Deepwater Reservoir Compartmentalization: Causes, Impacts on Production, and Methods of Identification
Authors: Chen Jiajie 
Published: May 2013

Deepwater reservoir compartmentalization is a critical issue that significantly impacts total and recoverable reserves. In any deepwater turbidite development projects, insufficient assessment of the compartmentalization issue results in unexpected disappointment about the productivity of the reservoirs, reducing the economic effects of the projects. The reverse impact does not only limit to reserve estimate, but also to surface facility and infrastructure planning, which creates further uncertainties for the projects. The main causes of reservoir compartmentalization are faulting and lateral stratigraphic pinch out, although diagenesis, geochemical variation, non-turbidite events such as slump or mass transport complexes, and facies alteration within a specific depositional sequence will also result in disconnectivities in the reservoir zones. An integrated approach must be applied to tackle reservoir compartmentalization issues. Available geosciences and reservoir engineer data should be checked with consistency and be utilized in a highly interacting manner. A structural analysis must be performed to understand the pattern of fault blocks and their sealing capabilities. A solid depositional model must be built to illustrate the distribution of reservoir compartments developed due to different depositional episodes and facies variation. Fluid fingerprinting and other geochemical data should be collected and analyzed to provide an independent evaluation on the connectivity of the reservoir. Finally, different types of geological and engineering data, such as core, log, seismic, pressure, and biostratigraphic analysis, must be integrated to achieve a synergy in order to understand the formation and development of reservoir compartmentalizations. Based on this integrated approach we conclude that, deepwater reservoir compartmentalization issue can be adequately identified, distribution of different compartments can be predicted with a robust structural and depositional model, and effective field development concepts can be formulated through multi-discipline integrated analyses.

Introduction

Reservoir compartmentalization refers to " the segregation of a petroleum accumulation into a number of individual fluid/pressure compartments - occurs when flow is prevented across ‘sealed’ boundaries in the reservoir?? (Jolly et al., 2010). There are two major types of boundaries, ‘static seals’ that are completely sealed and capable of withholding (trapping) petroleum columns over geological time, and ‘dynamic seals’ that are low to very low permeability flow baffles that reduce petroleum crossflow to infinitesimally slow rates (Jolly et al., 2010).

Reservoir compartmentalization is a critical issue impacting the total and recoverable reserves, in any deepwater reservoir development project (Smalley and Muggeridge, 2010). In many cases, both total and ultimate recoverable reserves reduce significantly during the entire value chain from discovery, appraisal and evaluation, project sanction, to post drill and production, accompanying the increasing in data and knowledge acquired, and the increase of abilities to recognize multi-reservoir compartments.