A Statistical Analysis Of The Early Peace River Thermal Project Performance

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Abstract A statistical correlation of well performance indices with geology is described for the steam soak phase of the Peace River Expansion Project (PREP), a thermal recovery project operated by Shell Canada Ltd. As expected from a confirmed, permeability-dominated steam underride through a basal lean bitumen zone, well performance correlates only with geology of the lean zone, and not at all with that of the overlying rich bitumen zone during this stage. However, the existence of extensive cross-correlations among the geological parameters, which in at least one instance has introduced a spurious correlation for calendar day oil rate, suggests that log analysis techniques need to be optimized in studies of this kind. In additionto the conventionally calculated bulk fraction shale volume Vsh)from logs, the introduction of other shale parameters is advantageous, and is discussed. Introduction In recent years there has been a growing interest in statistical studies of oil well performance indicators. Apart from the most common analyses, dictated by the need to reduce large data sets to some manageable size, statistical correlations of productiondata against geological parameters might be used to test theories of reservoir depletion that are provided by modelling. This work is intended to test a depletion theory, with the use of public data from the thermal Peace River Expansion Project (PREP), operated by Shell Canada Ltd. in northwestern Alberta. The PREP Project Shell Canada Ltd. has been operating the Peace River Expansion Project since 1986, following a very successful pilot which, as of October 1989, has recovered 53% of oil-in-place by a pressure cycle steam drive process(1). The project recovers bitumen from the 30 m thick Bluesky/Gething sands which have a thin basal zone of relatively low oil saturation (50% of pore volume) and high permeability. This lean pay zone, varying in thickness from 0.3 m to 7 m, allows injection of stream at high rates below fracture pressure in all but eight wells. All wells are perforated in this zone, except in Pads 12 and 15, where shale in the basal zone forced perforation in the rich zone, Thus, a permeability-dominated steam underride(2) permits heating or the richer zone from below(3). The operating strategy and facilities at the Peace River project have been described on several occasions(4–8); in essence it consists of alternating periods of high steam injection and low production rates (pressure-up) with periods of low or no steam injecrion and high production rates (blowdown). Figure 1 shows the well patterns at the Shell Peace River Project. To the west lies the original well cluster of the pilot (PRISP) project, consisting of seven inverted seven spots, Four clusters of thirteen patterns each represent the expansion project which will be considered in this paper. The small irregular "Multisoaks" pattern remains from a previous cyclic steam pattern. While the three eastern wells of this pattern have been incorporated into cluster A, they will be excluded owing to their prior operations history.