Innisfail-Clive-Nevis Reef Chain Revisit

Abstract Several pools in the Bashaw-Duhamel Reef Complex had experienced water efflux caused by high withdrawals from the Nevis Devonian gas pool. This water efflux phenomenon created an additional unknown for the detailed study of an individual pool. A 3-dimensional, 3-phase, unsteady-state, black oil numerical simulator was used to simulate the aquifer water movements caused by the production of hydrocarbons from various parts of the reef complex. A lumped model was utilized to investigate the pressure interference among the pools and to estimate quantitatively the historical water influx/efflux rates in the various pools. The model was also used to predict the future water influx/efflux rates for the various pools under different Nevis production scenarios. These estimates of water influx/efflux rates were then used as input to the detailed study of the individual pool. Introduction The Innisfail-Clive-Nevis Reef Chain, more commonly known as the Bashaw-Duhamel Reef Complex, is situated in south central Alberta. This Upper Devonian Leduc reef complex extends from Township 45, Range 20W4M southwesterly to Township 27, Range 3W5M for a distance of about 200 km. The major pools in the reef complex include the Duhamel D-3B, New Norway D-3, Malmo D-3A, Malmo D-38, Bashaw D-3A, Clive D-3, Nevis Devonian, Buffalo Lake D-3, Erskine –3, Wimborne 0–3, Lone Pine Creek D-3, and Innisfail 0–3. The locations of these pool are shown in Figure 1. Pressure interference among pools in the reef complex had been documented as early as 1966. 1 In 1971, a depletion study on the Bashaw D-3A oil pool2 led to the observation that pressure interference had been experienced in the Bashaw D-3A pool due to large withdrawals from the Nevis Devonian gas pool. In 1974, an interference study 3 was conducted on the reef complex after water injection projects failed to maintain the pressure of the Clive 0–2 and D-3 units. Recent detailed studies of the Clive D-2 and D-3 units necessitated an update of the 1974 study. This 1974 interference study and the 1982 update constitute the subject of this paper. In this study, a commercially available 3-dimensional, 3-phase, unsteady-state, black oil numerical simulator was used to investigate the pressure interferences and the movements of aquifer water among the major pools in the reef complex. A lumped model was constructed to simulate the various major pools and the aquifer. The production and pressure performances of the various pools were history-matched. After history match was achieved, estimates of water influx/efflux rates in the various pools were obtained. the model was also used to predict future water influx/efflux rates for the pools in the reef complex. GEOLOGY The Bashaw-Duhamel Reef Complex is founded on a platform of fragmental limestone of the Cooking Lake formation as shown in Figure 2. Slight topographic highs on the platform, possibly caused by localized shoaling, provided focal points for the Leduc D-3 reef growth. The underlying Cooking Lake platform likely provides the common connection for the D-3 pools in the reef complex.