Production Data from the Cardium Formation Evaluated within a Geologic Framework to Identify Criteria Useful in Selecting Areas for Exploitation by Multi-stage Fracturing of Horizontal Wells
The Cardium Formation in Alberta, Canada, has produced more than 1.7 billion barrels of light oil since 1953. This zone has been revived as a drilling target since 2008 by application of multi-stage fracture stimulations to horizontal wells. As of November 2011, 62,000 bopd is being produced from over 1100 horizontal wells. The oil rate in the 3rd month of production (IP3) is used here as a standard to correlate with geologic setting and reservoir properties. The objective is to develop methods to 1) identify where there are recoverable reserves remaining within the boundaries of established pools, including undeveloped tight sands, and 2) high-grade areas outside the known pool boundaries that will produce oil at economic rates from tight sands. The impact on IP3 of differing well stimulation strategies was not part of this analysis.
The objectives were explored in 2 steps. First, based on where the wells were placed relative to producing areas, over 900 wells having IP3 values were assigned to the following categories: primary recovery area, waterflood area, extensions to known pools, or exploration area. The IP3 data were analyzed by these categories to identify trends and statistics. Observations included 1) average IP3 rates from new wells in and around known pools are higher than average IP3 rates in exploration areas; 2) exploration wells accounted for a disproportionate share of poorly performing wells; 3) higher gas-oil-ratio (GOR) is associated with lower IP3 rates in every field area. To address the GOR issue, a screening tool was developed and applied regionally to identify areas where high GOR was expected in oil exploration targets.
Next, an area in Pembina, covering 5 townships, and containing a variety of prospect types was studied. Net pay, oil in place, oil recovery factor (RF), GOR, and depletion, were quantified in each of 3 zones over the map area: lower sand, main sand and conglomerate. To address exploration risk (i.e. low IP3 rates in exploration wells), multiple regression was used to predict expected IP3 in the tighter halo surrounding the producing area. Net pay in the “main sand” was the most significant variable for prediction of expected IP3. In legacy producing areas, RF varied from less than 4% to over 16%. A map of RF highlighted areas to be targeted by infill drilling. The approach used here should be applicable to the assessment of the Cardium Formation in other areas.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California