Production Problems in the Steam-stimulated Shaley Oil Sands of the Cold Lake Reservoir: Cause and Possible Solutions
- T. Chakrabarty (Imperial Oil Resources Limited) | J.M. Longo (Exxon Production Research Company)
- Document ID
- Petroleum Society of Canada
- Journal of Canadian Petroleum Technology
- Publication Date
- December 1994
- Document Type
- Journal Paper
- 34 - 39
- 1994. Petroleum Society of Canada
- 5.6.1 Open hole/cased hole log analysis, 4.1.2 Separation and Treating, 5.6.4 Drillstem/Well Testing, 5.8.5 Oil Sand, Oil Shale, Bitumen, 2.1.1 Perforating, 1.8 Formation Damage, 2.1.3 Sand/Solids Control, 5.4.2 Gas Injection Methods, 5.5.2 Core Analysis, 5.1.4 Petrology, 5.4.6 Thermal Methods, 5.6.2 Core Analysis, 4.3.4 Scale, 5.4 Enhanced Recovery
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The highly viscous bitumen from the Cold Lake reservoir in Alberta isproduced by the Cyclic Steam Stimulation (CSS) process. The clean oil sands ofthe Cold Lake reservoir generally produce well, but the shaley oil sands withimbedded clasts have experienced lower bitumen production and lower steaminjectivity.
This paper presents laboratory and field data that support the hypothesisthat the minerals in the clasts play a role in the production problems of theshaley oil sands. Laboratory tests reveal that clasts in the shaley oil sandshave an abundance of carbonate minerals such as siderite (iron carbonate) andaluminosilicate minerals such as kaolinite and feldspar. Laboratory studiesunder steam stimulation conditions show that the mineral reactions betweencarbonates and aluminosilicates can generate formation damaging products suchas swelling clay and carbon dioxide. Swelling clay can damage the formation byplugging the pore throats, whereas carbon dioxide can lead to near-wellborescaling. Calcium carbonate scales have been observed in downhole pumps andliners in Cold Lake wells. The field bitumen production appears to be inverselycorrelated with the carbonate content of the clasts. The field bitumenproduction is also inversely correlated with the amount of carbon dioxidegenerated in the laboratory by hydrothermal reactions of clasts. The paperdescribes the application of portable X-ray fluorescence (XRF) andnear-infrared instruments for rapid, nondestructive identification of reactiveminerals in cores, and of photoelectric absorption (Pe) logs for identifyingshaley oil sands with reactive minerals. It proposes diagnostic tests toidentify the extent and type of damage in a producing well. Finally, itdiscusses several potential methods for formation damage remediation andprevention.
Cold Lake reservoir in northeastern Alberta has a vast resource base of oilsands. The bitumen in the oil sands has a viscosity of about 100,000 cp atreservoir temperature. Imperial Oil Resources Limited is using the Cyclic SteamStimulation (CSS) process to recover the bitumen. The wells are drilleddirectionally from one surface location and there are twenty wells in one pad.In one cycle, steam is injected over a period of 30 to 40 days, and a hotbitumen and water mixture is produced over several months. Each well goesthrough several cycles of injection and production until steam injectionbecomes uneconomic.
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