Progress Reports: June 2006 December 2005
RISK ASSESSMENT OF SURFACE VS. SUBSURFACE BOP’S ON MOBILE OFFSHORE DRILLING UNITS
OBJECTIVE: We propose to study the applicability and risk of applying this technology to waters such as the Gulf of Mexico. In this study we intend to determine the risk of utilizing not only surface BOPs in floating operations, but also the advisability of using subsurface shear rams that may be needed to shear the drillstring during an emergency such as an unplanned disconnect.
INTRODUCTION: In an attempt to mitigate many of the problems associated with deepwater drilling, some operators such as Woodside Energy Ltd., Shell, TOTAL, and Unocal have either considered using or have used surface BOPs with small diameter, high pressure risers in floating drilling operations. The myriad of problems associated with drilling in deep water have been extensively covered in the literature. Some of the problems that this technology can help to alleviate are directly associated with the large diameter marine risers currently being utilized.
As water depth increases, the weight of conventional risers increases to a point that only a very few fifth generation floating rigs have the capability to drill in ultra-deep water. The deck loads increase tremendously, the volume of mud required to fill the riser increases, and the choke line friction increases to a point to where successfully circulating a kick from the well becomes almost impossible. The small diameter, high pressure riser can alleviate the deck load requirements, reduce the volume of mud required, and eliminate the high choke line friction pressure experienced with conventional marine risers. This will also, minimize the problems associated with riser gas.
However, this is relatively new technology, and there is inherent risk in applying any new practices. Even though this technology is relatively new, it has been successfully applied in a number of international locations, mostly in calm waters, where currents are low, and storms are not common. Now, some operators would like to apply this technology to waters that are susceptible to high currents, and storms.
We propose to study the applicability and risk of applying this technology to waters such as the Gulf of Mexico. In this study we intend to determine the risk of utilizing not only surface BOPs in floating operations, but also the advisability of using subsurface shear rams that may be needed to shear the drillstring during an emergency such as an unplanned disconnect.
BENEFITS TO MMS AND THE OIL & GAS INDUSTRY: MMS would have an important document to help assess the risk of utilizing relatively small diameter, high pressure risers and surface BOP systems with and without subsurface shear rams. This document will aid the MMS in their approval process of applications to drill submitted by the operators that propose the use of this technology in the Gulf of Mexico and other areas of the U.S. OCS. The Oil & Gas Industry would have accesses to a well written document that could be utilized by drilling engineers and companies alike as a guideline for the risk of utilizing surface BOPs and high pressure risers on MODUs.
DEPLOYMENT OF RESULTS: The results of this work will be conveyed to OTRC, the MMS, and the petroleum industry through an M.S. Thesis, conference presentations, publication in trade journals, progress reports, and a final progress report. All final versions of thesis and reports will be provided to the OTRC and MMS upon completion of the progress.
ANTICIPATED NUMBER OF PHASES: 2
PROJECT PLAN FOR PHASE 1 (2005-2006):
Scope and Plan:
1. A literature review to assess the state of the art in the use of surface BOPs on Mobile Offshore Drilling Units, MODUs. We will study the equipment that is currently being utilized by these operators and drilling contractors; where this technology is being applied; as well as sea conditions (e.g. current, wave height, and storm frequency and severity). We will compare the sea conditions where surface BOPs are utilized on MODUs to those in the Gulf of Mexico.
2. We will perform an analysis of the frequency of riser failures for both conventional large diameter risers as well as the smaller diameter high pressure risers. We will also review the causes of the failures. However, we do not intend to perform the failure analysis ourselves, just review the analysis performed by others.
3. Based on this failure analysis, we will determine the proper risk evaluation tools that are available today and analyze the risk of utilizing a surface BOP system in deep water on a MODU.Deliverables: A Final Report shall be prepared documenting the results from Phase 1.
PROJECT PLAN FOR PHASE 2 (2006-2007):
Scope and Plan:
1. Based on the above risk analysis, we will determine the value and/or need for subsea shear rams to be used with high pressure risers and surface BOP systems. We will finish this task with a shorter analysis of the risk involved with utilizing the subsea shear rams.
2. We will document the results of this work in a final report that will be provided to the OTRC and the MMS. The final report will include all M.S. theses written on the project.PRINCIPAL INVESTIGATORS AND OTHERS INVOLVED IN THE PROJECT:
PI’s: Jerome J. Schubert, Mahmood Amani, (Texas A&M University)
Others - One MS student
DATE: May 2006
Project Title: Risk Assessment of Surface vs. Subsurface BOP's on Mobile Offshore Drilling Units
MMS Project: 540 TO Number: 39226
PI: Jerome Schubert
COTR: S. Buffington
Estimated Completion Date: August 2006 (Phase I project term was 5/1/2006)
Project Description: Compare the use of a slim high-pressure riser system and a surface BOP (SBOP) to the conventional subsea BOP and large diameter low-pressure drilling riser in the deepwater Gulf of Mexico region.
