Practical Guidelines for the Diagnosis and Remediation of Pipeline Blockages

Practical Guidelines for the Diagnosis and Remediation of Pipeline Blockages

One of the primary flow assurance challenges in the production of hydrocarbons is the prevention of pipeline blockages. Blockages can occur from a combination of improper system design, improper selection of piping and insulation materials, production chemistry aspects, inadequate or improper commissioning, startup and operating procedures, deviation from the proven operating procedures, changes in the operating conditions, intervention operations and improper maintenance procedures. The nature of the blockages can vary from "not-so-severe" to "hard-to-remediate" depending on the type of blockage.

OTC-26007-MS Top of Line Corrosion: An Evaluation of Critical Parameters that Drive Mitigation Methods and System Design in Deepwater Gas Systems

Top of Line Corrosion (TOLC) occurs in deepwater wet gas systems when water vapor condenses on the upper internal walls of the flowline due to the heat exchange occurring between the hot fluid and the colder environment. The condensed liquid becomes enriched by the corrosive species naturally present in the gas stream and assumes a low pH because it does not contain any buffering species such as bicarbonate or iron. The predominant concern is carbon dioxide (CO2), which reacts with water to form carbonic acid (H2CO3), although hydrogen sulfide (H2S) and organic acids can also present significant challenges and drive the corrosion process.

SPE-173544-MS Risk Assessment in HAZOPs

A HAZOP is a team-based process hazard analysis (PHA) method. Its purpose is to identify hazards and operability issues in a process design. In some HAZOPs, identified issues are evaluated for risk. An effective risk assessment method allows the HAZOP participants and the project team to focus their time and energy on the more significant hazards.

Risk assessments in HAZOPs are typically performed using a simple risk matrix (Figure 2). In the risk matrix approach, participants make judgments as to the potential severity and the likelihood of an event. The combination of severity and likelihood indicates the risk. The risk matrix will often be color coded with green areas (OK), red areas (Unacceptable) and yellow areas (improvement suggested, subject to ALARP).

SPE-170824-MS Standard Operating Procedures (SOPs) as a Catalyst for Culture Change

Standard Operating Procedures (SOPs) for oil and gas production facilities are typically written by teams of subject matter experts including at least process engineers and experienced operators.  The team is tasked with identifying the most effective ways to operate the facility (based on safety, environmental protection and economic measures).  Operating the facility consistently in accordance with the SOPs should yield considerable benefits.

Yet, despite their obvious importance, often relatively little effort goes into SOP development and use.

SOPs are frequently developed late in the project, after the design is completed and construction is well underway.  They may be used for little other than operator training.  Following the initial facility startup, they may even end up on a shelf collecting dust.  In this environment SOPs have little influence on either the design or the operation of the facility. 

SPE-169633-MS A Selection Methodology for 13Cr-Type Alloy Oil Country Tubular Goods

Significant interest exists in the deployment of 13Cr martensitic stainless steels in offshore oil and gas projects. Several grades of 13Cr exist, with the seemingly negligible variations between their chemistries and fabrication processes. The different grades perform dramatically differently, especially regarding cracking resistance in sour or chloride-containing environments. Determination of the proper 13Cr grade for sour service involves the investigation of domain diagrams, and often requires further fitness-for-service testing. However, the validity of each domain diagram for only one chloride concentration or content greatly limits their practicality for selecting 13Cr, thus impeding the ability to determining if fitness-for-service testing should be performed and its potential outcome. 

SPE 147205 - Materials Selection: A Systems Engineering Approach

2011 Abstract, Eric Caldwell, Karthik Annadorai, Grant Gibson, Lee Jordan

Subsea and topsides materials selection is becoming a vital part in the development and long term sustainability of deepwater oil and gas production facilities. Increasing challenges associated with capital and operating cost constraints, schedule compression, remote locations, and the need to deploy materials ever closer to their known limits makes fit for purpose materials selection a complex and difficult issue that crosses many different discipline boundaries. Materials selection is primarily governed by corrosion engineering principles and applied chemical inhibition practices, and then by project specifics. However, there are two different practices that are generally followed that dictate how materials are ultimately selected. The first is by a standard materials selection process using guidance such as that provided in NORSOK M-001, and the second is by using a more informal system with limited guidance that involves individually selecting materials for a specific project.

