'Bugs' Showing the Path for Drillbit

This Story Will Bug You

The bug man cometh.

No, we're not talking about insect exterminators, nor electronic "bugging" devices, nor coughs and sneezes, nor people who are a real pain to have around.

We're talking about creepy, crawly bugs — you know, the very essence of hydrocarbons.

Why? Because today, more than ever, bugs are aiding in the exploration and production of oil and gas.

Except today, the "bug men" have left their white coats back in the laboratory and are working in the field alongside geologists, engineers and drilling teams to help maximize production and minimize costs.

Of all recent developments in the role of production biostratigraphy, none has had a more immediate and perceptible impact than biosteering, according to Simon Payne, biostrat network co-leader for BP in Aberdeen, Scotland.

Few companies have pursued this technology as enthusiastically as BP — to date the company has used biosteering on more than 200 wells in 20 fields worldwide, primarily in northwest Europe — and Payne is hopeful that the firm's efforts will prove the worth of biosteering to the global industry.

Payne, along with several colleagues from BP, submitted a paper titled "The Role and Value of Biosteering in Hydrocarbon Reservoir Exploitation" at the recent AAPG International Meeting in Cairo, Egypt. The paper was part of a session on advances in production technologies.

Driven by the need for reservoir-scale stratigraphic control to help say "where we are" during the drilling of high-angle and horizontal wells, biosteering has rapidly become an integral, cost-effective part of the geosteering toolkit, he said.

"We think the technology has added tens of thousands of barrels of oil a day to BP-operated global production," Payne said. "Today this is a fundamental tool for the company.

"We still have to sell partners on the technique," he added, "but we find that it only takes a bit of misfortune on one well where the 'bug men' save the day to make converts of the skeptics."

Knowing Where You Are

The tool, according to Payne, ties together several aspects of the subsurface spectrum:

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The bug man cometh.

No, we're not talking about insect exterminators, nor electronic "bugging" devices, nor coughs and sneezes, nor people who are a real pain to have around.

We're talking about creepy, crawly bugs — you know, the very essence of hydrocarbons.

Why? Because today, more than ever, bugs are aiding in the exploration and production of oil and gas.

Except today, the "bug men" have left their white coats back in the laboratory and are working in the field alongside geologists, engineers and drilling teams to help maximize production and minimize costs.

Of all recent developments in the role of production biostratigraphy, none has had a more immediate and perceptible impact than biosteering, according to Simon Payne, biostrat network co-leader for BP in Aberdeen, Scotland.

Few companies have pursued this technology as enthusiastically as BP — to date the company has used biosteering on more than 200 wells in 20 fields worldwide, primarily in northwest Europe — and Payne is hopeful that the firm's efforts will prove the worth of biosteering to the global industry.

Payne, along with several colleagues from BP, submitted a paper titled "The Role and Value of Biosteering in Hydrocarbon Reservoir Exploitation" at the recent AAPG International Meeting in Cairo, Egypt. The paper was part of a session on advances in production technologies.

Driven by the need for reservoir-scale stratigraphic control to help say "where we are" during the drilling of high-angle and horizontal wells, biosteering has rapidly become an integral, cost-effective part of the geosteering toolkit, he said.

"We think the technology has added tens of thousands of barrels of oil a day to BP-operated global production," Payne said. "Today this is a fundamental tool for the company.

"We still have to sell partners on the technique," he added, "but we find that it only takes a bit of misfortune on one well where the 'bug men' save the day to make converts of the skeptics."

Knowing Where You Are

The tool, according to Payne, ties together several aspects of the subsurface spectrum:

  • Reservoir geology.
  • Biostratigraphy.
  • Drilling.a

To begin the process, a precise stratigraphic layering of the field is undertaken. Production biostratigraphy aims to subdivide the reservoir into unique, correlatable time-slices using field-specific microfossil bioevents to "fingerprint" individual layers.

Layering the reservoir at a higher resolution than regional, exploration-scale biostratigraphy, typically provides greater precision than seismic — and greater dimension than log or lithological analysis. This enables heterogeneity to be better understood, and gives a notional idea of which packages may be connected.

Critically, it also sets up the anticipated sequence of high-resolution bioevents for use in biosteering.

"In a clastic package the fossil-bearing rocks are generally the muds and silts that envelop and subdivide the pay," Payne said. "In a carbonate setting the whole interval is often fossiliferous.

Biosteering entails making the reservoir defining bioevent calls at rig site while drilling, allowing a real-time monitoring of well path relative to the reservoir.

