Facies architecture and stratigraphical evolution of fluvio-deltaic reservoirs of the Echinocyamus Formation (Lower Eocene) in the Block 10 area (Talara Basin, Northwestern Peru)

Abstract

This article describes the facies architecture of the Echinocyamus Formation, Lower Eocene, Talara Basin (Northwestern Peru), presenting an evolutionary stratigraphical model to the studied section. This work is a first step towards the static characterization of this unit with the objective of better understanding the internal heterogeneities of this reservoir, thus reducing uncer-tainties in enhanced recovery projects management.
By integrating the core description (facies and facies associations) with the analysis of electrical logs (curve patterns) two different depositional domains were interpreted: a) a lower interval, deltaic prone, where parasequences and parasequence sets were developed during a highstand systems tract; and b) an upper interval, fluvial-dominated, developed during a lowstand systems tract. Later, the deltaic domain reap-pears as a transgressive interval over the fluvial system.
Four fourth-order kinds of stratigraphical surfaces were identified; which at least potentially may be vertical flow barriers: a) parasequence or parasequence sets boundaries, b) sequence boundary that preceded the fluvial system, c) transgressive surface that marks the beginning of the deltaic transgression on the fluvial deposits and d) the maximum flooding surface.
With this work, it was possible to establish a stratigraphically-controlled interpretation following a methodology that will allow these different domains to be mapped based on the electrical curves patterns, resulting in a better prediction of intervals with spe-cific permeability and porosity characteristics.