Prediction of effective fractures in limestone buried hills, South China Sea

Abstract

Because of the strong tectonic movement during the formation of limestone buried hills, lots of fractures came into being. The early formed structural fractures have undergone denudation, demorphism, leaching, dissolution from atmosphere precipitation, and surface runoff, which make some of the initial structural fractures enlarged and some half-filled or fully filled with calcite. The fractures formed in the later tectonic movement are not often filled and become the main channel connecting dissolution pores with cavities. This paper calculates the strain magnitude of buried hill formation resulting from every stage tectonic movement using the strain analysis methods such as inversion and forward modeling of structural evolution history of formations. The paper also predicts the 3D fracture network formed during every tectonic movement from the geological genesis standpoint, and therefore, distinguishes the early filled fractures formed during the period of buried hill formation from the unfilled fractures formed later, achieving the goal of predicting fracture reservoirs in the limestone buried hills. Key words: limestone, buried hill, multi-period fracture, effective fracture