A quick caprock integrity analysis for carbon dioxide storage sites in Malaysian fields

Abstract

The purpose of this research work is to establish a quick method for caprock integrity assessment for carbon dioxide (CO2) storage site selection. There are three main components to evaluate a seal potential which are through seal capacity, seal geometry, and seal integrity. This research work focuses on evaluation of seal characteristics through its pressure behavior and evidence of potential leakage. Various logs data such as gamma ray, sonic logs, density logs, and resistivity are utilized to establish 1D pore pressure analysis. At the same time mud logs data are used to investigate the similarity of hydrocarbon from reservoir and seal (if any). In this study, two fields namely Camos and Zhann have been identified and evaluated for their seal characteristics, thickness, environment of deposition and pressure regimes differences in order to determine their seal effectiveness through integration of pore pressure analysis, background gas or gas while drilling evidence and seal capacity from Mercury Injection Capillary Pressure (MICP) data. Camos field, a depleted carbonate field in Sarawak Basin with continuous seal shows an overpressure regime with gas chimney in immediate seal above it. Meanwhile Zhann field, a depleted clastic field in Malay Basin shows slight overpressure in deeper reservoirs and hydrostatic in most of the multistack sand reservoirs. Both fields show the evidence of effective seal through their own geological characteristics, pore pressure and gas component analysis. Nevertheless, both fields have their own challenges to be converted to potential storage sites. A detailed understanding and analysis is required for seal integrity evaluation which can lead to better plan establishment that may further reduce risks during selection of CO2 injection site and help to execute future well or field monitoring design.