ADVERTISEMENT

Instantaneous 4D Seismic Used to Monitor Offshore Water-Injector Wells

In this paper, the authors propose a new method for time-lapse-seismic surveys focused on water-injector wells. The “instantaneous 4D” (i4D) method aims to acquire dedicated high-quality 4D data with a short turnaround time at cost levels low enough to make it affordable to repeat such data-acquisition programs reasonably frequently. We have implemented the method as a variation on surveys that use ocean-bottom seismometers. We suspect that our method can also be combined with other means of seismic-data acquisition (for example, permanent reservoir-monitoring systems and vertical-seismic-profiling systems in wells).

Introduction

Time-lapse, or 4D, seismic is frequently used offshore to monitor fluid-movement processes such as waterflood or aquifer drive. These processes happen at relatively slow time scales (years). As a result, proper monitoring of these effects requires repeat surveys to be acquired every 3 to 5 years or so.

Recent examples in industry show that fast reservoir changes (months) also are taking place. The observed changes are often associated with water-injector wells. For example, one water-injection well documented in the literature produced large time-lapse signals in less than 1 year after its startup. Because of cost and other considerations, it is not feasible to repeat fieldwide 4D surveys often, nor to install permanent monitoring systems in many of those fields. Yet there is a need to monitor such phenomena more frequently and with short reaction times. This is where the authors believe that the i4D method can play an important role.

This method is not intended to replace full-field surveys. Rather, it adds small surveys more frequently in between regular full-field surveys to enable better observation of fast 4D reservoir effects along with slow changes. It can be seen as filling the gap between the current practice of infrequent full-field surveys and the installation of permanent reservoir-monitoring systems, which can be expensive.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 16901, “Instantaneous 4D (i4D) Seismic: An Innovative Concept To Monitor Offshore Water-Injector Wells,” by J.G.F. Stammeijer, M. Davidson, P.J. Hatchell, and J.L. Lopez, Shell, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26–28 March. The paper has not been peer reviewed. Copyright 2013 International Petroleum Technology Conference. Reproduced by permission.
...
This article is reserved for SPE members and JPT subscribers.
If you would like to continue reading,
please Sign In, JOIN SPE or Subscribe to JPT

Instantaneous 4D Seismic Used to Monitor Offshore Water-Injector Wells

01 March 2014

Volume: 66 | Issue: 3

ADVERTISEMENT