the successful completion in 2008 of the well Bonterra Nexstar 4-25-47-03W5/1-25-47-03W5, excitement in the formation was restored. In spite of the increase in drilling activity in exploratory halos of the fields, the recent developments have been inconsistent because some wells end up in zones with very high Gas to Oil Ratios (GOR). In part this has been the result of wells having been positioned too close to existing oil producing zones. On the other hand, unexpectedly high GOR have also been encountered at approximately the same stratigraphic level across areas were previous drilling and production was sparse. These difficulties arise in significant measure because there is much more limited geological understanding of these marginal areas. In this study, we are characterizing GOR trends, working on production forecasts and developing a GOR screen capable of assessing exploration risk. For that purpose, we have compiled a production & injection database with 15626 non-commingled wells. Risk assessment begins with the recognition of production values in the third month (IP3) versus net-pay cut offs, overall field performance and the postulation of a mappable variable to avoid areas with high GORs. Highlighted among the results is the recognition that production of horizontal wells demonstrates bypassed pay and compartmentalization in the legacy areas of most fields, early stage production forecasting from horizontals is much more difficult to predict than late stage production and that GOR behaviour can be assessed if tested against net pay, IP3, core and lithofacies distributions in the subsurface. The methodology developed here can be applied to any field in Alberta targeting the Cardium Fm. reservoir.