Formation mechanisms of deeply buried marine dolostone reservoirs: A review

Hong Zhang¹

¹Sinopec International Petroleum Exploration and Production Corporation, Beijing 100029, China.

^*Corresponding author: hzhang.sipc@sinopec.com.

Abstract

Deeply buried dolostone reservoirs have become a key exploration focus in recent years. However, there are debates regarding reservoir classification and dissolution mechanisms. This paper conducts a statistical analysis of deep dolostone reservoirs, summarizing aspects such as reservoir classification, dissolution mechanisms, and microbialite reservoirs. Based on depositional environments, deep to ultra-deep dolostone reservoirs worldwide are classified into ramp and platform facies. According to dolomitization mechanisms, deep to ultra-deep dolostone reservoirs are divided into three types: near-surface evaporation-reflux dolomitization, hydrothermal dolomitization, and multiphase dolomitization reservoirs. Key factors controlling the development of deep dolostone reservoirs include depositional environments, diagenesis (e.g., meteoric water dissolution, hydrocarbon emplacement, and deep dissolution processes) and tectonic activities. Clotted structures formed in high-energy depositional environments exhibit better physical properties, while stromatolites and laminates formed in low-energy depositional environments have poorer physical properties. Microbialite structures significantly influence pore types and structures. Deep dissolution mechanisms include hydrothermal activity, thermochemical sulfate reduction, and dedolomitization. This study is of great significance for those concerned with the exploration potential of deep dolostone reservoirs.

Key words:  Deep burial, dolostone reservoir, sedimentary environment, diagenesis, microbialite