Guarantee of flow or flow assurance (FA), has been credited to Petrobras originating sometime in the 1990s. Since its original designation, FA has evolved

to include nearly every production challenge from the reservoir to the production separation system associated with producing hydrocarbons. These challenges include integrity management of the flow lines and equipment (valves, chokes, pumps, etc.), deposition control (hydrates, paraffin, asphaltene, mineral scale), dealing with large variations in the flow of liquids and gases from the well (slugging), as well as emulsion formation and the resulting changes in the viscosity of the fluids.

Philosophically speaking, for a time frame that predates the FA era, an oil and gas producer is primarily concerned with two major areas – integrity of the system, i.e. assuring that the metallurgy throughout the system lasts as long as desired, and optimisation of the production – assuring that the fluids and gas may flow at the optimal rates, according to system design and production objectives.

From the perspective of a chemical supplier, this meant studying the production system and investigating potential root causes that would impact system integrity or production optimisation, major factors impacting an operator’s lifting costs.

With regards to integrity management, R&D groups focus on the many potential causes of corrosion, e.g. bacteria, acid

gases, brines, flow regimes, solids production, chemicals used, system pressure, and so forth. The objective is to ensure that the risk caused by corrosion’s impact on system integrity is mitigated to the lowest possible level, with consideration to the economic constraints of such programmes. There are many options available to do this, either in system design and modifications, or in chemical programmes.

As it applies to production optimisation, specialised research into the many causes which detract from optimal system performance, has taken place. There have been many industry groups formed to study FA in deepwater systems, funded both by the chemical suppliers and manufacturers, as well as oil and gas producers. Most of these studies are conducted in conjunction with educational and research institutions.

Intensive research regarding mineral scale inhibition has taken place in recent years and much more is currently underway. These studies investigate the many types of brines present in oilfield production systems and the conditions which cause instability, such as the innumerable pressure and temperature conditions present in oil and gas production systems. Similarly, system conditions which cause gas hydrates to form (especially in deepwater systems) and process design and chemical additives to manage hydrates are being studied in laboratories and universities throughout the world. Considerations include gas and brine

A D V A N C I N G

A S S U R A N C Eflow

SAM TOSCANO, GE, USA, EXPLAINS HOW NEW FLOW ASSURANCE TECHNOLOGY CAN COUNTER

PARAFFIN PRODUCTION CHALLENGES.

| Oilfield Technology Reprinted from November 2016

composition, temperature gradients and pressure changes, oil and condensate composition, chemical additives applied upstream of the hydrate forming envelope in the system, and so forth.

Deposits and plugging caused by asphaltene molecules is a serious issue as well. There are factors in production systems which contribute to asphaltene destabilisation, and solutions to mitigate asphaltene challenges are available via mechanical modifications and chemical treatments.

An equally important and problematic area of production optimisation or FA is paraffin deposition. Much has been done to study the mechanisms of paraffin precipitation under various flow regimes and system conditions. Paraffin deposition is a complex issue, for when it forms it represents a hit to the total lifting costs. It becomes a problematic remediation issue (affecting the cost side of the lifting cost equation as an increase in operational expenses) and it also represents a loss in a well’s revenue generating production (a decrease in the denominator of the lifting cost equation). It should be remembered that paraffin is a very valuable component of oil and the challenge is to transport as much of it as possible to the refinery. Paraffin adhering to pumps and pipe walls represents a failure waiting to happen.

New perspectives on the paraffin issueSeveral years ago, GE recognised the importance of providing improvements to the issue of paraffin in oil and gas production systems. A research effort was funded from the top levels of the organisation with the primary objective of developing superior products to mitigate paraffin issues in oil and gas systems, with the intent that these products would add millions of dollars in cost savings and increased production to the bottom lines of producers.

A multiphase approach to address the issues was established.Using commercially available chemistries, a benchmark would be determined for product performance and cost-effectiveness. Each product would be tested to determine its performance in a number of testing protocols commonly used in the industry to inhibit paraffin deposition and to prevent gelling.

To be a true global research effort, GE scientists developed surrogate crudes which had characteristics of real paraffinic crudes from around the globe. The surrogate crudes would allow the research centres to independently focus on various aspects of the research simultaneously, with each of the four global centres essentially working on the same oils, but allowing each centre to focus on what they do best. The results of these efforts would be aggregated to determine which products worked best in which test protocol.

One of the challenges is to look at each of the various tests currently used to evaluate wax appearance temperature (WAT) paraffin deposits, crude pour point reductions, viscosity, etc. and to determine how closely the results correlate. The idea is to determine how specific chemicals impact each of these factors, looking for a product that performs best in each test and ideally, in more than one test.

Some of the testing includes: Ì Cloud point. Ì Pour point reduction. Ì Cold finger testing (deposit analysis). Ì Flow through a pipe loop to study pressure changes,

indicating flowline deposition.

