Rock Types, Depositional History, and Diagenetic Effects, Ivishak Reservoir, Prudhoe Bay Field
- R.M. Sneider (Robert M. Sneider Exploration Inc.) | J.W. Erickson (Exxon Co. U.S.A.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- February 1997
- Document Type
- Journal Paper
- 23 - 30
- 1997. Society of Petroleum Engineers
- 5.1.1 Exploration, Development, Structural Geology, 1.6.9 Coring, Fishing, 5.6.1 Open hole/cased hole log analysis, 1.2.3 Rock properties, 5.2.1 Phase Behavior and PVT Measurements, 2.4.3 Sand/Solids Control, 5.1 Reservoir Characterisation, 1.14 Casing and Cementing
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The present-day pore system of the Sadlerochit reservoir is the result of depositional and post-depositional processes. The pore system is a dual system characterized by intergranular porosity enhanced by leaching, and intragranular microporosity. The combined interaction of deposition and diagenesis together with burial history have caused porosity, permeability, net pay and water saturation to be highly variable areally and vertically.
The major reservoir of the Prudhoe Bay field, Alaska is composed of sandstone and conglomerate of the Perm-Triassic Ivishak Formation, Sadlerochit Group. (In this paper, Sadlerochit is used in place of Ivishak.) The pore system of the Sadlerochit reservoir is a dual one which results from a complex but systematic depositional and diagenetic history. This history together with burial and hydrocarbon saturation changes, including partial hydrocarbon remigratlon from the trap, result in a highly variable vertical and areal distribution of net pay, porosity and water saturation.
This paper presents a summary of the major depositional and diagenetlc processes that significantly influence the magnitude and distribution of net pay, porosity and water saturation within the Sadlerochit reservoir. The discussions begin with (1) sources of data used, (2) the rock types, depositional system and reservoir zonation, (3) the effects of diagenesls (especially cementation and grain/cement dissolution) on reservoir rock properties, and (4) the development of a dual porosity system of macro and micro pores. Also discussed in this paper is the influence of the rock properties on the distribution of net pay, porosity and water saturation. SPE paper 28574 presents the structural development and hydrocarbon history of the Prudhoe Bay Sadlerochit reservoir.
The data sources available for geologic analysis are extensive and varied and include conventional cores, geophysical well logs and public domain information. Conventional cores were taken in 81 wells (Fig. 1) including 27 wells cored with oil base mud. A total recovery of 36,714 feet provides good areal and vertical sampling. Routine core analyses on all cores consists of foot-by-foot measurements of porosity, permeability, grain density and fluid saturations. On 69 cored wells, geologists made detailed foot-by-foot descriptions on 28,360 feet. A total of 3979 thin section samples from 82 wells were systematically examined to determine grain composition, mineral abundance and textural relationships. X-ray dIffraction and scanning electron microscopy were used to document mineralogy and pore structure.
|File Size||1 MB||Number of Pages||8|