07121-DW1201

Goal
This project will develop a fundamental understanding of alternatives for preventing wax formation in deep water, uninsulated subsea pipelines. This project involves two phases: (1) a comprehensive literature review concerning flow in subsea pipelines, hydrate and wax formation, and methods designed to prevent or mitigate deposition; and (2) experimental evaluation of “one or two” of the most promising technologies/concepts based on the review.

Performer
University of Utah, Salt Lake City, UT 84112

Background
Unique challenges are associated with transporting hydrocarbon fluids through long subsea pipelines associated with deepwater oil and gas production. Wax precipitation in these flow lines due to the extremely cold temperatures is a serious problem. One way of preventing wax precipitation in long subsea lines is to insulate them; an expensive solution. A number of other wax control technologies have been proposed, some of which are being employed commercially. These include mechanical methods such as pigging, chemical injection technologies, and thermal management strategies, which focus on preventing the problem. One concept that has been tested recently, but has not been implemented commercially, is a process termed “cold flow.” The idea is to actually encourage the controlled formation of a slurry made up of hydrate and/or wax particles. Flow of the oil-water mixture can be managed in the presence of this slurry. The seed particles in the slurry act as nucleation sites and prevent or minimize further wax deposition in areas that might restrict flow.

In previous studies, no single strategy has proven to be completely effective in preventing and/or remediating the problem. There is a need to carefully evaluate all available technologies and select one or two for further evaluation. The purpose of this study is to identify gaps, challenges, and the Technology Readiness Level (TRL) associated with each option for preventing wax precipitation in un-insulated pipelines. This will begin with a comprehensive literature review and the identification of two of the most promising technologies. The project will continue by evaluating a proof of concept for these two technologies and will recommend an approach suitable for them to mature to commercialization.

The general approach will be to look at broad classes of technologies: mechanical methods (e.g., cold seeding, sonic methods, scrapers (pigs), internal pipe coatings, coiled tubing services, etc.), chemical methods (e.g., inhibitor and solvent injections to prevent or minimize the rate of wax deposit accumulation), and thermal management techniques (which emphasize reducing the driving force for deposition).

The project will be made up of two phases, a literature search and wax management phase and a proof of concept screening phase. Phase 1 will identify new wax management strategies, determine TRL for all options, identify wax management technical gaps and areas for future improvement, and report the findings from this current technology evaluation. During Phase 1, the required oil sample testing methods for predicting wax deposition and an assessment of the state-of-the-art in wax deposition simulation models will be determined. Phase 2 will document the definition, performance, and data analysis for proof-of-concept testing and qualification plan development for promising technologies, to be performed. The specific concepts to be tested and the testing program to be followed will be determined based on Phase 1 results and a detailed scope and protocol for the proof-of-concept testing will be developed at that point in concert with RPSEA. The selected technologies will be tested at the pressures and temperatures of interest under cold-flow conditions using the testing facilities at the University of Utah.

There are two deliverables. The first will be a Phase 1 report on the comprehensive literature search and will include: a list of wax management technologies and their technical readiness level; a list of wax management technology gaps; an assessment of the state of development, availability and effectiveness for each identified technology; an assessment of the current oil sample testing methods for predicting wax deposition; and an assessment of the state-of-the-art in wax deposition simulation models. The second deliverable will be a Phase 2 report on the results of a more detailed investigation and proof-of-concept testing of “one or two” of the most promising cold-flow wax management techniques, that includes data analysis of the proof-of-concept testing and recommendations for identified promising technologies to be evaluated through follow-on research. Monthly and quarterly reports in compliance with contract requirements will also be delivered.

Potential Impacts
This research will identify and test two of the most promising technologies that can be commercially developed to prevent wax precipitation in subsea pipelines, and identify the steps needed to prove these concepts. This information will accelerate the pace of development of new and more effective ways to reduce or eliminate problems of wax deposition in deepwater pipelines. In turn, this will accelerate the speed with which deepwater Gulf of Mexico fields can be brought online, increasing the volume of domestic production of oil and gas. In some cases, these technologies may enable development of fields which would not have been economically producible with current wax deposition prevention technology.

Accomplishments
The Project Management Plan (objectives and approach for each task with all major milestones and decision points), Technology Status Assessment (state-of-the-art of the proposed technology),and Phase I Report have been completed.

The team held several meetings in Houston, Texas. Phase II of the project was planned, and the literature review and experimental work were discussed. The literature review examined and evaluated: a) Cold Seeding and/or production chilling strategies, b) Injected chemicals or internal coatings, c) Chemical Inhibition / dissolution, d) Sonic management methods, e) Pigging, f) Bio-degradation (microbial), g) Coiled tubing for flowline and export line remediation, h) Active heating (flowline, export line, etc.), and i) Innovative technologies.

The University of Utah has finalized the technology for evaluation having developed a final experimental plan for evaluating cold flow. The team has completed the design of the flow loop for testing, measured model oil properties, identified a particle analysis system for purchase, designed and built a steel loop, calibrated the pressure transducers, completed a heat exchanger design, identified a model oil with a wide difference between wax appearance temperature and pore point, and completed the construction of the stainless pipe-in-pipe heat exchanger.

Current Status
Work has begun on two initial tasks: the development of the Project Management Plan with work breakdown structure that concisely addresses the objectives and approach for each task with all major milestones and decision points, and the development of a Technology Status Assessment describing the state-of-the-art of the proposed technology. The key tasks to be undertaken following the submission of the Project Management Plan and Technology Status Assessment are outlined below.

Wax Management Technologies - The University of Utah will prepare a technical report on the findings from the literature review and deliver a presentation on the findings and recommendations for further investigation and one or two proof of concept testing programs to be performed in Phase 2. The report will also identify a testing plan.

Testing Program Development and Execution - The development of a flow system for cold start will be continued. Phase II of the project is halfway completed at this time.

Data Analysis and Reporting - This task will consist of the following activities: a) Analysis and evaluation of the testing data and development of recommendations (a qualification plan) for further development of the technical maturity levels and estimation of the costs for further development of significant wax management technologies in a future project, b) Preparation of a technical report documenting the testing and subsequent recommendations, and c) Development and presentation of the findings and recommendations resulting from this work in a face-to-face meeting.

Project Start: September 2, 2008
Project End: September 1, 2010

DOE Contribution: $ 400,000
Performer Contribution: $ 100,000

Contact Information:
RPSEA – Jim Chitwood (jchitwood@rpsea.org or 713-372-2820)
NETL - Jay Jikich (Sinisha.Jikich@netl.doe.gov or 304-285-4320)
University of Utah – Prof. Milind D. Deo (Milind.Deo@utah.edu or 801-581-7629)

Additional Information

Final Project Report [PDF-4.49MB]

Phase 1 Technical Report [PDF-3.48MB]