Integrated Water-Injection Analysis Uses Salinity as Tracer in Giant Brownfield
Authors: Wilson Adam 
Published: December 2017

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 185872, “Integrated Water-Injection Analysis for a Giant Brownfield,” by A. Ortega, S. Renna, G. Fanello, C. Callegaro, SPE, and I. Bergamo, SPE, Eni, and O.  Yehia, SPE, Petrobel, prepared for the 2017 EAGE Annual Conference and Exhibition/SPE Europec, Paris, 12–15 June. The paper has not been peer reviewed.

When dealing with giant brownfields, a systematic approach is mandatory to succeed

in identifying the main production mechanisms amid the geological and dynamic complexity of the reservoir. In this paper, an integrated work flow is proposed for brownfields where oil production is driven mainly by water injection. Produced-water salinity plays a key role, acting as a natural tracer and, thus, helping avoid additional costs for new data acquisition.

Introduction

Production-data analysis (PDA) is a well-known method of investigating field performance. Nevertheless, its application in a giant brownfield can be difficult. Analysis can be very complex and time-consuming because of the large quantity of data and data heterogeneity and reliability, especially if the data are gathered through different monitoring systems and technologies.

Considering this, a systematic integrated work flow has been developed that focuses on brownfields where water injection has played a key role in oil production.

The work flow allows a comprehensive analysis of the water injection through the following steps:

Identification of injector/producer connections

Fluid-path conceptual models

Evaluation of the current water-injection efficiency

Water-injection optimization

Phase 1, which includes the first two steps, is based mainly on advanced PDA. Integrated analysis of production, pressure, and salinity data allows for the detection of the evolution of injector/producer connections. The main fluid paths in the field then are identified and used to drive and integrate the geological knowledge of the field. The result is a more-robust 3D model, representative of the main highlighted production mechanisms.

Phase 2, which includes the third and fourth steps, instead is driven by streamline analysis traced on the dynamic model, which allows for the evaluation of the efficiency of the current water- injection strategy. Water injection then is optimized on the basis of a redistribution of the injection rates, promoting the most-efficient connections to the detriment of the least efficient. The consequent modification of the water paths allows for contact with new, unswept areas, leading to an increase in oil recovery with limited investments.

This paper shows the application of the work flow in the context of a wider brownfield-rejuvenation project. In particular, the paper is focused on the setup of easy-to-understand conceptual models and considers how they drive geological evaluations (e.g., faults, layering, contacts) in the realization of a new 3D model. A dynamic model able to reproduce the events since the preliminary history matching confirms the validity of the approach.