Figure 1. The paraffinic composition of crude oils, one of many molecules present in crude oil is shown here, which is important to understand when selecting the best inhibitors.

Figure 4. Behaviour of paraffin inhibitors will vary so it is important to make the proper selection.

Figure 3. Results of cloud point using various additives on the surrogate crude oil.

Figure 2. Impact of chemical treatment on wax deposition.

Crude oil properties:Wax content: 3.8%WAT: 22˚CPour Point: -3˚C

Cold finger experiment test details:∆T = 15˚CBulk temperature: 25˚CFinger temperature: 10˚CDuration: 4 hrsStarting crude oil in cup: 40.0 g

Reprinted from November 2016 Oilfield Technology |

In addition, several surrogate blends were developed which closely mimicked the characteristics of several produced crude oils, with comparable depositional problems related to the chemical composition of the wax.

GE began the process by an in-depth internal study to benchmark all chemistries used to control wax related flow assurance challenges.

In the first year alone, several chemical families known to modify wax crystal structure and alter deposition were studied. Several of these products were in the GE product database, but many were new chemistries with limited data on their performance.

With the knowledge gained in the internal study, GE was able to establish benchmarks for critical areas of performance and physical characteristics, enabling them to put creative thinking and imagination to work.

There have been some successes already. GE researchers have identified several chemistries which have really distinguished themselves in the testing. Notably, these chemistries are working repeatedly on a number of extremely problematic crudes from around the globe.

The real challenge comes in determining optimal performance, based on important criteria: Ì Looking for low treating amounts (cost-effectiveness and

dosage). Ì Optimum product activity, which can solubilised into a

stable formulation, for both onshore and offshore/deepwater usage.

Deepwater is especially challenging as long term product stability is important, as well as meeting flash point and particle size specifications, with chemistries compatible to elastomers and metals used in the umbilical injection systems. Additionally, the health, safety and environmental aspects of the chemistry have to be known. With any new chemistries, an underlying industry tenet is to develop chemicals which are safer to handle and are more environmentally friendly than the previous generation of chemistry. Long term sustainability in the communities served and in environmental protection is an aspect that is near and dear to all of us.

Without going into specific details, several of the identified chemistries are in final stages of development, awaiting the go ahead to commercialise. There are trade secrets and patent applications which have to be addressed as part of the commercialisation process, based on what has been discovered.

In addition to identifying solutions to address flow assurance challenges today, GE researchers are also focused on the studying the mechanistic aspects of wax inhibitors, with the hope of continued improvements in chemistry and cost performance, helping producers increase system reliability and optimise hydrocarbon production. Major efforts in this area include: Ì Studies of wax and chemical properties and how they are

correlated. Ì New efficacious compounds leading to products with

improved performance. Ì Product formulations with a wider range of flow

characteristics over a range of temperature and pressure conditions.

One major project currently underway is investigating the chemicals structures of the ‘best chemistries’ and modifying them to determine what types of impact the molecular changes have on product performance in the standard batteries of tests. Work so

far has led to GE’s first patent applications being rolled out on these new chemistries which are expected to hit the market in the near future. There is excitement around these new chemistries as they have worked very well on a number of different crudes in laboratory conditions and with several of the test protocols. These products will be released under GE’s ProSolv.

SummaryThe guarantee of flow remains a major challenge to oil and gas producers. Technology continues to evolve as production conditions create new and sometimes more difficult operating environments. Innovations by the industry drive continued process improvement, allowing producers to go after difficult oils in remote locations, successfully.

Operating philosophies as also evolving. Rather than total inhibition of FA deposition, producers are looking at producing controllable slurries instead. Situations which were unheard of five years ago are now accepted as best practices.

GE’s investments in research and development are made with the intent of being a long-term partner to oil and gas producers, delivering superior cost effective solutions and raising the bar on state-of-the-art performance.

Reference1. Perez, P., Boden, E., Chichak, K., Boden, E., Gurnon, A. K., Hu, L., Lee,

McDermott, J., Osanhei, J., Peng, W., Richards, W., Xie, X., ‘Evaluation of Paraffin Wax Inhibitors: An Experimental Comparison of Bench-Top Test Results and Small-Scale Deposition Rigs for Model Waxy Oils’, OTC25927-MS, Houston, TX (May, 2015).

Figure 5. Depending on the crude type, performance and inhibition will vary.

Figure 6. A high temperature gas chromatograph analysis of the carbon number distribution of wax molecules in a crude oil sample.

Crude oil properties:Wax content: 4.73%WAT: 26.5˚CPour Point: <0˚CAPI: 54.6

Cold finger experiment test details:∆T = 45˚CBulk temperature: 46˚CFinger temperature: 1˚CDuration: 24 hrsDosage: 800 ppm product