As soon as the steel-toes hit the ground on Indonesia’s rugged Sumatra island, the Boots & Coots well control specialists recognized that they faced an especially steep uphill battle. The cantankerous well they were to tame was in an extremely remote location with a skimpy logistical network, no well data, and, to top it off, the client was a small independent, which could generously be described as extremely cost-conscious.
The subject well had been drilled in 2014 to a vertical depth of 2,160 ft, when an undetected kick spawned uncontrolled flow to surface. The flow was diverted, but not before a brew of oil, gas and condensate escaped around the casing and spontaneously ignited, engulfing the rig and adjacent equipment in flames with broaching in several nearby locations. Fortunately, the crew had been evacuated safely.
Boots & Coots Senior Well Control Engineer Rolly Gomez recapped the successful drilling of the shallow relief well during the IADC Drilling Engineers Committee (DEC) Technology Forum on Nov. 15 in Houston. The presentation evolved into a case study on working through the logistical headaches intrinsic to operating in an isolated location with limited resources, and on a job where devotion to cost control amounted to stepping over $1 to retrieve a dime.
The issues surfaced immediately after the team arrived, intending to conduct a more straightforward surface intervention. “It took three days to get there, and by the time we arrived, the rig had collapsed, the crater had formed, and there was no physical way to do a surface intervention,” he said. “They only had 40 ft of casing, so we had problems from the get go, as there was not enough casing to shut in the well.”
The difficulties compounded from there. “When we plan relief wells, we need all the well information we can get. In this particular case, the operator had only taken four inclination surveys, so we’re starting off at a very bad disadvantage. We had no idea where the well was located, so we gathered offset information to try and determine the most likely area the well could have gone. Then, we designed the relief well to avoid the other wells and hopefully avoid any associated hazards. And, we had a back-up plan, in case we ran into hazards,” he said.
Intercept challenges. Owing to a communications gap, drilling the relief well got off to a less-than-auspicious start. Despite explicit instructions to locate the crew accommodations safely away from the drilling operation, the operator plunked the camp down directly on the drilling pad, forcing a four-day suspension while the facility was re-located.
With drilling finally set to begin, scant well information and limited total vertical depth (TVD) made locating an intercept point a daunting proposition. “Since we only had inclination surveys, we looked up the offset data to determine where this information is leading us. In this case, it was in a northwesterly direction, so we began drilling in that general direction. We also had only 300 ft of TVD to play with for the intercept,” said Gomez.
The well plan called for drilling a 61/8-in. pilot hole to head off any broaching-induced gas influx. Afterward, the hole would be opened to 26½ in. for installation of the 135/8-in. casing before kicking off at roughly 300 ft. Initially, the team considered an intercept point at 1,800 ft, with the target just above the 61/2-in. drill collar.
An issue soon arose, with conflicting signals from the passive magnetic interference tool and active ranging tool. The team decided to follow the direction indicated by the active ranging tool, albeit with limited confidence. “Try to explain to a customer that you’re drilling a relief well, which they don’t understand in the first place, and we’re drilling to a target that we think is not there, so we can confirm it’s not there, do a plug-back and go to the other target,” he said.
There also was the matter of working with a local directional driller, whose charter was to go straightaway from Point A to Point B. “With a relief well, that’s not the best thing to do,” Gomez said. “You want to take it in small segments and do your ranging to determine where your target is and correct. We begin with an unknown as to where the target is and every time we range, we take that unknown and make the box smaller.”
Once a final intercept point was selected, the relief hole was landed, and the well killed. Between drilling, ranging and data interpretation, the relief well took 60 days. The operator, however, pressed for a 45-day turnaround, which so happened, coincided with the discount package offered by the pump contractor.
Emphasis on cost. “Everything was built on cost and the lowest bidder,” Gomez said. “They had a local drilling contractor and were using a used wellhead that had been installed incorrectly, so we had problems testing. After about two weeks of trying to get a test, the operator finally bit the bullet and decided we needed a new wellhead.”
“We also recommended a top drive and they went with a mechanical rig. We recommended standard BOP equipment and they went with a local brand instead.”
Another bewildering economic decision caused a delay when it came time to pump the kill mud and cement. “In this case, we had to wait, because they didn’t order the cement running tool,” Gomez said. “We had two cement retainers on location, but the running tool was on another island and they didn’t want to pay for a flight that would cost $25,000 to fly it in. So, we waited four days at a cost of $4 million to get the running tool to location.”
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