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Gudmund Olsen

Wells can produce much more while spending no or relatively little financial resources. Our Production Technology experts discuss ways to increase well productivity by not having to spend yet another million of dollars.

Getting more from less approach is very obvious in the football world, where an astute manager can create a team with a low budget that can upset the giants of the game. Similarly an astute oilfield manager can deliver substantial returns from a producing field with only a limited budget. Getting more production from less expenditure is a real option, and like the football manager, excellence in the fundamentals count. Our Production Technology experts drill deeper on this topic.

Lesson 1: check pressure of the reservoir

The first approach should be to understand the pressure profile from reservoir to the wellbore, into the tubing and through the flowline to the separator. Where are the biggest pressure drops? How do these pressure drops compare to the other wells in the field?

This first step often highlights the areas where gains can be made at low cost. For instance, many wells are choked back in early field life when reservoir pressures are high, and facilities are full. However in a mature field, if chokes are not fully open, you need to ask – why not? Even if the choke is fully open, often the choke body is small, and there is still a significant pressure drop. This can easily be fixed.

Once fully open, wells “see” the first stage separator pressure, also set up for handling flow in early field life. Why not drop this? Obviously a discussion with facilities staff is required but often substantial gains can be made at low cost.

Lesson 2: Work in cross disciplinary teams

Moving onto the wells, the key driver to productivity is the interface between the well and the reservoir, ie the “near wellbore region”.

Historically wells were cased and cemented and this interface was created by perforations. It’s always worth looking back to see how the well was perforated. Was it with (cheap) small guns on wireline with overbalance, or with big guns on tubing under drawdown. If it was the former, reperforating is almost certainly a winner. Even if the wells were perforated properly, depending on rock properties, compaction, fines migration or scale build-up may have reduced the inflow, and again reperforation will work.

Of course if a well was fracced, similar questions should be asked – what was the size of the frac, what was the method, has its performance fallen off? Refraccing is a very successful option with modern frac fluids, higher pressures are available, along with better proppants allowing rejuvenation of existing fracs.

Lesson 3: Check data for correct gaslift

Excessive pressure drops near wellbore is collectively described as “skin”, and this can be measured and analysed with available advanced well modelling software to best select the method to reduce the skin.

In later field life, artificial lift usually becomes important on maintaining rates, and often, these systems are underperforming. If the field is gaslifted, are we sure gas is going through the deepest valve? Are we also sure the optimum amount of gas is going to each well? What if the compressor was upgraded? Similarly for ESP (electric submersible pump) wells, is the correct data being gathered to optimise the pump, is the available power distributed optimally?

Lesson 4: Check data for correct water injection

Similarly, water injection often becomes essential in later field life to maintain rates. Is the water being distributed between injectors optimally? Do you actually know where it goes in the reservoir and is sweeping the oil effectively? If not, tracers (very small quantities of chemicals that can be picked up in the produced water) can give the answer.

Also is there a huge effort being spent on filtering injection water? Why not frac it in, and bypass or decommission the surface facilities. Often Operators are fraccing anyway due to thermal cooling of the reservoir.

Also with water, has scale deposition been modelled? Where is it an issue in the well? Scale inhibition is an expensive process. This can also be optimised.

Lesson 5: Organise valuable historic data in efficient way

Finally, although the above deals mainly with mature wells and fields, infill drilling and sidetracks can pay off, especially if the way they are drilled and completed maximises reservoir access and productivity. If a new well is to be drilled, the difference in productivity between a well that is completed badly, and one that is completed well, can be 100% or more.

Erik-Lorange-cropped Erik Lorange
VP Reservoir Management
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In summary, wells can produce much more while spending no or relatively little money. Planned wells can be substantially improved with attention to avoiding skin and completing properly, again for little additional cost. All it takes is staff equipped with the know-how and tools to do the job.

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