Smallbore step for drilling, giant leap for oil recovery

There is the possibility that an enhanced oil recovery (EOR) technology, combined with an unusual yet seldom-used smallbore drilling technology, could precipitate a major change in production from hundreds of thousands of global mature wells, both onshore and offshore.

Organic Oil Recovery^® (OOR) is currently being promoted by Hunting Energy Services in 23 countries in cooperation with Titan Oil Recovery. The technology uses tiny micro-organisms to release oil trapped in reservoirs. These are called microbes, which are so small a tablespoon of garden soil contains 1 trillion microbes. Certain species live in the oil reservoirs with no oxygen. OOR technology allows the microbes to surround oil globules trapped in the reservoir pore spaces, and deform the droplets into micro oil droplets so that they can then escape the pore spaces they were trapped in (Figure 1). This is achieved by sending nutrients into the reservoir to feed only certain species of microbes. The current nutrient delivery system used by Titan could be enhanced even further with smallbore lateral drilling.

Figure 1. Simple diagram of how OOR creates micro oil droplets.

The seldom-used smallbore lateral drilling (often referred to as ‘spaghetti string’) technology has yet to find a ‘killer application’ for its different drilling approach. Essentially, it comprises a small diameter coil tubing enhanced drilling technology that takes a conventional vertical oil well, places a small diameter (1 in.) drilling unit downhole and redirects a smallbore hole horizontally within the pay matrix. This is repeated in four directions (Figure 2).

Figure 2. Small lateral drill holes are now extended out from the wellbore.

One can see from Figure 2 that the communication from the wellbore to the reservoir fluids consists of a small area along the wellbore that would be perforated for the length of the zone that is being accessed. The original low pressure zone is represented by the small circle where the reservoir fluids would be flowing towards the wellbore. With the small lateral holes now extending out from the wellbore, four new and considerably extended low pressure zones have been created, allowing reservoir fluids to be taken into the new lateral boreholes.

In the past, the problem with this drilling technology was that trapped oil only 1 cm from the new lateral borehole could not move into the lateral borehole: it was trapped oil. With the OOR nutrients (represented by the gold arrows in Figure 3) now being pushed out in four directions and in a cone-like manner, the reservoir matrix – having been saturated with the OOR nutrients – is increased significantly and that area contains microbes that should respond to the nutrients and release trapped oil.

Figure 3. Inexpensive smallbore (1 in. dia.) lateral drilling would allow Titan to saturate more reservoir matrix with lateral extensions from the wellbore.

Due to the fact that the drill string and cutting tool is so small the resistance from the rock is consequently reduced. Boring through rock with 5 – 10 in. dia. drill bits is considerably harder and more expensive than using a 1 in. dia. drill bit.

The concept behind the spaghetti laterals was to contact oil away from the wellbore, bypass wellbore damage and create multiple low pressure zones away from the wellbore. However, as stated earlier, trapped oil was still a problem. If the small laterals could be used with the OOR technology and so release trapped oil, then the delivery system of the OOR nutrients would change from a one-dimension point outward from the vertical wellbore perforations to a four-dimensional process extended out horizontally in four directions from the wellbore (Figure 3 shows the red arrows extending out in two directions).

Although Titan’s OOR technology is ideal for water-flooded fields, single well applications with a huff and puff method have proven successful.

The new lateral holes – by creating new multiple and extended low pressure zones – could allow for better pore space drainage from the existing reservoir pressure, combined with the micro oil droplet effect of the process. Radial drilling can also be applied to injection wells and offshore.

Considering that 65% of the oil surrounding these wells is trapped and OOR already releases substantial amounts of incremental oil, this new delivery system for the process could allow for even better recovery factors and production volumes in vertical oil wells.

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