New JIP Opportunities with Important Ramifications

New SSC Limits for Sour Service &
Deep Water Offshore Applications

Background

With the development of new, deeper water offshore locations, and the increasing H2S levels of both newer and older reservoirs, special considerations have arisen for material selection relative to sulfide stress cracking (SSC). Many of these completions are operating in water depths that subject materials to combinations of low temperatures down to 5 C and dynamic loading. As higher H2S partial pressures are being encountered from new and existing reservoirs, unresolved questions are being asked regarding resistance to SSC of many commonly used materials. In some cases, industry guidelines as found in NACE MR0175/ISO 15156 have been developed through consensus without verification by testing or evaluation.

Mostly, the concerns are for commonly utilized materials (up to 110 ksi SMYS) such as high strength steels, modified 13Cr, and for materials like 17-4 PH SS, 316 SS, and Monel 400. These later materials are widely used in sweet service, but have not been evaluated for SSC limits to the same degree as newer alloys included in NACE MR0175/ISO 15156 standard. However, as H2S partial pressures increase, tendencies for SSC will likely increase, but experience with the development of the new MR0175/ISO 15156 standard has shown that little data is available from which to develop SSC limits over a range of H2S partial pressure, pH, and temperature.

Problems

Evaluation and selection of materials for sour oil and gas service essentially started in the 1950’s, accelerated in the 1970’s with concerns for deep sour wells, and again in the 1980-90’s with North Sea applications. However, much of this effort has been directed at characterizing the behavior of materials used in onshore wellhead components and downhole tubulars where service temperatures were primarily higher than ambient temperature. In this work, it was found that the susceptibility to SSC generally decreased with increasing temperature over the range of around room temperature to over 125 C. Many of these studies utilize standard test methods conducted at
24 C which seemed to be an appropriate “reasonable worst case” for this type of service.

In limited studies, it was also learned that susceptibility to SSC is actually higher at a temperature somewhat below room temperature. However, there is only inadequate data on SSC of commonly used materials at temperatures below 24 C to develop SSC limits.

Furthermore, evaluations for SSC have been primarily ben conducted under conditions of static load (stress), with threshold stresses determined under this simple loading condition. This type of analysis is fine for designs that are based on primarily static loading. However, many companies utilizing offshore components such as risers and flow lines are using dynamic designs to achieve production from deeper water locations. The role of dynamic loading on threshold behavior has not been adequately examined to provide a rigorous design basis for dynamic designs.

Based on these considerations, three topics for testing and evaluation have been assembled in this proposal.

Program Description

InterCorr is pleased to announce that it has developed a new flexible joint industry program (JIP) format for evaluation of the abovementioned topics. Under this new effort, InterCorr has identified specific focused studies on these topics related to SSC. Each topic will be funded by multiclient support and each will have a fixed scope of work and deliverables which can be completed within a one-year project period (calendar year 2005 running from 1st Quarter through 4th Quarter 2005). Sponsors will have the ability to fund any or all projects identified below.

The JIP projects identified for FY 2005 are defined below:
  • Evaluation of SSC limits per NACE MR0175/ISO 15156 for commonly used materials: 17-4 PH, AISI 316 SS, and Monel K500; included balloting of resultant limits.
  • SSC of carbon steel and modified 13Cr materials at low subsea temperatures vs. commonly used room temperature tests.
  • Evaluation of Cyclic (Non-Fatigue) Loading on SSC Behavior of carbon steel and modified 13Cr materials vs. commonly used static load tests.

A special feature of this program is an option for the sponsors to have additional tests conducted under similar conditions on a proprietary and preferred price basis.

In most cases, alloy selection will focus on generics with alloys selected based on minimum composition and maximum strength considerations.

The details of the three experimental programs and funding levels for each follow:

Project 2005-A – Evaluation of SSC Resistance of “Sweet” Materials in H2S Environments for Development of Ballot Guidelines in MR0175/ISO 15156
The development of MR0175/ISO 15156 has indicated that there is little H2S data on commonly used sweet service materials. This project will provide an engineering data base on 17-4 PH SS, 316 SS, and Monel 400. It will include H2S partial pressure, pH and temperature as variables. The data will be collated and formatted for balloting of exposure limits for these materials.

