Use of a Computer Simulation Model to Analyze Processes that Created Braided-Stream Deposits of Ivishak Formation, Prudhoe Bay Field, Alaska: ABSTRACT

Abstract

This study deals with processes by which braided streams form deposits. First, braided-stream deposits in the Ivishak Formation at Prudhoe Bay field, Alaska, were studied. The principal focus of the study, however, involves use of a computer simulation procedure that represents processes that erode, transport, and deposit clastic sediment, producing simulated deposits similar to those in the Ivishak Formation. Much of the Ivishak Formation was deposited by braided streams. At Prudhoe Bay, the Ivishak has been sampled extensively by wells drilled within an area of about 20 km/sup 2/ permitting us to reconstruct the Ivishak's features in detail in three dimensions. The study focuses on shale bodies in the Ivishak. These shales affect the petroleum reservoir properties of the Ivishak. Improved understanding of the shale's spatial distribution would help management of the reservoir. The Ivishak's shales were formed either on flood plains, as abandoned-channel deposits, or as drape-eddy-slough deposits. Interpreting ancient stream deposits is challenging. While processes in modern streams can be observed directly, it is generally difficult to compare modern deposits with those formed by ancient streams. Use of a process-simulation model provides an alternative because the model can be operated under different environmental conditions and the results comparedmore » with ancient deposits. Using a computer model called SEDSIM, three-dimensional sequences of clastic deposits were produced that are similar to the Ivishak's braided-stream deposits. Repeated adjustment of SEDSIM's sedimentary environmental parameters were made, including stream gradient, sediment-particle size, and sediment volume, until reasonable accord with the Ivishak's deposits was attained. The challenge now is to predict in appropriate detail those features that are important in the Ivishak's reservoir at locations where wells have not been drilled.« less