Application of Truncated Gaussian simulation algorithm in alluvial fan reservoir architecture modeling

摘要

This article counted the distribution regularity and the spread pattern of each tertiary architecture through detailed study of alluvial fan reservoir architecture of the sealing core drilling well in the Karamay group which under the sixth middle area of Karamay oilfield. The tertiary architecture of middle-fan subfacies are: braided channel, sheetfloot microfacies and gritfloot microfacies. Truncated Gaussian simulation algorithm can be used to simulate the middle-fan subfacies of alluvial fan for they have an obvious zone law. Described the distribution regularity and spread pattern of middle-fan subfacies architecture effectively. Figured out the contact relationship among different architectural units preferably. It has a certain reference for other oilfields with the same type reservoir of architecture modeling. Truncated Gaussian simulation algorithm was first applied to Uranium deposit for conditional instruction simulation by A.G.Journel, etc[1,2](1984). The simulation process make a 3D distribution of discrete variable through truncated 3D continuous variable by a series of threshold values and truncation rules. The threshold values could be changed as the coordinates changed according to the practical situation. The distribution of 3D continuous variable was built by one kind of continuous Gaussian simulation algorithm, such as sequential Gaussian simulation algorithm. Some scholars used the truncated Gaussian simulation algorithm in the model of sedimentary microfacies distribution. But few in the reservoir architecture. This research takes the alluvial fan reservoir in Xinjiang Karamay oilfield triassic Karamay formation (we call it lower Karamay formation for short) as an example, using this method to model the reservoir architecture of middle-fan subfacies.