 In actuality, the materials selection process is a combination of both. The selection process to identify which materials are considered appropriate is routine and straightforward and is dictated by various corrosion parameters and associated risks. Often this high-level assessment does not appropriately address project specifics, so causing the final material selections to be substantially different from those initially proposed.

One of the specific items that often drives this change in materials selection philosophy is the use of chemical inhibitors for corrosion inhibition and the perceived feasibility and level of risk associated with this. Use of a systems engineering approach to material selection can be used beneficially as a process that accelerates the determination and initial optimization of the materials, and the selection of chemicals and their injection locations, and associated monitoring methods and locations in a given topsides, subsea or water injection system design.

Source: SPE Annual Technical Conference and Exhibition, 30 October-2 November 2011, Denver, Colorado, USA

Copyright 2011. Society of Petroleum Engineers

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SPE 147552 - Integrated Field Optimization Strategy Applied to an Offshore Water Injection Project

2011 Abstract, F.R. Chaban, SPE, L.C. Jordan, SPE, and K.M. Annadorai, SPE, Gibson Applied Technology and Engineering; T.W. Wilkinson, SPE, and P. Myers, Energy XXI

 Some of the most significant challenges faced with respect to the management of offshore water injection projects are associated with maintaining injectivity into the reservoir and with handling H2S produced due to reservoir souring. This paper presents the process followed and findings generated by a comprehensive review of a mature water injection project performed with the goal of delivering a coordinated operating strategy that would maximize the life of field revenues associated with water injection.

An integrated and comprehensive field optimization approach to maximize the whole-life value of the total asset was undertaken. Aspects covered included water injection system operating practices, mechanical design and integrity management of the injection system, the chemical treatment program followed for both the injection and production streams, and reservoir modeling and production management.

Recommendations resulting from this review were prioritized based on their impact on the whole-life performance of the asset, rather than the more common practice of separating the injection and production system reviews or the assessments of reservoir management and facility operation. Areas of particular benefit were identified in association with implementation of an active souring control strategy to reduce future risks to the production system metallurgy by sulfide stress cracking (SSC), a focus on integrity management of the water injection system to maximize long-term system availability, and the implementation of an inter-well water tracer injection program to enable the validation of current reservoir models and support the placement of future injectors and producers.

Source: SPE Annual Technical Conference and Exhibition, 30 October-2 November 2011, Denver, Colorado, USA

Copyright 2011. Society of Petroleum Engineers

SPE 141982 - Stream-based HAZOP - A More Effective HAZOP Method

Abstract 2011, H.J. Duhon

The Hazard and Operability Study (HAZOP) is probably the most commonly applied process hazard analysis method. As such, HAZOPs are a very important tool for improvement of process safety. But HAZOPs are not as effective as they should be. Duhon and Sutton (SPE 120735, 2010) identified many reasons why we don’t learn all we should from HAZOPs. These insights suggest a path towards a more effective HAZOP process.

The process described here differs from the standard HAZOP process in several important ways. The most important difference is the definition of stream-based nodes rather than equipment-based nodes. In a stream-based node, a stream is followed from its inception to its logical conclusion. This is especially useful when considering flow deviations, because a flow disruption in any part of the stream affects all parts or at least all downstream parts of the stream. These stream-based nodes are much larger than typical equipment-based nodes and hence overcome the tendency of HAZOPs to create tunnel vision.

HAZOPs are supposed to evaluate operability, but that can’t be done effectively without reviewing the operating procedures or at least discussing how the system will be operated. There is no point in a typical HAZOP, because small nodes are selected, in which the procedures can be effectively introduced. Stream-based nodes provide a natural bridge to the procedures. High level operating procedures can be introduced during the stream-based node discussion providing an opportunity to do a Process HAZOP and a Procedure HAZOP simultaneously. A Procedure HAZOP often provides more insight than the Process HAZOP.