"With this technique, reservoir penetration can be maximized," Payne said. "By discriminating between non-pay above, below and within the reservoir we can help explain unpredicted exits, for example, drilling out of the top or floor of the target or across sub-seismic scale faults.

"Biosteering helps guide well trajectory back into reservoir — drill up or drill down — boosting access to reserves," he added. "It is an addition to the geosteering armory, but a very handy one at that."

It also can help cut costs by optimizing casing and TD calls, giving the assurance that all targets have been penetrated.

"And above the target, well-angle build can be calibrated to optimize reservoir entry by an ongoing comparison with offset data," he said, "telling us if horizons are coming in deep or shallow, thereby helping to predict proximity to top reservoir."

A typical daily wellsite cost for all of this is about $1,500; a precursor high resolution reservoir layering study may be of the order of a few tens of thousands of dollars.

Biosteering is really "a happy combination of three things," he said:

  • The technology to drill high-angle wells.
  • The drive to define biostratigraphy at the well.
  • The application of biostrat at reservoir scale.

"In many people's minds biostrat is an exploration scale tool," he said, "but with this technology we can step beyond that application to a higher resolution and map the reservoir."

A Simple Science

BP has aggressively pursued the biosteering technique since 1995, when the tool was first applied at the Donan Field in the UK North Sea.

"The plan on Donan was to try and stay in the upper most reservoir package and have some control in terms of layering while drilling," Payne said. "We found that by going beyond broader exploration scale biozones and pushing the data really hard, well beyond our comfort zone, we could glean so much more.

"In the production arena we use bug events, delving into what would be dismissed as background 'noise' at the exploration scale," he said. "Across a field the use of these local bioevents can become powerful."

Payne acknowledged that biosteering is not rocket science — "low cost, low tech, big impact says it neatly," he added.

The subsurface community, however, has been quick to recognize the technique's value, he said.

"Engineers and geologists understand the value this tool brings," he said. "No need for them to get involved in the underpinning buggy detail — just use the results as part of the geosteering team effort."

During drilling, samples are cut, prepared and analyzed by a rig site bug man, which typically takes less than two hours.

"Rates of penetration within reservoir can be of the order of 10 meters per hour, we would only be 20 meters behind the bit with our results," he noted. "So, if there is a problem we can provide timely input."

The goal now is to push this new technology into the global industry.

"This tool has tremendous potential in the deepwater Gulf of Mexico, Angola, Azerbaijan, Egypt and Trinidad, to name but a few," he said. "It can work in shallow or deep marine clastics as well as shallow or deep marine carbonates — it should be considered wherever you have fossil-bearing rocks around and within your reservoir and a play to drill high-angle wells."

Valuable Experiences

It's easy to demonstrate what biosteering can bring to the table in terms of cost savings and enhanced reserves and production.

BP has proven the technology at several fields around the world in a wide variety of reservoir types, with impressive results. For example:

The Valhall Field in the Norwegian North Sea, in a Late Cretaceous deep marine carbonate reservoir.

"We have a six-fold reservoir subdivision in this field," Payne said. "The Valhall reservoir is a pretty monotonous chalk package on logs and lithologically, but biostrat can achieve a fine layering in the chalk, and biosteering technology has made it possible to stay within the target horizon while drilling horizontally.

"The target zone is actually below the highest porosity zone, because the highest porosity layer is unstable and prone to collapse when it is drawn down," Payne said. "By drilling just below this zone we avoid the problem of collapse but we gain good production."

Specifically, 25 percent of Valhall production can be attributed to placing the wells in the optimal part of the reservoir through biosteering.

The Cusiana Field in Colombia, a giant field that produces from several formations, including the Cretaceous Guadalupe Formation.

"We can break the reservoir into a number of units on the basis of high resolution biostrat," Payne said. "The time slices come down to a few tens of feet, which allows us to determine with a high degree of certainty where we are around the reservoir.

"Biosteering across a faulted reservoir section helps keep the wellbore on target," he added.

The high-angle biosteered wells have the potential to generate two to three times the production of conventional wells.

The Sajaa Field in Sharjah, where one of the key intervals can be broken down into 14 biozones across 1,000 feet.

"We drilled over 15 wells, including multi-laterals, supported by biosteering technology," Payne said, "and the tool was particularly useful here due to structural complexity, including sub-seismic faults that cut the reservoir.

"When we come out of the reservoir due to one of these faults, we have to know where the reservoir is so we can steer the well back into the target zone," he said.

"The technique definitely saved time and money at this field by averting potential side tracks."

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