The oilpatch is notorious for being “careful” about its approach to new technology. But sometimes you’ve just got to take a chance.

That was what Warren E&P decided to do in its Wilmington Townlot Unit (WTU) located in the city of Los Angeles, Calif. It tried a new and unique well placement technology, PeriScope 15, by Schlumberger. And the results are nothing short of amazing.

The field was originally discovered in 1936, and over the years it has been drilled extensively

Figure 1. PeriScope 15 deep imaging enabled the driller to keep the well bore entirely within the narrow, dipping target sand. (Images courtesy of Schlumberger)
with vertical wells chasing four producing horizons — the Tar, Ranger, Upper Terminal and Ford. Since 1971 the Upper Terminal has been under waterflood. It was this project that piqued Warren’s interest in the late 1990s.

Warren bought 50% of the field in 1999 from a small operator. “Oil prices went up almost immediately after we signed the deal,” said Ken Gobble, senior vice president of Warren. “The seller did everything it could to unwind the deal.”

In February 2005, Warren purchased the other 50% of the field, and work began on a sub-zone redevelopment.

While drilling new vertical wells to the upper terminal member, Warren engineers noticed that the shallower Tar formation still showed good oil saturation, albeit heavy oil. It also had a partial water drive, unlike the other zones. “With that heavy oil and partial water drive, the vertical wells that were originally drilled in the field tend to cone out quickly,” Gobble said. Other than a handful of wells drilled in areas with outstanding sands, he added, the economics of developing the tar with vertical wells were questionable.

New geologic data from the field gave the company a leg up over the older owners, and Gobble’s team began examining the potential for horizontal development. Despite advances in horizontal drilling over the years, however, this would be no walk in the park. The zone of interest contains a 30-ft to 50-ft (9.2-m to 15.3-m) column of oil on top of water. “We thought that if we could drill these wells and keep them as close to the top of the sand and as far away from the oil-water contact as possible, we could reduce the chance that they would cone,” Gobble said.

They also faced the formidable challenge of snaking the laterals past countless vertical well bores.

The first horizontal well was drilled in August 2006 with standard logging-while-drilling (LWD)
Figure 2. Significantly increasing production through optimal well placement in a heavy oil reservoir.
equipment. It was relatively successful, improving production significantly over the previous vertical wells. However, it immediately had problems with water cut. “We think we probably cut a fault about halfway through the lateral section,” he said. “At that point we didn’t know whether the zone went up or down; all we knew was that we had higher water saturation with no real explanation.

“Looking back at it, we knew we were in zone with the LWD with gamma ray, but we could not tell where we were all the time,” he added. “We had a high oil saturation, so things looked good even though we might have been only a foot from the water. When you’re a foot from the water, the well is not going to perform as well.”

Enter PeriScope
What was needed was an LWD tool that could report its position not only in respect to other zones but within the zone of interest as well. PeriScope provides both deep-reading and azimuthal (directional) resistivity measurements, making it a good choice for the situation, “although not an obvious choice economically for what we were doing and what we thought the wells would do,” Gobble said.

Though the tool had performed successfully in other parts of the world, it hadn’t been used extensively in the North American continent other than in Alaska and Canada, but there results were encouraging.

Gobble talked to Gary Lancaster, LWD business development manager in Schlumberger’s Drilling & Measurements group. Lancaster was confident enough in the performance of the service to set up a contract that would be performance-based for the first two wells. “We did a deal where we’d take a look-see for two wells to see how they performed and how it would improve our economics,” Gobble said.

Added Lancaster, “Warren had bought an older field. From public data that we found, the average well bore produced 23 b/d of oil. They needed to revitalize that field, and they used PeriScope to maximize production per well.

“Also, they wanted to lower the overall cost of the well. They were looking at the total cost of drilling rather than just looking at individual actions.”

Schlumberger modeled a well for Warren that indicated that the length of the lateral had a direct correlation to total production. Obviously a tool that could keep them in the upper part of the zone for a longer stretch would offer superior production results. So the two-well program commenced.

“Phenomenal”
It was a huge gamble for Warren, a small exploration and production company by almost any standards. The goal was to drill a 1,000-ft to 2,000-ft (305-m to 610-m) lateral at a cost of more than US $1 million per well. There was little room for error.

But Warren took the chance, partly because of Gobble’s trust in the Schlumberger team. “We had a lot of confidence in their well placement personnel,” Gobble said. He was also impressed with InterACT, the software tool that provides real-time information about the progress of the well.

The results of the first two wells were, Gobble said, “phenomenal.” The wells came in
Figure 3. Remote monitoring of real-time drilling operations enabled Warren Energy to maximize reservoir contact and increase production.
producing around 200 b/d of oil with a 10% water cut. Warren has gone on to drill seven additional PeriScope wells, The total field production prior to the horizontal program was less than 1,200 b/d of oil; the horizontal wells, while representing a fraction of the total number of well bores in the field, now account for 38% of the production.

The confidence instilled by PeriScope has changed a number of things for Gobble, including a reduced need for travel. Though he sat on the first several wells, he later viewed the well progress from his home in Casper, Wyo. “I can sit at home and do whatever I need to do and watch the well, knowing exactly where we are in relation to the top of zone every minute.”
It’s also enabled the company to feel more confident in its reserves statements due to the significant increase in its success ratio. “If we were to continue to drill without this type of technology, we would have to risk our reserves at 50%,” Gobble said. “And we wouldn’t really know why one well was successful and others weren’t. Now our success rate is almost at 100%. It’s really taken the ordinary mechanical risk completely out of the picture.”

It’s certainly changed the way Warren personnel view other potential opportunities, causing them to consider analogs that might otherwise have been of little interest. And most importantly, it’s given the WTU a new lease on life. “It’s possible that PeriScope has made such a dramatic difference that it saved a project that potentially could have failed,” Gobble said.

All it took was a little gentle persuasion. “To be honest, I was one of the skeptical ones,” Gobble said. “Any new technology is a tough sell for a small company.”

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