Source: SPE Americas E&P Health, Safety, Security, and Environmental Conference, 21-23 March 2011, Houston, Texas, USA

Copyright 2011. Society of Petroleum Engineers

NACE 11099 - Further Analysis On M13Cr-110 NACE TM0177 Method A Test Acceptability Prediction

2011 Abstract, Eric Caldwell, Grant Gibson, Lee Jordan

Martensitic stainless steels continue to be one of the most widely used corrosion resistant alloys in oil and gas developments. Determining if a martensitic stainless steel is acceptable in an unproven environment requires testing to confirm, but predicting the outcome of a given test environment is often initially based on personal experience rather than a qualitative and quantitative assessment. An empirical method for improving the predictability of NACE TM0177 Method A Tensile tests on modified 13Cr 110ksi grade martensitic stainless steels based on an H2S/Chloride/pH function has previously been developed based on published data in order to address this uncertainty. The environments considered by this function are only limited by the capabilities of the NACE TM0177 Method A test, and provide a method for rapidly estimating if a M13Cr 110ksi grade should pass or fail in multiple different environments. As a follow-on to the development of this empirical method, data points from new tests were used to check the general predictability of the H2S/Chloride/pH function. The general function was modified due to the addition of the new data, and subsequently checked again against a separate set of data. The nature and implications of these findings are discussed and conclusions drawn regarding the performance and value of the methodology for the evaluation of future materials applications.

Source: CORROSION 2011, March 13 - 17, 2011 , Houston, Texas

Copyright 2011. NACE International

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NACE-11346 Dealing With Uncertainty - Impact Of Scaling Prediction On Concept Selection For Deepwater Production Systems

Concept selection and initial design of deepwater subsea production systems can have a profound impact on the evaluation of the commercial viability of a discovery. Although detailed design comes later in the process, the decisions made at this early stage of a project will generally provide the template that is carried through to construction and operation. Scale management can be a significant factor in deciding the outcome of the concept selection phase, particularly for fields that are expected to require seawater injection at some stage in their design life. Early in a project it is common to have information from only one or two exploration wells and where water samples are often not available, are heavily contaminated, or have been gathered from locations away from the main production targets. 

SPE 123790 - Planning and Procedures for the Initial Startup of Subsea Production Systems

2010 Summary, H.J. Duhon, J.L. Garduno, and N.A. Robinson, GATE

Projects progress through phases of design, construction, installation, commissioning, initial startup, and operations. This paper addresses issues that arise at initial startup. Initial startup is defined here as the period when reservoir hydrocarbons are produced for the first time.

Initial startup of a subsea development is one of the most challenging periods in the operational life of the facility. Many issues complicate this period, including

People issues. Many people from many teams are required to execute a startup; roles and responsibilities may be unclear and will change over the course of the startup; persons-onboard (POB) issues limit the number of people who can participate; personnel involved may not be fully trained in the operation of the facility.

This will be the first time much or all of the equipment is used in live hydrocarbon service. Design flaws, commissioning omissions, and infant mortalities will reveal themselves.

Preserving completion integrity requires low rates and slow bean-ups during initial startup because of high formation skin. Chokes designed for high rates and low pressure drops may not be capable of controlling the well at low rates. Also, topside systems designed for peak rates may not function well at low flow rates.

Low flow rates and low initial temperatures result in hydrate risk, which may challenge the flow-assurance strategy.

Completion and stimulation fluids returned during the initial well cleanup are corrosive and are difficult to treat. Typically, specialized water-treatment equipment is installed temporarily at topside to treat these fluids. The flowback fluids may also contain solids from the reservoir and from construction debris that may cause problems such as plugging small ports in control valves.

Source: SPE Projects, Facilities & Construction, Volume 5, Number 4, December  2010

Copyright 2010. Society of Petroleum Engineers

SPE 120735 - Why We Don't Learn All We Should From HAZOPs

2010 Summary, Howard J. Duhon, SPE, GATE, and Ian Sutton, AMEC Paragon

During the last 15 years, the process industries have made dramatic improvements in occupational safety. Recordable injury rates have dropped by close to an order of magnitude (Pitlblado 2008). Accurate information pertaining to progress in process safety in the same time period is not available. However, it is likely that improvements in process safety are not nearly so great (Sutton 2010).

From its beginnings in the late 1980s and early 1990s, hazards analysis has been a key item in all process safety programs. After all, if hazards are not identified, they cannot be remediated. Of the various hazards-analysis techniques, the Hazard and Operability Method (HAZOP) has probably gained the greatest acceptance. Therefore, if the process industries are to achieve the same levels of success in process safety as they have in occupational-safety improvements, the effective use of HAZOPs is probably going to be of central importance.

