Summary
The formation of mineral scale (carbonate/sulfate/sulfide) within the near
wellbore, production tubing, and topside process equipment has presented a
challenge to the oil and gas industry for more than 50 years. Chemical methods
to control scale have been developed including scale squeeze treatments and
continual chemical injection. A key factor in the success of such treatments is
the understanding of chemical placement and the effectiveness of the treatment
chemicals. Evaluation of residual chemical concentration and scaling ion
chemistry have long been used in monitoring programs, and more recently, probes
have been developed that increase the rate of evaluation/interpretation. All
these methods prove that the chemical is present in the brine when sampled or
that scale formation is not occurring at the point of brine analysis.
Evaluation of suspended solids in terms of amount, mineral type, composition,
and texture has been used along with brine chemistry to improve our
understanding of the location of scale formation within production
environments. This paper outlines the experimental methods developed and will
cite examples from the North Sea of the use of suspended solids analysis by
environmental scanning electron microscopy (ESEM) and the associated brine
chemistry to evaluate the scale risk within the produced brine. The combination
of these methods has improved integrated scale management in terms of
evaluating scale squeeze placement effectiveness, squeeze lifetime, and topside
scale-control challenges vs. separation problems.
The publication of this method with clear examples of the value it can bring
to an integrated scale-management program for a field throughout its life cycle
will benefit both emerging deepwater operations (evaluation of placement) and
more established oilfield operations (reducing chemical costs).
Introduction
The development of subsea facilities (many with horizontal production wells)
to improve the economics of marginal oilfield developments has focused
attention on the need to monitor the performance of scale-control programs
applied both downhole and to flowlines. The following short section outlines
some of the monitoring methods used to date that can assist in the development
of a continuous improvement loop that is part of an integrated scalemanagement
program. An example of such a management program is presented in Fig.
1.
Scale-Inhibitor Monitoring Methods
Scale-Inhibitor-Performance Monitoring. Historically, the methods of
monitoring the performance of a scale-inhibitor program have relied on the
analysis of chemical residual and scaling ion concentration. More recently, the
development of real-time monitoring has taken the management of such programs
to a new level. Results are presented in the following sections that show that
an understanding of the types of scale present (and their textures within
produced fluids by means of ESEM) adds an extra dimension to the understanding
of scale management for downhole and topside applications.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
1 December 2004
- Revised manuscript received:
25 July 2005
- Manuscript approved:
2 August 2005
- Version of record:
20 February 2006
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