Progress: Virtually all work has been completed by a graduate student Jorge Melendez. He has documented the work in his MS thesis. The study included:
1. A literature review to assess the state of the art in the use of surface BOPs on Mobile Offshore Drilling Units, MODUs. The review included:
a. Equipment currently being utilized by operators and drilling contractors
b. Where this technology is being applied; as well as sea conditions (e.g. current, wave height, and storm frequency and severity).
c. Comparison of the sea conditions where surface BOPs are utilized on MODUs to those in the Gulf of Mexico.
2. An analysis of the frequency of riser failures for both conventional large diameter risers as well as the smaller diameter high pressure risers. The review included the causes of the failures based on analyses performed by others.
3. Based on these failure analyses, available risk evaluation tolls were identified and used to analyze the risk of utilizing a surface BOP system on a MODU in deep water.
4. The value and/or need for subsea shear rams to be used with high pressure risers and surface BOP systems were determined based on the above risk analysis. A shorter analysis of the risk involved with utilizing the subsea shear rams was also completed.
The results of this work are being documented in a final report that will consist of an executive summary and the M.S. thesis.Publications & Reports:
Masters Thesis: “Risk Assessment of Surface vs Subsea Blowout Preventers (BOPS) on Mobile Offshore Drilling Units Focusing on Riser Failure and the Use of Subsea Shear Rams,” Jorge Melendez, May, 2006.Abstracts have been submitted to various conferences.
DATE: December, 2005
Project Title: Risk Assessment of Surface vs. Subsurface BOPs on Mobile Offshore Drilling Units
MMS Project: 540 TO Number: 39226
PI: Jerome Schubert
COTR: S. Buffington
Estimated Completion Date: 12/31/2006
Project Description: Compare the use of a slim high-pressure riser system and a surface BOP (SBOP) to the conventional subsea BOP and large diameter low-pressure drilling riser in the deepwater Gulf of Mexico region. Tasks are:
We propose to asses the following focused study areas:
Phase I (Year 1)
1. A literature review to assess the state of the art in the use of surface BOPs on Mobile Offshore Drilling Units, MODUs. We will study the equipment that is currently being utilized by these operators and drilling contractors; where this technology is being applied; as well as sea conditions (e.g. current, wave height, and storm frequency and severity). We will compare the sea conditions where surface BOPs are utilized on MODUs to those in the Gulf of Mexico.
2. We will perform an analysis of the frequency of riser failures for both conventional large diameter risers as well as the smaller diameter high pressure risers. We will also review the causes of the failures. However, we do not intend to perform the failure analysis ourselves, just review the analysis performed by others.
3. Based on this failure analysis, we will determine the proper risk evaluation tools that are available today and analyze the risk of utilizing a surface BOP system in deep water on a MODU.Phase II (year 2)
4. Based on the above risk analysis, we will determine the value and/or need for subsea shear rams to be used with high pressure risers and surface BOP systems. We will finish this task with a shorter analysis of the risk involved with utilizing the subsea shear rams.
5. We will document the results of this work in a final report that will be provided to the OTRC and the MMS. The final report will include all M.S. thesis written on the project.Progress:
Completed Tasks
Literature review on SBOPs application on MODUs, and metocean conditions from the locations where they have been implemented.
o Recent BOP studies in the GOM and published guidelines.
o Latest accomplishments and challenges in the SBOP field (equipment, technique, metocean conditions)
o Sea and storm severities in 1, 5, 10, and 100- year return period in the GOM (including 2005 hurricane season).Analysis of drilling riser failures frequencies for conventional large-diameter risers as well as the slimmer high-pressure riser.
o Incidents reported to the MMS in the past five years from the GOM have been reviewed and built into a database.
o Deepwater (>1,000 ft) drilling riser relates failures have been sorted and incident description analyzed to determine root cause.
o Listed drilling riser and BOP critical components.
o Determine failure frequencies of components.
o Review recent worldwide public incidents reports to serve as reference and compare frequencies on drilling riser failure.
o Experiences from operators in deepwater GOM.On Going Tasks
Analyze the risk of using a SBOP system in deepwater GOM on a MODU.
o Develop fault tree models for the slim high-pressure and large low-pressure drilling riser system.
o Develop SBOP and BOP system fault tree array.
o Develop risk acceptance matrix to perform qualitative analysis for the SBOP and subsea BOP system based on riser reliability studies and components failure.
o Perform a quantitative analysis on the high-pressure and low pressure riser system.
o Rank components importance.
o Compare results.Determine the value and/or need for subsea shear rams to be used with high-pressure risers and surface BOP systems.
o Review usage and design of subsea disconnecting device.
o Estimate failure frequency of the subsea component based on BOP reliability studies.
o Incorporate subsea shear ram to SBOP fault tree models.
o Compare results.Undeveloped tasks
• Document the results in a final report provided to the OTRC and the MMS.
o Write thesis report for M.S requirement.Publications & Reports: Not at this time