This paper discusses some of the cognitive, social, organizational, and procedural factors that limit the effectiveness of projects in general and of HAZOPs in particular. From this discussion, insights can be developed that can provide ideas for improving the HAZOP process and process-safety-management systems in general.

Source: SPE Projects, Facilities & Construction, Volume 5, Number 2, June  2010


SPE 125785 - Effect of THPS on Discharge Water Quality: A Lessons Learned Study

2010 Abstract, Karthik Annadorai, SPE; Adam Darwin, GATE, LLC

Biocides typically have an adverse impact on overboard water. THPS (tetrakishydroxymethyl phosphonium sulfate), one of the most commonly used biocides offshore has a similar effect on produced water. The effect of THPS on seawater used for hydrotesting and bulk storage is seldom studied and rarely documented. The effect of temperature, pH, water depth, dissolved oxygen concentration and various ions in the system is important to note. Once a certain volume of water is treated with any chemical, it is now deemed to be chemically treated seawater which cannot be discharged unless verified using the NOEC (No Observable Effect Concentration) testing method.

This experience will provide a detailed understanding of the discharge of chemically treated seawater as well as the interaction of THPS with potential ions in the matrix. Additionally, regular sampling and associated analyses will be presented that demonstrate the degradation and half-life of the THPS molecule in varying temperatures.

Periodic sampling of the THPS chemical in the seawater has provided a detailed understanding of the half-life degradation of the chemical. The interaction of the chemical with the cations present in the system and subsequent aversion to the neutralization reaction with hydrogen peroxide has also been studied and presented.

Source: SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production, 12-14 April 2010, Rio de Janeiro, Brazil

Copyright 2010. Society of Petroleum Engineers

NACE 10401 - Prevention Of Corrosion In Carbon Steel Pipelines Containing Hydrotest Water - An Overview

2010 Abstract, Adam Darwin, Karthik Annadorai, Gibson Applied Technology and Engineering, LLC; Krista Heidersbach, Chevron Energy Technology Center

A critical step in proving a pipeline is fit for operational use is the hydrostatic test, in which it is filled with water and pressurized to 125% of its Maximum Allowable Operating Pressure (MAOP). The water that is used in this testing can cause corrosion of the pipe, potentially leading to failure early in its operating life. Failures have occasionally been reported even before a pipeline enters service.

The most common mechanisms by which carbon steel pipelines may undergo corrosion on exposure to hydrotest water are Microbially Induced Corrosion (MIC), oxygen-related corrosion, galvanic corrosion and under-deposit corrosion. An overview of these mechanisms is presented, along with a discussion of the influence of different environmental factors on them. Factors considered include water source, degree of filtration, exposure period and temperature, air pockets, presence of internal pipe coatings and future pipeline service conditions.

Maintaining the risk of pipe corrosion from hydrotest water within acceptable limits is discussed. Factors considered are:

How long the untreated water may be allowed to be present in the pipeline.

Should water treatment be required, what must be used?

Disposal requirements for the treated water, including chemical treatments.

Source: CORROSION 2010, March 14 - 18, 2010 , San Antonio, TX

Copyright 2010. NACE International

SPE 123790 - Planning and Procedures for the Initial Startup of Subsea Production Systems

2009 Abstract, H.J. Duhon, J.L. Garduno, and N.A. Robinson, GATE, LLC

Initial startup of a subsea development is one of the most challenging periods in the operational life of the facility.  Many issues complicate this period.  These include:

  • People issues: a great many people from many teams are required to execute a startup; roles and responsibilities may be unclear and will change over the course of the startup; persons on board (POB) issues limit the number of people who can participate; personnel involved may not be fully trained in the operation of the facility.
  • This will be the first time much or all of the equipment is used in live hydrocarbon service.   Design flaws, commissioning omissions and infant mortalities will rear their heads.
  • Preserving completion integrity requires low rates and slow bean-ups during initial startup because of high formation skin.  Chokes designed for high rates and low pressure drops may not be capable of controlling the well at low rates.  Also, topsides systems designed for peak rates may not function well at low flowrates.
  • Low flowrates and low initial temperatures result in hydrate risk which may challenge the flow assurance strategy.
  • Completion and stimulation fluids returned during the initial well cleanup are corrosive and are difficult to treat.  Specialized water treatment equipment is typically installed temporarily on topsides to treat these fluids.