Experimental Program Details.

Materials:  3 conditions: 17-4 PH SS, 316 SS, Monel K500 (all per NACE MR0175/ISO 15156)

Heats: 3 heats of each material will be selected in the upper range of sour service hardness.

H2S Partial Pressures:  1 condition per material (3.4 to 10 kPa H2S at pH 4.5 for 17-4 PH; 100 to 350 kPa at pH 3.5 for 316 and & Monel K500).

Solution pH:  See above.

Chloride Content: 1 condition (5 to 15 percent).

Temperatures:  3 conditions (23 C to 125 C) as may be required to define performance.

Stress Levels:  1 per condition with triplicate specimens at 90 percent actual yield strength.

Additional Conditions: In order to properly assess SSC limits an additional three conditions (H2S, pH, and/or chloride) will be utilized as required.

Total number of tests: 81 tests.  

Method: NACE TM0177 Method A

Data presentation: tabular data; threshold plots (stress versus time to failure). Ballot items for MR0175/ISO 15156 will be prepared for sponsor review.

Estimated Budget: $54,000

Project 2005-B – Appraisal of SSC at Low Temperature
This study will focus on the development of engineering data to support the use of common materials in subsea applications. It will utilize standard test methodologies and assessment of threshold stresses and KISSC at specific levels of H2S concentration, pH and temperature.  Materials of greatest interest are high strength steels and modified 13Cr alloys used for casing, risers and flow lines. However, the data may have implications for other materials and applications in subsea applications.

Experimental Program Details.

Materials: 4 conditions (API T-95 Type I; AISI 4130-40 (HRC 22max.)  13Cr L-80; and Modified 13Cr-110.

H2S partial pressure: 1 condition for each material type (100 kPa for steels and 10 kPa for Modified 13Cr)

Solution pH: 1 condition for each material type (3.0 for steels and 3.5 for 13Cr)

Chloride content: 1 condition (5 to 15 percent NaCl)

Test Temperatures: 2 conditions (5 C, 23 C)

Test Methods: NACE TM0177 Method A and Method D

Stress Conditions: 5 conditions - 2 applied tensile stresses per condition (90 percent actual yield stress; second stress condition to be selected to be the same stress or lower depending on results at 90 percent) for tension tests; 3 wedge loaded DCB specimens.

Total number of tests: 40 tests.

Data Presentation: Tabular data; stress versus time-to- failure for tension specimens; KISSC for DCB specimens.

Program Budget: $36,000

Project 2005-C – Evaluation of Cyclic (Non-Fatigue) Loading on SSC Behavior
This project will assess the impact of cyclic stresses on the threshold for SSC of a selected group of materials including a high strength steel, and a modified 13Cr alloy. It will document and provide engineering data to assess dynamic designs where hydrogen charging is obtained from H2S corrosion. Such results may also provide insights into the effects of hydrogen charging from external cathodic protection under dynamic loading conditions, as well.

Experimental Program Details:

Materials:  2 conditions: API T-95 Type 1 and Modified 13Cr-110 completion steels 

H2S Partial Pressures: 1 condition (100 kPa for steels and 10 kPa for Modified 13Cr)

Solution pH: 1 condition (3.0 for steels and 3.5 for Modified 13Cr)

Chloride Content: 1 condition (5 percent NaCl)

Temperatures: 2 conditions (40 F, 75 F)

Stress Conditions: 3 tests SSR Cyclic load + 10% of mean stress; 250 cycles maximum; where mean stress is to be 90 percent of actual yield or lower as needed to characterize materials and the impact of cyclic load (For example: 90, 80, or 70 percent of actual yield strength depending on initial results).

Total number of tests: 24 tests (duplicate tests at each condition).

