EOR going beyond giving a second lease of life to Omani oil wells

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Despite the lower oil price environment, Petroleum Development Oman (PDO) is ‘staying the course’ on its game-changing Enhanced Oil Recovery (EOR) journey and working aggressively towards EOR contributing strongly to total oil production in the near future. That is the clear message from Junaid M. Ghulam, PDO’s Field Development Centre Manager and Nasser Al Azri, EOR Studies Team Leader at the Field Development Centre, in a conversation with Akshay Bhatnagar. Excerpts of the conversation:

What are the focus areas of the Field Development Centre and how is it connected to EOR?

Junaid: The Field Development Centre was previously called the Study Centre but we have recently rebranded it. The previous name perhaps portrayed us as more of an academic-oriented centre. The new identity makes us more aligned with the business, getting more focused on business delivery while still retaining the depth of our technical capabilities and expertise. Inspired by PDO vision, our centre’s own vision is to leverage our collective talents to enable 50kboe/d over the next five years and develop additional two billion barrels over the next ten years. Within the Field Development Centre, we have a portfolio and capabilities based structure. So we have four main portfolios:

1 Improved Hydrocarbon Recovery, which is further sub-divided into North and South.

2 Contaminated Hydrocarbons

3 Gas

4 Enhanced Oil Recovery (EOR)

Talking specifically of the EOR stream, we have further sub-divisions – thermal and chemical. The third EOR application, miscible gas, is currently under the Contaminated Hydrocarbon portfolio because incidentally all our miscible gas is under the sour domain.

The way it works logically is, when fields come in, we look at the primary development first followed by infill; then we look at supplementing energy, which we call secondary recovery, say through water flooding or gas injection. Then we move into enhanced oil recovery. So the EOR teams are looking at brown fields that have gone through one or two cycles of development previously. We design the pilots for EOR, provide all the support required. The pilots are executed by the clusters from an operations point of view. Results are fed to us for analysis and, based on that, we recommend smart field development plans.

Can you take us through PDO’s EOR journey?

Nasser: PDO’s EOR journey started in the 1980s with a polymer flooding pilot project in Marmul field. We also tried a steam injection pilot during that same period. These efforts were directed towards extracting the oil which is heavy and viscous. The results were encouraging but due to the lower oil price environment at that time we could not take them to the full field development phase. However, the processes and leanings were captured and well documented.

With a more conducive environment in place and a focus on increasing our declining production, we went back to EOR during 2005-2006 and started working towards a field development plan for injecting polymer in Marmul. Consequently, the first field scale EOR development within PDO took off in early 2010.

The success in Marmul has been followed by field developments including steam injection in the Qarn Alam and Amal fields, and miscible gas injection in Harweel. In addition, there have been over a dozen EOR pilots at different phases of execution within PDO. The Company is aiming to maintain a sustainable long-term oil production plateau of 600,000 barrels a day by 2019 and EOR is expected to contribute strongly to this.

Let’s talk in detail about each of the four EOR field development projects. To start with, EOR at Marmul is completing six years of operations. Has it performed as per the expectations?

Nasser: Marmul has been under water injection since the early 1990s. With water injection, the recovery factor was around 28 per cent. Implementation of the polymer injection will lead to the recovery factor going beyond 35 per cent. The phase 1 development of polymer flooding started in early 2010, where polymer was injected into 27 injectors. The second phase started in 2015 with the addition of 19 polymer injectors. The phase 3 is currently in the Front End Engineering Design stage. The phase 1 led to an increase in oil production of 6,000 barrels a day. As a result, the field went back to producing at the high rate it had achieved during the early years of its production.

The value from the project is quite evident. The project paid back within 18 months of operations in terms of capital expenditure. Generally, the operational expenditure is very high in polymer injection as a very high volume (running into hundreds of thousands of barrels) of polymer solution is injected every day to the reservoir. This year, we started testing another EOR technique called alkaline-surfactant-polymer (ASP). If successful, the technology will have a wider application in PDO, and it is expected to improve the recovery factor by another 10 per cent.

Junaid: Talking of investments and returns, we have to understand how we grow our business. We have a natural resource (oil and gas) base, sitting below the ground. And we are adding to that resource base through active exploration. The last few years have been very healthy for us in terms of exploration. These new discoveries fall more in the scope of our conventional recovery mechanisms to start with. Meanwhile, we have billions and billions of barrels of existing resources. We must continue to increase our recovery factor; there is no doubt about this. The discussion is always how do we prioritise? How do we make it efficient? Have we found better ways to increase our recovery factors cost effectively? The mandate is to deliver quicker and at a much lower cost.

Moving towards Qarn Alam, it is a unique and world-class steam injection project despite high complexities. What have been its salient features and how is it doing currently?

Nasser: Qarn Alam, with its fractured carbonate rock containing heavy oil, is ideal for the EOR steam injection technique. We did a pilot project during 2002-2005 and the field development started producing oil by 2012. We are using the thermally assisted gas-oil gravity drainage (TAGOGD) technique, which has never previously been deployed on this scale in a reservoir featuring fractured carbonate rock. TAGOGD is ideal for highly fractured reservoir rock like that found in Qarn Alam, because the steam can be injected directly into the fractures. There, it heats the surrounding rock and lowers the viscosity of the oil by a factor of up to 100 times.

