A History Match of CSS Recovery in the Grosmont

Abstract The Upper Devonian Grosmont Formation, located in the Alberta oil sands region, contains an estimated 300 billion barrels of bitumen. The reservoir in the Grosmont is characterized by heavily karsted dolomite. The rock is fully charged with oil and has potentially very high bulk permeability. These properties make the Grosmont prospective for steam stimulation and extraction of its bitumen reserves. Throughout the 1970's and 80's, a variety of pilots were operated in the Grosmont. The Buffalo Creek pilot, operated by the Union Oil company from 1980 – 86, utilized a cyclic steam stimulation (CSS), or "huff and puff", injection scheme. The pilot achieved peak oil rates of 70m3/d and a low cycle SOR of 3.6 The first 2 years of the Buffalo Creek pilot were history matched, consisting of 5 injection/production cycles. The primary evaluated data were daily produced oil rate and producing BH temperature. After analyzing the pilot's performance and simulated reservoir model behavior, it has been concluded that the reservoir in the Grosmont can indeed be characterized with high bulk permeability. This aspect of the formation was the catalyst of the production volumes achieved in the Buffalo Creek pilot and is a key feature that must be considered in any future recovery operations. Introduction In 1977 the Union Oil company initiated what would eventually be a decade of steam drive, combustion floods, and steam stimulation tests in the Grosmont carbonate formation. Classified as the Buffalo Creek operations, this paper will focus on the single well cyclic steam stimulation tests ("Huff and Puff") performed from 1980–1981. This period consisted of 5 sequential injection and production cycles executed in well 10A-5-88-19W4. Drilled to a depth of 300m, well 10A was perforated in the interval 290mKB – 300mKB, a highly porous (25–30%), bitumen saturated (85%) streak in the Grosmont 2. 4 observational wells were also drilled within a 30m radius of well 10A in an effort to monitor the advance of the steam front (see Figure 1). Temperature response was observed with thermocouples placed at several intervals between the depths of 285 and 300m in each well. Figures 2 and 3 depict the producing day oil and water rates and the producing BH temperature in the field for each of the 5 cycles from 1980–1981. A comparison of simulated production data with these data sets will be the primary criteria in determining the accuracy of the simulator reservoir model. Steam Chamber Profile of the Pilot The observational wells drilled in an equilateral pattern around injection well 10A were intended to determine the speed and directional penetration of the steam front via temperature response in each well. First cycle steam infiltration occurred rapidly at observation well 10D and then at 10B during the first few days of injection. The initial response at wells 10D and 10B were over one narrow interval 288 to 289.5 mKB of porosity 35–40%. Temperature response at wells 7E and 10C did not occur until the 22nd day of injection.