Thin-Bedded Reservoirs - The Enigma, Value and Cross-disciplinary Characterization for Early Monetization

Abstract

Thin-beds are omnipresent in a variety of depositional settings, ranging from continental/fluvial, coastal/shallow marine to deepwater/turbidite environments. Being Low-Resistivity Low-Contrast Pays (LRLC) these are often difficult to detect from subsurface data using conventional acquisition methods (electrical logs and seismic) and, when detected, are complex to characterize and evaluate. Even when evaluated and found to contain pay, they are difficult to produce from. This paper draws upon experience gathered from many basins and fields globally, mostly from deepwater settings. Many are currently under production with substantial contribution from thin-bedded zones. Globally, several fields are known to have substantial pays in thin beds - North Sea (Forties), West Africa (offshore Nigeria and Angola), India (Krishna-Godavari Basin), South East Asia (offshore Sabah, Malaysia and Mahakam, Indonesia), North America (Ram Powell and Mahogany fields, deepwater Gulf of Mexico) as well as in Myanmar, the Rakhine and Moattama Basins. A detailed, cross-disciplinary technical workflow, encompassing petrophysical evaluation, seismic inversion, geological characterization, modelling and flow simulation is presented here and addresses both the detection and evaluation of thinly bedded pay zones. This approach focuses on reserve evaluation, production optimization and improved ultimate recovery factor, one of its purpose being to extend the lifecycle of the field beyond conventional thick-bedded reservoirs (e.g., the Ram Powell case). Integration of data acquisition plans, interpretation and modeling is of paramount importance when characterizing thin-bed reservoirs. Our novel, seamless seven-step technical workflow integrates all available multi-domain data and yields directly actionable results on thin bed potential. The steps are (1) high-resolution petrophysics/formation evaluation, (2) rock-physics analysis, tying well to seismic domains (3) a two-phased inversion using Qi methods, a standard resolution deterministic inversion and a high-resolution stochastic inversion, (4) a depositional systems analysis, with apt use of sedimentology/stratigraphy (5) generation of a structural framework, (6) facies and petrophysical modeling with due regards to depositional architecture, tied with seismic trends, finally followed by (7) reservoir simulation. Overall its intended for overcoming traditional Field Development Plan (FDP) challenges and enabling early monetization of hydrocarbons from LRLC/thin-bed zones.

AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018