The two reservoir zones undergoing steamflood are located at a depth of 140-230 m (155-245 ms), as depicted in Figure 2. The reservoir matrix is composed of unconsolidated sands, silts and clays. This very unconsolidated material has high porosity values of about 30-38%, and is very permeable at about 1-8 darcies Bee et al. (1994). In general, the lower portion of the P formation (210 ms) has the best reservoir quality, with only about 5% clay and mica content by weight from core measurements. In contrast, the upper part of the P formation and the K formation have clay contents of about 12-15%, and core samples from these zones tend to have lower porosity and permeability readings.
Duri oils are very viscous with an API gravity of 22, and viscosities of 100-1000 cp. The initial oil saturation before steam injection ranges from 29-69%, with an estimated initial gas saturation of about 10%. The initial free gas in pore space is a result of pressure depletion to below bubble point during primary oil recovery. Bubble point pressure is estimated to be about 110 psia, and the initial pore pressure in the reservoir is estimated to be just below that at about 100 psia, and as low as 50 psia at the production wells. The overburden pressure at the reservoir is about 530 psia, which means that initial differential pressures on rocks with 100 psia pore pressure are about 430 psia. Ambient reservoir temperature is about 100 F .