Geology Prediction Techniques for Reservoir Evolution Simulation

Abstract

Diagenesis is a necessary process for the development and formation of clastic reservoirs and ultimately determines the reservoir physical property. The evolution of pores is the comprehensive outcome of compaction, cementation, and dissolution in the process of burial history, and diagenetic material and diagenetic field control the type of diagenesis and its intensity. This systematic procedure and the coupling relationship among them are discussed using geology prediction technique to simulate the evolution of the diagenetic stages, diagenetic facies, and porosity of clastic reservoirs and ultimately for favorable reservoir prediction, particularly a reservoir of low porosity and low permeability. The essence of this method is illustrated using Ed₁ clastic sandstones in the Bozhong depression. Core data shows that the diagenetic stages of Ed₁ lake sandstones is classified into early diagenetic stage B, middle diagenetic stage A1.The major diagenetic processes that influence the porosity of the sandstones in study area are mechanical compaction (Com), carbonate cementation (C-Car), quartz cementation (C-Qua), clay cementation (C-Clay), feldspar dissolution (D-Fel), and carbonate dissolution (D-Car). Quantitative analysis of porosity evolution show that pore change rates in per million years caused by Com, C-Car, C-Qua, C-Clay, D-Fel, D-Car are 1~3, 0~2, 0~3, 1, 0~4, and 0~1%, respectively, in different diagenetic stages. C-Car is mainly in early diagenetic stage A and early diagenetic stage B, while D-Car is in middle diagenetic stage A1. D-Fel is mainly in early diagenetic stage B and middle diagenetic stage A1. Diagenesis including Com, C-Clay, and C-Qua is all well developed in these stages. Finally, based on single well simulation, diagenesis model and diagenesis strength model are summarized to simulate the porosity of the study area.