However, there is no requirement for Qarn Alam’s steam – either in its vaporous form or condensed back into water – to actually drive the oil into producing wells as it does in conventional steam flood processes. Instead, the ‘gravity drainage’ element of the technique’s name comes into play. This makes a virtue of the fractures in the rock, through which the now freer-flowing oil drains down into horizontally-drilled producer wells that are situated towards the bottom of the reservoir.

How much it is producing currently?

Nasser: About 10,000 barrels a day. The field was discovered in the 1970s and we hardly produced 5 per cent from the field using conventional methods. We expect the thermal EOR to boost the recovery to 30 per cent of the estimated oil in place in the coming years.

The Harweel (2AB) project where you have implemented miscible gas injection won an Award at ADIPEC 2015. Tell us more about it and what makes the project an important element in PDO’s EOR plans?

Nasser: The term ‘miscible’ means the gas injected into the reservoir dissolves completely into the oil, creating a less viscous fluid which therefore flows more easily and more preferentially through the reservoir to the surface. However, miscible gas will only dissolve in oil typically under very high pressure: around 500 times that of our atmosphere is the norm at Harweel (2AB), where we are running our first full-scale miscible gas injection project.

Generating sufficient pressure is one of the biggest – and most costly – challenges faced when deploying the technique. There’s a huge additional challenge at Harweel, in that the hydrocarbons in the reservoir are ‘sour’ – which means they contain significant levels of dangerous hydrogen sulphide gas. As a result, the surface facilities must be built to the highest possible levels of integrity, as well as featuring multiple safety mechanisms, in order to minimise the risks of leaks that would harm the workforce and the neighbouring environment. The implementation of such measures necessitates a complex balance between achieving HSE (health, safety and environment) goals and meeting cost targets.

Junaid: The Harweel miscible gas injection project came on stream in 2012 and by the end of 2013 production had risen to 30,000 barrels per day. It is in a highly sour environment. Generally, people don’t even look at sour let alone do an EOR in a sour domain. No wonder, the project won an ADIPEC Award last year. We originally earmarked an additional 160 million barrels of oil that could be produced through miscible gas EOR at Harweel (2AB), but now we are targeting a further 250 million barrels of oil that will be delivered by a new, $1 billion plus integrated project at Rabab-Harweel. This follow-up project, which is one-and-a-half times bigger than the existing Harweel (2AB) scheme, will see miscible gas injected into seven Harweel oil reservoirs. It will also involve recycling sour gas in the neighbouring Rabab field to develop condensate, which is a low density liquid hydrocarbon associated with natural gas. Production from the Rabab-Harweel EOR project is expected to begin in 2019.

How has the thermal EOR journey been at Amal?

Nasser: Amal is divided into two fields – Amal East and Amal West. Amal East has heavier oil compared to Amal West. We are injecting steam into the reservoir in Amal West to encourage the viscous oil to flow more freely. In Amal East we are currently doing Cyclic Steam Soak, where we inject and produce back from the same wells. The plan is to convert this to a steam flood at a later stage, once the pressure in the reservoir declined. The steam development in Amal is phased, with phase 1 currently under operation and phase 2 in design. Phase 1 is expected to deliver 30 per cent of the oil in place, and with phase 2 the recovery is expected to exceed 50 per cent.  Steam is generated in Amal through recycled heat from the power generation process as well as conventional steam boilers that utilise fuel gas. But gas is a precious commodity in Oman, so as part of our ‘Energy Efficiency Strategy’ and our drive to reduce our carbon footprint, we sought alternatives to natural gas for generating the steam required for our thermal EOR projects – starting with solar steam.

Junaid: Along with our partner, GlassPoint Solar we implemented a unique pilot project for over three years to harness the sun’s energy to produce steam used in heavy oil production in Amal West. Now, we are moving ahead with a field development project called ‘Miraah’. Once completed, it will be one of the world’s largest solar plants which at its peak will be able to generate in excess of one gigawatt of solar thermal energy. The gas saved can be used by other industries. To give you the scale of the project, Miraah will be 100 times larger than the pilot project. Miraah will save 5.6 trillion British Thermal Units (BTUs) of natural gas each year. The project also won the ‘Best Oil and Gas Innovation or Technology (Surface)’ at ADIPEC 2015.

Apart from these field development projects, we believe you have over a dozen EOR pilots and concepts in various stages in the pipeline. So what’s the vision for EOR in the Field Development Centre?

Junaid: The Field Development Centre has a vision, inspired by PDO’s corporate vision. We have a very highly skilled technical community here. Even under the current low oil price environment, we are focusing on further building our capability. The Company’s board and management are very supportive to us and have emphasised on various occasions that ‘we (the Company) will stay the course’ while ensuring commerciality even under such challenging economic climate. That’s very encouraging for us.

Our collective talent is leveraged to enable production of 50,000 barrels of oil equivalent a day (on an average) over the next five years. Here, I’m talking about new oil only, excluding production from field development projects that have already been delivered. The number of EOR pilots and concepts keep changing. Some of them may mature into field development projects and some may not, depending on the findings and the Company’s priorities.

We are among the few companies in the world implementing such a diverse range of EOR projects. In the long term, that is beyond 10 years, PDO has to develop an additional 2 billion barrels and we have to ensure EOR enables the Company to achieve its goal by creating new opportunities and maximizing our reservoirs’ potential.

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