Chasing black gold: inside Tullow’s oilrigs
Written by Devapriyo Das | Sunday, 13 September 2009 18:15
The whine of heavy, drilling equipment cuts through the evening breeze along the southern shore of Lake Albert in western Uganda. At Kaiso-Tonya, perhaps fifty metres from the steel-grey waters, an oilrig peeks above the palm trees that dot the sandy beach. This is the Ngassa-2 exploration site being prospected by Tullow Oil, and even in the fading light, it is easy to grasp the grand scale of Uganda's oil adventure.
LIKE NEVER BEFORE
"We have a rich seam of oil in East Africa, the likes of which have never been seen before", says Brian Glover, Tullow Uganda's Managing Director. Tullow (and its partner Heritage Oil & Gas) have drilled 27 exploration wells in the Lake Albert basin and an astonishing 26 have hit oil.
The usual success rate is just 10%-15%; and, Glover says, Tullow is only 40% into its drilling campaign. He estimates that 700-800 million barrels of oil can be extracted and commercially processed; but up to 2 billion barrels are likely to lie in Lake Albert in Western Uganda.
The Ngassa-2 well has been drilled to a depth of nearly 4,000 metres before sloping to one side. This was done to explore potentially oil-bearing zones under the lakebed. While the presence of hydrocarbons is still to be confirmed, given the outcomes from neighbouring wells, there is every chance that Ngassa-2 will prove to be a lucrative site.
ON THE RIG
"This is a fairly typical land drilling site", explains Laurie McCollum, Ngassa-2's site supervisor, "except we have a few environmental considerations that we have to take care of. We have some considerations regarding cuttings that we've taken from the well. We have to dispose of them at another site." Being close to the lake, Tullow must ensure that no ‘cuttings' (wastes) pumped from underground can contaminate the waters. Mud, stone and rocks drilled from underground and drilling fluids, must be isolated and treated elsewhere.
"On a normal land rig operation", McCollum continues, "we would have a huge pit dug behind the rig. We would quite simply put all the cuttings in there and then when we're finished, we would fill that in. But here, we can't do that because of where we're at, and restrictions in the size of the site [which is probably only about 100 square metres]."
Geographical features also make drilling a challenge here. "We're actually going out [drilling] underneath the lake", McCollum says. "We're drilling at an angle of about 30 degrees. There's been quite a lot of seismic and volcanic activity in this area which is complicating the drilling." The drilling itself, as in most rigs around the world, is done using a drill bit that extends pipes five inches in diameter underground, and lowers increasingly narrower pipes into the drill shaft and secures them in place.
Other challenges include the structure of the untapped oilfields below ground. The oil zones here can be ‘compartmentalized' so that oil does not flow from one zone to another naturally, being trapped in rock. This means drilling multiple wells at a high cost to extract the oil.
"I wish it was as simple as drilling a water well!" muses Glover. "But Ngassa is over 4 km long [and] we're drilling through sediments that are very unstable." That is why, "Overall, it becomes a very expensive business. Over half a billion dollars have been invested in Uganda's oil exploration to date and it will require much more money as we move into the next stages."
MULTIPLE WELLS
Tullow, and Heritage, which has hit significant oil deposits in the Kingfisher site on the Bugoma flats at the southern tip of the lake, are jointly exploring the Lake Albert basin. Tullow, the big brother in Ugandan oil exploration, owns 50% equity in the Kingfisher site, and pays half of Heritage's exploration costs, while keeping half of their finds. On Kaiso-Tonya itself, a string of wells, named Maputa 1 to 5, have shown hydrocarbon potential of varying degrees.
Mputa 1, the first well to be drilled in the Kaiso-Tonya area, and representing the first oil discovery in Uganda in more than half a century, is likely to produce 1,000 barrels of oil per day, and may be used as an Early Production Site, pending government approval. It was initially cited as a source of heavy fuel oil (which requires less refining than petrol and diesel) for Uganda's oil powered electricity generators, but the crash in global oil prices last year has halted the scheme.
Wells that have hit oil, and are now awaiting production, are ‘suspended' i.e. they are sealed and capped with a complicated array of red pipes, and valves that monitor the pressure of the trapped fluids below. Also known as "Christmas Trees" in oil industry parlance, these devices can be seen on many wells in Kaiso-Tonya and Bugoma.
Back at Ngassa-2, hard-hat and overalls-wearing technicians swarm around the bewildering network of pipes, metal grids, barrels, containers and wires, as a stream of trucks and earth-moving equipment pours in and out of the site. Drilling takes place all day throughout the week, with workers deployed in twelve-hour shifts, and about thirty people working at any given time.
The rigs themselves are rented from specialist drilling companies at a cost of $20,000 to $50,000 per day, depending on the size of the rig. Rigs are in demand around the world, and it is not uncommon for the equipment to ship in from other oil producing countries like Angola, be used in Kaiso-Tonya, and later be re-deployed in Ghana.
As Ngassa-2 rumbles on, its prospects remain strong. "We successfully sampled the oil from the well", Glover reveals. "In the course of the next few days we expect to release further information on what the implications are in terms of volumes that have been discovered in that area."
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