Subsurface Faults Permeability study: Utilization of production data in an exploratory phase, Njord field Heltan Terrace Norwegian Continental Shelf (NCS)

Abstract

Faults in the subsurface can either aid or block fluid movement based on rock permeability. Analytical techniques measure fault seal capacity for hydrocarbon exploration and carbon capture and storage (CCS) planning. Fault rock, influenced by composition and fluid properties, forms a low-permeability matrix during fault movement. In sand-shale sequences, clay-rich smears signify sealing fault rocks, while quartz cementation at high temperatures or depths decreases porosity, strengthening their sealing potential. The importance and complexity of the fault zone paradigm is the root cause of this study.

To this end, this thesis is an effort to test available analytical techniques for fault seal estimation and calibrating pressure data measurements acquired during the production phase. The motivation for this work is to build the applicability of production data for fault seal analysis during the exploration phase in similar geological settings. This study processes the SGR-based and Depth-based fault seal estimation methods with the reservoir simulation models which consist of pressure and production information. The study area for the thesis is the Njord asset Operated by Equinor AS, and partnered by Wintershall DEA Norge, and Neptune Energy. Njord field was discovered in 1986 and commencement of production started in 1997. This is a long production history, and it gives a comprehensive amount of data that enables us to carry out this study. The computer language “Python” is used to arrange, sort, clean, and analyze data. while some Commercial software’s RMS, PETREL-ECLIPSE are used for static and dynamic modeling just to be aligned with the industry standard practices.

The biggest challenge during this study was to address the uncertainties in situ with the geological model and make this data suitable for our analysis. A new approach proposed in this study to evaluate the fault permeability multiplier with geological parameters is successfully tested. A data-driven suggestion to improve the fault seal modeling Job for commercial software is also proposed as a result of this study. The main results from the investigations carried out during this study show that the fault permeability reduces with increasing depth and that the importance of SGR on fault permeability may have been overemphasized at Njord field, NCS. A new approach to analyzing fault seal multiplier works and Systematic trends have been seen in the data. These results imply that the approach of using multipliers to determine permeability functions should be tested elsewhere, to improve general fault permeability predictions.