Source: SPE Annual Technical Conference and Exhibition, 4-7 October 2009, New Orleans, Louisiana

Copyright 2009. Society of Petroleum Engineers

SPE 124857 - A Unified, Multidisciplinary Approach to the Planning and Design of Deepwater Waterflooding Projects

2009 Abstract, Fady R. Chaban, SPE, GATE LLC; Mukul M. Sharma, SPE, and Ajay Suri, SPE, University of Texas at Austin; and Grant Gibson, SPE, GATE LLC

 Today and in the future many of the deepwater projects in the Gulf of Mexico and elsewhere around the world will be producing under waterflooding conditions to increase hydrocarbon recovery and support reservoir pressure. The success of the water injection program is critical to the overall project economics. As such a clear methodology, workflow and attention to detail are needed in the planning, design and implementation of these projects.

This paper presents an integrated and practical approach for implementation at the Front End Engineering Design (FEED) stage of a project to optimize the future field development strategy, injectors design, facilities planning, and to maximize the total value of the asset. The proposed method efficiently interconnect elements related to surface facilities, topsides process, subsea architecture, subsurface equipment, water quality, well completion, down-hole flow controls and target injection rates in a common context.

Source: SPE Annual Technical Conference and Exhibition, 4-7 October 2009, New Orleans, Louisiana

Copyright 2009. Society of Petrolem Engineers

SPE 110211 - Why It Is Difficult To Learn Lessons: Insights from Decision Theory and Cognitive Science

2008 Summary, H.J. Duhon, SPE, and J.S. Elias, Gibson Applied Technology and Engineering

Though engineers and managers routinely express the desire to learn from previous project experience, we typically do not learn effectively from our projects. The failure to learn valid and valuable lessons from project experiences can be attributed to a number of cognitive and social factors.

Fortunately, a great deal of literature in the fields of decision theory and cognitive science is relevant to the subject. Unfortunately, much of this literature is unknown to most practicing engineers. This paper presents a structured method for identifying learning limits, an introduction to current thinking in areas of knowledge required to implement the method, a summary of the results of applying of the method, and suggestions for improving our ability to learn from project experiences.

Source: SPE Projects, Facilities & Construction, Volume 3, Number 3, September  2008

Copyright 2008. Society of Petroleum Engineers

SPE 110205 - Successful Application of Chemical Injection Rate Control Valves

2007 Abstract, H.J. Duhon, SPE, and K.M. Annadorai, SPE, Gibson Applied Technology and Engineering

This paper presents an overview of a systems approach to the design and troubleshooting of IRCVs (Injection Rate Control Valves) used in deepwater chemical injection systems.  The inherent problems associated with these simple flow regulators stem largely from the failure of design engineers to take a systems view in design.  Along with the application of lessons learned from previous IRCV system failures, this systems approach provides a design method which will allow users to avoid many of the pitfalls inherent in design, installation, testing, commissioning and operation of IRCV systems.

Source: SPE Annual Technical Conference and Exhibition, 11-14 November 2007, Anaheim, California, U.S.A.

Copyright 2007. Society of Petroleum Engineers

OTC-18340-MS Waterflood Operability-Process and Chemical Issues

In the last few years, Shell has implemented three deepwater waterflood systems. They are all on floating installations, employ relatively compact and light weight facility designs and are roughly the same capacity. While their overall designs are similar, important details of the designs are different, and the project management strategies were significantly different as well. The startup and initial run time experience of these waterfloods facilities differed greatly, ranging from significant downtime for the first project to nearly complete success for the last one. Shell is in the process of sanctioning a forth deepwater waterflood system that is larger and more complex than the previous three. Obviously, Shell has already learned a great deal about how to successfully implement a deepwater waterflood project. Before we develop the new project however, we are capturing our waterflood experience to date. 

NACE 06106 Application of Learnings from the Assessment of Cathodic Protection and Coatings on a Recovered Marine Pipeline End Termination

There is limited data on the performance of coatings, materials and cathodic protection systems installed subsea. Most systems remain submerged for their useful life and are often abandoned on the seabed. The recovery of the hardware provided an opportunity to autopsy the hardware for the purposes of validating cathodic protection designs and coating systems; specifically coating performance, anode consumption, and internal wall thickness allowances.