Water Injection Profile Modification In a Layered Reservoir Using Polymer Treatment
Authors: El-Hadidi S.M. , Falade G.K. , Dabbouk C. , Al-Ansari F. 
Published: December 2007

S.M. El-Hadidi, Abu Dhabi National Oil Company (ADNOC); G.K. Falade, C. Dabbouk, and F. Al-Ansari, Zakum Development Company (ZADCO); Abu Dhabi U.A.E. SPE Members

The main focus of this paper is the applications of polymer treatment in controlling injectivity profiles and the improvement of the conformance of the near-wellbore injection profiles. Reservoir high permeability zones causing distortions of water injection profiles at the wellbore, and the possible existence of layer barriers were identified using conventional investigation tools such as Open Hole Logs, Production Logging Tools, Formation and Micro Scanners.

A polymer screening procedure was put in place so that appropriate polymer formulations for use as agents for reducing fluid mobility in the high permeability zones at the wellbore can be identified. The use of these polymer formulations facilitated the improvement of near-wellbore conformance of injectivity profiles.

The field performance of the polymer treatment program was ascertained by using a monitoring program which combined the application of the Production Logging Tools with well test analyses.

Introduction

The presence of high permeability streaks and fractures is a common occurrence in stratified carbonate reservoirs. If these reservoirs are subjected to patterned water-flooding operations, it is not uncommon for the highly permeable zones to accept most, if not all, of the water injected. This tends to distort the injectivity profile at the wellbore, and raises the possibility of an eventual poor reservoir coverage and sweep efficiency. Therefore, a successful water-flood project necessarily demands a clear understanding of reservoir characteristics with a view to identifying the incidence of high permeability streaks, channels, and layer barriers, so that adequate remedial actions that can reduce their adverse effects on water-flood performance can be put in place. One of such remedial actions which have gained prominence in the recent past, is the use of Polymer and Non-polymer agent for injection/Production wellbore profile modification.

In this paper, we present the screening, monitoring and evaluation procedures for a successful application of a cross-linked polymer formulation on water injection wells in order to improve the wellbore conformance of injectivity profiles.

Background History

The reservoir under consideration is a mature reservoir under five spot patterned water injection. The injection pattern size has been under continual modification by implementing a carefully planned program of infill drilling and conversion of some original producers to injectors. This progressive review of pattern size has reduced the distance of producers to injectors from an original value of 2.8 km to a current value of about 1.4 km. Simulation studies indicated that water production from this reservoir is not expected to start before 2010. However, it has been observed that some of the producing wells have started experiencing premature water breakthrough. Analysis of produced water confirmed that water being produced by these wells comes largely from injected sea water.

Field wide investigation as to the cause(s) of premature water breakthrough in some wells was initiated. These investigations involved a complete reevaluation of all available open- and cased-hole logs of all producers and the neighboring injectors within the pattern in which premature water breakthrough has been observed. In addition to the newly acquired data, special consideration was given to PLT logs, particularly newly acquired PLT, Dynamic Testing, Pulse Neutron Logs and Core data from in-fill drillings. This data acquisition program was designed to correlate injection profiles of the various water injection wells in the reservoir.

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