Field Development Options for a Waterflooded Heavy-Oil Reservoir
- Mahnaz Kasrale (Petroleum Recovery Inst.) | P.H. Sammon (Computer Modelling Group) | P.J. Jespersen (Sceptre Resources Ltd.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 1993
- Document Type
- Journal Paper
- 888 - 894
- 1993. Society of Petroleum Engineers
- 2.5.2 Fracturing Materials (Fluids, Proppant), 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.5.8 History Matching, 2.4.3 Sand/Solids Control, 5.4.1 Waterflooding, 6.5.2 Water use, produced water discharge and disposal, 5.7.2 Recovery Factors, 6.5.5 Oil and Chemical Spills, 1.6 Drilling Operations, 5.4.6 Thermal Methods, 5.8.5 Oil Sand, Oil Shale, Bitumen, 1.6.6 Directional Drilling, 5.2.1 Phase Behavior and PVT Measurements, 5.1.1 Exploration, Development, Structural Geology
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Battrum Unit 4 is a moderately heavy-oil reservoir in Saskatchewan producingunder waterflood from a thin sand. This paper describes a producing underwaterflood from a thin sand. This paper describes a history match of previousfield behavior and systematically analyzes through the use of numericalsimulation the potential benefits to production of further waterflooding (withand without infill production of further waterflooding (with and without infilldrilling), steamflooding, and horizontal drilling. It is found that theremaining oil recovery potential of a steamflood with horizontal wells issignificantly higher than that of any of the waterflood options.
This reservoir study concerns oil recovery options for a waterflooded,moderately heavy-oil reservoir. the Battrum Northeast pool, located 45 kmnorthwest of Swift Current, Sask. Various pool, located 45 km northwest ofSwift Current, Sask. Various field development plans were examined throughnumerical simulation and screening for a suitable EOR method. Steamflooding wasthe EOR technique selected, although the reservoir conditions were somewhatborderline for application of this process. Use of horizontal wells also wasstudied.
Reservoir Characteristics and Geology
The pool, discovered in 1955, started to produce under natural depletion inAug. 1963. A waterflood was initiated in 1966 to arrest declining pressures.The field was later unitized and divided into four units. Mobil Oil Canada Ltd.operates Units 1 through 3, which are being fireflooded; Sceptre Resources Ltd.operates Unit 4, the subject of this study. BP Resources Canada Ltd. (nowTalisman Energy Inc.) has a 25 % interest in Unit 4. The original pattern usedfor the waterflood was an inverted nine-spot drifted on a 32-ha spacing. In1979, when water cuts became excessive, infill wells were drilled on a 16-haspacing to improve sweep efficiency. Further infill drilling was carried out in1983. Fluid migration across the boundary between Unit 3 and the more easterlyUnit 4 was thought to have been controlled by water injection at the boundary.Oil production peaked initially in 1970 and subsequently in 1985, with anapparent rapid decline underway at the time the study began. The pay zone inUnit 4 consists of the Roseray (main producing zone) and Success sands. Fig. 1shows the isopachs for the Roseray, which communicates with the Success over agood portion of the reservoir. The well pattern can also be seen. Unit 4 has nogas cap. Table 1 lists the main characteristics of the reservoir rock and itsfluids. The reservoir varies considerably in quality, especially in the moreproductive Roseray sand. Table 2 gives some of the variations in Roserayproperties. These variations are included automatically in the history-matchingprocess through the usual specification of reservoir data for the field. Theyalso play a direct role in steamflood modeling when decisions must be made onwhere to locate a pattern element and what local reservoir properties to usefor the pattern model. properties to use for the pattern model. Note thatfieldwide fracturing was carried out at Unit 4 for two reasons: to improveproductivity from the tighter sand and to prevent plugging of the near-wellformation and sand screens by prevent plugging of the near-well formation andsand screens by fines. While the fracturing program only marginally improvedproductivity from the tighter sand, its effect on preventing sand productivityfrom the tighter sand, its effect on preventing sand plugging was much morebeneficial. plugging was much more beneficial. Preliminary Reservoir ScreeningPreliminary Reservoir Screening Battrum Unit 4 was screened carefully forapplicability of various EOR methods. Miscible processes (hydrocarbon or CO2)were rejected because the required pressures would have exceeded fracturepressures. Immiscible CO2 might have been successful, but there pressures.Immiscible CO2 might have been successful, but there was no economical CO2source in the area. Alkaline and surfactant processes were discarded because oftheir complexity and their processes were discarded because of their complexityand their generally mixed field performance. Polymer flooding was rejectedbecause the foreseeable benefits were few; sweep has been good in thisreservoir. Polymer diversion similarly was judged to be of little benefitbecause of existing crossflow between the two formations. In-situ combustionhad been in operation in the neighboring Unit 3 and had not yet proved itseffectiveness. Laboratory and reservoir studies indicated that Unit 4 may be acandidate for steamflooding, considering the advanced state of technologyavailable for operating steamfloods and completing thermal wells. Thisinvestigation was intended partly to provide additional information on theviability of steamflooding Unit 4.
The main objective of this study was to determine the best way to operateBattrum Unit 4. A history match of previous production was carried out first todetermine present conditions and reservoir parameters. parameters.
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