Test Method: NACE TM0198 slow strain rate specimen 

Data Presentation: tabular data; threshold plots (stress versus time to failure)

Program Budget: $30,000

Program Benefits

The initial benefit of this new flexible JIP format is that participating companies will pay only a portion of the total cost of these projects. Additionally, the program will set specific one year goals for funding and deliverables. All reporting will be paperless providing data in electronic format and a secure JIP website which will be used to archive the program data and deliverables for easy access by participating companies.

Additionally, InterCorr will utilize the secure website to develop any ballot items for MR0175/ISO 15156. This will include the use of an online forum for reviewing ballot items that may results from this program.

Sponsors may fund individual and multiple projects. To build further consensus and support, each sponsor will have an option to conduct a designated number of tests within certain parameters on a proprietary and preferred price basis at extra cost, if they choose.

Furthermore, the results from this program will be held in confidence among the sponsoring companies for a period of at least two years from their release to the program sponsors or until approval is given from the sponsors to release the data for purposes of NACE ballot preparation or industry standards initiatives.

Companies desiring to join the program after the 1st quarter 2005 will have to pay 15 percent higher fees than those paid by the original program sponsors. This arrangement gives the initial program sponsors maximum leveraging of their sponsorship fee. Sponsors can utilize year end FY 2004 or FY 2005 funding to participate in this program.

Budget

The budget for each of these projects has been formulated is summarized below:·        

Project 2005-A (17-4 PH, 316 SS & Monel 400; Evaluation for MR0175/ISO 15156)
$54,000 total ($9,000 per company)·        

Project 2005-B (Influence of low temperature on SSC)
$36,000 total ($6,000 per company)

Project 2005-C (Evaluation of Cyclic loading on SSC)
$30,000 total ($5,000 per company)

Optional Project Addendum (This fee will cover a limited number of additional tests conducted by InterCorr on a proprietary basis under same conditions used in this program; the number of tests will depend on the conditions selected. These will be performed at 10 percent less than normal commercial rates). $5,000 per company

Per company fee for participation in all three projects (Projects 2005 A-C) is $20,000 or $25,000 including the Optional Project Addendum. The fees will be payable in two installments at the start and completion of the projects.

The cost of participation in these tasks is based on the participation of six (6) companies and includes costs associated for testing, engineering, program management and administration, and reporting.  If additional companies agree to participate additional scope may be added to particular projects. The scope of the additional studies will be determined by the specific funding level available and needs of the sponsoring group. Alternatively, greater shared costs may be considered (with the approval of the sponsors) to accomplish the project deliverables of specific tasks should less than six companies agree to participate.

Background & Experience

InterCorr International, Inc. is one of the foremost corrosion and materials testing and research organizations. It has over 20 years of experience with evaluation of materials in H2S environments for upstream and downstream petroleum applications. It has over 1000 clients in 40 countries, worldwide.

This program will involve Dr. Russell D. Kane, InterCorr Vice President, as the program manager. He has extensive experience with evaluation of materials for sour service applications and development of the NACE MR0175 document. Dr. Kane is currently a member of the NACE TG 299 Oversight Committee for the new NACE MR0175/ISO 15156 International Standard. Dr. Kane will be assisted by the engineering and laboratory staff of InterCorr.

Action

Input for this program has been received from prospective sponsors resulting from the initial solicitation submitted earlier this year. The projects have been modified according to this input. Interest and support is being solicited for this program planned for initiation in 1st Quarter 2005.

Those interested to obtain more information, discuss the details of this program, or review a participation agreement, please contact Dr. R.D. Kane or Ms Dawn Eden at +1 (281) 444-2282 or by email at: rkane@intercorr.com or dceden@intercorr.com.

We look forward to your support of this interesting and timely program.

Figure 1 - SSC domains as a function of pH and H2S partial pressure



InterCorr International, Inc.
14503 Bammel-N. Houston, Suite 300
Houston, Texas USA 77014
Tel: 281 444-2282, Fax: 281 444-0246
E-mail: inquiry@intercorr.com
copyright 2000 InterCorr International, Inc
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