Tuesday, April 22, 2014

Kulim KHT Cortest HPHT Autoclave Inhibitor Testing




Traditional HPHT Autoclave designs have been enhanced by the introduction of real-time corrosion measurement instruments and probes, to accurately reproduce the multiphase flowing field conditions of operating pipelines and industrial environments.


Corrosion Measurement
- Early Practices

Shear Stress Measurement
- Effect of Velocity on Corrosion
- Laminar Flow Studies

Corrosion Modeling
- Multiphase Studies Accelerated

Pipeline Integrity

Automated Inhibitor Injection (A.I.I.)
- “Feedback” Chemical Pump Control

Key Words:     Corrosion monitoring, new, rapid technique, LPR, ER, field trial results, corrosion rate measurement, corrosion probe, high velocity, corrosion inhibitor, chemical inhibitor, high shear, flow loop, multiphase, jet impingement, rotating cylinder electrode, oilfield, pipeline, pipeline integrity, rotating cylinder autoclave, system’s design, wet gas


INTRODUCTION

This paper is intended to update the knowledgeable reader, as well as inform the uninitiated with a basic overview of modern corrosion testing laboratory equipment and field instrumentation. It is only intended as a starting point and is in no way to be construed as comprehensive.

Perusing Internet advertising is not a substitute for rigorous investigation of corrosion measurement equipment suppliers. Manufacturers must also be involved in day to day scientific corrosion studies, as well as R&D toward new products and faster results.

A catalog “bomb” may allow an end user results found similar to those in 1939, but today’s competitive global marketplace for produced finished products requires real-time corrosion monitoring and control, all the way from the geological formation up to and past the point of custody transfer.

Corrosion Measurement
For many decades’ production and pipeline operators used simple corrosion coupons as an intermittent corrosion weight loss measurement. NACE, ASTM and others made exhaustive attempts to upgrade the method, Conducting Corrosion Coupon Tests in Plant Equipment, ASTM G4-84 originating (A224-39) in 1939.

Additional test methods were developed by NACE and others, as example TM01-77-96, Laboratory Testing of Metals for Resistance to Sulfide Stress Corrosion Cracking in H2S Environments. The standard addressed “the testing of metals for resistance to cracking failure under combined action of tensile stress and corrosion in aqueous environments containing Hydrogen Sulfide (H2S)”.

Shear Stress Measurement
The 1995 NACE Publication 5A195 State Of-The-Art on Controlled Flow Laboratory Corrosion Tests was a “compilation of experimental techniques intended to provide the most up to date information available at the time on evaluating the effect of velocity on corrosion”, called Shear Stress. Included in NACE #5A195 (but not limited to) were the contents:

-          Interpretation of Lab Measurements
-          Philosophy Behind Experimental Design
-          Experimental Systems
-          References
-          Appendix B Governing Equations:
-          Rotating Disk
-          Rotating Cylinder
-          Impingement Jet
-          Flow-Loop System

In 1996 NACE Publication #1D196 Laboratory Test Methods for Evaluating Oilfield Corrosion Inhibitors, coupled the above NACE #5A195 with the effects of chemical inhibitor applications under multiphase flow controlled test equipment for lab simulations.

During recent decades, ER/LPR became viable techniques adapted from lab studies and applied in the form of probes and instruments developed for long-term field studies.

Modern electronic components and high speed data acquisition evolution allowed a more rapid response corrosion rate measurement to be made in real time. Trade named MICROCOR*, the new probe/instrument system could be used to make measurements not only in electrolytic, but in non-conductive gas environments as well. The rapid response/Microcor Systems have been readily accepted by the corrosion community as touted in NACE Papers 1997 #288 A Critical Comparison of Corrosion Monitoring Techniques in Industrial Applications, and later in NACE 2000 #00090 Field Trial Results of a New Rapid Corrosion Monitoring System. 

Corrosion  Modeling
Multiphase Flow Regimes Simulation studies became more important around the 1960’s and evolved (1980s to 1990s) into modern laboratory test equipment assemblies. As example, Corrosion in Multiphase Systems Center (Ohio University) and Multiphase Interactive Systems & Technologies, Inc., Orlando, Florida, built full-scale loops and tilt-up sections were brought on-line around 1993. NACE 2000 Paper #00070 Corrosion Inhibition of Wet Gas Pipelines Under High Gas & Liquid Velocities is a good representative case study of the use of such systems as supported through consulting contracts, which were client sponsored by global operators and producers.

Recently several Universities and industry corrosion laboratories have built large scale Multiphase Flow Loops. As example, NACE 2002 Paper No. 02502 The Design & Development of a Large Scale, Multiphase Flow Loop for the Study of Corrosion in Sour Gas Environments and the 9th Middle East Corrosion Conference proceeding’s papers, including Modeling the Effects of Multiphase Flow on Corrosion in Oil & Gas Production by Prof. P. Jepson, bring focus to the necessity of state-of-the-art laboratory testing equipment and components to make fast and reliable decisions and predictions about corrosion control in multiphase operations.

Pipeline Integrity
Another paper presented by CC Technologies titled “Engineering Challenge of Pipeline Integrity Management” emphasizes the importance of 1. Preserve Pipeline Infrastructure and 2. Pipeline Integrity Management Program. In the CCT summary is the key statement, “to maximize the cost benefit, pipeline integrity management programs must be established that optimize monitoring and inspection on specific pipeline conditions, which are integrated into risk models.”

An interesting reference work from CCT, sponsored by U.S. D.O.T./FHA should also be consulted, which can be easily accessed on the Internet at www.corrosioncost.com. The 733 page compendium, Corrosion Cost and Preventative Strategies in the United States presents a partial view of the global expense due to corrosion, as well as other associated expenses which are not direct corrosion costs, but instead management/measurement and remediation long term higher costs. 

NACE 2000 Paper #00068 Oilfield Corrosion Inhibitor Under Extremely High Shear Conditions by Nalco/Exxon Energy Chemicals emphasizes the importance of “high shear conditions, which must be carefully modeled in lab simulations using a new Jet Impingement test technique supported by a flow loop for accurate experimental control.

With the above developments came faster and easier development and evaluation of anti-corrosion inhibitor chemicals and drag reducing agents. Other lab test methods, such as Rotating Cylinder Electrode (RCE) as found in example NACE 2002 Papers #02286 Corrosion Inhibitor Film Life Studies Using RCE Flow-Through Test and #02497 Reproducibility in Rotating Cylinder Autoclave Testing of Corrosion Inhibitors also make important points about accurate modeling and simulation of field application operating conditions.

Automated Inhibitor Injection
Complimenting the high shear and impingement measurements, new Automated Inhibitor Injection (A.I.I.) systems are in operation since 1998 using the rapid response (Microcor) corrosion rate output signal to determine and control the optimum inhibitor chemical dose rate using variable flow rate inhibitor chemical injection pumps. 
CONCLUSION


Cost of corrosion and its associated long terms costs can be significantly reduced with properly configured laboratory HPHT simulation systems, in combination with the newest state-of-the-art A.I.I. skid installations. The initial cost of these systems is quite small compared to the potential savings in material assets, non-productive downtime, the global environment and personnel safety.

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