Novel Brownfield-Rejuvenation Approach Uses Near-Wellbore-Saturation Monitoring
Authors: Wilson Adam 
Published: December 2017

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 187345, “A Novel Approach To Rejuvenate a Brownfield by Validating Dynamic-Model Response With Near-Wellbore-Saturation Monitoring,” by Shubham Mishra, SPE, Karthik Kumar Natarajan, SPE, Akshay Aggarwal, SPE, Aditya Ojha, SPE, Alexander Rincon, SPE, Isha Khambra, SPE, Ajit Kumar, SPE, and Gaurav Agrawal, SPE, Schlumberger, and Pankaj Kakoty, SPE, Neelimoy Baruah, and Sanjay Kumar Dhiraj, SPE, Oil India Limited, prepared for the 2017 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 9–11 October. The paper has not been peer reviewed.

Fields in the Upper Assam-Arakan Basin have been studied intensely to find prospective sweet spots, perforation intervals for new wells, and potential workover candidates. These forecasts, guided only by dynamic-numerical-model results, have had mixed results when implemented in the field. A validation of the dynamic-model forecasts with near-wellbore-saturation logs can help reduce uncertainty. The validation was carried out in old wells, which helped in making informed decisions about tapping bypassed hydrocarbon pockets.

Introduction

An integrated seismic-to-simulation study was conducted on 42 reservoirs in 375 km2 of the Upper Assam Basin. As a result of this study, the overall structural framework, well correlations, and fault mapping have been revised considerably compared with previous interpretations. Previously, the only data available to manage these fields were from paper-based 2D maps, from which some volumes were estimated by use of simplistic techniques. Now, the numerical-model-based approach can provide a better understanding of stock-tank oil initially in place and leftover pockets of oil. A phased field-development plan (FDP) for the next 5–10 years was proposed from this study.

After completion of the FDP study, executing the recommendations in a timely manner was essential and the dynamic model was updated with the production results accordingly. Therefore, a work flow was created to increase the effectiveness of workover activities by incorporating validation with near-wellbore-saturation-log readings.

Workover Planning

Using the dynamic model, the following eight factors were considered for each candidate well before a workover was recommended:

Remaining mobile oil and pressure distribution at the end of history

Performance of offset wells

Quality of history match around the wells

Porosity, permeability, and rock type

Connectivity around the well

Distance from gas/oil contact and free-water level

Location of faults

Hydrocarbon pore volume at the end of the prediction period

A method was implemented to validate the near-wellbore hydrocarbon saturations predicted in the history-matched dynamic model though integration of FDP results with pulsed-neutron-tool-log interpretations for the recommended workover candidates. Perforations were then proposed for the validated intervals. The study also aimed to eliminate preplanned workovers that were not predicted as prospective by the FDP after confirmation with near-wellbore- saturation logs.